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تسجيل مستخدم جديدAntikaon Interactions with Nucleons and Nuclei - AMADEUS At Da$Phi$ne
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The aim of AMADEUS is to provide unprecedented experimental information on K$^-$ absorption in light nuclear targets, to face major open problems in hadron nuclear physics in the strangeness sector, namely the nature of the $Lambda$(1405), strongly related to the possible existence of kaonic nuclear clusters, kaons and hyperon scattering cross sections on nucleons and nuclei. These issues are fundamental for a better understanding of the non-perturbative QCD in the strangeness sector. AMADEUS step 0 deals with the analysis of the 2004-2005 KLOE collected data. The interactions of the negative kaons produced by the DA$Phi$NE collider (a unique source of monochromatic low-momentum kaons) with the materials of the KLOE detector, used as active targets, provide samples of K$^-$ absorptions on H, ${}^4$He, ${}^{9}$Be and ${}^{12}$C, both at-rest and in-flight. A second step deals with the data from the implementation in the central region of the KLOE detector of a pure graphite target, providing a high statistic sample of K$^- , {}^{12}$C nuclear captures at rest. For the future a new setup, with various dedicated gaseous and solid targets, is under preparation.
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The low-energy strong interaction of antikaons (K-) with nuclei has many facets and rep- resents a lively and challenging research field. It is interconnected to the peculiar role of strangeness, since the strange quark is rather light, but still muc
h heavier than the up and down quarks. Thus, when strangeness is involved one has to deal with spontaneous and explicit symmetry breaking in QCD. It is well known that the antikaon interaction with nucleons is attractive, but how strong ? Is the interaction strong enough to bind nucleons to form kaonic nuclei and, if so, what are the properties (binding energy, decay width)? There are controversial indications for such bound states and new results are expected to come soon. The existence of antikaon mediated bound states might have important consequences since it would open the possibility for the formation of cold baryonic matter of high density which might have a severe impact in astrophysics for the understanding of the composi- tion of compact (neutron) stars. New experimental opportunities could be provided by the AMADEUS experiment at the DA?NE electron-positron collider at LNF-INFN (Frascati, Italy). Pre-AMADEUS studies on the antikaon interaction with nuclei are carried out by analysis of data collected by KLOE in till 2005 and in special data runs using a carbon target insert. Studies for the dedicated AMADEUS detector setup taking advantage of the low-energy antikaons from Phi-meson decay delivered by DAFNE are in progress. Some re- sults obtained so far and the perspectives of the AMADEUS experiment are presented and discussed.
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The interaction of antikaons with nucleons and nuclei in the low-energy regime represents an active research field in hadron physics with still many important open questions. The investigation of light kaonic atoms, in which one electron is replaced
by a negatively charged kaon, is a unique tool to provide precise information on this interaction; the energy shift and the broadening of the low-lying states of such atoms, induced by the kaon-nucleus hadronic interaction, can be determined with high precision from the atomic X-ray spectroscopy, and this experimental method provides unique information to understand the low energy kaon-nucleus interaction at the production threshold. The lightest atomic systems, like the kaonic hydrogen and the kaonic deuterium deliver, in a model-independent way, the isospin-dependent kaon-nucleon scattering lengths. The most precise kaonic hydrogen measurement to-date, together with an exploratory measurement of kaonic deuterium, were carried out in 2009 by the SIDDHARTA collaboration at the DA{Phi}NE electron-positron collider of LNF-INFN, combining the excellent quality kaon beam delivered by the collider with new experimental techniques, as fast and very precise X-ray detectors, like the Silicon Drift Detectors. The SIDDHARTA results triggered new theoretical work, which achieved major progress in the understanding of the low-energy strong interaction with strangeness reflected by the antikaon-nucleon scattering lengths calculated with the antikaon-proton amplitudes constrained by the SIDDHARTA data. The most important open question is the experimental determination of the hadronic energy shift and width of kaonic deuterium; presently, a major upgrade of the setup, SIDDHARTA-2, is being realized to reach this goal. In this paper, the results obtained in 2009 and the proposed SIDDHARTA-2 upgrades are presented.
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