Phys. Rev. Lett.
94,
012002
(2005)
[6 pages]
Single-Spin Asymmetries in Semi-Inclusive Deep-Inelastic Scattering on a Transversely Polarized Hydrogen Target
A. Airapetian et al. The HERMES Collaboration
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A. Airapetian18, N. Akopov30, Z. Akopov30, M. Amarian8,30, A. Andrus16, E. C. Aschenauer8, W. Augustyniak29, R. Avakian30, A. Avetissian30, E. Avetissian12, A. Bacchetta23, P. Bailey16, D. Balin21, M. Beckmann7, S. Belostotski21, N. Bianchi12, H. P. Blok20,28, H. Böttcher8, A. Borissov15, A. Borysenko12, M. Bouwhuis16, A. Brüll17, V. Bryzgalov22, G. P. Capitani12, M. Cappiluppi11, T. Chen4, G. Ciullo11, M. Contalbrigo11, P. F. Dalpiaz11, R. De Leo3, M. Demey20, L. De Nardo1, E. De Sanctis12, E. Devitsin19, P. Di Nezza12, M. Düren14, M. Ehrenfried10, A. Elalaoui-Moulay2, G. Elbakian30, F. Ellinghaus8, U. Elschenbroich13, R. Fabbri20, A. Fantoni12, A. Fechtchenko9, L. Felawka26, S. Frullani24, G. Gapienko22, V. Gapienko22, F. Garibaldi24, K. Garrow26, G. Gavrilov7,26, V. Gharibyan30, O. Grebeniouk21, I. M. Gregor8, C. Hadjidakis12, K. Hafidi2, M. Hartig14, D. Hasch12, M. Henoch10, W. H. A. Hesselink20,28, A. Hillenbrand10, M. Hoek14, Y. Holler7, B. Hommez13, I. Hristova8, G. Iarygin9, A. Ilyichev7, A. Ivanilov22, A. Izotov21, H. E. Jackson2, A. Jgoun21, R. Kaiser15, E. Kinney6, A. Kisselev6, T. Kobayashi27, M. Kopytin8, V. Korotkov22, V. Kozlov19, B. Krauss10, V. G. Krivokhijine9, L. Lagamba3, L. Lapikás20, A. Laziev20,28, P. Lenisa11, P. Liebing8, L. A. Linden-Levy16, W. Lorenzon18, H. Lu5, J. Lu26, S. Lu14, B.-Q. Ma4, B. Maiheu13, N. C. R. Makins16, Y. Mao4, B. Marianski29, H. Marukyan30, F. Masoli11, V. Mexner20, N. Meyners7, T. Michler10, O. Mikloukho21, C. A. Miller1,26, Y. Miyachi27, V. Muccifora12, A. Nagaitsev9, E. Nappi3, Y. Naryshkin21, A. Nass10, M. Negodaev8, W.-D. Nowak8, K. Oganessyan7,12, H. Ohsuga27, A. Osborne15, N. Pickert10, D. H. Potterveld2, M. Raithel10, D. Reggiani11, P. E. Reimer2, A. Reischl20, A. R. Reolon12, C. Riedl10, K. Rith10, G. Rosner15, A. Rostomyan30, L. Rubacek14, J. Rubin16, D. Ryckbosch13, Y. Salomatin22, I. Sanjiev2,21, I. Savin9, A. Schäfer23, C. Schill12, G. Schnell8,27, K. P. Schüler7, J. Seele16, R. Seidl10, B. Seitz14, R. Shanidze10, C. Shearer15, T.-A. Shibata27, V. Shutov9, K. Sinram7, W. Sommer14, M. Stancari11, M. Statera11, E. Steffens10, J. J. M. Steijger20, H. Stenzel14, J. Stewart8, F. Stinzing10, P. Tait10, H. Tanaka27, S. Taroian30, B. Tchuiko22, A. Terkulov19, A. Trzcinski29, M. Tytgat13, A. Vandenbroucke13, P. B. van der Nat20, G. van der Steenhoven20, Y. van Haarlem13, M. C. Vetterli25,26, V. Vikhrov21, M. G. Vincter1, C. Vogel10, J. Volmer8, S. Wang5, J. Wendland25,26, J. Wilbert10, G. Ybeles Smit20,28, Y. Ye5, Z. Ye5, S. Yen26, B. Zihlmann13, and P. Zupranski29 (The HERMES Collaboration)
1Department of Physics, University of Alberta, Edmonton, Alberta T6G 2J1, Canada
2Physics Division, Argonne National Laboratory, Argonne, Illinois 60439-4843, USA
3Istituto Nazionale di Fisica Nucleare, Sezione di Bari, 70124 Bari, Italy
4School of Physics, Peking University, Beijing 100871, China
5Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
6Nuclear Physics Laboratory, University of Colorado, Boulder, Colorado 80309-0446, USA
7DESY, 22603 Hamburg, Germany
8DESY, 15738 Zeuthen, Germany
9Joint Institute for Nuclear Research, 141980 Dubna, Russia
10Physikalisches Institut, Universität Erlangen-Nürnberg, 91058 Erlangen, Germany
11Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara and Dipartimento di Fisica, Università di Ferrara, 44100 Ferrara, Italy
12Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, 00044 Frascati, Italy
13Department of Subatomic and Radiation Physics, University of Gent, 9000 Gent, Belgium
14Physikalisches Institut, Universität Gießen, 35392 Gießen, Germany
15Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, United Kingdom
16Department of Physics, University of Illinois, Urbana, Illinois 61801-3080, USA
17Laboratory for Nuclear Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
18Randall Laboratory of Physics, University of Michigan, Ann Arbor, Michigan 48109-1120, USA
19Lebedev Physical Institute, 117924 Moscow, Russia
20Nationaal Instituut voor Kernfysica en Hoge-Energiefysica (NIKHEF), 1009 DB Amsterdam, The Netherlands
21Petersburg Nuclear Physics Institute, St. Petersburg, Gatchina, 188350 Russia
22Institute for High Energy Physics, Protvino, Moscow region, 142281 Russia
23Institut für Theoretische Physik, Universität Regensburg, 93040 Regensburg, Germany
24Istituto Nazionale di Fisica Nucleare, Sezione Roma 1, Gruppo Sanità and Physics Laboratory, Istituto Superiore di Sanità, 00161 Roma, Italy
25Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
26TRIUMF, Vancouver, British Columbia V6T 2A3, Canada
27Department of Physics, Tokyo Institute of Technology, Tokyo 152, Japan
28Department of Physics and Astronomy, Vrije Universiteit, 1081 HV Amsterdam, The Netherlands
29Andrzej Soltan Institute for Nuclear Studies, 00-689 Warsaw, Poland
30Yerevan Physics Institute, 375036 Yerevan, Armenia
Received 6 August 2004; published 6 January 2005
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)⟩UTπ is a signal of the previously unmeasured quark transversity distribution, in conjunction with the Collins fragmentation function, also unknown. The component ⟨sin(ϕ-ϕS⟩UTπ 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.
© 2005 The American Physical Society
URL:
http://link.aps.org/doi/10.1103/PhysRevLett.94.012002
DOI:
10.1103/PhysRevLett.94.012002
PACS:
13.60.–r, 13.88.+e, 14.20.Dh, 14.65.–q
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