Single spin asymmetries in $p\uparrow p \rightarrow \pi X$ and $\bar{p} \uparrow p \rightarrow \pi X$

Abstract.

We study the inclusive production of charged and neutral pions in the reactions $p \uparrow p \rightarrow \pi X$ and $\bar{p} \uparrow p \rightarrow \pi X$ in the framework of single spin asymmetries. We propose a two components model where production of pions occurs both by recombination of the constituents present in the initial state and by fragmentation of quarks in the final state. Taking the Thomas precession mechanism in the recombination component into account, we obtain a good description of the experimentally observed single spin asymmetries. We show that the observed single spin asymmetries are consistent with the measured spin alignment in the polarized proton as measured by HERMES and SMC.