Extraction of Beam-Spin Asymmetries from the Hard Exclusive $\pi^+$ Channel off Protons in a Wide Range of Kinematics

S. Diehl , K. Joo , A. Kim , H. Avakian , P. Kroll , K. Park , D. Riser , K. Semenov-Tian-Shansky , K. Tezgin , K.P. Adhikari , S. Adhikari , M.J. Amaryan , G. Angelini , G. Asryan , H. Atac , L. Barion , M. Battaglieri , I. Bedlinskiy , F. Benmokhtar , A. Bianconi , A.S. Biselli , F. Bossù (1) , S. Boiarinov , W.J. Briscoe , W.K. Brooks , D. Bulumulla , V.D. Burkert , D.S. Carman , J.C. Carvajal , A. Celentano , P. Chatagnon (2) , T. Chetry , G. Ciullo , L. Clark , P.L. Cole , M. Contalbrigo , V. Crede , A. d'Angelo , N. Dashyan , R. de Vita , M. Defurne (1) , A. Deur , C. Dilks , C. Djalali , R. Dupre (2) , H. Egiyan , M. Ehrhart , A. El Alaoui , L. El Fassi , P. Eugenio , A. Filippi , T.A. Forest , Y. Ghandilyan , G.P. Gilfoyle , K.L. Giovanetti , F.X. Girod , D.I. Glazier , E. Golovatch , R.W. Gothe , K.A. Griffioen , M. Guidal (2) , L. Guo , H. Hakobyan , N. Harrison , M. Hattawy , T.B. Hayward , D. Heddle , K. Hicks , M. Holtrop , Y. Ilieva , D.G. Ireland , B.S. Ishkhanov , E.L. Isupov , D. Jenkins , H.S. Jo , S. Joosten , D. Keller , M. Khachatryan , A. Khanal , M. Khandaker , C.W. Kim , W. Kim , V. Kubarovsky , S.E. Kuhn , L. Lanza , M. Leali , P. Lenisa , K. Livingston , I.J.D. Macgregor , D. Marchand (2) , N. Markov , L. Marsicano , V. Mascagna , B. Mckinnon , Z.E. Meziani , T. Mineeva , M. Mirazita , V. Mokeev , C. Munoz Camacho (2) , P. Nadel-Turonski , G. Niculescu , M. Osipenko , M. Paolone , L.L. Pappalardo , E. Pasyuk , W. Phelps , O. Pogorelko , J.W. Price , Y. Prok , B.A. Raue , M. Ripani , A. Rizzo , P. Rossi , J. Rowley , F. Sabatié (1) , C. Salgado , A. Schmidt , R.A. Schumacher , Y.G. Sharabian , U. Shrestha , O. Soto , N. Sparveris , S. Stepanyan , P. Stoler , I.I. Strakovsky , S. Strauch , J.A. Tan , N. Tyler , M. Ungaro , L. Venturelli , H. Voskanyan , E. Voutier (2) , D.P. Watts , X. Wei , M.H. Wood , N. Zachariou , J. Zhang , Z.W. Zhao

1 IRFU - Institut de Recherches sur les lois Fondamentales de l'Univers
2 IJCLab - Laboratoire de Physique des 2 Infinis Irène Joliot-Curie

We have measured beam-spin asymmetries to extract the sinϕ moment ALUsinϕ from the hard exclusive e→p→e′nπ+ reaction above the resonance region, for the first time with nearly full coverage from forward to backward angles in the center of mass. The ALUsinϕ moment has been measured up to 6.6  GeV2 in -t, covering the kinematic regimes of generalized parton distributions (GPD) and baryon-to-meson transition distribution amplitudes (TDA) at the same time. The experimental results in very forward kinematics demonstrate the sensitivity to chiral-odd and chiral-even GPDs. In very backward kinematics where the TDA framework is applicable, we found ALUsinϕ to be negative, while a sign change was observed near 90° in the center of mass. The unique results presented in this Letter will provide critical constraints to establish reaction mechanisms that can help to further develop the GPD and TDA frameworks.

Mots clés: Elementary Particles and Fields; parton: distribution function; generalized parton distribution; kinematics; asymmetry; moment; distribution amplitude; electroproduction; CLAS; experimental results

Domaines: Physique Nucléaire Expérimentale [nucl-ex]; Physique des Hautes Energies - Expérience [hep-ex]; Physique des Hautes Energies - Phénoménologie [hep-ph]

S. Diehl, K. Joo, A. Kim, H. Avakian, P. Kroll, et al.. Extraction of Beam-Spin Asymmetries from the Hard Exclusive $\pi^+$ Channel off Protons in a Wide Range of Kinematics. Physical Review Letters, 2020, 125 (18), pp.182001. ⟨10.1103/PhysRevLett.125.182001⟩. ⟨hal-02917239⟩