Quark fragmentation to $\pi^{\pm}$, $\pi^{0}$, $K^{\pm}$, $p$ and $\bar{p}$ in the nuclear environment

TL;DR

This study investigates how the nuclear environment affects the production and transverse momentum distribution of various identified hadrons in semi-inclusive deep-inelastic scattering, revealing medium-induced modifications and broadening effects.

Contribution

First measurement of hadron multiplicity ratios in krypton versus deuterium for multiple hadron types in lepto-production, highlighting nuclear medium effects on hadronization.

Findings

Multiplicity ratios are suppressed at low energy transfer and high energy fraction.

Transverse momentum distributions are broadened in the nuclear medium.

Differences among hadron types indicate varying nuclear medium interactions.

Abstract

The influence of the nuclear medium on lepto-production of hadrons was studied in the HERMES experiment at DESY in semi-inclusive deep-inelastic scattering of 27.6 GeV positrons off deuterium, nitrogen and krypton targets. The differential multiplicity for krypton relative to that of deuterium has been measured for the first time for various identified hadrons ($\pi^+$, $\pi^-$, $\pi^0$, $K^+$, $K^-$, $p$ and $\bar{p}$) as a function of the virtual photon energy $\nu$, the fraction $z$ of this energy transferred to the hadron, and the hadron transverse momentum squared $p_t^2$. The multiplicity ratio is strongly reduced in the nuclear medium at low $\nu$ and high $z$, with significant differences among the various hadrons. The distribution of the hadron transverse momentum is broadened towards high $p_t^2$ in the nuclear medium, in a manner resembling the Cronin effect previously observed in collisions of heavy ions and protons with nuclei.