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

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• 作者：I. Senderovich^b ; ^{senderov@jlab.org" class="auth_mail" title="E-mail the corresponding author} ; B.T. Morrison^b ; M. Dugger^b ; B.G. Ritchie^b ; ^{barry.ritchie@asu.edu" class="auth_mail" title="E-mail the corresponding author} ; E. Pasyuk^b ; R. Tucker^b ; J. Brock^ag ; C. Carlin^ag ; C.D. Keith^ag ; D.G. Meekins^ag ; M.L. Seely^ag ; D. Rö ; nchen^aq ; M. Dö ; ring^l ; ^ag ; P. Collins^b ; ^f ; K.P. Adhikari^z ; D. Adikaram^z ; ¹ ; Z. Akbar^k ; M.D. Anderson^aj ; S. Anefalos Pereira^o ; R.A. Badui^j ; J. Ball^g ; N.A. Baltzell^a ; ^ae ; ¹ ; M. Battaglieri^p ; V. Batourine^ag ; I. Bedlinskiy^t ; A.S. Biselliⁱ ; S. Boiarinov^ag ; W.J. Briscoe^l ; W.K. Brooks^ah ; ^ag ; V.D. Burkert^ag ; D.S. Carman^ag ; A. Celentano^p ; S. Chandavar^y ; G. Charles^s ; L. Colaneri^q ; ^ac ; P.L. Cole^m ; M. Contalbrigoⁿ ; O. Cortes^m ; V. Credé ; ^k ; A. D'Angelo^q ; ^ac ; N. Dashyan^an ; R. De Vita^p ; E. De Sanctis^o ; A. Deur^ag ; C. Djalali^ae ; R. Dupre^s ; H. Egiyan^ag ; ^w ; A. El Alaoui^ah ; L. El Fassi^z ; L. Elouadrhiri^ag
• 关键词：Eta photoproduction ; Polarization observable ; Helicity asymmetry
• 刊名：Physics Letters B
• 出版年：2016
• 出版时间：10 April 2016
• 年：2016
• 卷：755
• 期：Complete
• 页码：64-69
• 全文大小：496 K

文摘

Results are presented for the first measurement of the double-polarization helicity asymmetry E for the η   photoproduction reaction γp→ηp$\gamma p\to \eta p$. 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 Jülich–Bonn model to examine the case for the existence of a narrow N^⁎$N^{⁎}$ 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 from that model. Further comparison with several theoretical approaches indicates these data will significantly enhance our understanding of nucleon resonances.