Single-spin asymmetries in semi-inclusive deep-inelastic scattering on a transversely polarized hydrogen target

A. Airapetian, N. Akopov, Z. Akopov, M. Amarian, A. Andrus, E. C. Aschenauer, W. Augustyniak, R. Avakian, A. Avetissian, E. Avetissian, A. Bacchetta, P. Bailey, D. Balin, M. Beckmann, S. Belostotski, N. Bianchi, H. P. Blok, H. Böttcher, A. Borissov, A. BorysenkoM. Bouwhuis, A. Brüll, V. Bryzgalov, G. P. Capitani, M. Cappiluppi, T. Chen, G. Ciullo, M. Contalbrigo, P. F. Dalpiaz, R. De Leo, M. Demey, L. De Nardo, E. De Sanctis, E. Devitsin, P. Di Nezza, M. Düren, M. Ehrenfried, A. Elalaoui-Moulay, G. Elbakian, F. Ellinghaus, U. Elschenbroich, R. Fabbri, A. Fantoni, A. Fechtchenko, L. Felawka, S. Frullani, G. Gapienko, V. Gapienko, F. Garibaldi, K. Garrow, G. Gavrilov, V. Gharibyan, O. Grebeniouk, I. M. Gregor, C. Hadjidakis, K. Hafidi, M. Hartig, D. Hasch, M. Henoch, W. H.A. Hesselink, A. Hillenbrand, M. Hoek, Y. Holler, B. Hommez, I. Hristova, G. Iarygin, A. Ilyichev, A. Ivanilov, A. Izotov, H. E. Jackson, A. Jgoun, R. Kaiser, E. Kinney, A. Kisselev, T. Kobayashi, M. Kopytin, V. Korotkov, V. Kozlov, B. Krauss, V. G. Krivokhijine, L. Lagamba, L. Lapikás, A. Laziev, P. Lenisa, P. Liebing, L. A. Linden-Levy, W. Lorenzon, H. Lu, J. Lu, S. Lu, B. Q. Ma, B. Maiheu, N. C.R. Makins, Y. Mao, B. Marianski, H. Marukyan, F. Masoli, V. Mexner, N. Meyners, T. A. SHIBATA

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Single-spin asymmetries for semi-inclusive electroproduction of charged pions in deep-inelastic scattering of positrons are measured for the first time with transverse target polarization. The asymmetry depends on the azimuthal angles of both the pion (φ) and the target spin axis (φS) about the virtual-photon direction and relative to the lepton scattering plane. The extracted Fourier component 〈sin(φ + φS) 〉UT π is a signal of the previously unmeasured quark transversity distribution, in conjunction with the Collins fragmentation function, also unknown. The component 〈sin(φ - φSUT π arises from a correlation between the transverse polarization of the target nucleon and the intrinsic transverse momentum of quarks, as represented by the previously unmeasured Sivers distribution function. Evidence for both signals is observed, but the Sivers asymmetry may be affected by exclusive vector meson production.

Original languageEnglish (US)
Article number012002
Pages (from-to)1-6
Number of pages6
JournalPhysical review letters
Issue number1
StatePublished - Jan 14 2005

ASJC Scopus subject areas

  • General Physics and Astronomy


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