SEMINARIO DE FISICA TEORICA I Y II

Titulo:         K^- absorption in nuclei 
Conferenciante: V. Magas (Universitat de Barcelona-ECM)
Dia y hora:     10, 14:30 (Aula 5A)

Resumen:

The process of two and three nucleon $K^-$ absorption in nuclei will be
discussed in connection with recent FINUDA experiments [1,2], which claim the
existence of deeply bound kaonic states from the observation of some peaks in
the ($Lambda p$) [1] and ($Lambda d$) [2] invariant mass distribution,
following the absorption of stopped $K^-$ in different nuclei.

It will be shown that the observed peaks are naturally explained in terms of
$K^-$ absorption by two [1,3] or three [2,4] nucleons leaving the rest of the
original nuclei as spectator. For the reactions on heavy nuclei the subsequent
interactions of the particles produced in the primary absorption process
($Lambda$, $p$, $d$ etc.) with the residual nucleus are very important. In such
a modeling the positions and widths of the peaks, interpreted by the FINUDA
collaboration as deeply bound kaonic states, do not depend on the exact strength
of the $K^- N$ interaction and are completely determined by the kinematics of
the studied process.


Since our modeling can reproduce all the observables measured in the experiments
[1,2] and used to support the hypothesis of the deeply bound kaon state, we
conclude that at present there is no experimental evidence of deeply bound K-
state in nuclei.

Although the FINUDA experiments [1,2] have been done for reasons which are not
supported a posteriori, some new physics can be extracted from the data. Our
analysis reveals interesting aspects of kaon absorption in nuclei, a process
that must be understood in order to make progress in the search for possible
$K^-$ deeply bound states in nuclei.