Baryonic resonances close to the Kbar-N threshold: the case of Lambda(1405) in pp collisions

TL;DR

This paper reports the first measurement of the Lambda(1405) resonance in proton-proton collisions at 3.5 GeV, revealing a peak below 1400 MeV/c^2 and providing new insights into its production and spectral shape.

Contribution

First reconstruction of Lambda(1405) in p+p collisions with detailed spectral and angular analysis at 3.5 GeV.

Findings

Peak position below 1400 MeV/c^2 in spectral shape

Total production cross section of 9.2 μb

Isotropic production in p-p center of mass

Abstract

We present an analysis of the Lambda(1405) resonance produced in the reaction p+p->Sigma^{pm}+pi^{mp}+K+p at 3.5 GeV kinetic beam energy measured with HADES at GSI. The two charged decay channels Lambda(1405) -> Sigma^{\pm}+pi^{\mp} have been reconstructed for the first time in p+p collisions. The efficiency and acceptance-corrected spectral shapes show a peak position clearly below 1400 MeV/c^2. We find a total production cross section of sigma_{Lambda(1405)}=9.2 +- 0.9 +- 0.7 +3.3-1.0 mub. The analysis of its polar angle distribution suggests that the Lambda(1405) is produced isotropically in the p-p center of mass system.