Single Spin Asymmetries in High Energy Reactions and Nonperturbative QCD Effects

Abstract

We discuss some experimental and theoretical results on single spin asymmetries (SSA) in high energy lepton-hadron and hadron-hadron reactions. In particular, recent results on meson SSA obtained by HERMES are considered in detail. We also discuss the SSA results obtained recently by COMPASS, as well as those from BRAHMS, PHENIX and STAR. Special attention is paid to a possible nonperturbative QCD mechanism that might be responsible for the observed meson SSA. This mechanism originates from the spin-flip quark-gluon chromomagnetic interaction induced by the complex topological structure of the QCD vacuum. We argue that in semi-inclusive deep-inelastic scattering a large SSA is expected not only for mesons but also for baryons due to strong nonperturbative final state interactions between $ud$-diquark and $u$-quark in the fragmenting proton.

9 pages,8 figures

References in corpus (10)

• Sivers Effect for Pion and Kaon Production in Semi-Inclusive Deep Inelastic Scattering
• Collins and Sivers asymmetries for pions and kaons in muon-deuteron DIS
• Azimuthal and Single Spin Asymmetries in Hard Scattering Processes
• Forward Neutral Pion Transverse Single Spin Asymmetries in p+p Collisions at \sqrt{s}=200 GeV
• A quark model analysis of the Sivers function
• Single Transverse-Spin Asymmetry in Very Forward and Very Backward Neutral Particle Production for Polarized Proton Collisions at sqrt{s} = 200 GeV
• Instanton contribution to the Sivers function
• Single Spin Asymmetries on a transversely polarised proton target at COMPASS
• Leading neutrons from polarized pp collisions
• Transversity and Transverse-Momentum-Dependent Distribution Measurements from PHENIX and BRAHMS

Cited by in corpus (7)

• Anomalous Quark Chromomagnetic Moment and Single-Spin Asymmetries
• Single Spin Asymmetry through QCD Instantons
• Spin Physics through QCD Instantons
• Double Spin Asymmetries through QCD Instantons
• Cross-sections and Single Spin Asymmetries of Identified Hadrons in $p^{\uparrow }+p$ at $\sqrt{s}$ = 200 GeV
• P-Odd Pion Azimuthal Charge Correlations in Heavy Ion Collisions
• Spin-Directed Momentum Transfers in SIDIS Baryon Production