Antikaon-induced $K_1(1270)^+$ meson production on nuclei near threshold

TL;DR

This paper investigates the near-threshold production of the $K_1(1270)^+$ meson in antikaon-nucleus reactions, analyzing how in-medium mass shifts affect production cross sections, with implications for experimental measurements at J-PARC.

Contribution

It introduces a nuclear spectral function approach to study $K_1(1270)^+$ production and explores the sensitivity of cross sections to in-medium mass shifts near threshold.

Findings

Cross sections are sensitive to in-medium $K_1(1270)^+$ mass shifts.

Production cross sections are significant at momenta 2.8--3.5 GeV/c.

Potential for experimental evaluation of meson mass shifts at J-PARC.

Abstract

We study the inclusive strange axial-vector meson $K_1(1270)^+$ production in ${K^-}A$ reactions at near-threshold laboratory incident antikaon momenta within a nuclear spectral function approach, which describes incoherent direct $K_1(1270)^+$ meson production in $K^-$ meson--proton ${K^-}p \to {K_1(1270)^+}\Xi^-$ production processes and accounts for three different options for its in-medium mass shift (or for its effective scalar potential) at central density $\rho_0$. We calculate the absolute differential and total cross sections for the production of $K_1(1270)^+$ mesons on $^{12}$C and $^{184}$W target nuclei at laboratory angles of 0$^{\circ}$--45$^{\circ}$ by $K^-$ mesons with momenta of 2.5, 2.8 and 3.5 GeV/c, which are close to the threshold momentum ($\approx$ 2.95 GeV/c) for $K_1(1270)^+$ meson production off the free target proton at rest. The intrinsic properties of carbon and tungsten target nuclei have been described in terms of their spectral functions, which take into account the momenta of target protons and the energies of their separation from the considered nuclei. We show that the differential and total (absolute and relative) $K_1(1270)^+$ antikaon-induced production cross sections at initial momenta not far from threshold -- at momenta $\sim$ 2.8--3.5 GeV/c, at which there is yet no strong drop in their strength, reveal a distinct sensitivity to changes in the in-medium shift of the $K_1(1270)^+$ mass, studied in the paper, both in the $K_1(1270)^+$ meson low-momentum (0.1--1.0 GeV/c) and in its full-momentum ranges. This would permit evaluating this shift. Experimental data necessary for this aim can be obtained in a dedicated experiment at the J-PARC Hadron Experimental Facility.