First measurement of the helicity asymmetry E in η photoproduction on the proton

I. Senderovich , B.T. Morrison , M. Dugger , B.G. Ritchie , E. Pasyuk , R. Tucker , J. Brock , C. Carlin

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C.D. Keith D.G. Meekins M.L. Seely D. R M. D P. Collins K.P. Adhikari D. Adikaram Z. Akbar M.D. Anderson S. Anefalos Pereira R.A. Badui J. Ball N.A. Baltzell M. Battaglieri V. Batourine I. Bedlinskiy A.S. Biselli S. Boiarinov W.J. Briscoe W.K. Brooks V.D. Burkert D.S. Carman A. Celentano S. Chandavar G. Charles L. Colaneri P.L. Cole M. Contalbrigo O. Cortes V. Crede A. D'Angelo N. Dashyan R. De Vita E. De Sanctis A. Deur C. Djalali R. Dupre H. Egiyan A. El Alaoui L. El Fassi A. Fradi L. Elouadrhiri P. Eugenio G. Fedotov S. Fegan A. Filippi J.A. Fleming B. Garillon Y. Ghandilyan G.P. Gilfoyle K.L. Giovanetti F.-X. Girod D.I. Glazier J.T. Goetz W. Gohn E. Golovatch R.W. Gothe K.A. Griffioen M. Guidal L. Guo K. Hafidi H. Hakobyan C. Hanretty M. Hattawy K. Hicks D. Ho M. Holtrop S.M. Hughes Y. Ilieva D.G. Ireland B.S. Ishkhanov D. Jenkins H. Jiang H.S. Jo K. Joo S. Joosten D. Keller G. Khachatryan M. Khandaker A. Kim F.J. Klein V. Kubarovsky M.C. Kunkel P. Lenisa K. Livingston H.Y. Lu I.J.D. MacGregor P. Mattione B. McKinnon C.A. Meyer T. Mineeva V. Mokeev R.A. Montgomery A. Movsisyan C. Munoz Camacho P. Nadel-Turonski L.A. Net S. Niccolai G. Niculescu I. Niculescu M. Osipenko K. Park S. Park P. Peng W. Phelps S. Pisano O. Pogorelko J.W. Price Y. Prok A.J.R. Puckett M. Ripani A. Rizzo G. Rosner P. Roy F. Sabatie C. Salgado D. Schott R.A. Schumacher E. Seder A. Simonyan Iu. Skorodumina G.D. Smith D.I. Sober D. Sokhan N. Sparveris S. Stepanyan P. Stoler I.I. Strakovsky S. Strauch V. Sytnik Ye Tian M. Ungaro H. Voskanyan E. Voutier N.K. Walford X. Wei M.H. Wood N. Zachariou L. Zana J. Zhang Z.W. Zhao I. Zonta

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keywords dataresultsasymmetrycenter-of-massfirsthelicitymeasurementmodel

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Results are presented for the first measurement of the double-polarization helicity asymmetry E for the $\eta$ photoproduction reaction $\gamma p \rightarrow \eta p$. Data were obtained using the FROzen Spin Target (FROST) with the CLAS spectrometer in Hall B at Jefferson Lab, covering a range of center-of-mass energy W from threshold to 2.15 GeV and a large range in center-of-mass polar angle. As an initial application of these data, the results have been incorporated into the J\"ulich model to examine the case for the existence of a narrow $N^*$ resonance between 1.66 and 1.70 GeV. The addition of these data to the world database results in marked changes in the predictions for the E observable using that model. Further comparison with several theoretical approaches indicates these data will significantly enhance our understanding of nucleon resonances.

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First measurement of the helicity asymmetry E in η photoproduction on the proton

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