Final-State Interactions and Single-Spin Asymmetries in Semi-inclusive Deep Inelastic Scattering
Recent measurements from the HERMES and SMC collaborations show a remarkably large azimuthal single-spin asymmetries A{sub UL} and A{sub UT} of the proton in semi-inclusive pion leptoproduction {gamma}*(q)p {yields} {pi}X. We show that final-state interactions from gluon exchange between the outgoing quark and the target spectator system leads to single-spin asymmetries in deep inelastic lepton-proton scattering at leading twist in perturbative QCD; i.e., the rescattering corrections are not power-law suppressed at large photon virtuality q{sup 2} at fixed x{sub bj}. The existence of such single-spin asymmetries requires a phase difference between two amplitudes coupling the proton target with J{sup z}{sub p} = {+-}1/2 to the same final-state, the same amplitudes which are necessary to produce a nonzero proton anomalous magnetic moment. We show that the exchange of gauge particles between the outgoing quark and the proton spectators produces a Coulomb-like complex phase which depends on the angular momentum L{sup z} of the proton's constituents and thus is distinct for different proton spin amplitudes. The single-spin asymmetry which arises from such final-state interactions does not factorize into a product of structure function and fragmentation function, and it is not related to the transversity distribution {delta}q(x;Q) which correlates transversely polarized quarks with the spin of the transversely polarized target nucleon.
- Research Organization:
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC02-76SF00515
- OSTI ID:
- 919783
- Report Number(s):
- SLAC-PUB-13002; TRN: US0806486
- Journal Information:
- Int.J.Mod.Phys.A18:1327-1334,2003, Conference: Prepared for 3rd Circum-Pan-Pacific Symposium on High Energy Spin Physics (SPIN 2001), Beijing, China, 8-13 Oct 2001
- Country of Publication:
- United States
- Language:
- English
Similar Records
Novel Spin Effects in QCD
Final-state interaction as origin of single-spin asymmetry in semi-inclusive DIS