Initial-state temperature of light meson emission source from squared momentum transfer spectra in high-energy collisions

Abstract

The squared momentum transfer spectra of light mesons, π 0 , π + , η, and ρ 0 , produced in high-energy virtual photon-proton (γ * p) → meson + nucleon process in electron-proton (ep) collisions measured by the CLAS Collaboration are analyzed by the Monte Carlo calculations, where the transfer undergoes from the incident γ * to emitted meson or equivalently from the target proton to emitted nucleon. In the calculations, the Erlang distribution from a multi-source thermal model is used to describe the transverse momentum spectra of emitted particles. Our results show that the average transverse momentum ( pT ) and the initial-state temperature (Ti) increase from lower squared photon virtuality (Q 2 ) and Bjorken variable (xB) to higher one. This renders that the excitation degree of emission source, which is described by pT and Ti, increases with increasing of Q 2 and xB.