A. Airapetian

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

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 (

Observation of the Naive-T-odd Sivers Effect in Deep-Inelastic Scattering

\phi

Evidence for a Single-Spin Azimuthal Asymmetry in Semi-inclusive Pion Electroproduction

) and the target spin axis (

Measurement of the spin asymmetry in the photoproduction of pairs of high-pT hadrons at HERMES

\phi_S

Single-spin azimuthal asymmetries in electroproduction of neutral pions in semi-inclusive deep-inelastic scattering

) about the virtual photon direction and relative to the lepton scattering plane. The extracted Fourier component

Hadron formation in deep-inelastic positron scattering in a nuclear environment.

\cmpi

Exclusive leptoproduction of \(\rho^0\) mesons from hydrogen at intermediate virtual photon energies

is a signal of the previously unmeasured quark transversity distribution, in conjunction with the so-called Collins fragmentation function, also unknown. The Fourier component

Evidence for a Transverse Single-Spin Asymmetry in Leptoproduction of pi+pi- Pairs

\smpi

Cross-sections for hard exclusive electroproduction of pi+ mesons on a hydrogen target

of the asymmetry 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

Q(2) dependence of nuclear transparency for exclusive rho(0) production

A. Airapetian, 15 N. Akopov, Z. Akopov, E.C. Aschenauer, W. Augustyniak, A. Avetissian, E. Avetisyan, A. Bacchetta, B. Ball, N. Bianchi, H.P. Blok, 24 H. Böttcher, C. Bonomo, A. Borissov, V. Bryzgalov, J. Burns, M. Capiluppi, G.P. Capitani, E. Cisbani, G. Ciullo, M. Contalbrigo, P.F. Dalpiaz, W. Deconinck, 15 R. De Leo, L. De Nardo, 5 E. De Sanctis, M. Diefenthaler, 8 P. Di Nezza, J. Dreschler, M. Düren, 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, 9 S. Gliske, C. Hadjidakis, M. Hartig, D. Hasch, G. Hill, A. Hillenbrand, M. Hoek, Y. Holler, I. Hristova, Y. Imazu, A. Ivanilov, H.E. Jackson, H.S. Jo, S. Joosten, 11 R. Kaiser, T. Keri, 12 E. Kinney, A. Kisselev, V. Korotkov, V. Kozlov, P. Kravchenko, L. Lagamba, R. Lamb, L. Lapikás, I. Lehmann, P. Lenisa, L.A. Linden-Levy, A. López Ruiz, W. Lorenzon, X.-G. Lu, X.-R. Lu, B.-Q. Ma, D. Mahon, N.C.R. Makins, S.I. Manaenkov, L. Manfré, Y. Mao, B. Marianski, A. Martinez de la Ossa, H. Marukyan, C.A. Miller, Y. Miyachi, A. Movsisyan, M. Murray, A. Mussgiller, 8 E. Nappi, Y. Naryshkin, A. Nass, M. Negodaev, W.-D. Nowak, L.L. Pappalardo, R. Perez-Benito, P.E. Reimer, A.R. Reolon, C. Riedl, K. Rith, G. Rosner, A. Rostomyan, J. Rubin, D. Ryckbosch, Y. Salomatin, F. Sanftl, A. Schäfer, G. Schnell, 11 K.P. Schüler, B. Seitz, T.-A. Shibata, V. Shutov, M. Stancari, M. Statera, J.J.M. Steijger, H. Stenzel, J. Stewart, F. Stinzing, S. Taroian, A. Terkulov, A. Trzcinski, M. Tytgat, A. Vandenbroucke, P.B. van der Nat, Y. Van Haarlem, C. Van Hulse, M. Varanda, D. Veretennikov, V. Vikhrov, I. Vilardi, C. Vogel, S. Wang, S. Yaschenko, 8 H. Ye, Z. Ye, S. Yen, W. Yu, D. Zeiler, B. Zihlmann, and P. Zupranski