Photoproduction of $K^+\Lambda(1405) \rightarrow K^+\pi^0\Sigma^0$ extending to forward angles and low momentum transfer

TL;DR

This study measures $K^+\Lambda(1405)$ photoproduction at the BGOOD experiment, revealing the influence of a triangle singularity and providing detailed angular and energy-dependent data that align with theoretical models.

Contribution

It extends the measurement of $K^+\Lambda(1405)$ photoproduction to forward angles and low momentum transfer, highlighting the role of a triangle singularity and improving data resolution.

Findings

Evidence for a triangle singularity involving $N^*(2030)$

Cross section and line shape measurements over broad angles

Agreement with previous experiments and $ ext{ChPT}$ models

Abstract

$K^+\Lambda(1405)$ photoproduction has been studied at the BGOOD experiment via the all neutral decay, $\Lambda(1405)\rightarrow\Sigma^0\pi^0$. The unique BGOOD experimental setup allows both the cross section and $\Lambda(1405)$ invariant mass distribution (line shape) to be measured over a broad $K^+$ polar angle range, extending to extreme forward $K^+$ angles unattainable at previous experiments. Evidence is provided for the role of a triangle singularity driven by the $N^*(2030)$ resonance, which appears to contribute significantly to $K^+\Lambda(1405)$ photoproduction. This is observed in both the angular distributions and the integrated cross section which was determined with unprecedented energy resolution. The measured line shape is also in agreement with the previous results of CLAS and ANKE, and is consistent with two poles derived in $\chi$PT based models.