Search for eta mesic 3He with the WASA-at-COSY facility in the pd-> 3He 2gamma and pd-> 3He 6gamma reactions
P. Adlarson, ..., E. Czerwiński, O. Khreptak, W. Krzemień, P. Moskal, O. Rundel, I. Schätti-Ozerianska, M. Skurzok, M.J. Zieliński, et al.
abstract
We report on the experimental search for the bound state of an eta meson and 3He nucleus performed using the WASA-at-COSY detector setup. In order to search for the eta-mesic nucleus decay, the pd->3He2gamma and pd->3He6gamma channels have been analysed. These reactions manifest the direct decay of eta meson bound in 3He nucleus. This non-mesonic decay channel has been considered for the first time. When taking into account only statistical errors, the obtained excitation functions reveal a slight indication for a possible bound state signal corresponding to an 3He-eta nucleus width Gamma above 20 MeV and binding energy Bs between 0 and 15 MeV. However, the determined cross sections are consistent with zero in the range of the systematic uncertainty. Therefore, as final result we estimate only the upper limit for the cross section of the eta-mesic 3He nucleus formation followed by the eta meson decay which varies between 2 nb and 15 nb depending on possible bound state parameters.
Examination of the Production of an Isotensor Dibaryon in the pp->pppi+pi- Reaction
P. Adlarson, ..., E. Czerwiński, O. Khreptak, W. Krzemień, P. Moskal, O. Rundel, I. Schätti-Ozerianska, M. Skurzok, M.J. Zieliński, et al.
abstract
Exclusive measurements of the quasi-free pp->pppi+pi- reaction have been performed by means of pd collisions at Tp = 1.2 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region Tp=1.08-1.36 GeV (sqrt(s) = 2.35 - 2.46 GeV), which includes the regions of N*(1440) and Delta(1232)Delta(1232) resonance excitations. Calculations describing these excitations by t-channel meson exchange are at variance with experimental differential cross sections and underpredict substantially the measured total cross section. An isotensor DeltaN dibaryon resonance with I(JP)=2(1+) produced associatedly with a pion is able to overcome these deficiencies. Such a dibaryon was predicted by Dyson and Xuong and more recently calculated by Gal and Garcilazo.
Backward single-pion production in the pd->3Hepi0 reaction with WASA-at-COSY
P. Adlarson, ..., E. Czerwiński, O. Khreptak, W. Krzemień, P. Moskal, O. Rundel, I. Schätti-Ozerianska, M. Skurzok, M.J. Zieliński, et al.
abstract
New data on the production of single neutral pions in the pd->3Hepi0 reaction are presented. For fifteen proton beam momenta between pp=1.60GeV/c and pp=1.74GeV/c, differential cross sections are determined over a large fraction of the backward hemisphere. Since the only previous systematic measurements of single-pion production at these energies were made in collinear kinematics, the present work constitutes a significant extension of the current knowledge on this reaction. Even this far above the production threshold, significant changes are found in the behaviour of the angular distributions over small intervals in beam momentum.
Isotensor Dibaryon in the pp->pppi+pi- Reaction?
P. Adlarson, ..., E. Czerwiński, O. Khreptak, W. Krzemień, P. Moskal, O. Rundel, I. Schätti-Ozerianska, M. Skurzok, M.J. Zieliński, et al.
abstract
Exclusive measurements of the quasi-free pp->pppi+pi- reaction have been carried out at WASA@COSY by means of pd collisions at Tp = 1.2 GeV. Total and differential cross sections have been extracted covering the energy region Tp=1.08-1.36 GeV, which is the region of N*(1440) and Delta(1232)Delta(1232) resonance excitations. Calculations describing these excitations by t-channel meson exchange are at variance with the measured differential cross sections and underpredict substantially the experimental total cross section. An isotensor DeltaN dibaryon resonance with I(JP)=2(1+) produced associatedly with a pion is able to overcome these deficiencies.
Isotensor Dibaryon in the pp -> pp pi(+)pi(-) Reaction?
P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, FS. Bergmann, M. Berlowski, A. Bondar, M. Buscher, H. Calen, I. Ciepal, H. Clement, E. Czerwinski, K. Demmich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Fohl, K. Fransson, F. Goldenbaum, A. Goswami, K. Grigoryev, L. Heijkenskjold, V. Hejny, N. Husken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, A. Khoukaz, O. Khreptak, DA. Kirillov, S. Kistryn, H. Kleines, B. Klos, W. Krzemien, P. Kulessa, A. Kupsc, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Marianski, HP. Morsch, P. Moskal, H. Ohm, W. Parol, EP. del Rio, NM. Piskunov, D. Prasuhn, D. Pszczel, K. Pysz, J. Ritman, A. Roy, Z. Rudy, O. Rundel, S. Sawant, S. Schadmand, I. Schatti-Ozerianska, T. Sefzick, V. Serdyuk, B. Shwartz, T. Skorodko, M. Skurzok, J. Smyrski, et al.
abstract
Exclusive measurements of the quasifree pp -> pp pi(+)pi(-) reaction have been carried out at WASA@ COSY by means of pd collisions at T-p = 1.2 GeV. Total and differential cross sections have been extracted covering the energy region T-p = 1.08-1.36 GeV, which is the region of N* (1440) and Delta(123)Delta(1232) resonance excitations. Calculations describing these excitations by t-channel meson exchange are at variance with the measured differential cross sections and underpredict substantially the experimental total cross section. An isotensor Delta N dibaryon resonance with I(J(P)) = 2(1(+)) produced associatedly with a pion is able to overcome these deficiencies.
Importance of d-wave contributions in the charge symmetry breaking reaction dd->4Hepi0
P. Adlarson, ...,E. Czerwiński, O. Khreptak, W. Krzemień, P. Moskal, O. Rundel, M. Skurzok, M. Zieliński et al. (WASA-at-COSY Collaboration)
abstract
This letter reports the first measurement of the contribution of higher partial waves in the charge symmetry breaking reaction dd->4Hepi0 using the WASA-at-COSY detector setup at an excess energy of Q=60 MeV. The determined differential cross section can be parametrized as dsigma/domega=a+bcos2theta?, where theta? is the production angle of the pion in the center-of-mass coordinate system, and the results for the parameters are a=(1.55+-0.46(stat)+0.32-0.8(syst))pb/sr and b=(13.1+-2.1(stat)+1.0-2.7(syst))pb/sr. The data are compatible with vanishing p-waves and a sizable d-wave contribution. This finding should strongly constrain the contribution of the Delta isobar to the dd->4Hepi0 reaction and is therefore crucial for a quantitative understanding of quark mass effects in nuclear production reactions.
Importance of d-wave contributions in the charge symmetry breaking reaction dd -> He-4 pi(0)
P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, FS. Bergmann, M. Berlowski, A. Bondar, M. Buscher, H. Calen, I. Ciepal, H. Clement, E. Czerwinski, K. Demmich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Fohl, K. Fransson, F. Goldenbaum, A. Goswami, K. Grigoryev, CO. Gullstrom, C. Hanhart, L. Heijkenskjold, V. Hejny, N. Husken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, G. Khatri, A. Khoukaz, O. Khreptak, DA. Kirillov, S. Kistryn, H. Kleines, B. Klos, W. Krzemien, P. Kulessa, A. Kupsc, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Marianski, HP. Morsch, P. Moskal, H. Ohm, W. Parol, EP. del Rio, NM. Piskunov, D. Prasuhn, D. Pszczel, K. Pysz, A. Pyszniak, J. Ritman, A. Roy, Z. Rudy, O. Rundel, S. Sawant, S. Schadmand, I. Schatti-Ozerianska, T. Sefzick, et al.
abstract
This letter reports a first quantitative analysis of the contribution of higher partial waves in the charge symmetry breaking reaction dd -> He-4 pi(0) using the WASA-at-COSY detector setup at an excess energy of Q = 60 MeV. The determined differential cross section can be parametrized as d sigma/d Omega = a + b cos(2) theta*, where theta* is the production angle of the pion in the center-of-mass coordinate system, and the results for the parameters are a = (1.55 +/- 0.46(stat)(-0.8)(+0.32)(syst)) pb/sr and b = (13.1 +/- 2.1(stat)(-2.7)(+1.0)(syst)) pb/sr. The data are compatible with vanishing p-waves and a sizable d-wave contribution. This finding should strongly constrain the contribution of the A isobar to the dd -> He-4 pi(0) reaction and is, therefore, crucial for a quantitative understanding of quark mass effects in nuclear production reactions. (C) 2018 The Author(s). Published by Elsevier B.V.
Spin dependence of eta meson production in proton-proton collisions close to threshold
P. Adlarson, ...,E. Czerwiński, O. Khreptak, W. Krzemień, P. Moskal, O. Rundel, M. Skurzok, M. Zieliński et al. (WASA-at-COSY Collaboration)
abstract
Taking advantage of the high acceptance and axial symmetry of the WASA-at-COSY detector, and
the high degree of the polarized proton beam of COSY, the reaction ~pp->pp eta has been measured
close to threshold to explore the analyzing power Ay. The angular distribution of Ay is determined
with the precision improved by more than one order of magnitude with respect to previous results
allowing a first accurate comparison with theoretical predictions. The determined analyzing power
is consistent with zero for an excess energy of Q=15 MeV signaling s wave production with no
evidence for higher partial waves. At Q=72 MeV the data reveals strong interference of Ps and
Pp partial waves and cancellation of (Pp) and Ss?Sd contributions. These results rule out the
presently available theoretical predictions for the production mechanism of the eta meson.
Spin Dependence of eta Meson Production in Proton-Proton Collisions Close to Threshold
P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, SD. Bass, FS. Bergmann, M. Berlowski, A. Bondar, M. Buscher, H. Calen, I. Ciepal, H. Clement, E. Czerwinski, K. Demmich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Fohl, K. Fransson, F. Goldenbaum, A. Goswami, K. Grigoryev, CO. Gullstrom, L. Heijkenskjold, V. Hejny, N. Husken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, G. Khatri, A. Khoukaz, O. Khreptak, DA. Kirillov, S. Kistryn, H. Kleines, B. Klos, W. Krzemien, P. Kulessa, A. Kupsc, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Marianski, HP. Morsch, P. Moskal, H. Ohm, W. Parol, EP. del Rio, NM. Piskunov, D. Prasuhn, D. Pszczel, K. Pysz, A. Pyszniak, J. Ritman, A. Roy, Z. Rudy, O. Rundel, S. Sawant, S. Schadmand, I. Schatti-Ozerianska, T. Sefzick, et al.
abstract
Taking advantage of the high acceptance and axial symmetry of the WASA-at-COSY detector, and the high polarization degree of the proton beam of COSY, the reaction (p) over right arrowp -> pp eta has been measured close to threshold to explore the analyzing power A(y). The angular distribution of A(y) is determined with the precision improved by more than 1 order of magnitude with respect to previous results, allowing a first accurate comparison with theoretical predictions. The determined analyzing power is consistent with zero for an excess energy of Q = 15 MeV, signaling s-wave production with no evidence for higher partial waves. At Q = 72 MeV the data reveal strong interference of Ps and Pp partial waves and cancellation of (Pp)(2) and Ss*Sd contributions. These results rule out the presently available theoretical predictions for the production mechanism of the eta meson.
Isoscalar single-pion production in the region of Roper and d*(2380) resonances
P. Adlarsona, W. Augustyniak, W. Bardan, M. Bashkanov, FS. Bergmann, M. Berlowski, H. Bhatt, A. Bondar, M. Buscher, H. Calen, I. Ciepal, H. Clement, E. Czerwinski, K. Demmich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Fohl, K. Fransson, F. Goldenbaum, A. Goswami, K. Grigoryev, CO. Gullstrom, L. Heijkenskjold, V. Hejny, N. Husken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, G. Khatri, A. Khoukaz, O. Khreptak, DA. Kirillov, S. Kistryn, H. Kleines, B. Klos, W. Krzemien, P. Kulessa, A. Kupsc, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Marianski, HP. Morsch, P. Moskal, H. Ohm, W. Parol, EP. del Rio, NM. Piskunov, D. Prasuhn, D. Pszczel, K. Pysz, A. Pyszniak, J. Ritman, A. Roy, Z. Rudy, O. Rundel, S. Sawant, S. Schadmand, I. Schatti-Ozerianska, T. Sefzick, et al.
abstract
Exclusive measurements of the quasi-free pn -> pp pi(-) and pp -> pp pi(0) reactions 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 T-p= 0.95-1.3 GeV (root s = 2.3-2.46 GeV), which includes the regions of triangle(1232), N*(1440) and d*(2380) resonance excitations. From these measurements the isoscalar single-pion production has been extracted, for which data existed so far only below T-p = 1 GeV. We observe a substantial increase of this cross section around 1 GeV, which can be related to the Roper resonance N*(1440), the strength of which shows up isolated from the triangle resonance in the isoscalar (N pi)(I=0) invariant-mass spectrum. No evidence for a decay of the dibaryon resonance d*(2380) into the isoscalar (NN pi)(I=0) channel is found. An upper limit of 180 mu b (90% CL.) corresponding to a branching ratio of 9% has been deduced. (c) 2017 The Author(s). Published by Elsevier B.V.
Search for the eta-mesic Helium in Proton-Deuteron Reaction
O. Rundel, M. Skurzok, O. Khreptak, P. Moskal
abstract
We briefly report on the search for eta-mesic helium nuclei with WASA-at-COSY detection setup. The description of the experimental method as well as the status of the data analysis of the proton?deuteron reactions are presented.
Measurement of the omega->pi+pi-pi0 Dalitz plot distribution
P. Adlarson, ..., E. Czerwiński, O. Khreptak, W. Krzemień, P. Moskal, O. Rundel, I. Schätti-Ozerianska, M. Skurzok, M.J. Zieliński, et al.
abstract
Using the production reactions pd->3Heomega and pp->pp omega, the Dalitz plot distribution for the omega->pi+pi-pi0 decay is studied with the WASA detector at COSY, based on a combined data sample of (4.408+-0.042)*10^4 events. The Dalitz plot density is parametrised by a product of the P-wave phase space and a polynomial expansion in the normalised polar Dalitz plot variables Z and phi. For the first time, a deviation from pure P-wave phase space is observed with a significance of 4.1 sigma. The deviation is parametrised by a linear term 1+2 alpha Z, with alpha determined to be +0.147+-0.036, consistent with the expectations of rho-meson-type final-state interactions of the P-wave pion pairs.
Measurement of the omega -> pi(+)pi(-)pi(0) Dalitz plot distribution The WASA-at-COSY Collaboration
P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, FS. Bergmann, M. Berlowski, H. Bhatt, A. Bondar, M. Buscher, H. Calen, I. Ciepal, H. Clement, E. Czerwinski, K. Demmich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Fohl, K. Fransson, F. Goldenbaum, A. Goswami, K. Grigoryev, CO. Gullstrom, L. Heijkenskjold, V. Hejny, N. Husken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, FA. Khan, G. Khatri, A. Khoukaz, O. Khreptak, DA. Kirillov, S. Kistryn, H. Kleines, B. Klos, W. Krzemien, P. Kulessa, A. Kupsc, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Marianski, HP. Morsch, P. Moskal, H. Ohm, EP. del Rio, NM. Piskunov, D. Prasuhn, D. Pszczel, K. Pysz, A. Pyszniak, J. Ritman, A. Roy, Z. RudyC, O. Rundel, S. Sawant, S. Schadmand, I. Schatti-Ozerianska, T. Sefzick, et al.
abstract
Using the production reactions pd -> He-3 omega and pp -> pp omega, the Dalitz plot distribution for the omega -> pi(+)pi(-)pi(0)decay is studied with the WASA detector at COSY, based on a combined data sample of (4.408 +/- 0.042) x 10(4) events. The Dalitz plot density is parametrised by a product of the P-wave phase space and a polynomial expansion in the normalised polar Dalitz plot variables Z and phi. For the first time, a deviation from pure P-wave phase space is observed with a significance of 4.1 sigma. The deviation is parametrised by a linear term 1+2 alpha Z, with alpha determined to be +0.147 +/- 0.036, consistent with the expectations of rho-meson-type final-state interactions of the P-wave pion pairs. (C) 2017 The Author. Published by Elsevier B.V.
Search for eta-mesic He-4 in the dd -> (3)Hen pi(0) and dd -> (3)Hep pi(-) reactions with the WASA-at-COSY facility
P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, FS. Bergmann, M. Berlowski, H. Bhatt, A. Bondar, M. Buscher, H. Calen, I. Ciepal, H. Clement, E. Czerwinski, K. Demmich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Fohl, K. Fransson, E. Goldenbaum, A. Goswami, K. Grigoryev, CO. Gullstrom, L. Heijkenskjold, V. Hejny, N. Husken, L. Jarczyk, T. Johansson, B. Kamys, NG. Kelkar, G. Kemmerling, G. Khatri, A. Khoukaz, O. Khreptak, DA. Kirillov, S. Kistryn, H. Kleines, B. Klos, W. Krzemien, P. Kulessa, A. Kupsc, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magierae, R. Maier, P. Marciniewski, B. Marianski, HP. Morsch, P. Moskal, H. Ohm, EP. del Rio, NM. Piskunov, D. Prasuhn, D. Pszczel, K. Pysz, A. Pyszniak, J. Ritman, A. Roy, Z. Rudy, O. Rundel, S. Sawant, S. Schadmand, I. Schatti-Ozerianska, T. Sefzick, et al.
abstract
The search for He-4-eta bound states was performed with the WASA-at-COSY facility via the measurement of the excitation function for the dd -> (3)Hen pi(0) and dd -> (3)Hep pi(-) processes. The deuteron beam momentum was varied continuously between 2.127 GeV/c and 2.422 GeV/c, corresponding to the excess energy for the dd -> He-4 eta reaction ranging from Q = 70 MeV to Q = 30 MeV. The luminosity was determined based on the dd -> (3)Hen reaction and the quasi-free proton proton scattering via dd -> ppn(spectator)n(spectator) reactions. The excitation functions, determined independently for the measured reactions, do not reveal a structure which could be interpreted as a narrow mesic nucleus. Therefore, the upper limits of the total cross sections for the bound state production and decay in dd -> (4He-eta)(bound) -> (3)Hen pi(0) and dd -> (He-4-eta)(bound) -> (3)Hep pi(-) processes were determined taking into account the isospin relation between the both of the considered channels. The results of the analysis depend on the assumptions of the N* (1535) momentum distribution in the anticipated mesic-He-4. Assuming, as in the previous works, that this is identical with the distribution of nucleons bound with 20 MeV in He-4, we determined that (for the mesic bound state width in the range from 5 MeV to 50 MeV) the upper limits at 90% confidence level are about 3 nb and about 6 nb for n pi(0) and p pi(-) channels, respectively. However, based on the recent theoretical findings of the N*(1535) momentum distribution in the N*-He-3 nucleus bound by 3.6 MeV, we find that the WASA-at-COSY detector acceptance decreases and hence the corresponding upper limits are 5 nb and 10 nb for n pi(0) and p pi(-) channels respectively. (C) 2017 Elsevier B.V. All rights reserved.
Search for eta-mesic 4He in the dd->3He n pi0 and dd->3He p pi- reactions with the WASA-at-COSY facility
P. Adlarson, ..., E. Czerwiński, O. Khreptak, W. Krzemień, P. Moskal, O. Rundel, I. Schätti-Ozerianska, M. Skurzok, M.J. Zieliński, et al.
abstract
The search for 4He-eta bound states was performed with the WASA-at-COSY facility via the measurement of the excitation function for the dd->3Henpi0 and dd->3Hepi- processes. The deuteron beam momentum was varied continuously between 2.127 GeV/c and 2.422 GeV/c, corresponding to the excess energy for the dd-> 4He eta reaction ranging from Q = -70 MeV to Q = 30 MeV. The luminosity was determined based on the dd-> 3Hen reaction and the quasi-free proton-proton scattering via dd -> ppn_spectator n_spectator reactions. The excitation functions, determined independently for the measured reactions, do not reveal a structure which could be interpreted as a narrow mesic nucleus. Therefore, the upper limits of the total cross sections for the bound state production and decay in dd->(4He-eta)bound->3Henpi0 and dd->(4He-eta)bound->3Hepi- processes were determined taking into account the isospin relation between the both of the considered channels. The results of the analysis depend on the assumptions of the N*(1535) momentum distribution in the anticipated mesic-4He. Assuming, as in the previous works, that this is identical with the distribution of nucleons bound with 20 MeV in 4He, we determined that (for the mesic bound state width in the range
from 5 MeV to 50 MeV) the upper limits at 90% confidence level are about 3 nb and about 6 nb for npi0 and p pi- channels, respectively. However, based on the recent theoretical findings of the N*(1535) momentum distribution in the N* -3He nucleus bound by 3.6 MeV, we find that the WASA-at-COSY detector acceptance decreases and hence the corresponding upper limits are 5 nb and 10 nb for n pi0 and p pi- channels respectively.
Search for an isospin I=3 dibaryon
P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, FS. Bergmann, M. Berlowski, H. Bhatt, A. Bondar, M. Buscher, H. Calen, I. Ciepal, H. Clement, E. Czerwinski, K. Demmich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Fohl, K. Fransson, F. Goldenbaum, A. Goswami, K. Grigoryev, CO. Gullstrom, L. Heijkenskjold, V. Hejny, N. Husken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, FA. Khan, G. Khatri, A. Khoukaz, O. Khreptak, DA. Kirillov, S. Kistryn, H. Kleines, B. Klos, W. Krzemien, P. Kulessa, A. Kupsc, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Marianski, HP. Morsch, P. Moskal, H. Ohm, EP. del Rio, NM. Piskunov, D. Prasuhnl, D. Pszczel, K. Pysz, A. Pyszniak, J. Ritman, A. Roy, Z. Rudy, O. Rundel, S. Sawant, S. Schadmand, I. Schatti-Ozerianska, T. Sefzick, et al.
abstract
Various theoretical calculations based on QCD or hadronic interactions predict that in addition to the recently observed dibaryon resonance d*(2380) with I(J(P)) = 3(0(+)) there should also exist a dibaryon resonance with mirrored quantum numbers I(J(P)) = 3(0(+)). We report here on a search for such a NN-decoupled state in data on the pp -> pp pi(+) pi(+) pi(-) pi(-) reaction. Since no clear-cut evidence has been found, we give upper limits for the production cross section of such a resonance in the mass range 2280-2500 MeV. (C) 2016 The Author(s). Published by Elsevier B.V.
Search for an Isospin I =3 Dibaryon
P. Adlarson, ..., E. Czerwiński, O. Khreptak, W. Krzemień, P. Moskal, O. Rundel, I. Schätti-Ozerianska, M. Skurzok, M.J. Zieliński, et al.
abstract
Various theoretical calculations based on QCD or hadronic interactions predict that in addition to the recently observed dibaryon resonance d*(2380) with I(JP)=0(3+) there should also exist a dibaryon resonance with mirrored quantum numbers I(JP)=3(0+). We report here on a search for such a NN-decoupled state in data on the pp -> pp pi+ pi+ pi- pi- reaction.
Studies of discrete symmetries in a purely leptonic system using the Jagiellonian Positron Emission Tomograph
P. Moskal, D. Alfs, T. Bednarski, P. Bialas, C. Curceanu, E. Czerwinski, K. Dulski, A. Gajos, B. Glowacz, N. Gupta-Sharma, M. Gorgol, BC. Hiesmayr, B. Jasinska, D. Kaminska, O. Khreptak, G. Korcyl, P. Kowalski, W. Krzemien, N. Krawczyk, E. Kubicz, M. Mohammed, S. Niedzwiecki, M. Pawlik-Niedzwiecka, L. Raczynski, Z. Rudy, M. Silarski, J. Smyrski, A. Wieczorek, W. Wislicki, B. Zgardzinska, M. Zielinski
abstract
Discrete symmetries such as parity (P), charge-conjugation (C) and time reversal (T) are of fundamental importance in physics and cosmology. Breaking of charge conjugation symmetry (C) and its combination with parity (CP) constitute necessary conditions for the existence of the asymmetry between matter and antimatter in the observed Universe. The presently known sources of discrete symmetries violations can account for only a tiny fraction of the excess of matter over antimatter. So far CP and T symmetries violations were observed only for systems involving quarks and they were never reported for the purely leptonic objects. In this article we describe briefly an experimental proposal for the test of discrete symmetries in the decays of positronium atom which is made exclusively of leptons. The experiments are conducted by means of the Jagiellonian Positron Emission Tomograph (J-PET) which is constructed from strips of plastic scintillators enabling registration of photons from the positronium annihilation. J-PET tomograph together with the positronium target system enable to measure expectation values for the discrete symmetries odd operators constructed from (i)spin vector of the ortho-positronium atom, (ii) momentum vectors of photons originating from the decay of positronium, and (iii) linear polarization direction of annihilation photons. Linearly polarized positronium will be produced in the highly porous aerogel or polymer targets, exploiting longitudinally polarized positrons emitted by the sodium Na-22 isotope. Information about the polarization vector of ortho-positronium will be available on the event by event basis and will be reconstructed from the known position of the positron source and the reconstructed position of the ortho-positronium annihilation. In 2016 the first tests and calibration runs are planned, and the data collection with high statistics will commence in the year 2017.
