Near-threshold photoproduction of $\Lambda(1520)$ from protons and deuterons

TL;DR

This study measures the differential cross sections of $\Lambda(1520)$ photoproduction from protons and deuterons at energies below 2.4 GeV, revealing asymmetries and the significance of contact terms in the production mechanism.

Contribution

First measurement of differential cross sections at low energies and from deuterium targets, highlighting the role of contact terms in $\Lambda(1520)$ photoproduction.

Findings

Large asymmetry between proton and neutron production cross sections.

Contact term plays a significant role in the production mechanism.

Compatibility of data with gauge-invariant models involving contact terms.

Abstract

Photoproduction of $\Lambda$(1520) with liquid hydrogen and deuterium targets was examined at photon energies below 2.4 GeV in the SPring-8 LEPS experiment. For the first time, the differential cross sections were measured at low energies and with a deuterium target. A large asymmetry of the production cross sections from protons and neutrons was observed at backward K$^{+/0}$ angles. This suggests the importance of the contact term, which coexists with t-channel K exchange under gauge invariance. This interpretation was compatible with the differential cross sections, decay asymmetry, and photon beam asymmetry measured in the production from protons at forward K$^+$ angles.