Transverse momentum dependence of semi-inclusive pion production

Abstract

Cross sections for semi-inclusive electroproduction of charged pions ($\ddot{I}{€}^{\pm }$) 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 $\ddot{I}{€}^{+}$ and $\ddot{I}{€}^{-}$, 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.

15 pages, 4 figures. Fit form changed to include Cahn effect Minor revisions. Added one new figure