**Search for Deeply Bound Kaonic Nuclear States with AMADEUS**

*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 Sigma0p channel following K- absorption on 12C and outline future perspectives for this work.

**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.

**Investigating the low-energy K- interactions in nuclear matter with AMADEUS**

*R. Del Grande, ...., P. Moskal, et al. (AMADEUS Collaboration)*

abstract

The AMADEUS collaboration studies low-energy K- interactions with light nuclei in order to clarify some aspects related to the behaviour of hadrons containing strangeness in nuclear medium. One of the main topics is the quest about the possible formation of Kaonic Nuclear Clusters (KNC), which depends on the strength of the anti-kaons interaction with nucleons. In kaonic absorption experiments, the search for KNC is strictly connected with the measurement of the yields of the so-called multi-nucleon absorption processes. In this paper, the study of Sigma0p correlated production from K? absorption in 12C, using the KLOE 2004-2005 data set, is reported. The yield of the two nucleon absorption (2NA), when the produced Sigma0 and p particles are free from any final state interaction process, was measured for the first time. The contribution of a ppK- bound state was also tested. The best fit is obtained for a ppK? state with a binding energy of 45 MeV and a width of 30 MeV, but the statistical significance is at the level of 1? only.

**K- multi-nucleon absorption processes in hadronic interaction studies**

*R. Del Grande, ..., E. Czerwinski, ..., W. Krzemien, ..., P. Moskal, ..., M. Silarski, et al. (AMADEUS Collaboration)*

abstract

The AMADEUS collaboration aims to afford unprecedented informations on the K- low-energy
interactions with light nuclei, thanks to the unique monochromatic low-momentum kaons pro-
vided by the DAFNE collider and the excellent acceptance and resolution of the KLOE detector,
used as an active target. We will report on the measurement of the yield of the K ? two nucleon
absorption process, obtained by studying Sigma0 p pairs produced in the final state of the K-12C ab-
sorptions. Further, the possible contribution of a ppK- bound state was investigated. The best fit
corresponding to a gives space to a yield of ppK-/K- stop = (0.044 ? 0.009 stat +0.004 ?0.005 syst) ×10 binding energy and a width of 45 and 30 MeV/c 2 , respectively. A statistical analysis of this result shows although that its significance is only at the level of 1sigma.