Study of $\Sigma^+\pi^-$ Invariant Mass spectrum with the KLOE detector; preliminary results and possible hints for $\Sigma^+n$ internal conversion

TL;DR

The paper presents preliminary analysis of KLOE data revealing invariant mass spectra of Lambda(1405) and hints of Sigma+pi- decay and Sigma-Lambda internal conversion, advancing low-energy kaon-nuclei interaction studies.

Contribution

First-time extraction of Lambda(1405) invariant mass spectra across all decay channels using KLOE data, and preliminary insights into Sigma+pi- decay and internal conversion effects.

Findings

Invariant mass spectra of Lambda(1405) obtained for all decay channels

Preliminary results on Sigma+pi- decay channel

Initial evidence of Sigma->Lambda internal conversion

Abstract

The AMADEUS collaboration has the goal to perform unprecedented measurements in the field of the low-energy charged kaons-nuclei interactions, by implementing the existing KLOE detector with a dedicated setup in the inner region. As a preliminary step towards the realization, the AMADEUS team has analyzed the existent 2002-2005 KLOE data, studying the processes resulting from the negative kaons nuclear absorption in the entrance wall of the KLOE Drift Chamber (containing mostly carbon) and in the gas filling it, mostly helium. Processes containing Lambda-p and Lambda-d in the final state were looked for, together with the search for the Lambda(1405) going in both the neutral and the charged Sigma-pi channels. These analyses produced unique results, proving the possibility to obtain, for the first time, invariant mass spectra of the Lambda(1405) for all the possible decay channels. This was possible thanks to the unique features of the KLOE detector, including the excellent photon detection of its calorimeter. In addition to these results, other interesting effects like the Sigma->Lambda internal conversion could be investigated. Preliminary results on the Sigma+pi- decay channel and on the Sigma->Lambda internal conversion will be presented.