Transverse momentum dependence of semi-inclusive pion production

TL;DR

This study measures the transverse momentum dependence of semi-inclusive pion production in electron scattering, revealing differences between proton and deuteron targets and providing insights into quark transverse momentum distributions and fragmentation functions.

Contribution

It presents new measurements of semi-inclusive pion production cross sections across various kinematic ranges, highlighting differences in transverse momentum widths for quarks and fragmentation functions.

Findings

Azimuthal dependence is small at low $P_t$.

Deuteron $P_t$ dependence is slightly weaker than proton.

Transverse momentum width of $d$ quarks is larger than $u$ quarks.

Abstract

Cross sections for semi-inclusive electroproduction of charged pions ($\pi^{\pm}$) from both proton and deuteron targets were measured for $0.2<x<0.5$, $2<Q^2<4$ GeV$^2$, $0.3<z<1$, and $P_t^2<0.2$ GeV$^2$. For $P_t<0.1$ GeV, we find the azimuthal dependence to be small, as expected theoretically. For both $\pi^+$ and $\pi^-$, the $P_t$ dependence from the deuteron is found to be slightly weaker than from the proton. In the context of a simple model, this implies that the initial transverse momenta width of $d$ quarks is larger than for $u$ quarks and, contrary to expectations, the transverse momentum width of the favored fragmentation function is larger than the unfavored one.