Near-threshold $K^*(892)^+$ meson production in the interaction of $\pi^-$ mesons with nuclei

TL;DR

This study investigates how the in-medium mass shift of the $K^*(892)^+$ meson affects its production in pion-nucleus collisions near threshold, proposing experimental measurements to determine its in-medium properties.

Contribution

It introduces a nuclear spectral function approach to analyze $K^*(892)^+$ production and demonstrates high sensitivity of observables to the meson's in-medium mass shift.

Findings

$K^*(892)^+$ momentum distributions are sensitive to in-medium mass shifts.

Differential and total cross sections vary significantly with the $K^*(892)^+$ in-medium mass.

Measurement of these observables can reveal the $K^*(892)^+$ in-medium properties.

Abstract

We study the inclusive strange vector meson $K^*(892)^+$ production in ${\pi^-}A$ reactions at near-threshold laboratory incident pion momenta of 1.4--2.0 GeV/c within a nuclear spectral function approach. The approach accounts for incoherent primary $\pi^-$ meson--proton ${\pi^-}p \to {K^*(892)^+}\Sigma^-$ production processes as well as the influence of the scalar $K^*(892)^+$--nucleus potential (or the $K^*(892)^+$ in-medium mass shift) on these processes. We calculate the absolute differential and total cross sections for the production of $K^*(892)^+$ mesons off carbon and tungsten nuclei at laboratory angles of 0$^{\circ}$--45$^{\circ}$ and at these momenta within five scenarios for the above shift. We show that the $K^*(892)^+$ momentum distributions and their excitation functions (absolute and relative) possess a high sensitivity to changes in the in-medium $K^*(892)^+$ mass shift in the low-momentum region of 0.1--0.6 GeV/c. Therefore, the measurement of such observables in a dedicated experiment at the GSI pion beam facility in the near-threshold momentum domain will allow to get valuable information on the $K^*(892)^+$ in-medium properties.