Effects of transversity in deep-inelastic scattering by polarized   protons

HERMES collaboration; A. Airapetian; N. Akopov; Z. Akopov; E.C.; Aschenauer; W. Augustyniak; R. Avakian; A. Avetissian; E. Avetisyan; A.; Bacchetta; S. Belostotski; N. Bianchi; H.P. Blok; A. Borissov; J. Bowles; I.; Brodski; V. Bryzgalov; J. Burns; M. Capiluppi; G.P. Capitani; E. Cisbani; G.; Ciullo; M. Contalbrigo; P.F. Dalpiaz; W. Deconinck; R. De Leo; L. De Nardo,; E. De Sanctis; M. Diefenthaler; P. Di Nezza; M. Dueren; M. Ehrenfried; G.; Elbakian; F. Ellinghaus; U. Elschenbroich; R. Fabbri; A. Fantoni; L. Felawka,; S. Frullani; D. Gabbert; G. Gapienko; V. Gapienko; F. Garibaldi; V.; Gharibyan; F. Giordano; S. Gliske; M. Golembiovskaya; C. Hadjidakis; M.; Hartig; D. Hasch; G. Hill; A. Hillenbrand; M. Hoek; Y. Holler; I. Hristova,; Y. Imazu; A. Ivanilov; A. Izotov; H.E. Jackson; H.S. Jo; S. Joosten; R.; Kaiser; G. Karyan; T. Keri; E. Kinney; A. Kisselev; N. Kobayashi; V.; Korotkov; V. Kozlov; P. Kravchenko; L. Lagamba; R. Lamb; L. Lapikas; I.; Lehmann; P. Lenisa; L.A. Linden-Levy; A. Lopez Ruiz; W. Lorenzon; X.-G. Lu,; X.-R. Lu; B.-Q. Ma; D. Mahon; N.C.R. Makins; S.I. Manaenkov; L. Manfre; Y.; Mao; B. Marianski; A. Martinez de la Ossa; H. Marukyan; C.A. Miller; Y.; Miyachi; A. Movsisyan; M. Murray; A. Mussgiller; E. Nappi; Y. Naryshkin; A.; Nass; M. Negodaev; W.-D. Nowak; L.L. Pappalardo; R. Perez-Benito; N. Pickert,; M. Raithel; P.E. Reimer; A.R. Reolon; C. Riedl; K. Rith; G. Rosner; A.; Rostomyan; J. Rubin; D. Ryckbosch; Y. Salomatin; F. Sanftl; A. Schaefer; G.; Schnell; B. Seitz; T.-A. Shibata; V. Shutov; M. Stancari; M. Statera; E.; Steffens; J.J.M. Steijger; H. Stenzel; J. Stewart; F. Stinzing; S. Taroian,; A. Terkulov; A. Trzcinski; M. Tytgat; P.B. van der Nat; Y. Van Haarlem; C.; Van Hulse; D. Veretennikov; V. Vikhrov; I. Vilardi; C. Vogel; S. Wang; S.; Yaschenko; H. Ye; Z. Ye; S. Yen; W. Yu; D. Zeiler; B. Zihlmann; P. Zupranski

arXiv:1006.4221·hep-ex·November 21, 2014

Effects of transversity in deep-inelastic scattering by polarized protons

HERMES collaboration, A. Airapetian, N. Akopov, Z. Akopov, E.C., Aschenauer, W. Augustyniak, R. Avakian, A. Avetissian, E. Avetisyan, A., Bacchetta, S. Belostotski, N. Bianchi, H.P. Blok, A. Borissov, J. Bowles, I., Brodski, V. Bryzgalov, J. Burns, M. Capiluppi, G.P. Capitani

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TL;DR

This paper measures single-spin asymmetries in semi-inclusive deep-inelastic scattering, revealing significant sin(phi+phi_S) modulations for pions and kaons, which relate to transversity and Collins fragmentation functions.

Contribution

It provides experimental evidence of transversity distributions and Collins fragmentation functions through azimuthal asymmetries in polarized proton scattering.

Findings

01

Significant sin(phi+phi_S) modulation for pi+ pi- and K+ production.

02

Zero or negligible modulation for pi0 and K- production.

03

Supports the existence of non-zero transversity and Collins functions.

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 (phi_S)and the produced hadron (phi) is found to have a substantial sin(phi+phi_S) modulation for the production of pi+, pi- 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 pi0 and K- production the amplitude of this Fourier component is consistent with zero.

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