Photoproduction of J / ψ and of high mass e+ e- in ultra-peripheral Au + Au collisions at sqrt(sN N) = 200 GeV

S. V. Afanasiev,Christine Angela Aidala,N. N. Ajitanand,Y. Akiba,James Alexander,Ahmed Al-Jamel,K. Aoki,L. Aphecetche, R. Armendariz,S. H. Aronson,R. Averbeck,T. C. Awes,B. Azmoun, V. Babintsev, A. Baldisseri,K. N. Barish, P. D. Barnes,B. Bassalleck,S. Bathe, S. Batsouli, V. Baublis,Florian Bauer, A. Bazilevsky, S. Belikov, R. Bennett,Y. Berdnikov, M. T. Bjorndal, J. G. Boissevain, H. Borel, K. Boyle,M. L. Brooks,D. S. Brown, D. Bucher,Henner Buesching,V. Bumazhnov, G. Bunce, J. M. Burward-Hoy, S. Butsyk,S. Campbell, J. S. Chai, S. Chernichenko, J. Chiba,C. Y. Chi,M. Chiu,I. J. Choi,Tatsuya Chujo, V. Cianciolo, C. R. Cleven, Y. Cobigo,Brian Cole,M. P. Comets,Z. Conesa del Valle,P. Constantin,M. Csanad,Tamas Ferenc Csorgo,T. Dahms,K. Das,G. David, H. Delagrange,A. Denisov,David D'Enterria, A. Deshpande,E. J. Desmond,O. Dietzsch,A. Dion, J. L. Drachenberg, O. Drapier,A. Drees,A. K. Dubey,A. Durum, V. Dzhordzhadze,Yu. Efremenko, J. Egdemir,A. Enokizono,H. En'yo, B. Espagnon, S. Esumi,D. E. Fields,François Fleuret,Sergey Fokin, B. Forestier, Z. Fraenkel,J. E. Frantz, A. Franz,A. D. Frawley, Y. Fukao,S. Y. Fung,S. Gadrat, F. Gastineau,Marie Germain,A. Glenn, M. Gonin,J. Gosset,Y. Goto,R. Granier de Cassagnac, N. Grau,Senta Greene,M. Grosse Perdekamp,Taku Gunji

Physics Letters B(2009)

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摘要
We present the first measurement of photoproduction of J/psi and of two-photon production of high-mass e(+)e(-) pairs in electromagnetic (or ultra-peripheral) nucleus-nucleus interactions, using Au + Au data at root s(NN) = 200 GeV. The events are tagged with forward neutrons emitted following Coulomb excitation of one or both Au* nuclei. The event sample consists of 28 events with m(e+e-) > 2 GeV/c(2) with zero like-sign background. The measured cross sections at midrapidity of d sigma/dy (J/psi + Xn, y = 0) = 76 +/- 33 (stat) +/- 11 (syst) pb and d(2)sigma /dm dy (e(+) e(-) + Xn, y = 0) = 86 +/- 23(stat) +/- 16(syst) mu b/ (GeV/c(2)) for m(e+e-) epsilon vertical bar 2.0, 2.8 vertical bar GeV/c(2) have been compared and found to be consistent with models for photoproduction of J/psi and QED based calculations of two-photon production of e(+)e(-) pairs. (C) 2009 Elsevier B.V. All rights reserved.
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