**K- multi-nucleon absorption cross sections and branching ratios in Lambda p and Sigma0 p final states**

*R. Del Grande, K. Piscicchia, O. Vazquez Doce, M. Cargnelli, C. Curceanu, L. Fabbietti, J. Marton, P. Moskal, A. Ramos, A. Scordo, D. L. Sirghi, M. Skurzok, S. Wycech, J. Zmeskal, E. Czerwiński, V. De Leo, P. Fermani, G. Mandaglio, M. Martini, N. Raha, A. Selce, M. Silarski*

abstract

The determination of low-energy cross sections and branching ratios of the K- multi-nucleon absorption processes in Lambda p and Sigma0 p final states performed by the AMADEUS collaboration is presented. Low momentum K- (pK? 127 MeV/c) produced at the DAFNE collider are impinged on a Carbon target within the KLOE detector and the two and three nucleon absorption processes are disentangled by comparing the experimental data to phenomenological calculations. The Lambda p spectra are entirely interpreted in terms of K- multi-nucleon absorption processes; the possible contribution of a K-pp bound state is demonstrated to overlap with the two nucleon capture process, its absolute yield thus resulting indistinguishable.

**Feasibility studies of the polarization of photons beyond the optical wavelength regime with the J-PET detector**

*P. Moskal, N. Krawczyk, B. C. Hiesmayr, M. Bała, C. Curceanu, E. Czerwinski, K. Dulski, A. Gajos, M. Gorgol, R. Del Grande, B. Jasinska, K. Kacprzak, L. Kapłon, D. Kisielewska, K. Klimaszewski, G. Korcyl, P. Kowalski, T. Kozik, W. Krzemien, E. Kubicz, M. Mohammed, Sz. Niedźwiecki, M. Pałka, M. Pawlik-Niedźwiecka, L. Raczynski, J. Raj, Z. Rudy, S. Sharma, M. Silarski, Shivani, R. Y. Shopa, M. Skurzok, W. Wislicki, B. Zgardzinska*

abstract

J-PET is a detector optimized for registration of photons from the electron-positron annihilation via plastic scintillators where photons interact predominantly via Compton scattering. Registration of both primary and scattered photons enables to determinate the linear polarization of the primary photon on the event by event basis with a certain probability. Here we present quantitative results on the feasibility of such polarization measurements of photons from the decay of positronium with the J-PET and explore the physical limitations for the resolution of the polarization determination of 511keV photons via Compton scattering. For scattering angles of about 82? (where the best contrast for polarization measurement is theoretically predicted) we find
that the single event resolution for the determination of the polarization is about 40? (predominantly due to properties
of the Compton effect). However, for samples larger than ten thousand events the J-PET is capable of determining relative average polarization of these photons with the precision of about few degrees. The obtained results open new perspectives for studies of various physics phenomena such as quantum entanglement and tests of discrete symmetries in decays of positronium and extend the energy range of polarization measurements by five orders of magnitude beyond the optical wavelength regime.

**First measurement of the K-n->Lambda pi- non-resonant transition amplitude below threshold**

*K. Piscicchia, S. Wycech, L. Fabbietti, M. Cargnelli, C. Curceanu, R. Del Grande, J. Marton, P. Moskal, A. Scordo, M. Silarski, D. Sirghi, M. Skurzok, I. Tucakovic, O. Vazquez Doce, J. Zmeskal, P. Branchini, E. Czerwinski, V. De Leo, E. De Lucia, A. Di Cicco, P. Fermani, S. Fiore, W. Krzemien, G. Mandaglio, M. Martini, E. Perez del Rio , A. Selce*

abstract

We present the analysis of K- absorption processes on 4He leading to Lambda pi- final states, measured with the KLOE e+e- spectrometer at the DAFNE collider and extract, for the first time, the modulus of the non-resonant K-n->Lambda pi- direct production amplitude about 33 MeV below the KbarN threshold. This analysis also allows to disentangle the K- nuclear absorption at-rest from the in-flight capture, for K- momenta of about 120 MeV. The data are interpreted with the help of a phenomenological model, and the modulus of the non-resonant K-n->Lambda pi- amplitude for K- absorption at-rest is found to be |A_K-n->Lambda pi-| = (0.334+-0.018(stat.)+0.034 -0.058 (syst.)) fm.

**Search for Deeply Bound Kaonic Nuclear States in AMADEUS experiment**

*M. Skurzok, M. Cargnelli, C. Curceanu, R. Del Grande, L. Fabbietti, C. Guaraldo, J. Marton, P. Moskal, K. Piscicchia, A. Scordo, M. Silarski, D. L. Sirghi, I. Tucakovic, O. Vazquez Doce, S. Wycech, E. Widmann, J. Zmeskal*

abstract

We briefly report on the search for Deeply Bound Kaonic Nuclear States with AMADEUS in the Sigma0 p channel and future perspectives.

**Low-energy Kaon-Nuclei Interaction Studies at DAFNE: SIDDHARTA-2 and AMADEUS**

*C. Curceanu, A. Amirkhani, M. Bazzi, G. Bellotti, C. Berucci, D. Bosnar, A.M. Bragadireanu, M. Cargnelli, A. Dawood Butt, R. Del Grande, L. Fabbietti, C. Fiorini, F. Ghio, C. Guaraldo, R.S. Hayano, M. Iliescu, M. Iwasaki, P. Levi Sandri, J. Marton, M. Miliucci, P. Moskal, D. Pietreanu, K. Piscicchia, A. Scordo, H. Shi, M. Silarski, D. Sirghi, F. Sirghi, M. Skurzok, H. Tatsuno, O. Vazquez Doce, E. Widmann, J. Zmeskal*

abstract

The DAFNE electron?positron collider of the Laboratori Nazionali di Frascati of INFN has made available a unique quality low-energy negatively charged kaons ?beam?, which is being used to study the kaon?nucleon/nuclei interactions by the SIDDHARTA-2 experiment and the AMADEUS Collaboration. The dynamics of the strong interaction processes in the non-perturbative regime is approached by lattice calculations and effective field theories (ChPT) which are still lacking experimental results in the low-energy regime, fundamental for their good understanding. The studies of kaonic atoms and of the kaonic nuclear processes performed by SIDDHARTA-2 and AMADEUS play in this context a key-role.

** Low-energy Antikaon-Nucleon/Nuclei Interaction Studies by AMADEUS**

*K. Piscicchia, M. Cargnelli, C. Curceanu, R. Del Grande, L. Fabbietti, C. Guaraldo, J. Marton, P. Moskal, A. Scordo, M. Silarski, D. Sirghi, M. Skurzok, I. Tucakovic, O. Vazquez Doce, S. Wycech, E. Widmann, J. Zmeskal*

abstract

The AMADEUS experiment deals with the investigation of the low-energy kaon?nuclei hadronic interaction at the DA?NE collider at LNF-INFN, which is fundamental to solve longstanding questions in the non-perturbative strangeness QCD sector. AMADEUS step 0 consisted in the reanalysis of the 2004/2005 KLOE data, exploiting K- absorptions in H, 4He, 9Be and 12C, leading to the first invariant mass spectroscopy study with very low-momentum (100 MeV) in-flight K? captures. With AMADEUS step 1, a dedicated pure carbon target was implemented in the central region of the KLOE detector, providing a high statistic sample of pure at-rest K? nuclear interaction. The results obtained in the analyses of the hyperon?pion correlated events, searching for the resonant shapes of Y states, will be described.