Effects of transversity in deep-inelastic scattering by polarized protons

В А Коротков ,S Joosten,P Kravchenko,В А Гапиенко ,J Bowles,A Nass,H.P Blok,L Lapikás,P Lenisa,N Bianchi,Y Van Haarlem,Z Ye,A Fantoni,D Hasch,F Garibaldi,W Deconinck,E C Aschenauer ,M Murray,D Gabbert,F Sanftl,A Borissov,S Belostotski,B Mariański ,P Dalpiaz ,L De Nardo,A Kisselev,M Hartig,F Giordano,S Taroian,P B Van Der Nat ,J Stewart,Alessandro Bacchetta ,G P Capitani ,P Żuprański ,Y Salomatin,C A Miller ,W.-D Nowak,M Diefenthaler,M Capiluppi,S Frullani,V Bryzgalov,D Veretennikov,H Ye,T Keri,M Golembiovskaya,N Makins ,S Gliske,P Di Nezza,M Statera,Klaus Rith ,A Ivanilov,W Yu,D Ryckbosch,B Seitz,I Lehmann,E Steffens,A Movsisyan,I Vilardi,E Nappi,V Kozlov,H Stenzel,B Zihlmann,M Hoek,S I Manaenkov ,R Kaiser,M Tytgat,M Düren,L Lagamba,U Elschenbroich,Z Akopov,F Ellinghaus,A Rostomyan,J Burns,J Rubin,L L Pappalardo ,G Ciullo,C Van Hulse,S Yen,G Elbakian,A Airapetian,S Yaschenko,A Mussgiller,G Gapienko,E Avetisyan,H E Jackson ,A Trzciński ,L A Linden-Levy ,W Augustyniak,R Avakian,P E Reimer ,D Mahon,V Shutov,M Stancari,A Terkulov,G Schnell,R Pérez-Benito ,F Stinzing,A Avetissian,M Ehrenfried,V Vikhrov,X R Lu ,I V Brodsky ,D Zeiler,E Cisbani,Andreas Schäfer ,J J M Steijger ,S Wang,Р Де Лео ,C Riedl,N Kobayashi,G Karyan,Y Imazu,X.-G Lu,A Hillenbrand,V Gharibyan,H S Jo ,A Ruiz ,Y Holler,G Hill,C Hadjidakis,R Fabbri,M Contalbrigo,Н Акопов ,A R Reolon ,M Negodaev,Y Naryshkin,L Manfré,Martin Raithel ,H Marukyan,Bo-Qiang Ma ,A Martínez De La Ossa,I Hristova,R Lamb,E Kinney,T A Shibata ,W Lorenzon,N Pickert,Y Mao,Christian Vogel ,E De Sanctis,Y Miyachi,L Felawka,G Rosner

doi:10.1016/j.physletb.2010.08.012

Abstract

Single-spin asymmetries for pions and charged kaons are measured in semi-inclusive deep-inelastic scattering of positrons and electrons off a transversely nuclear-polarized hydrogen target. The dependence of the cross section on the azimuthal angles of the target polarization (ϕS) and the produced hadron (ϕ) is found to have a substantial sin(ϕ+ϕS) modulation for the production of π+, π− and K+. This Fourier component can be interpreted in terms of non-zero transversity distribution functions and non-zero favored and disfavored Collins fragmentation functions with opposite sign. For π0 and K− production the amplitude of this Fourier component is consistent with zero.

Highlights

Single-spin asymmetries for pions and charged kaons are measured in semi-inclusive deep-inelastic scattering of positrons and electrons off a transversely nuclear-polarized hydrogen target
Z in the targetrest frame denotes the fraction of the virtual photon energy carried by the produced hadron h, pT denotes the transverse momentum of the quark with respect to the parent nucleon direction, and kT denotes the transverse momentum of the fragmenting quark with respect to the direction of the produced hadron. This structure function manifests itself as a sin(φ+ φS) modulation in the semi-inclusive deep-inelastic scattering (DIS) cross section with a transversely polarized target
Non-zero Collins amplitudes were previously published for charged pions from a hydrogen target [17], based on a small subset of the data reported here, consisting of about 8.76 million DIS events

Summary

Introduction

Single-spin asymmetries for pions and charged kaons are measured in semi-inclusive deep-inelastic scattering of positrons and electrons off a transversely nuclear-polarized hydrogen target. This structure function manifests itself as a sin(φ+ φS) modulation in the semi-inclusive DIS cross section with a transversely polarized target.

Results

Conclusion