Measurement of the reaction $\gamma p \TO K^ + \Lambda(1520)$ at photon energies up to 2.65 GeV

TL;DR

This paper reports on measurements of the $ ext{γ} p o K^+ ext{Λ}(1520)$ reaction at photon energies up to 2.65 GeV, analyzing cross sections, angular distributions, and decay modes to understand the production mechanism and resonance behavior.

Contribution

First detailed measurement of the $ ext{γ} p o K^+ ext{Λ}(1520)$ reaction across a wide energy range, providing new insights into its production dynamics and decay channels.

Findings

Cross section peaks at ~2.0 GeV photon energy.

Cross section decreases exponentially with momentum transfer $t$.

Angular distributions do not favor $K$ or $K^*$ exchange dominance.

Abstract

The reaction $\gamma p \TO K^+\Lambda(1520)$ was measured in the energy range from threshold to 2.65 GeV with the SAPHIR detector at the electron stretcher facility ELSA in Bonn. The $\Lambda(1520)$ production cross section was analyzed in the decay modes $pK^-$, $n \bar{K}^0$, $\Sigma^{\pm}\pi^{\mp}$, and $\Lambda\pi^+\pi^-$ as a function of the photon energy and the squared four-momentum transfer $t$. While the cross sections for the inclusive reactions rise steadily with energy, the cross section of the process $\gamma p \TO K^+\Lambda(1520)$ peaks at a photon energy of about 2.0 GeV, falls off exponentially with $t$, and shows a slope flattening with increasing photon energy. The angular distributions in the $t$-channel helicity system indicate neither a $K$ nor a $K^\star$ exchange dominance. The interpretation of the $\Lambda(1520)$ as a $\Sigma(1385)\pi$ molecule is not supported.