Deeply virtual and exclusive electroproduction of $\omega$-mesons

L. Morand , D. Doré , M. Garçon , M. Guidal (1) , J.-M. Laget , S. Morrow , F. Sabatié , E. Smith , G. Adams , P. Ambrozewicz , M. Anghinolfi , G. Asryan , G. Audit , H. Avakian , H. Bagdasaryan , J. Ball , J.P. Ball , N.A. Baltzell , S. Barrow , V. Batourine , M. Battaglieri , M. Bektasoglu , M. Bellis , N. Benmouna , B.L. Berman , A.S. Biselli , S. Boiarinov , B.E. Bonner , S. Bouchigny (1) , R. Bradford , D. Branford , W.J. Briscoe , W.K. Brooks , S. Bültmann , V.D. Burkert , C. Butuceanu , J.R. Calarco , S.L. Careccia , D.S. Carman , A. Cazes , S. Chen , P.L. Cole , D. Cords , P. Corvisiero , D. Crabb , J.P. Cummings , E. de Sanctis , R. Devita , P.V. Degtyarenko , H. Denizili , L. Dennis , A. Deur , K.V. Dharmawardane , K.S. Dhuga , C. Djalali , G.E. Dodge , J. Donnelly , D. Doughty , M. Dugger , S. Dytman , O.P. Dzyubak , H. Egiyan , K.S. Egiyan , L. Elouadrhiri , P. Eugenio , R. Fatemi , G. Feldman , R.G. Fersch , R.J. Feuerbach , H. Funsten , G. Gavalian , G.P. Gilfoyle , K.L. Giovanetti , F.-X. Girod , J.T. Goetz , C.I.O. Gordon , R.W. Gothe , K.A. Griffioen , M. Guillo , N. Guler , L. Guo , V. Gyurjyan , C. Hadjidakis (1) , R.S. Hakobyan , J. Hardie , D. Heddle , F.W. Hersman , K. Hicks , I. Hleiqawi , M. Holtrop , C.E. Hyde-Wright , Y. Ilieva , D.G. Ireland , M.M. Ito , D. Jenkins , H.-S. Jo , K. Joo , H.G. Juengst , J.D. Kellie , M. Khandaker , W. Kim , A. Klein , F. J. Klein , A.V. Klimenko , M. Kossov , V. Kubarovski , L.H. Kramer , S.E. Kuhn , J. Kuhn , J. Lachniet , J. Langheinrich , D. Lawrence , T. Lee , Ji Li , K. Livingston , C. Marchand , L.C. Maximon , S. Mcaleer , B. Mckinnon , J.W.C. Mcnabb , B.A. Mecking , S. Mehrabyan , J.J. Melone , M.D. Mestayer , C.A. Meyer , K. Mikhailov , R. Minehart , M. Mirazita , R. Miskimen , V. Mokeev , J. Mueller , G.S. Mutchler , J. Napolitano , R. Nasseripour , S. Niccolai , G. Niculescu , I. Niculescu , B.B. Niczyporuk , R.A. Niyazov , M. Nozar , G.V. O'Rielly , M. Osipenko , A.I. Ostrovidov , K. Park , E. Pasyuk , S.A. Philips , N. Pivnyuk , D. Pocanic , O. Pogorelko , E. Polli , I. Popa , S. Pozdniakov , B.M. Preedom , J.W. Price , Y. Prok , D. Protopopescu , B.A. Raue , G. Riccardi , G. Ricco , M. Ripani , B.G. Ritchie , F. Ronchetti , G. Rosner , P. Rossi , P.D. Rubin , C. Salgado , J.P. Santoro , V. Sapunenko , R.A. Schumacher , V.S. Serov , Y.G. Sharabian , J. Shaw , A.V. Skabelin , L.C. Smith , D.I. Sober , A. Stavinsky , S. Stepanyan , S.S. Stepanyan , B.E. Stokes , P. Stoler , I.I. Strakovsky , S. Strauch , M. Taiuti , D.J. Tedeschi , U. Thoma , A. Tkabladze , L. Todor , C. Tur , M. Ungaro , M.F. Vineyard , A.V. Vlassov , L.B. Weinstein , D.P. Weygand , M. Williams , E. Wolin , M.H. Wood , A. Yegneswaran , L. Zana

1 IPNO - Institut de Physique Nucléaire d'Orsay

The exclusive $\omega$ electroproduction off the proton was studied in a large kinematical domain above the nucleon resonance region and for the highest possible photon virtuality (Q$^2$) with the 5.75 GeV beam at CEBAF and the CLAS spectrometer. Cross-sections were measured up to large values of the four-momentum transfer (- t < 2.7 GeV$^2$) to the proton. The contributions of the interference terms $\sigma_{TT}$ and $\sigma_{TL}$ to the cross-sections, as well as an analysis of the $\omega$ spin density matrix, indicate that helicity is not conserved in this process. The t-channel $\pi^0$ exchange, or more generally the exchange of the associated Regge trajectory, seems to dominate the reaction $\gamma^*p \to \omega p$, even for Q$^2$ as large as 5 GeV$^2$. Contributions of handbag diagrams, related to Generalized Parton Distributions in the nucleon, are therefore difficult to extract for this process. Remarkably, the high-t behaviour of the cross-sections is nearly Q$^2$-independent, which may be interpreted as a coupling of the photon to a point-like object in this kinematical limit.

Domains: High Energy Physics - Experiment [hep-ex]

L. Morand, D. Doré, M. Garçon, M. Guidal, J.-M. Laget, et al.. Deeply virtual and exclusive electroproduction of $\omega$-mesons. European Physical Journal A, 2005, 24, pp.445-458. ⟨10.1140/epja/i2005-10032-4⟩. ⟨in2p3-00024374⟩