Physics Letters B (Feb 2019)

Measurement of the beam spin asymmetry of e→p→e′p′η 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,
  • 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,
  • 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,
  • A. Deur,
  • S. Diehl,
  • C. Djalali,
  • R. Dupre,
  • H. Egiyan,
  • M. Ehrhart,
  • A. El Alaoui,
  • L. El Fassi,
  • P. Eugenio,
  • A. Filippi,
  • T.A. Forest,
  • G. Gavalian,
  • Y. Ghandilyan,
  • G.P. Gilfoyle,
  • F.X. Girod,
  • E. Golovatch,
  • R.W. Gothe,
  • K.A. Griffioen,
  • M. Guidal,
  • 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,
  • 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,
  • N. Markov,
  • B. McKinnon,
  • C.A. Meyer,
  • Z.E. Meziani,
  • M. Mirazita,
  • V. Mokeev,
  • R.A. Montgomery,
  • C. Munoz Camacho,
  • P. Nadel-Turonski,
  • S. Niccolai,
  • 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,
  • 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,
  • R. Wang,
  • X. Wei,
  • M.H. Wood,
  • N. Zachariou,
  • J. Zhang,
  • Z.W. Zhao

Journal volume & issue
Vol. 789
pp. 426 – 431

Abstract

Read online

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. Keywords: Nucleon structure, CLAS collaboration, Deeply Virtual Meson Production, Chiral-odd generalized parton distributions