In-medium pion dispersion relation and medium correction of $N\pi\leftrightarrow \Delta$ near the threshold energy of pion production

TL;DR

This paper investigates how the pion dispersion relation and in-medium $N ext{-} ext{pi} o ext{Delta}$ cross sections are affected near the pion production threshold in asymmetric nuclear matter, aiming to improve transport model predictions.

Contribution

It provides a detailed analysis of in-medium pion properties and $N ext{-} ext{pi} o ext{Delta}$ cross sections near threshold using a one-boson-exchange model, considering energy conservation effects.

Findings

In-medium $N ext{-} ext{pi} o ext{Delta}$ cross sections are enhanced below 1.11 GeV.

Pion multiplicity and charge ratio predictions are affected by medium modifications.

Energy conservation significantly influences in-medium pion interactions.

Abstract

Transport models cannot simultaneously explain very recent data on pion multiplicities and pion charged ratios of Sn+Sn in the reaction at 0.27 A GeV. This stimulates further investigations on the pion dispersion relation, in-medium $N\pi\to \Delta$ cross sections and $\Delta \to N \pi$ decay widths near the threshold energy or at subthreshold energy of pion production in isospin asymmetric nuclear matter. In this study, the pion dispersion relation, in-medium $N\pi\to \Delta$ cross section and $\Delta \to N \pi$ decay width near the threshold energy are investigated in isospin asymmetric nuclear matter by using the one-boson-exchange model. With the consideration of the energy conservation effect, the in-medium $N\pi\to\Delta$ cross sections are enhanced at $s^{1/2}<1.11$ GeV in nuclear medium. The prediction of pion multiplicity and $\pi^-/\pi^+$ ratios near the threshold energy can be modified if this effect is considered in transport model simulations.