Measurement of $K^- p$ radiative capture to $\gamma \Lambda$ and $\gamma \Sigma^0$ for $p_{K^-}$ between 514 and 750 MeV/$c$

TL;DR

This study measures the differential cross sections of $K^-$ radiative capture on protons leading to $\gamma\Lambda$ and $\gamma\Sigma^0$ final states at various momenta, providing improved data for hyperon decay analysis.

Contribution

It presents new experimental measurements of $K^-$ radiative capture cross sections and offers an exploratory Regge-plus-resonance theoretical analysis of hyperon resonance contributions.

Findings

$\gamma\Sigma^0$ final state dominated by hyperon resonance exchange.

Evidence of a resonance around 1700 MeV in $\gamma\Sigma^0$ channel.

Resonant contributions in $\gamma\Lambda$ channel suggest a resonance near 1550 MeV.

Abstract

Differential cross sections for $K^-$ radiative capture in flight on the proton, leading to the $\gamma\Lambda$ and $\gamma\Sigma^0$ final states, have been measured at eight $K^-$ momenta between 514 and 750 MeV/$c$. The data were obtained with the Crystal Ball multiphoton spectrometer installed at the separated $K/\pi$ beam line C6 of the BNL Alternating Gradient Synchrotron. The results substantially improve the existing experimental data available for studying radiative decays of excited hyperon states. An exploratory theoretical analysis is performed within the Regge-plus-resonance approach. According to this analysis, the $\gamma\Sigma^0$ final state is dominated by hyperonresonance exchange and hints at an important role for a resonance in the mass region of 1700 MeV. In the $\gamma\Lambda$ final state, on the other hand, the resonant contributions account for only half the strength, and the data suggest the importance of a resonance in the mass region of 1550 MeV.