Measurement of ep->ep $\pi^0$ beam spin asymmetries above the resonance region

R. de Masi (1, 2) , M. Garcon (1) , B. Zhao , M.J. Amaryan , P. Ambrozewicz , M. Anghinolfi , G. Asryan , H. Avakian , H. Bagdasaryan , N. Baillie , J. Ball (1) , J.P. Ball , N.A. Baltzell , V. Batourine , M. Battaglieri , I. Bedlinskiy , M. Bellis , N. Benmouna , B.L. Berman , P.Y. Bertin (3) , A.S. Biselli , L. Blaszczyk , S. Bouchigny (2) , S. Boiarinov , R. Bradford , D. Branford , W.J. Briscoe , W.K. Brooks , S. Bultmann , V.D. Burkert , C. Butuceanu , J.R. Calarco , S.L. Careccia , D.S. Carman , L. Casey , Si Chen , L. Cheng , P.L. Cole , P. Collins , P. Coltharp , D. Crabb , V. Crede , N. Dashyan , E. de Sanctis , R. de Vita , P.V. Degtyarenko , A. Deur , K.V. Dharmawardane , R. Dickson , C. Djalali , G.E. Dodge , J. Donnelly , D. Doughty , M. Dugger , O.P. Dzyubak , H. Egiyan , K.S. Egiyan , L. El Fassi , L. Elouadrhiri , P. Eugenio , G. Fedotov , G. Feldman , A. Fradi (2) , H. Funsten , G. Gavalian , G.P. Gilfoyle , K.L. Giovanetti , F.X. Girod (1) , J.T. Goetz , A. Gonenc , R.W. Gothe , K.A. Griffioen , M. Guidal (2) , N. Guler , L. Guo , V. Gyurjyan , K. Hafidi , H. Hakobyan , C. Hanretty , F.W. Hersman , K. Hicks , I. Hleiqawi , M. Holtrop , C.E. Hyde-Wright , Y. Ilieva , D.G. Ireland , B.S. Ishkhanov , E.L. Isupov , M.M. Ito , D. Jenkins , H.S. Jo (2) , J.R. Johnstone , K. Joo , H.G. Juengst , N. Kalantarians , J.D. Kellie , M. Khandaker , W. Kim , A. Klein , F.J. Klein , A.V. Klimenko , M. Kossov , Z. Krahn , L.H. Kramer , V. Kubarovsky , J. Kuhn , S.E. Kuhn , S.V. Kuleshov , J. Lachniet , J.M. Laget , J. Langheinrich , D. Lawrence , T. Lee , K. Livingston , H.Y. Lu , M. Maccormick (2) , N. Markov , P. Mattione , M. Mazouz (4) , B. Mckinnon , B.A. Mecking , M.D. Mestayer , C.A. Meyer , T. Mibe , B. Michel (3) , K. Mikhailov , M. Mirazita , R. Miskimen , V. Mokeev , B. Moreno (2) , K. Moriya , S.A. Morrow (1, 2) , M. Moteabbed , E. Munevar , G.S. Mutchler , P. Nadel-Turonski , R. Nasseripour , S. Niccolai (2) , G. Niculescu , I. Niculescu , B.B. Niczyporuk , M.R. Niroula , R.A. Niyazov , M. Nozar , M. Osipenko , A.I. Ostrovidov , K. Park , E. Pasyuk , C. Paterson , S. Anefalos Pereira , J. Pierce , N. Pivnyuk , D. Pocanic , O. Pogorelko , S. Pozdniakov , J.W. Price , S. Procureur (1) , Y. Prok , D. Protopopescu , B.A. Raue , G. Ricco , M. Ripani , B.G. Ritchie , F. Ronchetti , G. Rosner , P. Rossi , F. Sabatie (1) , J. Salamanca , C. Salgado , J.P. Santoro , V. Sapunenko , R.A. Schumacher , V.S. Serov , Y.G. Sharabian , D. Sharov , N.V. Shvedunov , E.S. Smith , L.C. Smith , D.I. Sober , D. Sokhan , A. Stavinsky , S. Stepanyan , S.S. Stepanyan , B.E. Stokes , P. Stoler , I.I. Strakovsky , S. Strauch , M. Taiuti , D.J. Tedeschi , A. Tkabladze , S. Tkachenko , C. Tur , M. Ungaro , M.F. Vineyard , A.V. Vlassov , E. Voutier (4) , D.P. Watts , L.B. Weinstein , D.P. Weygand , M. Williams , E. Wolin , M.H. Wood , A. Yegneswaran , L. Zana , J. Zhang , Z.W. Zhao

1 DPHN - Département de Physique Nucléaire (ex SPhN)
2 IPNO - Institut de Physique Nucléaire d'Orsay
3 LPC - Laboratoire de Physique Corpusculaire - Clermont-Ferrand
4 LPSC - Laboratoire de Physique Subatomique et de Cosmologie

The beam spin asymmetry (BSA) in the exclusive reaction ep->ep pi0 was measured with the CEBAF 5.77 GeV polarized electron beam and Large Acceptance Spectrometer(CLAS). The xB, Q2, t and phi dependences of the pi0 BSA are presented in the deep inelastic regime. The asymmetries are fitted with a sin(phi) function and their amplitudes are extracted. Overall, they are of the order of 0.04 - 0.11 and roughly independent of t. This is the signature of a non-zero longitudinal-transverse interference. The implications concerning the applicability of a formalism based on generalized parton distributions, as well as the extension of a Regge formalism at high photon virtualities, are discussed.

Domaines: Physique des Hautes Energies - Expérience [hep-ex]

R. de Masi, M. Garcon, B. Zhao, M.J. Amaryan, P. Ambrozewicz, et al.. Measurement of ep->ep $\pi^0$ beam spin asymmetries above the resonance region. Physical Review C, 2008, 77, pp.042201. ⟨10.1103/PhysRevC.77.042201⟩. ⟨in2p3-00192985⟩