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

¹ The Catholic University of America, Washington, D.C. 20064, USA
² Carnegie Mellon University, Pittsburgh, PA 15213, USA

^* e-mail: wickramaarachchi@cua.edu

Published online: 9 November 2022

Abstract

Among the light baryons, the J^π = 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/dM_Σ⁰π⁰ and fits to the line shape of the Λ(1405) region in the −(t − t_min) range 0 - 1.5 GeV² from analyzing the reaction γp → K⁺Λ^* using the data collected during the first phase of the GlueX program.