Measurement of the vec{n} p->d pi0 pi0 Reaction with Polarized Beam in the Region of the d*(2380) Resonance
P. Adlarson, ..., E. Czerwiński, M. Hodana, J. Klaja, W. Krzemień, P. Moskal, I. Ozerianska, O. Rundel, M. Skurzok, M. Zieliński et al.
abstract
We report on a high-statistics measurement of the most basic double pionic fusion reaction vec{n}p -> dpi0pi0 over the energy region of the d*(2380) resonance by use of a polarized deuteron beam and observing the double fusion reaction in the quasifree scattering mode. The measurements were performed with the WASA detector setup at COSY. The data reveal substantial analyzing powers and confirm conclusions about the d? resonance obtained from unpolarized measurements. We also confirm the previous unpolarized data obtained under complementary kinematic conditions.
Determination of the eta '-Proton Scattering Length in Free Space
E. Czerwinski, P. Moskal, M. Silarski, SD. Bass, D. Grzonka, B. Kamys, A. Khoukaz, J. Klaja, W. Krzemien, W. Oelert, J. Ritman, T. Sefzick, J. Smyrski, A. Taschner, M. Wolke, M. Zielinski
abstract
Taking advantage of both the high mass resolution of the COSY-11 detector and the high energy resolution of the low-emittance proton beam of the cooler synchrotron COSY, we determine the excitation function for the pp --> pp eta' reaction close to threshold. Combining these data with previous results, we extract the scattering length for the eta'-proton potential in free space to be Re(alpha(p eta)') = 0 +/- 0.43 fm and Im(alpha(p eta)') = 0.37(-0.16)(+0.40) fm.
Evidence for a New Resonance from Polarized Neutron-Proton Scattering
P. Adlarson, ..., E. Czerwiński, M. Hodana, J. Klaja, W. Krzemień, P. Moskal, I. Ozerianska, M. Skurzok, M. Zieliński et al.
abstract
Exclusive and kinematically complete high-statistics measurements of quasifree polarized vec_n p scattering have been performed in the energy region of the narrow resonance structure d* with I(JP)=0(3+), M ~2380 MeV/c2 and Gamma 70 MeV observed recently in the double-pionic fusion channels pn->dpi0pi0 and pn->dpi+pi-. The experiment was carried out with the WASA detector setup at COSY having a polarized deuteron beam impinged on the hydrogen pellet target and utilizing the quasifree process d p->np+p_spectator. That way the np analyzing power Ay was measured over a large angular range. The obtained Ay angular distributions deviate systematically from the current SAID SP07 NN partial-wave solution. Incorporating the new Ay data into the SAID analysis produces a pole in the 3D3->3G3 waves as expected from the d* resonance hypothesis.
Determination of the eta prime - proton scattering length in free space
E. Czerwiński, P. Moskal, M. Silarski, S. D. Bass, D. Grzonka, B. Kamys, A. Khoukaz, J. Klaja, W. Krzemień, W. Oelert, J. Ritman, T. Sefzick, J. Smyrski, A. Täschner, M. Wolke, M. Zieliński
abstract
Taking advantage of both the high mass resolution of the COSY--11 detector and the high energy resolution of the low-emittance proton-beam of the Cooler Synchrotron COSY we determine the excitation function for the pp --> pp eta' reaction close-to-threshold. Combining these data with previous results we extract the scattering length for the eta'-proton potential in free space to be Re (a p eta') = 0 +/- 0.43 fm and Im a_(p eta') = 0.37^{+0.40}_{-0.16} fm.
Measurement of the pn -> pp pi(0)pi(-) reaction in search for the recently observed resonance structure in d pi(0)pi(0) and d pi(+)pi(-) systems
P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, FS. Bergmann, M. Berlowski, H. Bhatt, M. Buscher, H. Calen, I. Ciepal, H. Clement, D. Coderre, E. Czerwinski, K. Demmich, E. Doroshkevich, R. Engels, W. Erven, W. Eyrich, P. Fedorets, K. Fohl, K. Fransson, F. Goldenbaum, P. Goslawski, A. Goswami, K. Grigoryev, CO. Gullstrom, F. Hauenstein, L. Heijkenskjold, V. Hejny, F. Hinterberger, M. Hodana, B. Hoistad, A. Jany, BR. Jany, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, FA. Khan, A. Khoukaz, DA. Kirillov, S. Kistryn, J. Klaja, H. Kleines, B. Klos, M. Krapp, W. Krzemien, P. Kulessa, A. Kupsc, K. Lalwani, D. Lersch, L. Li, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Marianski, M. Mikirtychiants, HP. Morsch, P. Moskal, BK. Nandi, H. Ohm, I. Ozerianska, EP. del Rio, NM. Piskunov, P. Plucinski, P. Podkopal, et al.
abstract
Exclusive measurements of the quasifree pn -> pp pi(0)pi(-) reaction have been performed by means of pd collisions at T-p = 1.2 GeV using the wide angle shower apparatus (WASA) detector setup at the cooler synchrotron COSY (Institut fur Kernphysik, Julich). Total and differential cross sections have been obtained covering the energy region root s = (2.35-2.46) GeV, which includes the region of the ABC effect and its associated resonance structure. NoABCeffect, i.e., low-mass enhancement is found in the pi(0)pi(-) -invariant mass spectrum, in agreement with the constraint from Bose statistics that the isovector pion pair can not be in relative s wave. At the upper end of the covered energy region t-channel processes for Roper, Delta(1600) and Delta Delta excitations provide a reasonable description of the data, but at low energies the measured cross sections are much larger than predicted by such processes. Adding a resonance amplitude for the resonance at m = 2.37 GeV with Gamma = 70 MeV and I (J(P)) = 0(3(+)) observed recently in pn -> d pi(0)pi(0) and pn -> d pi(+)pi(-) reactions leads to an agreement with the data also at low energies.
Search for a dark photon in the pi(0) -> e(+)e(-)gamma decay
P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, FS. Bergmann, M. Berlowski, H. Bhatt, A. Bondar, M. Buscher, H. Calen, I. Ciepal, H. Clement, D. Coderre, E. Czerwinski, K. Demmich, E. Doroshkevich, R. Engels, W. Erven, W. Eyrich, P. Fedorets, K. Fohl, K. Fransson, E. Goldenbaum, P. Goslawski, A. Goswami, K. Grigoryev, CO. Gullstrom, F. Hauensteinn, L. Heijkenskjold, V. Hejny, F. Hinterberger, M. Hodana, B. Hoistad, A. Jany, BR. Jany, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, FA. Khan, A. Khoukaz, S. Kistryn, J. Klaja, H. Kleines, DA. Kirillov, B. Klos, M. Krapp, W. Krzemien, P. Kulessa, A. Kupsc, A. Kuzmin, K. Lalwani, D. Lersch, L. Li, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Marianski, UG. Meissner, M. Mikirtychiants, HP. Morsch, P. Moskal, BK. Nandi, H. Ohm, I. Ozerianska, EP. del Rio, et al.
abstract
The presently world largest data sample for pi(0) -> gamma e(+)e(-) decays studies containing nearly 5 x 10(5) events was collected using the WASA detector at COSY. A search for a dark photon U produced in the pi(0) -> gamma U -> gamma e(+)e(-) decay from the pp -> pp pi(0) reaction was carried out. An upper limit on the square of the U -> gamma mixing strength parameter epsilon(2) of 5 x 10(-6) at 90% CL was obtained for the mass range 20 MeV < M-U < 100 MeV. This result together with other recent experimental limits significantly reduces the M-U vs. epsilon(2) parameter space which could explain the presently seen deviation between the Standard Model prediction and the direct measurement of the anomalous magnetic moment of the muon. (C) 2013 Elsevier B.V. All rights reserved.
Investigation of the dd -> (3)Hen pi(0) reaction with the FZ Julich WASA-at-COSY facility
P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, FS. Bergmann, M. Berlowski, H. Bhatt, M. Buscher, H. Calen, I. Ciepal, H. Clement, D. Coderre, E. Czerwinski, K. Demmich, E. Doroshkevich, R. Engels, W. Erven, W. Eyrich, P. Fedorets, K. Fohl, K. Fransson, F. Goldenbaum, P. Goslawski, A. Goswami, K. Grigoryev, CO. Gullstrom, C. Hanhart, F. Hauenstein, L. Heijkenskjold, V. Hejny, F. Hinterberger, M. Hodana, B. Hoistad, A. Jany, BR. Jany, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, FA. Khan, A. Khoukaz, DA. Kirillov, S. Kistryn, J. Klaja, H. Kleines, B. Klos, M. Krapp, W. Krzemien, P. Kulessa, A. Kupsc, K. Lalwani, D. Lersch, L. Li, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Marianski, M. Mikirtychiants, HP. Morsch, P. Moskal, BK. Nandi, H. Ohm, I. Ozerianska, EP. del Rio, NM. Piskunov, P. Plucinski, et al.
abstract
An exclusive measurement of the dd -> (3)Hen pi(0) reaction was carried out at a beam momentum of p(d) = 1.2 GeV/c using the WASA-at-COSY facility. Information on the total cross section as well as differential distributions was obtained. The data are described by a phenomenological approach based on a combination of a quasifree model and a partial wave expansion for the three-body reaction. The total cross section is found to be sigma(tot) = ( 2.89 +/- 0.01(stat) +/- 0.06(sys) +/- 0.29(norm)) mu b. The contribution of the quasifree processes ( with the beam or target neutron being a spectator) accounts for 38% of the total cross section and dominates the differential distributions in specific regions of phase space. The remaining part of the cross section can be described by a partial wave decomposition indicating the significance of p-wave contributions in the final state.
Measurement of the pn->pp pi0pi- Reaction in Search for the Recently Observed Resonance Structure in dpi0pi0 and dpi+pi-systems
P. Adlarson, ..., E. Czerwiński, M. Hodana, J. Klaja, W. Krzemień, P. Moskal, I. Ozerianska, M. Skurzok, M. Zieliński et al.
abstract
Exclusive measurements of the quasi-free $pn o pppi^0pi^-$ reaction have been performed by means of $pd$ collisions at $T_p$ = 1.2 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region $sqrt s$ = (2.35 - 2.46) GeV, which includes the region of the ABC effect and its associated resonance structure. No ABC effect, {it i.e.} low-mass enhancement is found in the $pi^0pi^-$-invariant mass spectrum -- in agreement with the constraint from Bose statistics that the isovector pion pair can not be in relative s-wave. At the upper end of the covered energy region $t$-channel processes for Roper, $Delta(1600)$ and $DeltaDelta$ excitations provide a reasonable description of the data, but at low energies the measured cross sections are much larger than predicted by such processes. Adding a resonance amplitude for the resonance at $m$=~2.37 GeV with $Gamma$ =~70 MeV and $I(J^P)=~0(3^+)$ observed recently in $pn o dpi^0pi^0$ and $pn o dpi^+pi^-$ reactions leads to an agreement with the data also at low energies.
Isospin decomposition of the basic double-pionic fusion in the region of the ABC effect
P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, T. Bednarski, FS. Bergmann, M. Berlowski, H. Bhatt, M. Buscher, H. Calen, H. Clement, D. Coderre, E. Czerwinski, K. Demmich, E. Doroshkevich, R. Engels, W. Erven, W. Eyrich, P. Fedorets, K. Fohl, K. Fransson, F. Goldenbaum, P. Goslawski, A. Goswami, K. Grigoryev, CO. Gullstrom, F. Hauenstein, L. Heijkenskjold, V. Hejny, F. Hinterberger, M. Hodana, B. Hoistad, A. Jany, BR. Jany, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, FA. Khan, A. Khoukaz, S. Kistryn, J. Klaja, H. Kleines, B. Klos, M. Krapp, W. Krzemien, P. Kulessa, A. Kupsc, K. Lalwani, D. Lersch, L. Li, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Marianski, M. Mikirtychiants, HP. Morsch, P. Moskal, BK. Nandi, S. Niedzwiecki, H. Ohm, I. Ozerianska, EP. del Rio, P. Plucinski, P. Podkopal, et al.
abstract
Exclusive and kinematically complete high-statistics measurements of the basic double-pionic fusion reactions pn -> d pi(0)pi(0), pn -> d pi(+)pi(-) and pp -> d pi(+)pi(0) have been carried out simultaneously over the energy region of the ABC effect using the WASA detector setup at COSY. Whereas the isoscalar reaction part given by the d pi(0)pi(0) channel exhibits the ABC effect, i.e. a low-mass enhancement in the pi pi-invariant mass distribution, as well as the associated resonance structure in the total cross section, the isovector part given by the d pi(+)pi(0) channel shows a smooth behavior consistent with the conventional t-channel Delta Delta process. The d pi(+)pi(-) data are very well reproduced by combining the data for isovector and isoscalar contributions, if the kinematical consequences of the isospin violation due to different masses for charged and neutral pions are taken into account. (C) 2013 Elsevier B.V. All rights reserved.
Investigation of the dd -> 3henpi0 reaction with the FZ Jülich WASA-at-COSY facility
P. Adlarson, ..., W. Bardan, I. Ciepał, E. Czerwiński, M. Hodana, J. Klaja, W. Krzemień, I. Ozerianska, P. Moskal, M. Skurzok,M. Zieliński, et al.
abstract
An exclusive measurement of the dd?3Hen?0 reaction was carried out at a beam momentum of pd= 1.2 GeV/c using the WASA-at-COSY facility. Information on the total cross section as well as differential distributions was obtained. The data are described by a phenomenological approach based on a combination of a quasifree model and a partial wave expansion for the three-body reaction. The total cross section is found to be ?tot=(2.89?0.01stat?0.06sys?0.29norm) ?b. The contribution of the quasifree processes (with the beam or target neutron being a spectator) accounts for 38% of the total cross section and dominates the differential distributions in specific regions of phase space. The remaining part of the cross section can be described by a partial wave decomposition indicating the significance of p-wave contributions in the final state.
Search for the eta-mesic 4He with WASA-at-COSY detector
P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, T. Bednarski, FS. Bergmann, M. Berlowski, H. Bhatt, M. Buscher, H. Calen, H. Clement, D. Coderre, E. Czerwinski, K. Demmich, E. Doroshkevich, R. Engels, W. Erven, W. Eyrich, P. Fedorets, K. Fohl, K. Fransson, F. Goldenbaum, P. Goslawski, A. Goswami, K. Grigoryev, CO. Gullstrom, F. Hauenstein, L. Heijkenskjold, V. Hejny, F. Hinterberger, M. Hodana, B. Hoistad, A. Jany, BR. Jany, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, FA. Khan, A. Khoukaz, S. Kistryn, J. Klaja, H. Kleines, B. Klos, M. Krapp, W. Krzemien, P. Kulessa, A. Kupsc, K. Lalwani, D. Lersch, L. Li, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Marianski, M. Mikirtychiants, HP. Morsch, P. Moskal, BK. Nandi, S. Niedzwiecki, H. Ohm, I. Ozerianska, EP. del Rio, P. Plucinski, P. Podkopal, et al.
abstract
An exclusive measurement of the excitation function for the dd->3Heppi- reaction was performed at the Cooler Synchrotron COSY-Juelich with the WASA-at-COSY detection system. The data were taken during a slow acceleration of the beam from 2.185 GeV/c to 2.400 GeV/c crossing the kinematic threshold for the eta meson production in the dd->4He-eta reaction at 2.336 GeV/c. The corresponding excess energy with respect to the 4He-eta system varied from -51.4MeV to 22MeV. The integrated luminosity in the experiment was determined using the dd->3Hen reaction. The shape of the excitation function for the dd->3Heppi- was examined. No signal of the 4He-eta bound state was observed. An upper limit for the cross-section for the bound state formation and decay in the process dd->(4He-eta)bound->3Heppi- was determined on the 90% confidence level and it varies from 20nb to 27nb for the bound state width ranging from 5MeV to 35MeV, respectively.
Abashian-Booth-Crowe resonance structure in the double pionic fusion to He-4
P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, T. Bednarski, FS. Bergmann, M. Berlowski, H. Bhatt, KT. Brinkmann, M. Buscher, H. Calen, H. Clement, D. Coderre, E. Czerwinski, K. Demmich, E. Doroshkevich, R. Engels, W. Erven, W. Eyrich, P. Fedorets, K. Fohl, K. Fransson, F. Goldenbaum, P. Goslawski, K. Grigoryev, CO. Gullstrom, F. Hauenstein, L. Heijkenskjold, V. Hejny, F. Hinterberger, M. Hodana, B. Hoistad, C. Husmann, A. Jany, BR. Jany, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, FA. Khan, A. Khoukaz, S. Kistryn, J. Klaja, H. Kleines, B. Klos, W. Krzemien, P. Kulessa, A. Kupsc, K. Lalwani, D. Lersch, L. Li, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Marianski, M. Mikirtychiants, HP. Morsch, P. Moskal, BK. Nandi, S. Niedzwiecki, H. Ohm, I. Ozerianska, C. Pauly, EP. del Rio, Y. Petukhov, et al.
abstract
Exclusive and kinematically complete high-statistics measurements of the double pionic fusion reaction dd?4He?0?0 have been performed in the energy range 0.8?1.4 GeV covering thus the region of the Abashian-Booth-Crowe effect, which denotes a pronounced low-mass enhancement in the ?? invariant mass spectrum. The experiments were carried out with the WASA detector setup at the cooler synchrotron at Forshungszentrum Julich GmbH. Similar to the observation in the basic pn?d?0?0 reaction, the data reveal a correlation between the ABC effect and a resonancelike energy dependence in the total cross section. The maximum occurs at m=2.37 GeV + 2mN, i.e., at the same position as in the basic reaction. The observed resonance width ??160 MeV can be understood from broadening due to Fermi motion of the nucleons in initial and final nuclei together with collision damping. Differential cross sections are described equally well by the hypothesis of a pn resonance formation during the reaction process.
Exclusive measurement of the eta->pi+ pi- gamma decay
P. Adlarson, C. Adolph, W. Augustyniak, W. Bardan, M. Bashkanov, T. Bednarski, FS. Bergmann, M. Berlowski, H. Bhatt, KT. Brinkmann, M. Buscher, H. Calen, H. Clement, D. Coderre, E. Czerwinski, E. Doroshkevich, R. Engels, W. Erven, W. Eyrich, P. Fedorets, K. Fohl, K. Fransson, F. Goldenbaum, P. Goslawski, K. Grigoryev, CO. Gullstrom, C. Hanhart, L. Heijkenskjold, J. Heimlich, V. Hejny, F. Hinterberger, M. Hodana, B. Hoistad, M. Jacewicz, A. Jany, BR. Jany, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, O. Khakimova, A. Khoukaz, S. Kistryn, J. Klaja, H. Kleines, B. Klos, F. Kren, W. Krzemien, P. Kulessa, A. Kupsc, K. Lalwani, S. Leupold, B. Lorentz, A. Magiera, R. Maier, B. Marianski, P. Marciniewski, UG. Meissner, M. Mikirtychiants, HP. Morsch, P. Moskal, BK. Nandi, S. Niedzwiecki, H. Ohm, A. Passfeld, C. Pauly, et al.
abstract
An exclusive measurement of the decay eta --> pi+ pi- gamma has been performed at the WASA facility at COSY. The eta mesons were produced in the fusion reaction pd --> 3He X at a proton beam momentum of 1.7 GeV/c. Efficiency corrected differential distributions have been extracted based on 13340pm140 events after background subtraction. The measured pion angular distribution is consistent with a relative p-wave of the two-pion system, whereas the measured photon energy spectrum was found at variance with the simplest gauge invariant matrix element of eta --> pi+ pi- gamma. A parameterization of the data can be achieved by the additional inclusion of the empirical pion vector form factor multiplied by a first-order polynomial in the squared invariant mass of the pi+ pi- system.
pi0 pi0 Production in proton-proton collisions at Tp=1.4 GeV
P. Adlarson, C. Adolph, W. Augustyniak, M. Bashkanov, T. Bednarski, FS. Bergmann, M. Berlowski, H. Bhatt, KT. Brinkmann, M. Buscher, H. Calen, H. Clement, D. Coderre, E. Czerwinski, E. Doroshkevich, R. Engels, W. Erven, W. Eyrich, P. Fedorets, K. Fohl, K. Fransson, F. Goldenbaum, P. Goslawski, K. Grigoryev, CO. Gullstrom, L. Heijkenskjold, J. Heimlich, V. Hejny, F. Hinterberger, M. Hodana, B. Hoistad, M. Jacewicz, M. Janusz, A. Jany, BR. Jany, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, O. Khakimova, A. Khoukaz, S. Kistryn, J. Klaja, H. Kleines, B. Klos, F. Kren, W. Krzemien, P. Kulessa, A. Kupsc, K. Lalwani, B. Lorentz, A. Magiera, R. Maier, B. Marianski, P. Marciniewski, M. Mikirtychiants, HP. Morsch, P. Moskal, BK. Nandi, S. Niedzwiecki, H. Ohm, A. Passfeld, C. Pauly, EP. del Rio, Y. Petukhov, N. Piskunov, et al.
abstract
The reaction pp->pppi0pi0 has been investigated at a beam energy of 1.4 GeV using the WASA-at-COSY facility. The total cross section is found to be (324 +- 21_systematic +- 58_normalization) mub. In order to to study the production mechanism, differential kinematical distributions have been evaluated. The differential distributions indicate that both initial state protons are excited into intermediate Delta(1232) resonances, each decaying into a proton and a single pion, thereby producing the pion pair in the final state. No significant contribution of the Roper resonance N*(1440) via its decay into a proton and two pions is found
Abashian-Booth-Crowe effect in basic double fusion: A new resonance?
P. Adlarson, C. Adolph, W. Augustyniak, V. Baru, M. Bashkanov, T. Bednarski, FS. Bergmann, M. Berlowski, H. Bhatt, KT. Brinkmann, M. Buscher, H. Calen, H. Clement, D. Coderre, E. Czerwinski, E. Doroshkevich, C. Ekstrom, R. Engels, W. Erven, W. Eyrich, P. Fedorets, K. Fohl, K. Fransson, F. Goldenbaum, P. Goslawski, K. Grigoryev, V. Grishina, CO. Gullstrom, J. Hampe, C. Hanhart, L. Heijkenskjold, V. Hejny, F. Hinterberger, M. Hodana, B. Hoistad, M. Jacewicz, M. Janusz, A. Jany, BR. Jany, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, O. Khakimova, A. Khoukaz, S. Kistryn, J. Klaja, H. Kleines, B. Klos, F. Kren, W. Krzemien, P. Kulessa, S. Kullander, A. Kupsc, K. Lalwani, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Marianski, M. Mikirtychiants, P. Moskal, HP. Morsch, BK. Nandi, S. Niedzwiecki, H. Ohm, et al.
abstract
We report on an exclusive and kinematically complete high-statistics measurement of the basic double-pionic fusion reaction pn->dpi0pi0 over the full energy region of the ABC effect, a pronounced low-mass enhancement in the pipi-invariant mass spectrum. The measurements, which cover also the transition region to the conventional t-channel DeltaDelta process, were performed with the upgraded WASA detector setup at COSY. The data reveal the Abashian-Booth-Crowe effect to be uniquely correlated with a Lorentzian energy dependence in the integral cross section. The observables are consistent with a narrow resonance with m=2.37??GeV, Gamma aprox 70 MeV and I(JP)=0(3+) in both pn and DeltaDelta systems. Necessary further tests of the resonance interpretation are discussed.
Determination of the total width of the eta-prime meson
E. Czerwiński, P. Moskal, D. Grzonka, R. Czyżykiewicz, D. Gil, B. Kamys, A. Khoukaz, J. Klaja, P. Klaja, W. Krzemień, W. Oelert, J. Ritman, T. Sefzick, M. Siemaszko, M. Silarski, J. Smyrski, A. Täschner, M. Wolke, P. Wüstner, J. Zdebik, M. Zieliński, W. Zipper
abstract
Taking advantage of both the low-emittance proton beam of the cooler synchrotron COSY and the high momentum precision of the COSY-11 detector system, the mass distribution of the eta-prime meson was measured with a resolution of 0.33??MeV/c2 (FWHM), improving the experimental mass resolution by almost an order of magnitude with respect to previous results. Based on the sample of more than 2300 reconstructed pp->pp eta-prime events, the total width of the eta-prime meson was determined to be Gamma(eta-prime) = 0.226+-0.017(stat)+-0.014(syst)??MeV/c2.
Two-proton correlation function for the pp -> pp + eta and pp to pp + pions reactions
P. Klaja, P. Moskal, E. Czerwiński, R. Czyżykiewicz, A. Deloff, D. Gil, D. Grzonka, B. Kamys, A. Khoukaz, J. Klaja, W. Krzemień, W. Oelert, J. Ritman, T. Sefzick, M. Siemaszko, M. Silarski, J. Smyrski, A. Täschner, M. Wolke, J. Zdebik, M. Zieliński, W. Zipper
abstract
For the very first time, the correlation femtoscopy method is applied to a kinematically complete measurement of meson production in the collisions of hadrons. A two-proton correlation function was derived from the data for the pp -> ppX reaction, measured near the threshold of eta meson production. A technique developed for the purpose of this analysis permitted the correlation function to be established separately for the production of the pp + eta and of the pp + pions systems. The shape of the two-proton correlation function for pp-eta differs from that for pp(pions) and both do not show a peak structure, opposite to the results determined for inclusive measurements of heavy ion collisions.
Two-proton correlation function for the pp -> pp plus eta and pp -> pp plus pions reactions
P. Klaja, P. Moskal, E. Czerwinski, R. Czyzykiewicz, A. Deloff, D. Gil, D. Grzonka, B. Kamys, A. Khoukaz, J. Klaja, W. Krzemien, W. Oelert, J. Ritman, T. Sefzick, M. Siemaszko, M. Silarski, J. Smyrski, A. Taschner, M. Wolke, J. Zdebik, M. Zielinski, W. Zipper
abstract
For the very first time, the correlation femtoscopy method is applied to a kinematically complete measurement of meson production in the collisions of hadrons. A two-proton correlation function was derived from the data for the pp -> ppX reaction, measured near the threshold of eta meson production. A technique developed for the purpose of this analysis permitted the correlation function to be established separately for the production of the pp + eta and of the pp + pions systems. The shape of the two-proton correlation function for pp eta differs from that for pp(pions) and both do not show a peak structure, opposite to the results determined for inclusive measurements of heavy ion collisions.
Upper limit of the total cross section for the pn->pn eta-prime reaction
J. Klaja, P. Moskal, S. D. Bass, E. Czerwiński, R. Czyżykiewicz, D. Gil, D. Grzonka, T. Johansson, B. Kamys, A. Khoukaz, P. Klaja, W. Krzemień, W. Oelert, B. Rejdych, J. Ritman, T. Sefzick, M. Siemaszko, M. Silarski, J. Smyrski, A. Täschner, M. Wolke, P. Wüstner, J. Zdebik, M. Zieliński, W. Zipper
abstract
The upper limit of the total cross section for the pn->pneta-prime reaction has been determined near the kinematical threshold in the excess energy range from 0 to 24 MeV. The measurement was performed using the COSY-11 detector setup, a deuteron cluster target, and the proton beam of COSY with a momentum of 3.35 GeV/c. The energy dependence of the upper limit of the cross section was extracted exploiting the Fermi momenta of nucleons inside the deuteron. Comparison of the determined upper limit of the ratio R(eta-prime)=sigma(pn->pneta-prime)/sigma(pp->ppeta-prime) with the corresponding ratio for eta-meson production does not favor the dominance of the N*(1535) resonance in the production process of the eta-prime meson and suggests nonidentical production mechanisms for eta and eta-prime mesons.
Measurement of the invariant mass distributions fot he pp->pp eta-prime reaction at excess energy of Q = 16.4 MeV
P. Klaja, P. Moskal, E. Czerwiński, R. Czyżykiewicz, A. Deloff, D. Gil, D. Grzonka, L. Jarczyk, B. Kamys, A. Khoukaz, J. Klaja, K. Nakayama, W. Oelert, J. Ritman, T. Sefzick, M. Siemaszko, M. Silarski, J. Smyrski, A. Täschner, M. Wolke, J. Zdebik, M. Zieliński, W. Zipper
abstract
The proton?proton and proton? invariant mass distributions have been determined for the reaction at an excess energy of . The measurement was carried out using the COSY-11 detector setup and the proton beam of the cooler synchrotron COSY. The shapes of the determined invariant mass distributions are similar to those of the reaction and reveal an enhancement for large relative proton?proton momenta. This result, together with the fact that the proton?? interaction is much stronger that the proton? interaction, excludes the hypothesis that the observed enhancement is caused by the interaction between the proton and the meson.
Upper limit of the total cross section for the pn -> pn eta' reaction
J. Klaja, P. Moskal, SD. Bass, E. Czerwinski, R. Czyzykiewicz, D. Gil, D. Grzonka, T. Johansson, B. Kamys, A. Khoukaz, P. Klaja, W. Krzemien, W. Oelert, B. Rejdych, J. Ritman, T. Sefzick, M. Siemaszko, M. Silarski, J. Smyrski, A. Taschner, M. Wolke, P. Wustner, J. Zdebik, M. Zielinski, W. Zipper
abstract
The upper limit of the total cross section for the pn -> pn eta' reaction has been determined near the kinematical threshold in the excess energy range from 0 to 24 MeV. The measurement was performed using the COSY-11 detector setup, a deuteron cluster target, and the proton beam of COSY with a momentum of 3.35 GeV/c. The energy dependence of the upper limit of the cross section was extracted exploiting the Fermi momenta of nucleons inside the deuteron. Comparison of the determined upper limit of the ratio R-eta' = sigma(pn -> pn eta')/sigma(pp -> pp eta') with the corresponding ratio for eta-meson production does not favor the dominance of the N*(1535) resonance in the production process of the eta' meson and suggests nonidentical production mechanisms for eta and eta' mesons.
Measurement of the invariant mass distributions for the pp -> pp eta ' reaction at excess energy of Q=16.4 MeV
P. Klaja, P. Moskal, E. Czerwinski, R. Czyzykiewicz, A. Deloff, D. Gil, D. Grzonka, L. Jarczyk, B. Kamys, A. Khoukaz, J. Klaja, K. Nakayama, W. Oelert, J. Ritman, T. Sefzick, M. Siemaszko, M. Silarski, J. Smyrski, A. Taschner, M. Wolke, J. Zdebik, M. Zielinski, W. Zipper
abstract
The proton-proton and proton-eta' invariant mass distributions have been determined for the pp -> pp eta' reaction at an excess energy of Q = 16.4 MeV. The measurement was carried Out using the COSY-11 detector setup and the proton beam of the cooler synchrotron COSY. The shapes of the determined invariant mass distributions are similar to those of the pp -> pp eta reaction and reveal an enhancement for large relative proton-proton momenta. This result, together with the fact that the proton-eta interaction is Much stronger that the proton-eta' interaction, excludes the hypothesis that the observed enhancement is caused by the interaction between the proton and the meson. (C) 2010 Elsevier B.V. All rights reserved.
Invariant-mass distributions for the pp -> pp eta reaction at Q=10 MeV
P. Moskal, R. Czyzykiewicz, E. Czerwinski, D. Gil, D. Grzonka, L. Jarczyk, B. Kamys, A. Khoukaz, J. Klaja, P. Klaja, W. Krzemien, W. Oelert, J. Ritman, T. Sefzick, M. Siemaszko, M. Silarski, J. Smyrski, A. Taschner, M. Wolke, P. Wustner, J. Zdebik, MJ. Zielinski, W. Zipper
abstract
Proton-proton and proton-eta invariant-mass distributions and the total cross-section for the pp -> pp eta reaction have been determined near the threshold at an excess energy of Q = 10 MeV. The experiment has been conducted using the COSY-11 detector setup and the cooler synchrotron COSY. The determined invariant-mass spectra reveal significant enhancements in the region of low proton-proton relative momenta, similarly as observed previously at higher excess energies of Q = 15.5 MeV and Q = 40 MeV.
Studies of properties of the eta' meson at the COSY-11 facility
E. Czerwiński, J. Klaja, P. Klaja, P. Moskal
abstract
We shortly discuss results on the isospin dependence of the eta-prime production cross section in nucleon-nucleon collisions, results of comparative analysis of the invariant mass distributions for the pp->pp eta-prime and pp->pp eta reactions, and we present the value of the total width of the eta-prime meson as derived directly from the mass distribution measured with the mass resolution of 0.3~MeV/c^2.
Invariant mass distributions for the pp->pp eta reaction at Q = 10 MeV
P. Moskal, R. Czyżykiewicz, E. Czerwiński, D. Gil, D. Grzonka, L. Jarczyk, B. Kamys, A. Khoukaz, J. Klaja, P. Klaja, W. Krzemień, W. Oelert, J. Ritman, T. Sefzick, M. Siemaszko, M. Silarski, J. Smyrski, A. Taschner, M. Wolke, P. Wustner, J. Zdebik, M. Zieliński, W. Zipper
abstract
Proton-proton and proton-eta invariant-mass distributions and the total cross-section for the pp -> pp h reaction have been determined near the threshold at an excess energy of Q = 10 MeV. The experiment has been conducted using the COSY-11 detector setup and the cooler synchrotron COSY. The determined invariant-mass spectra reveal significant enhancements in the region of low proton-proton relative momenta, similarly as observed previously at higher excess energies of Q = 15.5 MeV and Q = 40 MeV.
Generalized Dalitz plot analysis of the near-threshold pp -> ppK(+)K(-) reaction in view of the K+K- final state interaction
M. Silarski, P. Moskal, E. Czerwinski, R. Czyzykiewicz, D. Gil, D. Grzonka, L. Jarczyk, B. Kamys, A. Khoukaz, J. Klaja, P. Klaja, W. Krzemien, W. Oelert, J. Ritman, T. Sefzick, M. Siemaszko, J. Smyrski, A. Taschner, P. Winter, M. Wolke, P. Wustner, M. Zielinski, W. Zipper, J. Zdebik
abstract
The excitation function for the pp -> ppK(+)K(-) reaction revealed a significant enhancement close to threshold that may plausibly be assigned to the influence of the pK(-) and K+K- final-state interactions. In an improved reanalysis of COSY-11 data for the pp -> ppK(+)K(-) reaction at excess energies of Q = 10 and 28 MeV, including the proton-K- interaction, the enhancement is confirmed. Invariant mass distributions for the two- and three-particle subsystems allow us to test at low excess energies the ansatz and parameters for the description of the interaction in the ppK(+)K(-) system as derived from the COSY-ANKE data. Finally, based for the first time on the low-energy K+K- invariant mass distributions and the generalized Dalitz plot analysis, we estimate the scattering length for the K+K- interaction to be vertical bar Re(a(K+K-))vertical bar = 0.5(-0.5)(+4.0) fm and Im(a(K+K-)) = 3.0 +/- 3.0 fm.
Generalized Dalitz plot analysis of the near-threshold pp->ppK+K- reaction in view of the K+K- final state interaction
M. Silarski, P. Moskal, E. Czerwiński, R. Czyżykiewicz, D. Gil, D. Grzonka, L. Jarczyk, B. Kamys, A. Khoukaz, J. Klaja, P. Klaja, W. Krzemień, W. Oelert, J. Ritman, T. Sefzick, M. Siemaszko, J. Smyrski, A. Täschner, P. Winter, M. Wolke, P. Wüstner, M. Zieliński, W. Zipper, J. Zdebik
abstract
The excitation function for the pp->ppK+K- reaction revealed a significant enhancement close to threshold which may plausibly be assigned to the influence of the pK- and K+K- final state interactions. In an improved reanalysis of COSY-11 data for the pp-> ppK+K- reaction at excess energies of Q = 10 MeV and 28 MeV including the proton-K- interaction the enhancement is confirmed. Invariant mass distributions for the two- and three-particle subsystems allow to test at low excess energies the ansatz and parameters for the description of the interaction in the ppK+K- system as derived from the COSY-ANKE data. Finally, based for the first time on the low energy K+K- invariant mass distributions and the generalized Dalitz plot analysis, we estimate the scattering length for the K+K- interaction to be |Re(a_K+K-)| = 0.5 + 4.0 -0.5 fm and Im(a_K+K-) = 3.0 +- 3.0 fm.
Measurement of the eta->3pi0 Dalitz plot distribution with the WASA detector at COSY
WASA-at-COSY Collaboration: C. Adolph, ..., E. Czerwiński, R. Czyżykiewicz, M. Hodana, M. Janusz, J. Klaja, P. Klaja, W. Krzemień, P. Moskal, M. Zieliński, et al.
abstract
In the first production run of the WASA experiment at COSY, the eta decay into three neutral pions was measured in proton?proton interactions at a proton beam kinetic energy of 1.4 GeV. The Dalitz plot of the three pions was studied using fully reconstructed events, and the quadratic slope parameter ? was determined to be . The result is consistent with previous measurements and further corroborates the importance of pion?pion final state interactions.
Measurement of the eta -> 3 pi(0) Dalitz plot distribution with the WASA detector at COSY
C. Adolph, M. Angelstein, M. Bashkanov, U. Bechstedt, S. Belostotski, M. Berlowski, H. Bhatt, J. Bisplinghoff, A. Bondar, B. Borasoy, M. Buscher, H. Calen, K. Chandwani, H. Clement, E. Czerwinski, R. Czyzykiewicz, G. D'Orsaneo, D. Duniec, C. Ekstrom, R. Engels, W. Erven, W. Eyrich, P. Fedorets, O. Felden, K. Fransson, D. Gil, F. Goldenbaum, K. Grigoryev, A. Heczko, C. Hanhart, V. Hejny, F. Hinterberger, M. Hodana, B. Hoistad, A. Izotov, M. Jacewicz, M. Janusz, BR. Jany, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, I. Keshelashvili, O. Khakimova, A. Khoukaz, K. Kilian, N. Kimura, S. Kistryn, J. Klaja, P. Klaja, H. Kleines, B. Klos, A. Kowalczyk, F. Kren, W. Krzemien, P. Kulessa, S. Kullander, A. Kupsc, A. Kuzmin, V. Kyryanchuk, J. Majewski, H. Machner, A. Magiera, R. Maier, R. Marciniewski, W. Migdal, UG. Meissner, et al.
abstract
In the first production run of the WASA experiment at COSY, the eta decay into three neutral pions was measured in proton-proton interactions at a proton beam kinetic energy of 1.4 GeV. The Dalitz plot of the three pious was Studied using 1.2 x 10(5) fully reconstructed events. and the quadratic slope parameter alpha was determined to be -0.027 +/- 0.008(stat) +/- 0.005(syst). The result is consistent with previous measurements and further corroborates the importance of pion-pion final state interactions. (C) 2009 Elsevier B.V. All rights reserved.
Near-threshold production of the eta meson via the quasi-free pn->pneta reaction
P. Moskal, R. Czyżykiewicz, H.-H. Adam, S. D. Bass, A. Budzanowski, E. Czerwiński, D. Gil, D. Grzonka, M. Janusz, L. Jarczyk, T. Johansson, B. Kamys, A. Khoukaz, K. Kilian, P. Klaja, J. Majewski, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, B. Rejdych, J. Ritman, T. Rozek, T. Sefzick, M. Siemaszko, M. Silarski, J. Smyrski, A. Taeschner, M. Wolke, P. Wuestner, M. Zieliński, W. Zipper, J. Zdebik
abstract
Total cross sections for the quasifree pn->pn? reaction in the range from the kinematical threshold up to 20 MeV excess energy have been determined. At threshold they exceed corresponding cross sections for the pp?pp? reaction by a factor of about 3 in contrast to the factor of 6 established for higher excess energies. To large extent, the observed decrease of the ratio sigma(pn->pn?)/sigma(pp->pp?) toward threshold may be assigned to the different energy dependence of the proton-proton and proton-neutron final-state interactions. The experiment was conducted using a proton beam of the cooler synchrotron COSY and a cluster jet deuteron target. The proton-neutron reactions were tagged by the spectator proton whose momentum was measured for each event. Protons and neutron outgoing from the pn?pn? reaction have been registered by means of the COSY-11 facility, an apparatus dedicated for threshold meson production.
Isospin dependence of the eta-prime meson production in nucleon-nucleon collisions
J. Przerwa, P. Moskal, A. Budzanowski, E. Czerwiński, R. Czyżykiewicz, D. Gil, D. Grzonka, L. Jarczyk, T. Johansson, B. Kamys, A. Khoukaz, P. Klaja, W. Krzemień, W. Oelert, C. Piskor-Ignatowicz, J. Ritman, B. Rejdych, T. Sefzick, M. Siemaszko, M. Silarski, J. Smyrski, A. Taschner, M. Wolke, P. Wustner, J. Zdebik, M. Zieliński, W. Zipper
abstract
A comparison of the close-to-threshold total cross section for the eta prime production in pp -> pp eta prime and pn -> pn eta prime reactions constitutes a tool to investigate the eta prime meson structure and the reaction mechanism in the channels of isospin I=0 and I=1 and may provide insight into the flavour-singlet (perhaps also into gluonium) content of the eta prime meson. In this contribution we present preliminary results of measurement of the quasi-free production of the eta prime meson in the proton-neutron collisions conducted using the COSY-11 facility.
ISOSPIN DEPENDENCE OF THE eta ' MESON PRODUCTION IN NUCLEON-NUCLEON COLLISIONS
J. Przerwa, P. Moskal, A. Budzanowski, E. Czerwinski, R. Czyzykiewicz, D. Gil, D. Grzonka, L. Jarczyk, T. Johansson, B. Kamys, A. Khoukaz, P. Klaja, W. Krzemien, W. Oelert, C. Piskor-Ignatowicz, J. Ritman, B. Rejdych, T. Sefzick, M. Siemaszko, M. Silarski, J. Smyrski, A. Taschner, M. Wolke, P. Wustner, J. Zdebik, MJ. Zielinski, W. Zipper
abstract
A comparison of the close-to-threshold total cross section for the eta' production in pp -> pp eta' and pn -> pn eta' reactions constitutes a tool to investigate the eta' meson structure and the reaction mechanism in the channels of isospin I = 0 and I = 1 and may provide insight into the flavour-singlet (perhaps also into gluonium) content of the eta' meson. In this contribution we present preliminary results of measurement of the quasifree production of the eta' meson in the proton-neutron collisions conducted using the COSY-11 facility.
SEARCH FOR THE He-3-eta BOUND STATE AT COSY-11
W. Krzemien, J. Smyrski, A. Budzanowski, E. Czerwinski, R. Czyzykiewicz, D. Gil, D. Grzonka, L. Jarczyk, B. Kamys, A. Khoukaz, P. Klaja, P. Moskal, W. Oelert, J. Przerwa, J. Ritman, T. Sefzick, M. Siemaszko, M. Silarski, A. Taschner, M. Wolke, P. Wustner, J. Zdebik, MJ. Zielinski, W. Zipper
abstract
We have measured excitation function for dp -> ppp pi(-) reaction near the. production threshold. We observe an enhancement of the counting rate above the threshold which can originate from the production of the. meson in the reaction dp -> He-3 eta and its subsequent absorption on neutron in the 3He nucleus leading to creation of the p pi(-) pair.
Search for the 3He-eta bound state at COSY-11
W. Krzemien, J. Smyrski, A. Budzanowski, E. Czerwiński, R. Czyżykiewicz, D. Gil, D. Grzonka, L. Jarczyk, B. Kamys, A. Khoukaz, P. Klaja, P. Moskal, W. Oelert, J. Przerwa, J. Ritman, T. Sefzick, M. Siemaszko, M. Silarski, A. Taeschner, M. Wolke, P. Wuestner, J. Zdebik, M. Zieliński, W. Zipper
abstract
We have measured excitation function for dp -> ppp_pi- reaction near the eta production threshold. We observe an enhancement of the counting rate above the threshold which can originate from the production of the eta meson in the reaction dp -> 3He eta and its subsequent absorption on neutron in the 3He nucleus leading to creation of the p_pi- pair.
Near-threshold production of the eta meson via the quasifree pn -> pn eta reaction
P. Moskal, R. Czyzykiewicz, HH. Adam, SD. Bass, A. Budzanowski, E. Czerwinski, D. Gil, D. Grzonka, M. Janusz, L. Jarczyk, T. Johansson, B. Kamys, A. Khoukaz, K. Kilian, P. Klaja, J. Majewski, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, B. Rejdych, J. Ritman, T. Rozek, T. Sefzick, M. Siemaszko, M. Silarski, J. Smyrski, A. Taschner, M. Wolke, P. Wustner, M. Zielinski, W. Zipper, J. Zdebik
abstract
Total cross sections for the quasifree pn -> pn eta reaction in the range from the kinematical threshold up to 20 MeV excess energy have been determined. At threshold they exceed corresponding cross sections for the pn -> pn eta reaction by a factor of about 3 in contrast to the factor of 6 established for higher excess energies. To large extent, the observed decrease of the ratio s(pn -> pn eta)/s=sigma(pn -> pn eta) toward threshold may be assigned to the different energy dependence of the proton-proton and proton-neutron final-state interactions. The experiment was conducted using a proton beam of the cooler synchrotron COSY and a cluster jet deuteron target. The proton- neutron reactions were tagged by the spectator proton whose momentum was measured for each event. Protons and neutron outgoing from the pn -> pn eta reaction have been registered by means of the COSY-11 facility, an apparatus dedicated for threshold meson production.
Study of the hadronic production of kaon pairs below the threshold for the phi meson
P. Moskal, M. Silarski, A. Budzanowski, E. Czerwinski, R. Czyzykiewic, D. Gil, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, P. Klaja, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, B. Rejdych, J. Ritman, T. Sefzick, M. Siemaszko, J. Smyrski, A. Taschner, P. Winter, M. Wolke, P. Wustner, MJ. Zielinski, W. Zipper, J. Zdebik
abstract
The near threshold production of K(+)K(-) pairs in proton-proton collisions has been investigated at the cooler synchrotron COSY below and above the threshold for the phi meson using the COSY-11 and ANKE facilities., respectively. The excitation function determined for the pp -> ppK(+)K(-) reaction revealed a statistically significant enhancement close to the threshold which may plausibly be assigned to the influence of the K(-)p interaction. In addition, observed consistently by both groups, a strong enhancement at low values of the ratio of the K(-)p to K(+)p invariant mass distributions shows that the proton interacts much stronger with K(-) than with K(+). In this report we focus on the measurements performed by the COSY-11 collaboration. We explain the experimental method used and present main results of completed analyses as well as a new qualitative elaboration of the ppK(+)K(-) events population on the Goldhaber plot. We conclude with the observation that event densities increase at the region where the influence from the K(+)K(-) interaction is expected.
Near threshold production of the pseudoscalar mesons at the COSY-11 facility
P. Moskal, R. Czyzykiewicz, HH. Adam, A. Budzanowski, E. Czerwinski, D. Gil, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, X. Kilian, P. Klaja, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, B. Rejdych, J. Ritman, T. Sefzick, M. Siemaszko, M. Silarski, J. Smyrski, A. Taschner, M. Wolke, P. Winter, P. Wustner, M. Zielinski, W. Zipper
abstract
We summarise measurements of the COSY-11 collaboration concerning the excitation functions of the near threshold pseudoscalar meson production in the proton-proton interaction. The results are discussed in the context of the meson-nucleon and hyperon-nucleon interactions. We conclude that the eta-proton interaction is significantly stronger than the eta'-proton interaction. Similarly, we found that the hyperon Lambda interacts with the nucleon considerably stronger than the hyperon Sigma, and that the interaction of K--proton is much stronger than this of the K+-proton.
Dynamics of the near threshold eta meson production in proton-proton interaction
R. Czyzykiewicz, P. MoSkal, HH. Adam, A. Budzanowski, E. Czerwinski, D. Gil, D. Grzonka, M. Hodana, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, K. Kilian, P. Klaja, B. Lorentz, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, B. Rejdych, J. Ritman, T. Sefzick, M. Siemaszko, M. Silarski, J. Smyrski, A. Taschner, K. Ulbrich, P. Winter, M. Wolke, P. Wustner, M. Zielinski, W. Zipper
abstract
We present the results of measurements of the analysing power for the pp -> pp eta reaction at the excess energies of Q = 10 and 36 MeV, and interpret these results within the framework of the meson exchange models. The determined values of the analysing power at both excess energies are consistent with zero implying that the eta meson is produced predominantly in s-wave.
Study of the He-3-eta system in d-p collisions
J. Smyrski, HH. Adam, A. Budzanowski, E. Czerwinski, R. Czyzykiewicz, D. Gil, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, P. Klaja, P. Moskal, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, J. Ritman, T. Rozek, T. Sefzick, A. Siemaszko, A. Taschner, P. Winter, M. Wolke, P. Wustner, W. Zipper
abstract
We have measured excitation functions for the dp -> He-3 X, (X = pi(0),eta) channels near the eta production threshold. The data were taken during a slow ramping of the COSY internal deuteron beam scattered on a proton target. The excitation function for the reaction dp -> He-3 pi(0) does not show any structure which could originate from the decay of He-3 - eta bound state. We measured also the threshold excitation curve for the dp -> He-3 X process, however, contrary to the SATURNE results, we observe no cusp near the eta threshold.
Measurement of the dp -> He-3 eta reaction near threshold
J. Smyrski, HH. Adam, A. Budzanowski, E. Czerwinski, R. Czyzykiewicz, D. Gil, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, P. Klaja, T. Mersmann, P. Moskal, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, B. Rejdych, J. Ritman, T. Rozek, T. Sefzick, M. Siemaszko, A. Taschner, P. Winter, M. Wolke, P. Wustner, W. Zipper
abstract
Total and differential cross sections for the dp -> He-3 eta reaction have been measured near threshold for He-3 center-of-mass momenta in the range from 17.1 MeV/c to 87.5 MeV/c. The data were taken during a slow ramping of the COSY internal deuteron beam scattered on a proton target detecting the He-3 ejectiles with the COSY-11 facility. The forward-backward asymmetries of the differential cross sections deviate clearly from zero for center-of-mass momenta above 50 MeV/c indicating the presence of higher partial waves in the final state. Below 50 MeV/c center-of-mass momenta a fit of the final state enhancement factor to the data of the total cross sections results in the He-3-eta scattering length of vertical bar a vertical bar = 4.3 +/- 0.5fm. (C) 2007 Elsevier B.V. All rights reserved.
Mechanism of near-threshold production of the eta meson
R. Czyzykiewicz, P. Moskal, HH. Adam, A. Budzanowski, E. Czerwinski, D. Gil, D. Grzonka, M. Hodana, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, K. Kilian, P. Klaja, B. Lorentz, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, B. Rejdych, J. Ritman, T. Sefzick, M. Siemaszko, J. Smyrski, A. Taschner, K. Ulbrich, P. Winter, M. Wolke, P. Wustner, W. Zipper
abstract
Measurements of the analyzing power for the pp -> pp eta reaction have been performed at excess energies of Q=10 and 36 MeV. The determined analyzing power is essentially consistent with zero, implying dominance of the s wave at both excess energies. The angular dependence of the analyzing power, combined with the isospin dependence of the total cross section for the eta meson production in nucleon-nucleon collisions, reveal that the excitation of the nucleon to the S-11(1535) resonance is predominantly due to the exchange of the pi meson between the colliding nucleons.
Eta and eta-prime mesons production at COSY-11
P. Moskal, H.-H. Adam, A. Budzanowski, E. Czerwinski, R. Czyzykiewicz, D. Gil, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, P. Klaja, J. Majewski, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, J. Ritman, B. Rejdych, T. Rozek, T. Sefzick, M. Siemaszko, J. Smyrski, A. Taeschner, P. Winter, M. Wolke, P. Wuestner, W. Zipper
abstract
The low emittance and small momentum spread of the proton and deuteron beams of the Cooler Synchrotron COSY combined with the high mass resolution of the COSY-11 detection system permit to study the creation of mesons in the nucleon-nucleon interaction down to the fraction of MeV with respect to the kinematical threshold. At such small excess energies, the ejectiles possess low relative momenta and are predominantly produced with the relative angular momentum equal to zero. Taking advantage of these conditions we have performed investigations aiming to determine the mechanism of the production of eta and eta' mesons in the collision of hadrons as well as the hadronic interaction of these mesons with nucleons and nuclei. In this proceedings we address the ongoing studies of the spin and isospin dependence for the production of the eta and eta' mesons in free and quasi-free nucleon-nucleon collisions. New results on the spin observables for the vec(p)p --> pp eta reaction, combined with the previously determined total cross section isospin dependence, reveal a statistically significant indication that the excitation of the nucleon to the S11(1535) resonance, the process which intermediates the production of the eta meson in the nucleon-nucleon interactions, is predominantly due to the exchange of the pi meson between the colliding nucleons.
General thoughts to the Kaon pair production in the threshold region
W. Oelert, H.-H. Adam, A. Budzanowski, E. Czerwinski, R. Czyzykiewicz, D. Gil, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, P. Klaja, P. Moskal, C. Piskor-Ignatowicz, J. Przerwa, T. Rozek, R. Santo, T. Sefzick, M. Siemaszko, J. Smyrski, A. Taschner, P. Winter, M. Wolke, P. Wustner, W. Zipper
abstract
Simple--minded thoughts about the cross sections for the reactions pp-->ppK+K- and pp-->ppK0K0 are presented, which certainly do not account for the complex coupled channel problem but rather provide some ideas into the mutual reaction dynamics.
Study of the production mechanism of the eta meson by means of analysing power measurements
R. Czyżykiewicz, P. Moskal, H.-H. Adam, A. Budzanowski, E. Czerwiński, D. Gil, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, P. Klaja, B. Lorentz, J. Majewski, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, J. Ritman, H. Rohdjess, T. Rozek, T. Sefzick, M. Siemaszko, J. Smyrski, A. Taeschner, K. Ulbrich, P. Winter, M. Wolke, P. Wuestner, W. Zipper
abstract
Information about the production mechanism of the eta meson in proton-proton collisions can be inferred by confronting the experimental studies on the analysing power for the p(pol)p --> pp eta reaction with the theoretical predictions of this observable. Results show that the predictions of pure pseudoscalar- or vector meson exchange model are insufficient to describe the analysing powers.
Near threshold eta meson production in dp collisions
C. Piskor-Ignatowicz, J. Smyrski, P. Moskal, H.-H. Adam, A. Budzanowski, E. Czerwiński, R. Czyżykiewicz, D. Gil, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, P. Klaja, J. Majewski, W. Oelert, J. Przerwa, J. Ritman, T. Rozek, T. Sefzick, M. Siemaszko, A. Taeschner, P. Winter, M. Wolke, P. Wuestner, W. Zipper
abstract
Preliminary results of recent measurements of the near threshold eta meson production in the dp-->dp eta reaction are presented. The experiment was performed at the COSY-Juelich accelerator with the use of the COSY-11 detection system. Data were taken for three values of deuteron beam momenta corresponding to excess energies of 3.2, 6.1 and 9.2 MeV. The energy dependence of the total cross section confirms a strong effect of the final state interaction.
General thoughts to the kaon pair production in the threshold region
W. Oelert, HH. Adam, A. Budzanowski, E. Czerwinski, R. Czyzykiewicz, D. Gil, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, P. Klaja, P. Moskal, C. Piskor-Ignatowicz, J. Przerwa, T. Rozek, R. Santo, T. Sefzick, M. Siemaszko, J. Smyrski, A. Taschner, P. Winter, M. Wolke, P. Wustner, W. Zipper
abstract
Simple-minded thoughts about the cross sections for the reactions pp -> ppK(+)K(-) and pp. ppK(0)K(0) are presented, which certainly do not account for the complex coupled channel problem but rather provide some ideas into the mutual reaction dynamics.
Study of the production mechanism of the eta meson by means of analysing power measurements
R. Czyzykiewicz, P. Moskal, HH. Adam, A. Budzanowski, E. Czerwinski, D. Gil, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, P. Klaja, B. Lorentz, J. Majewski, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, J. Ritman, H. Rohdjess, T. Rozek, T. Sefzick, M. Siemaszko, J. Smyrski, A. Taschner, K. Ulbrich, P. Winter, M. Wolke, P. Wustner, W. Zipper
abstract
Information about the production mechanism of the eta meson in proton-proton collisions can be inferred by confronting the experimental studies on the analysing power for the (p) over right arrowp -> pp eta reaction with the theoretical predictions of this observable. The determined analysing powers for Q=10 MeV and Q=36 MeV are consistent with zero. Results show that the predictions of pure pseudoscalar meson exchange model fairly describe the experimental data, while the predictions of pure vector meson exchange dominance model disagree with the data at the level of 4.3 sigma.
Near threshold eta meson production in dp collisions
C. Piskor-Ignatowicz, J. Smyrski, P. Moskal, HH. Adam, A. Budzanowski, E. Czerwinski, R. Czyzykiewicz, D. Gil, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, P. Klaja, J. Majewski, W. Oelert, J. Przerwa, J. Ritman, T. Rozek, T. Sefzick, M. Siemaszko, A. Taschner, P. Winter, M. Wolke, P. Wustner, W. Zipper
abstract
Preliminary results of recent measurements of the near threshold. meson production in the dp -> dp eta reaction are presented. The experiment was performed at the COSY-Juelich accelerator with the use of the COSY-11 detection system. Data were taken for three values of deuteron beam momenta corresponding to excess energies of 3.2, 6.1 and 9.2 MeV. The energy dependence of the total cross section con. rms a strong e. ect of the. nal state interaction.
Study of the low energy interaction of hadrons at COSY-11
P. Moskal, R. Czyżykiewicz, E. Czerwiński, D. Grzonka, A. Budzanowski, D. Gil, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, P. Klaja, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, B. Rejdych, J. Ritman, T. Sefzick, M. Siemaszko, M. Silarski, J. Smyrski, A. Täschner, M. Wolke, P. Wüstner, M. Zieliński, W. Zipper
abstract
We summarize the studies of the low energy hadronic interaction of the KK and pK system performed by the COSY-11 collaboration. We discuss also the question of the existence of the ??3He bound state in the context of the experiments conducted by means of the COSY-11 facility
Measurement of the dp -> He-3 eta reaction near threshold
J. Smyrski, H.-H. Adam, A. Budzanowski, E. Czerwiński, R. Czyżykiewicz, D. Gil, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, P. Klaja, T. Mersmann, P. Moskal, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, B. Rejdych, J. Ritman, T. Rozek, T. Sefzick, M. Siemaszko, A. Taeschner, P. Winter, M. Wolke, P. Wuestner, W. Zipper
abstract
Total and differential cross sections for the dp --> 3He eta reaction have been measured near threshold for 3He center-of-mass momenta in the range from 17.1 MeV/c to 87.5 MeV/c. The data were taken during a slow ramping of the COSY internal deuteron beam scattered on a proton target detecting the 3He ejectiles with the COSY-11 facility. The forward-backward asymmetries of the differential cross sections deviate clearly from zero for center-of-mass momenta above 50 MeV/c indicating the presence of higher partial waves in the final state. Below 50 MeV/c center-of-mass momenta a fit of the final state enhancement factor to the data of the total cross sections results in the 3He eta scattering length of a = |2.9 +/- 0.6| + i (3.2 +/- 0.4) fm.
Direct measurement of the total width of the eta prime meson
E. Czerwiński, P. Moskal, D. Grzonka, A. Budzanowski, R. Czyżykiewiczy, D. Gil, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, P. Klaja, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, B. Rejdych, J. Ritman, T. Sefzick, M. Siemaszko, M. Silarski, J. Smyrski, A. Täschner, M. Wolke, P. Wüstner, M. Zieliński, W. Zipper
abstract
Using stochastically cooled proton beam of the cooler synchrotron COSY and the COSY-11 apparatus we have measured the mass distribution of the eta prime meson producing it via the pp->ppeta' reaction. The preliminary analysis shows that the achieved experimental mass resolution amounts to about 0.3 MeV (FWHM). Such precision with about 2300 events gathered at five excess energies should permit for the extraction of the width of the eta' meson with an accuracy of about 10 keV. In this article we describe the method of the mea-surement and present preliminary results.
Hadronic He-3 eta production near threshold
H.-H. Adam, I. Geck, A. Khoukaz, T. Lister, R. Santo, S. Steltenkamp, A. Täschner, E. Czerwiński, R. Czyżykiewicz, M. Janusz, L. Jarczyk, B. Kamys, P. Klaja, P. Moskal, C. Piskor-Ignatowicz, J. Przerwa, J. Smyrski, D. Grzonka, K. Kilian, W. Oelert, T. Sefzick, P. Winter, M. Wolke, P. Wüstner, A. Budzanowski, T. Rożek, M. Siemaszko, W. Zipper
abstract
Measurements of ? meson production in proton-deuteron collisions have been performed using the COSY-11 facility at COSY (Jülich). Results on total and differential cross sections for the pd?3He? reaction are presented at five excess energies between Q=5.0 and Q=40.6 MeV. The angular distributions show a transition from an almost isotropic emission close to threshold to a highly anisotropic distribution at higher excess energies. The total cross sections reveal a strong ?-3He final state interaction, corresponding to a scattering length of |?(a)|=(4.2?0.5) fm and ?(a)=(0.4?1.9) fm
Study of the He-3 eta system in d p collisions
J. Smyrski, H.-H. Adam, A.Budzanowski, E. Czerwiński, R. Czyżykiewicz, D. Gil, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, P. Klaja, P. Moskal, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, J. Ritman, T. Rozek, T. Sefzick, M. Siemaszko, A. Taeschner, P. Winter, M. Wolke, P. Wuestner, W. Zipper
abstract
We have measured excitation functions for the d+p->3He+X, (X=pi0, eta) channels near the eta production threshold. The data were taken during a slow ramping of the COSY internal deuteron beam scattered on a proton target. The excitation function for the reaction d+p->3He+pi0 does not show any structure which could originate from the decay of 3He-eta bound state. We measured also the threshold excitation curve for the d+p->3He+X process, however, contrary to the SATURNE results, we observe no cusp near the eta threshold.
Mechanism of the close-to-threshold production of the eta meson
R. Czyzykiewicz, P. Moskal, H. -H. Adam, A. Budzanowski, E. Czerwinski, D. Gil, D. Grzonka, M. Hodana, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, K. Kilian, P. Klaja, B. Lorentz, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, B. Rejdych, J. Ritman, T. Sefzick, M. Siemaszko, J. Smyrski, A. Taeschner, K. Ulbrich, P. Winter, M. Wolke, P. Wuestner, W. Zipper
abstract
Measurements of the analysing power for the p(pol)p --> ppeta reaction have been performed in the close-to-threshold energy region at beam momenta of p_{beam}=2.010 and 2.085 GeV/c, corresponding to excess energies of Q=10 and 36 MeV, respectively. The determined analysing power is essentially consistent with zero implying that the eta meson is produced predominantly in the s-wave at both excess energies. The angular dependence of the analysing power, combined with the hitherto determined isospin dependence of the total cross section for the eta meson production in nucleon-nucleon collisions, reveal a statistically significant indication that the excitation of the nucleon to the S_{11}(1535) resonance, the process which intermediates the production of the eta meson, is predominantly due to the exchange of the pi meson between the colliding nucleons.
Hadronic He-3 eta production near threshold
HH. Adam, I. Geck, A. Khoukaz, T. Lister, R. Santo, S. Steltenkamp, A. Taschner, E. Czerwimski, R. Czyzykiewicz, M. Janusz, L. Jarczyk, B. Kamys, P. Klaja, P. Moskal, C. Piskor-Ignatowicz, J. Przerwa, J. Smyrski, D. Grzonka, K. Kilian, W. Oelert, T. Sefzick, P. Winter, M. Wolke, P. Wustner
abstract
Measurements of eta meson production in proton-deuteron collisions have been performed using the COSY-11 facility at COSY (Julich). Results on total and differential cross sections for the pd -> He-3 eta reaction are presented at five excess energies between Q=5.0 and Q=40.6 MeV. The angular distributions show a transition from an almost isotropic emission close to threshold to a highly anisotropic distribution at higher excess energies. The total cross sections reveal a strong eta-He-3 final state interaction, corresponding to a scattering length of vertical bar(a)vertical bar=(4.2 +/- 0.5) fm and (a)=(0.4 +/- 1.9) fm.
Threshold hyperon production in proton-proton collisions at COSY-11
T. Rozek, D. Grzonka, HH. Adam, A. Budzanowski, R. Czyzykiewicz, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, K. Kilian, P. Klaja, P. Kowina, P. Moskal, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, J. Ritman, T. Sefzick, M. Siemaszko, J. Smyrski, A. Taschner, P. Winter, M. Wolke, P. Wustner, Z. Zhang, W. Zipper
abstract
The Sigma(+) hyperon production was measured at the COSY-11 spectrometer via the pp -> nK(+)Sigma(+) reaction at excess energies of Q = 13 MeV and Q = 60 MeV. These measurements continue systematic hyperon production studies via the pp -> pK(+)Lambda/Sigma(0) reactions where a strong decrease of the cross section ratio close-to-threshold was observed. In order to verify models developed for the description of the Lambda and Sigma(0) production we have performed the measurement on the Sigma(+) hyperon and found unexpectedly that the total cross section is by more than one order of magnitude larger than predicted by all anticipated models. After the reconstruction of the kaon and neutron four momenta, the Sigma(+) is identified via the missing mass technique. Details of the method and the measurement will be given and discussed in view of theoretical models. (c) 2006 Elsevier B.V. All rights reserved.
Study of the He-3-eta system in d-p collisions at COSY-11
J. Smyrski, HH. Adam, A. Budzanowski, E. Czerwinski, R. Czyzykiewicz, D. Gil, D. Grzonka, A. Heczko, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, K. Kilian, P. Klaja, J. Majewski, P. Moskal, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, J. Ritman, T. Rozek, R. Santo, T. Sefzick, M. Siemaszko, A. Taschner, P. Winter, M. Wolke, P. Wustner, Z. Zhang, W. Zipper
abstract
We present preliminary results from dp -> He-3 X, (X = pi(0),eta) measurements near the eta production threshold. The data were taken during a slow ramping of the COSY internal deuteron beam scattered on a proton target. The He-3 ejectiles were registered with the COSY-11 detection setup. The ongoing data analysis should deliver high precision data for the dp -> He-3 eta total and differential cross sections for the excess energies in the range from threshold up to 9 MeV. The preliminary excitation function for the reaction dp -> 3 He pi(0) does not show any structure which Could originate from the decay of He-3 - eta bound state. We present also a threshold excitation curve for the dp - He-3 X channel. Contrary to corresponding results from SATURNE we see no cusp in the vicinity of the eta threshold.
The analyzing power for the (p)over-right-arrowp -> pp eta reaction at Q=10 MeV
R. Czyzykiewicz, P. Moskal, HH. Adam, A. Budzanowski, E. Czerwinski, D. Gil, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, K. Kilian, P. Klaja, B. Lorentz, J. Majewski, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, J. Ritman, H. Rohdjess, T. Rozek, R. Santo, T. Sefzick, M. Siemaszko, J. Smyrski, A. Taschner, K. Ulbrich, P. Winter, M. Wolke, P. Wustner, Z. Zhang, W. Zipper
abstract
The analyzing power A(y) for the (p) over right arrowp -> pp eta reaction has been determined at the beam momentum p(beam) = 2010 MeV/c, corresponding to the excess energy Q = 10 MeV. In the paper the method of the data analysis is briefly presented.
The Analysing power for the polarized-p p ---> p p eta reaction at Q=10MeV
R. Czyzykiewicz, P. Moskal, H.-H. Adam, A. Budzanowski, E. Czerwinski, D. Gil, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, K. Kilian, P. Klaja, B. Lorentz, J. Majewski, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, J. Ritman, H. Rohdjess, T. Rozek, R. Santo, T. Sefzick, M. Siemaszko, J. Smyrski, A. Taeschner, K. Ulbrich, P. Winter, M. Wolke, P. Wuestner, Z. Zhang, W. Zipper
abstract
The analyzing power A_y for the p(pol)p --> pp eta reaction has been determined at the beam momentum p_{beam}=2010 MeV/c, corresponding to the excess energy Q=10 MeV. In the paper the method of the data analysis is briefly presented.
Study of the He-3 - eta system in d-p collisions at COSY-11
J. Smyrski, H.-H. Adam, A. Budzanowski, E. Czerwinski, R. Czyzykiewicz, D. Gil, D. Grzonka, A. Heczko, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, K. Kilian, P. Klaja, J. Majewski, P. Moskal, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, J. Ritman, T. Rozek, R. Santo, T. Sefzick, M. Siemaszko, A. Taeschner, P. Winter, M. Wolke, P. Wuestner, Z. Zhang, W. Zipper
abstract
We present preliminary results from dp --> 3He X (X=pi0,eta) measurements near the eta production threshold. The data were taken during a slow ramping of the COSY internal deuteron beam scattered on a proton target. The 3He ejectiles were registered with the COSY-11 detection setup. The ongoing data analysis should deliver high precision data for the dp --> 3He eta total and differential cross sections for the excess energies in the range from threshold up to 9 MeV. The preliminary excitation function for the reaction dp --> 3He pi0 does not show any structure which could originate from the decay of 3He-eta bound state. We present also a threshold excitation curve for the dp --> 3He X channel. Contrary to corresponding results from SATURNE we see no cusp in the vicinity of the eta threshold.
Correlation femtoscopy for studying eta meson production mechanism
P. Klaja, P. Moskal, H.-H. Adam, A. Budzanowski, E. Czerwinski, R. Czyzykiewicz, D. Gil, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, K. Kilian, J. Majewski, W. Migdal, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, J. Ritman, T. Rozek, R. Santo, T. Sefzick, M. Siemaszko, J. Smyrski, A. Taeschner, P. Winter, M. Wolke, P. Wuestner, Z. Zhang, W. Zipper
abstract
The high statistics data from the pp -> ppeta reaction measurement, delivered by the COSY-11 collaboration, are now being evaluated using the correlation femtoscopy technique. This method is based on the relative momentum correlations of two emitted protons and may permit determination of the size of the reaction volume. For the very first time, we apply an intensity interferometry technique to study the mechanism of the meson production via the nucleon-nucleon interaction close to the kinematical threshold. We invented a method to determine correlation function for the ppeta system free from the physical multi-pion production background. We show the comparison of experimental results with theoretical predictions and appraise the accuracy achieved for the determination of the size of the emission source.
Kaon pair production close to threshold
P. Winter, M. Wolke, HH. Adam, A. Budzanowski, R. Czyzykiewicz, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, K. Kilian, P. Klaja, P. Moskal, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, J. Ritman, T. Rozek, T. Sefzick, M. Slemaszko, J. Smyrski, A. Taschner, P. Wustner, Z. Zhang, W. Zipper
abstract
The total cross section of the reaction pp -> ppK(+)K(-) has been measured at excess energies Q = 10 MeV and 28 MeV with the magnetic spectrometer COSY-11. The new data show a significant enhancement of the total cross section compared to pure phase space expectations or calculations within a one boson exchange model. In addition, we present invariant mass spectra of two particle subsystems. While the K+K- system is rather constant for different invariant masses, there is an enhancement in the pK(-) system towards lower masses which could at least be partially connected to the influence of the Lambda (1405) resonance. (c) 2006 Elsevier B.V. All rights reserved.
Threshold hyperon production in proton-proton collisions at COSY-11
T. Rozek, D. Grzonka, H.-H. Adam, A. Budzanowski, R. Czyzykiewicz, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, K. Kilian, P. Klaja, P. Kowina, P. Moskal, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, J. Ritman, T. Sefzick, M. Siemaszko, J. Smyrski, A. Taschner, P. Winter, M. Wolke, P. Wustner, Z. Zhang, W. Zipper
abstract
Sigma+ hyperon production was measured at the COSY-11 spectrometer via the p p --> n K+ Sigma+ reaction at excess energies of Q = 13 MeV and Q = 60 MeV. These measurements continue systematic hyperon production studies via the p p --> p K+ Lambda/Sigma0 reactions where a strong decrease of the cross section ratio close-to-threshold was observed. In order to verify models developed for the description of the Lambda and Sigma0 production we have performed the measurement on the Sigma+ hyperon and found unexpectedly that the total cross section is by more than one order of magnitude larger than predicted by all anticipated models.
After the reconstruction of the kaon and neutron four momenta, the Sigma+ is identified via the missing mass technique. Details of the method and the measurement will be given and discussed in view of theoretical models.
Kaon pair production close to threshold
P. Winter, M. Wolke, H.-H. Adam, A. Budzanowski, R. Czyzykiewicz, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, K. Kilian, P. Klaja, P. Moskal, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, J. Ritman, T. Rozek, T. Sefzick, M. Siemaszko, J. Smyrski, A. Taschner, P. Wustner, Z. Zhang, W. Zipper
abstract
The total cross section of the reaction pp->ppK+K- has been measured at excess energies Q=10 MeV and 28 MeV with the magnetic spectrometer COSY-11. The new data show a significant enhancement of the total cross section compared to pure phase space expectations or calculations within a one boson exchange model. In addition, we present invariant mass spectra of two particle subsystems. While the K+K- system is rather constant for different invariant masses, there is an enhancement in the pK- system towards lower masses which could at least be partially connected to the influence of the Lambda(1405) resonance.
A method to disentangle single- and multi-meson production in missing mass spectra from quasi-free pn ---> pn X reactions
P. Moskal, H.-H. Adam, A. Budzanowski, R. Czyzykiewicz, D. Grzonka, M. Janusz, L. Jarczyk, T. Johansson, B. Kamys, P. Klaja, A. Khoukaz, K. Kilian, J. Majewski, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, J. Ritman, T. Rozek, T. Sefzick, M. Siemaszko, J. Smyrski, A. Taeschner, J. Wessels, P. Winter, M. Wolke, P. Wuestner, Z. Zhang, W. Zipper
abstract
The separation of contributions from multi- and single-meson production in the missing mass spectrum of the quasi-free pn --> pnX reaction constitutes a~challenging task when the reaction is studied close to threshold. This is especially true if the resolution of the mass determination is comparable with the excess energy and if the investigated signal appears close to the kinematical limit. In this article we outline a method which permits the extraction of the signal originating from the creation of a single meson without the necessity of conducting model-dependent simulations. For the pd --> pnXp(spectator) reactions, the method allows one to combine events corresponding to multi-meson production at various excess energies with respect to the pn --> pn meson process, and hence leads to an increase of the statistics needed for the determination of the shape of the multi-meson background.
As an example of the application of the method, we demonstrate that the evaluation of the data from the pd --> pnXp(sp) process according to the described technique enables one to extract a signal of the pn --> pn eta reaction whose shape is consistent with expectations, supporting the correctness and usefulness of the method introduced.
Hadronic interaction of the 77 meson with two nucleons
P. Moskal, HH. Adam, A. Budzanowski, R. Czyzykiewicz, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, K. Kilian, P. Klaja, J. Majewski, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, T. Rozek, T. Sefzick, M. Siemaszko, J. Smyrski, A. Taschner, P. Winter, M. Wolke, P. Wustner, W. Zipper
abstract
The COSY-11 collaboration has conducted experiments aiming at the determination of the excitation function and phase-space population of the pp -> pp eta reaction close to the kinematical threshold. The precise data obtained with the stochastically cooled proton beam of the cooler synchrotron COSY and the high resolution zero-degree magnetic spectrometer allowed for the observation of the significant deviations - in the shape of the excitation function and two-particle invariant masses - from the predictions based on the assumption that the reaction phase space is homogenously populated. Comparison of the shape of the excitation function for the pp -> pp eta and pp -> pp eta' reaction allows to distinquish in the model independent way an influence originating from the protonproton and proton-eta interaction. For the comparison the full data set from experiments performed at COSY and other laboratories is used.
Search for Bremsstrahlung radiation in quasi-free np -> np gamma reactions
J. Przerwa, HH. Adam, A. Budzanowski, R. Czyzykiewicz, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, K. Kilian, P. Klaja, N. Lang, P. Moskal, W. Oelert, C. Piskor-Ignatowicz, T. Rozek, R. Santo, T. Sefzick, M. Siemaszko, J. Smyrski, A. Taschner, P. Winter, M. Wolke, P. Wustner, W. Zipper
abstract
Due to the high sensitivity of the NN -> NN gamma reaction to the nucleon-nucleon potential, Bremsstrahlung radiation is used as a tool to investigate details of the nucleon-nucleon interaction. Such investigations can be performed at the cooler synchrotron COSY in the Research Centre Julich, by dint of the COSY-11 detection system. The results of the identification of Bremsstrahlung radiation emitted via the dp -> dp gamma reaction in data taken with a proton target and a deuteron beam are presented and discussed.
Threshold hyperon production at COSY-11
T. Rozek, D. Grzonka, K. Kilian, P. Kowina, W. Oelert, T. Sefzick, P. Winter, M. Wolke, P. Wustner, M. Siemaszko, W. Zipper, R. Czyzykiewicz, M. Janusz, L. Jarczyk, B. Kamys, P. Klaja, P. Moskal, C. Piskor-Ignatowicz, J. Przerwa, J. Smyrski, HH. Adam, A. Khoukaz, R. Santo, A. Taschner, A. Budzanowski
abstract
The Lambda, Sigma(0) and Sigma(+) hyperon production in NN collisions is studied at the COSY - 11 installation in order to investigate the production mechanism as well as to extract information about the Y-N interaction.
Production of eta mesons in proton-proton collisions close to threshold
R. Czyzykiewicz, HH. Adam, A. Budzanowski, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, K. Kilian, P. Klaja, P. Kowina, P. Moskal, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, T. Rozek, R. Santo, T. Sefzick, M. Siemaszko, J. Smyrski, A. Taschner, P. Winter, M. Wolke, P. Wustner, W. Zipper
abstract
A brief experimental overview on the close-to-threshold eta meson production in proton-proton interactions is presented and the available observables in measurements with unpolarized and polarized beam and target are discussed.
New results on the pd -> He-3 eta production near threshold
HH. Adam, A. Khoukaz, N. Lang, T. Lister, R. Santo, S. Steltenkamp, R. Czyzykiewicz, M. Janusz, L. Jarczyk, B. Kamys, P. Moskal, C. Piskor-Ignatowicz, J. Przerwa, J. Smyrski, D. Grzonka, K. Kilian, W. Oelert, T. Sefzick, P. Winter, M. Wolke, P. Wustner, A. Budzanowski, T. Rozek, M. Siemaszko, W. Zipper
abstract
Measurements on the eta meson production in proton-deuteron collisions have been performed using the COSY-11 facility at COSY (Julich). Here we present preliminary results on total and differential cross sections for the pd -> He-3 eta reaction at five excess energies between Q = 5.1 and Q = 40.6 MeV. The obtained angular distributions for the emitted eta mesons in the center of mass system expose a transition from an almost isotropic emission to a highly anisotropic distribution. The extracted total cross sections support a strong eta-He-3 final state interaction and will be compared with model predictions.
Drift chamber with a c-shaped frame
J. Smyrski, Ch. Kolf, H.-H. Adam, A. Budzanowski, R. Czyzykiewicz, D. Grzonka, A. Heczko, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, K. Kilian, P. Kowina, A. Misiak, P. Moskal, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, C. Quentmeier, T. Rozek, R. Santo, G. Schepers, T. Sefzick, M. Siemaszko, A. Taschner, P. Winter, M. Wolke, P. Wustner, W. Zipper
abstract
We present the construction of a planar drift chamber with wires stretched between two arms of a c-shaped aluminium frame. The special shape of the frame allows to extendthe momentum acceptance of the COSY-11 detection system towards lower momenta without suppressing the high momentum particles. The proposed design allows for construction of tracking detectors covering small angles with respect to the beam, which can be installed and removed without dismounting the beam-pipe. For a three-dimensional track reconstruction a computer code was developed using a simple algorithm of hit preselection.
New results on pd -> He-3 eta production from threshold up to Q=40 MeV
HH. Adam, A. Khoukaz, N. Lang, T. Lister, R. Santo, S. Steltenkamp, R. Czyzykiewicz, M. Janusz, L. Jarczyk, B. Kamys, P. Klaja, P. Moskal, C. Piskor-Ignatowicz, J. Przerwa, J. Smyrski, D. Grzonka, K. Kilian, W. Oelert, T. Sefzick, P. Winter, M. Wolke, P. Wustner, A. Budzanowski, T. Rozek, M. Siemaszko, W. Zipper
abstract
Measurements on the eta meson production in proton-deuteron collisions have been performed using the COSY-11 facility at COSY (Julich). Here we present preliminary results on total and differential cross sections for the pd -> He-3 eta reaction at five excess energies between Q = 5.1 and Q = 40.6 MeV. The obtained angular distributions for the emitted eta mesons in the center of mass system expose a transition from an almost isotropic emission to a highly anisotropic distribution. The extracted total cross sections support a strong eta-He-3 final state interaction and will be compared with model predictions.
Isospin dependence of the eta' meson production in nucleon-nucleon collisions
J. Przerwa, HH. Adam, A. Budzanowski, R. Czyzykiewicz, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, K. Kilian, P. Klaja, P. Moskal, W. Oelert, C. Piskor-Ignatowicz, J. Ritman, T. Rozek, T. Sefzick, M. Siemaszko, J. Smyrski, A. Taschner, J. Wessels, P. Winter, M. Wolke, P. Wustner, W. Zipper
abstract
According to the quark model, the masses of eta and eta' mesons should be almost equal. However, the empirical values of these masses differ by more than a factor of two. Similarly, though they have almost the same quark-antiquark content, the total cross section for the creation of these mesons close to the kinematical thresholds in the pp -> ppX reaction differs significantly. Using the COSY-11 detection setup we intend to determine whether this difference will also be so significant in the case of the production of these mesons in the proton-neutron scattering. Additionally, the comparison of the pp -> pp eta' and pn -> pn eta' total cross sections will allow to learn about the production of the eta' meson in the channels of isospin 1 = 0 and 1 = 1 and to investigate aspects of the gluonium component of the eta' meson.
Energy dependence of the Lambda/Sigma(0) production cross-section ratio in p-p interactions
P. Kowina, M. Wolke, HH. Adam, A. Budzanowski, R. Czyzykiewicz, D. Grzonka, J. Haidenbauer, M. Janusz, L. Jarczyk, A. Khoukaz, K. Kilian, P. Moskal, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, C. Quentmeier, T. Rozek, R. Santo, G. Schepers, T. Sefzick, M. Siemaszko, J. Smyrski, S. Steltenkamp, A. Strzalkowski, P. Winter, P. Wustner, W. Zipper
abstract
The production of the Lambda- and Sigma(0)-hyperous has been measured via the pp --> pK(+)Lambda/Sigma(0) reaction at the internal COSY-11 facility in the excess energy range between 14 and 60 MeV. The transition of the Lambda/Sigma(o) cross-section ratio from about 28 at Q less than or equal to 13 MeV to the high-energy level of about 2.5 is covered by the data showing a strong decrease of the ratio between 10 and 20 MeV excess energy. Effects from the final-state interactions in the p-Sigma(o) channel seem to be much smaller than in the p-A channel. Estimates of the effective range parameters are given for the NLambda and the NSigma systems.
Production of eta and eta ' mesons via the quasi-free proton-neutron interaction
P. Moskal, HH. Adam, A. Budzanowski, R. Czyzykiewicz, D. Grzonka, M. Janusz, L. Jarczyk, T. Johansson, B. Kamys, A. Khoukaz, K. Kilian, P. Kowina, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, T. Rozek, R. Santo, G. Schepers, T. Sefzick, M. Siemaszko, J. Smyrski, A. Strzalkowski, A. Taschner, P. Winter, M. Wolke, P. Wustner, W. Zipper
abstract
A comparison of the close-to-threshold total cross sections for the eta' meson production in both the pp --> ppeta' and pn --> pneta' reactions should provide insight into the flavour-singlet (perhaps also into gluonium) content of the eta' meson and the relevance of quark-gluon or hadronic degrees of freedom in the creation process. The excitation function for the reaction pp --> ppeta' has been already established. At present, experimental investigations of the quasi-free pn --> pnX reactions are carried out at the COSY-11 facility using a beam of stochastically cooled protons and the deuteron cluster target. A method of measurement and preliminary results from the test experiments of the pn --> pneta reaction are presented in this report.
Energy dependence of the Lambda/Sigma(0) production cross section ratio in p-p interactions.
P. Kowina, HH. Adam, A. Budzanowski, R. Czyzykiewicz, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, K. Kilian, P. Moskal, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, T. Rozek, R. Santo, G. Schepers, T. Sefzick, M. Siemaszko, J. Smyrski, A. Taschner, P. Winter, M. Wolke, P. Wustner, W. Zipper
abstract
Measurements of the near threshold Lambda and Sigma(0) production via the pp --> pK(+)Lambda/Sigma(0) reaction at COSY-11 have shown that the Lambda/Sigma(0) cross section ratio exceeds the value at high excess energies (Q greater than or equal to 300 MeV) by an order of magnitude. For a better understanding additional data have been taken between 13 MeV and 60 MeV excess energy. Within the first 20 MeV excess energy a strong decrease of the cross section ratio is observed, with a less steep decrease in the higher excess energy range. A description of the data with a parametrisation including p - Y final state interactions suggests a much smaller p - Sigma(0) FSI compared to the p - Lambda system.
Analysis of the eta meson production mechanism via the (p)over-barp -> pp eta reaction
R. Czyzykiewicz, HH. Adam, A. Budzanowski, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, K. Kilian, P. Kowina, P. Moskal, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, T. Rozek, R. Santo, G. Schepers, T. Sefzick, M. Siemaszko, J. Smyrski, A. Taschner, P. Winter, P. Wustner, W. Zipper
abstract
Polarisation observables constitute a powerful tool for establishing the production mechanism of the eta meson and for infering the presence of higher partial waves in the final system. Measurements of the proton analysing power for the (p) over right arrowp --> ppeta reaction have been performed by the COSY-11 group at three different excess energies: Q = 10, 37 and 40 MeV. Data at Q = 40 MeV indicate that the eta meson is probably produced in partial waves higher than s wave.
Upper limit for the cross-section of the overlapping scalar resonances f(0)(980) and a(0)(980) produced in proton-proton collisions in the range of the reaction threshold
P. Moskal, HH. Adam, A. Budzanowski, R. Czyzykiewicz, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys, A. Khoukaz, K. Kilian, C. Kolf, P. Kowina, T. Lister, W. Oelert, C. Piskor-Ignatowicz, J. Przerwa, C. Quentmeier, T. Rozek, R. Santo, G. Schepers, T. Sefzick, M. Siemaszko, J. Smyrski, A. Strzalkowski, A. Taschner, P. Winter, M. Wolke, P. Wustner, W. Zipper
abstract
Utilizing a missing mass technique we investigate the pp --> ppX reaction scanning beam energies in the range permitting to create a mass close to that of the f(0) (980) and a(0) (980) scalar resonances, but still below the K+ K- threshold where they decay dominantly into pi pi and pi eta mesons, respectively. Prior to the data analysis we introduce a notion of the close to threshold total cross-section for broad resonances. We estimated for the overlapping mesons a(0) and f(0) the total cross-section to be smaller than 430 nb at excess energy of Q = 5 MeV. The experiment has been performed at the Cooler Synchrotron (COSY) using the COSY-11 facility.
