Single spin asymmetry through QCD instantons

Abstract

We revisit the effects of QCD instantons in semi-inclusive deep inelastic scattering. We show that large single spin asymmetry (SSA) effects can be induced in longitudinally and transversely polarized proton targets. The results are in agreement with most of the reported data for pion and kaon production. The same effects are found to be important in polarized proton on proton scattering for both charged and chargeless pion productions. The results agree with the reported data in a wide range of $\sqrt{s}=19.4--200\text{ }\text{ }\mathrm{GeV}$. We predict the SSA for ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ production in ${p}_{\ensuremath{\uparrow}}p$ in the collider range of $\sqrt{s}=62.4--500\text{ }\text{ }\mathrm{GeV}$. The backward ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ and ${\ensuremath{\pi}}^{0}$ productions for the SSA in ${p}_{\ensuremath{\uparrow}}p$ collisions are predicted to coincide at large $\sqrt{s}$.