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Measurement of the generalized form factors near threshold via $\gamma^* p \to n\pi^+$ at high $Q^2$

K. Park R.W. Gothe K.P. Adhikari D. Adikaram M. Anghinolfi H. Baghdasaryan J. Ball 1 M. Battaglieri V. Batourine I. Bedlinskiy R. P. Bennett A.S. Biselli C. Bookwalter S. Boiarinov D. Branford W.J. Briscoe W.K. Brooks V.D. Burkert D.S. Carman A. Celentano S. Chandavar G. Charles 1 P.L. Cole M. Contalbrigo V. Crede A. d'Angelo A. Daniel N. Dashyan R. de Vita E. de Sanctis A. Deur C. Djalali D. Doughty R. Dupre A. El Alaoui L. El Fassi P. Eugenio G. Fedotov A. Fradi M.Y. Gabrielyan N. Gevorgyan G.P. Gilfoyle K.L. Giovanetti F.X. Girod J.T. Goetz W. Gohn E. Golovatch L. Graham K.A. Griffioen M. Guidal L. Guo K. Hafidi H. Hakobyan C. Hanretty D. Heddle K. Hicks M. Holtrop C. E. Hyde Y. Ilieva D.G. Ireland B.S. Ishkhanov E.L. Isupov D. Jenkins H.S. Jo K. Joo N. Kalantarians M. Khandaker P. Khetarpal A. Kim W. Kim A. Klein F.J. Klein A. Kubarovsky V. Kubarovsky S.E. Kuhn S.V. Kuleshov N.D. Kvaltine K. Livingston H.Y. Lu I..J .D. Macgregor N. Markov M. Mayer B. Mckinnon M.D. Mestayer C.A. Meyer T. Mineeva M. Mirazita V. Mokeev H. Moutarde 1 E. Munevar P. Nadel-Turonski R. Nasseripour S. Niccolai G. Niculescu I. Niculescu M. Osipenko A.I. Ostrovidov M. Paolone L. Pappalardo R. Paremuzyan S. Park S. Anefalos Pereira E. Phelps S. Pisano O. Pogorelko S. Pozdniakov J.W. Price S. Procureur 1 Y. Prok G. Ricco D. Rimal M. Ripani B.G. Ritchie G. Rosner P. Rossi F. Sabatié 1 M.S. Saini C. Salgado D. Schott R.A. Schumacher H. Seraydaryan Y.G. Sharabian E.S. Smith G.D. Smith D.I. Sober D. Sokhan S.S. Stepanyan S. Stepanyan P. Stoler I.I. Strakovsky S. Strauch M. Taiuti W. Tang C.E. Taylor Y. Tian S. Tkachenko A. Trivedi M. Ungaro B. Vernarsky A.V. Vlassov E. Voutier 2 D.P. Watts D.P. Weygand M.H. Wood N. Zachariou B. Zhao Z.W. Zhao
Abstract : We report the first extraction of the pion-nucleon multipoles near the production threshold for the $n\pi^+$ channel at relatively high momentum transfer ($Q^2$ up to 4.2 $\rm{GeV^2}$). The dominance of the s-wave transverse multipole ($E_{0+}$), expected in this region, allowed us to access the generalized form factor $G_1$ within the light-cone sum rule (LCSR) framework as well as the axial form factor $G_A$. The data analyzed in this work were collected by the nearly $4\pi$ CEBAF Large Acceptance Spectrometer (CLAS) using a 5.754 $\rm{GeV}$ electron beam on a proton target. The differential cross section and the $\pi-N$-multipole $E_{0+}/G_D$ were measured using two different methods, the LCSR and a direct multipole fit. The results from the two methods are found to be consistent and almost $Q^2$ independent.
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Submitted on : Thursday, January 5, 2012 - 9:19:06 AM
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K. Park, R.W. Gothe, K.P. Adhikari, D. Adikaram, M. Anghinolfi, et al.. Measurement of the generalized form factors near threshold via $\gamma^* p \to n\pi^+$ at high $Q^2$. Physical Review C, American Physical Society, 2012, 85, pp.035208. ⟨10.1103/PhysRevC.85.035208⟩. ⟨in2p3-00656770⟩



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