Measurement of the beam spin asymmetry of $\overrightarrow e p \to e′p′ \eta$ in the deep-inelastic regime with CLAS

B. Zhao , A. Kim , K. Joo , I. Bedlinskiy , W. Kim , V. Kubarovsky , M. Ungaro , S. Adhikari , Z. Akbar , G. Angelini , H. Avakian , J. Ball (1) , N.A. Baltzell , L. Barion , M. Bashkanov , M. Battaglieri , V. Batourine , A.S. Biselli , S. Boiarinov , W.J. Briscoe , W.K. Brooks , V.D. Burkert , D.S. Carman , A. Celentano , P. Chatagnon (2) , T. Chetry , G. Ciullo , L. Clark , B.A. Clary , P.L. Cole , M. Contalbrigo , V. Crede , A. d'Angelo , N. Dashyan , R. de Vita , E. de Sanctis , M. Defurne (1) , A. Deur , S. Diehl , C. Djalali , R. Dupre (2) , H. Egiyan , M. Ehrhart (2) , A. El Alaoui , L. El Fassi , P. Eugenio , A. Filippi , T.A. Forest , G. Gavalian , Y. Ghandilyan , G.P. Gilfoyle , F.X. Girod (1) , E. Golovatch , R.W. Gothe , K.A. Griffioen , M. Guidal (2) , L. Guo , K. Hafidi , H. Hakobyan , N. Harrison , M. Hattawy , D. Heddle , K. Hicks , M. Holtrop , Y. Ilieva , D.G. Ireland , B.S. Ishkhanov , E.L. Isupov , D. Jenkins , H.S. Jo (2) , S. Johnston , M.L. Kabir , D. Keller , G. Khachatryan , M. Khachatryan , M. Khandaker , A. Klein , F.J. Klein , S.E. Kuhn , S.V. Kuleshov , L. Lanza , P. Lenisa , K. Livingston , I.J.D. Macgregor , D. Marchand (2) , N. Markov , B. Mckinnon , C.A. Meyer , Z.E. Meziani , M. Mirazita , V. Mokeev , R.A. Montgomery , C. Munoz Camacho (2) , P. Nadel-Turonski , S. Niccolai (2) , G. Niculescu , M. Osipenko , A.I. Ostrovidov , M. Paolone , R. Paremuzyan , K. Park , O. Pogorelko , J.W. Price , Y. Prok , D. Protopopescu , M. Ripani , A. Rizzo , G. Rosner , P. Rossi , F. Sabatié (1) , C. Salgado , R.A. Schumacher , Y.G. Sharabian , Iu. Skorodumina , G.D. Smith , D. Sokhan , N. Sparveris , S. Stepanyan , I.I. Strakovsky , S. Strauch , M. Taiuti , J.A. Tan , H. Voskanyan , E. Voutier (2) , R. Wang (2) , 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 IPNO - Institut de Physique Nucléaire d'Orsay

The beam spin asymmetry of the exclusive pseudoscalar channel e→p→e′p′η was measured for the first time in the deep-inelastic regime ( W>2 GeV/c2 and Q2>1 GeV2/c2 ) using a longitudinally polarized 5.78 GeV electron beam at Jefferson Lab with the CEBAF Large Acceptance Spectrometer. The data were accumulated in 144 four-dimensional bins of Q2 , xB , − t and ϕ over a wide kinematic range, where ϕ is the azimuthal angle between the lepton and hadron scattering planes, The measured azimuthal dependence with large amplitudes of the sin⁡ϕ moments is a clear indication of a substantial contribution to the polarized cross-section from transversely polarized virtual photons. In the framework of generalized parton distributions (GPDs) this contribution is expressed via longitudinal-transverse interference between chiral-even and chiral-odd GPDs. The experimental results are compared to the existing theoretical models demonstrating the sensitivity to the product of chiral-odd and chiral-even GPDs and provide new constraints to the existing GPD parameterizations.

Mots clés: Nucleon structure; CLAS collaboration; Deeply Virtual Meson Production; Chiral-odd generalized parton distributions; electron p: deep inelastic scattering; deeply virtual Compton scattering; eta: electroproduction; spin: asymmetry; parton: distribution function; electron: polarized beam; polarization: longitudinal; polarization: transverse; hadron: scattering; meson: electroproduction; photon: virtual; dimension: 4; generalized parton distribution; CLAS; experimental results; angular dependence; Jefferson Lab; interference; pseudoscalar; sensitivity; kinematics; nucleon: structure function

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

B. Zhao, A. Kim, K. Joo, I. Bedlinskiy, W. Kim, et al.. Measurement of the beam spin asymmetry of $\overrightarrow e p \to e′p′ \eta$ in the deep-inelastic regime with CLAS. Phys.Lett.B, 2019, 789, pp.426-431. ⟨10.1016/j.physletb.2018.12.065⟩. ⟨hal-01999737⟩