Measurement of differential cross sections for $\Sigma^+p$ elastic scattering in the momentum range 0.44-0.80 GeV/c

TL;DR

This study measured differential cross sections for $oldsymbol{ ext{Sigma}^+ p}$ elastic scattering in a specific momentum range, providing new phase shift data and challenging some theoretical model predictions with higher-precision experimental results.

Contribution

It presents the first experimental derivation of phase shifts for the $ ext{Sigma}^+ p$ system, with improved precision and new insights into the interaction channels.

Findings

Differential cross sections are around 2 mb/sr or less, lower than some model predictions.

Phase shifts for the $^3 S_1$ channel are between 20° and 35°, indicating moderate repulsion.

Experimental data challenge existing short-range interaction models.

Abstract

We performed a novel $\Sigma^+ p$ scattering experiment at the J-PARC Hadron Experimental Facility. Approximately 2400 $\Sigma^+ p$ elastic scattering events were identified from $4.9 \times 10^7$ tagged $\Sigma^+$ particles in the $\Sigma^+$ momentum range 0.44 -- 0.80 GeV/$c$. The differential cross sections of the $\Sigma^+ p$ elastic scattering were derived with much better precision than in previous experiments. The obtained differential cross sections were approximately 2 mb/sr or less, which were not as large as those predicted by the fss2 and FSS models based on the quark cluster model in the short-range region. By performing phase-shift analyses for the obtained differential cross sections, we experimentally derived the phase shifts of the $^3 S_1$ and $^1 P_1$ channels for the first time. The phase shift of the $^3 S_1$ channel, where a large repulsive core was predicted owing to the Pauli effect between quarks, was evaluated as $20^\circ<|\delta_{^3S_1}|<35^\circ$. If the sign of $\delta_{^3S_1}$ is assumed to be negative, the interaction in this channel is moderately repulsive, as the Nijmegen extended-sort-core models predicted.