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Measurement of exclusive π0 electroproduction structure functions and their relationship to transverse generalized parton distributions
Journal
Physical Review Letters
Date Issued
2012-09-10
Author(s)
Bedlinskiy, I.
Kubarovsky, V.
Niccolai, S.
Stoler, P.
Adhikari, K. P.
Aghasyan, M.
Amaryan, M. J.
Anghinolfi, M.
Avakian, H.
Baghdasaryan, H.
Ball, J.
Baltzell, N. A.
Battaglieri, M.
Bennett, R. P.
Biselli, A. S.
Bookwalter, C.
Boiarinov, S.
Briscoe, W. J.
Burkert, V. D.
Carman, D. S.
Celentano, A.
Chandavar, S.
Charles, G.
Contalbrigo, M.
Crede, V.
D'Angelo, A.
Daniel, A.
Dashyan, N.
De Vita, R.
De Sanctis, E.
Deur, A.
Djalali, C.
Doughty, D.
Dupre, R.
Egiyan, H.
El Alaoui, A.
El Fassi, L.
Elouadrhiri, L.
Eugenio, P.
Fedotov, G.
Fegan, S.
Fleming, J. A.
Forest, T. A.
Fradi, A.
Garçon, M.
Gevorgyan, N.
Giovanetti, K. L.
Girod, F. X.
Gohn, W.
Gothe, R. W.
Graham, L.
Griffioen, K. A.
Guegan, B.
Guidal, M.
Guo, L.
Hafidi, K.
Hanretty, C.
Heddle, D.
Hicks, K.
Holtrop, M.
Ilieva, Y.
Ireland, D. G.
Ishkhanov, B. S.
Isupov, E. L.
Jo, H. S.
Joo, K.
Keller, D.
Khandaker, M.
Khetarpal, P.
Kim, A.
Kim, W.
Klein, F. J.
Koirala, S.
Kubarovsky, A.
Kuhn, S. E.
Kvaltine, N. D.
Livingston, K.
Lu, H. Y.
MacGregor, I. J.D.
Mao, Y.
Markov, N.
Martinez, D.
Mayer, M.
McKinnon, B.
Meyer, C. A.
Mineeva, T.
Mirazita, M.
Mokeev, V.
Moutarde, H.
Munevar, E.
Munoz Camacho, C.
Nadel-Turonski, P.
Niculescu, G.
Niculescu, I.
Osipenko, M.
Ostrovidov, A. I.
Pappalardo, L. L.
Abstract
Exclusive 0 electroproduction at a beam energy of 5.75 GeV has been measured with the Jefferson
Lab CLAS spectrometer. Differential cross sections were measured at more than 1800 kinematic values in
Q2, xB, t, and , in the Q2 range from 1.0 to 4:6 GeV2, t up to 2 GeV2, and xB from 0.1 to 0.58.
Structure functions T þ L, TT, and LT were extracted as functions of t for each of 17 combinations
of Q2 and xB. The data were compared directly with two handbag-based calculations including both
longitudinal and transversity generalized parton distributions (GPDs). Inclusion of only longitudinal
GPDs very strongly underestimates T þ L and fails to account for TT and LT, while inclusion of
transversity GPDs brings the calculations into substantially better agreement with the data. There is very
strong sensitivity to the relative contributions of nucleon helicity-flip and helicity nonflip processes. The
results confirm that exclusive 0 electroproduction offers direct experimental access to the transversity
GPDs.
Lab CLAS spectrometer. Differential cross sections were measured at more than 1800 kinematic values in
Q2, xB, t, and , in the Q2 range from 1.0 to 4:6 GeV2, t up to 2 GeV2, and xB from 0.1 to 0.58.
Structure functions T þ L, TT, and LT were extracted as functions of t for each of 17 combinations
of Q2 and xB. The data were compared directly with two handbag-based calculations including both
longitudinal and transversity generalized parton distributions (GPDs). Inclusion of only longitudinal
GPDs very strongly underestimates T þ L and fails to account for TT and LT, while inclusion of
transversity GPDs brings the calculations into substantially better agreement with the data. There is very
strong sensitivity to the relative contributions of nucleon helicity-flip and helicity nonflip processes. The
results confirm that exclusive 0 electroproduction offers direct experimental access to the transversity
GPDs.
Subjects
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