Decay of the Λ(1405) hyperon to Σ0π0 measured at GlueX

Abstract

Among the light baryons, the Jπ = 1/2− Λ(1405) hyperon is an important special case as it sits just below the N K̅ threshold and decays almost exclusively to Σπ. Some long-standing hypotheses for Λ(1405) are that it could be a N K̅ bound state or a Σπ continuum resonance. It may also be considered as a simple quark-model resonance, the P-wave companion of the Λ(1520). In recent years chiral unitary models have suggested that there are two isospin zero poles present in this mass region, and that the “line shape" of the Λ(1405) depends to what extent each of the two poles are stimulated in a given reaction. Below the N K̅ threshold, the Λ(1405) decays to the three Σπ charge combinations. The Σ0π0 mode is purely I = 0 and it is uncontaminated by complications arising from I = 1 scattering processes contributing to the reaction mechanism in the Σ+π− and Σ−π+ decays. It is also not affected from production and decay of the nearby Σ0(1385) hyperon. The GlueX experiment at Jefferson Lab has been used to study the Λ(1405) → Σ0π0 decay mode. We focus on the preliminary results of dσ/dMΣ0π0 and fits to the line shape of the Λ(1405) region in the −(t − tmin) range 0 - 1.5 GeV2 from analyzing the reaction γp → K+Λ* using the data collected during the first phase of the GlueX program.