rho^0$ photoproduction in ultraperipheral relativistic heavy ion collisions at $\sqrt{S_{NN}}$=200 GeV

rho^0$ photoproduction in ultraperipheral relativistic heavy ion collisions at $\sqrt{S_{NN}}$=200 GeV

Photoproduction reactions occur when the electromagnetic field of a relativistic heavy ion interacts with another heavy ion. The STAR collaboration presents a measurement of rho^0 and direct pi^+pi^- photoproduction in ultra-peripheral relativistic heavy ion collisions at sqrt(s_{NN})=200 GeV. We ob...

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Veröffentlicht in:Physical review. C 2008, Vol.77
Hauptverfasser: Abelev, B.I., Aggarwal, M.M., Ahammed, Z., Anderson, B.D., Arkhipkin, D., Averichev, G.S., Bai, Y., Balewski, J., Barannikova, O., Barnby, L.S., Baudot, J., Baumgart, S., Beavis, D.R., Bellwied, R., Benedosso, F., Betts, R.R., Bhardwaj, S., Bhasin, A., Bhati, A.K., Bichsel, H., Bielcik, J., Bielcikova, J., Bland, L.C., Blyth, S.-L., Bombara, M., Bonner, B.E., Botje, M., Bouchet, J., Braidot, E., Brandin, A.V., Bueltmann, S., Burton, T.P., Bystersky, M., Cai, X.Z., Caines, H., Calderon de La Barca Sanchez, M., Callner, J., Catu, O., Cebra, D., Cervantes, M.C., Chajecki, Z., Chaloupka, P., Chattopadhyay, S., Chen, H.F., Chen, J.H., Chen, J.Y., Cheng, J., Cherney, M., Chikanian, A., Choi, K.E., Christie, W., Chung, S.U., Clarke, R.F., Codrington, M.J.M., Coffin, J.P., Cormier, T.M., Cosentino, M.R., Cramer, J.G., Crawford, H.J., Das, D., Dash, S., Daugherity, M., de Moura, M.M., Dedovich, T.G., Dephillips, M., Derevschikov, A.A., Derradi de Souza, R., Didenko, L., Dietel, T., Djawotho, P., Dogra, S.M., Dong, X., Drachenberg, J.L., Draper, J.E., Du, F., Dunlop, J.C., Dutta Mazumdar, M.R., Edwards, W.R., Efimov, L.G., Elhalhuli, E., Emelianov, V., Engelage, J., Eppley, G., Erazmus, B., Estienne, Magali, Eun, L., Fachini, P., Fatemi, R., Fedorisin, J., Feng, A., Filip, P., Finch, E., Fine, V., Fisyak, Y., Fu, J., Gagliardi, C.A., Gaillard, L., Ganti, M.S., Garcia-Solis, E., Ghazikhanian, V.
Format: Artikel
Sprache:eng
Schlagworte:
Nuclear Experiment
Physics
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Zusammenfassung:Photoproduction reactions occur when the electromagnetic field of a relativistic heavy ion interacts with another heavy ion. The STAR collaboration presents a measurement of rho^0 and direct pi^+pi^- photoproduction in ultra-peripheral relativistic heavy ion collisions at sqrt(s_{NN})=200 GeV. We observe both exclusive photoproduction and photoproduction accompanied by mutual Coulomb excitation. We find a coherent cross-section of sigma(AuAu) -> Au^*Au^*rho^0 = 530 pm 19 (stat.) pm 57 (syst.) mb, in accord with theoretical calculations based on a Glauber approach, but considerably below the predictions of a color dipole model. The rho^0 transverse momentum spectrum (p_{T}^2 ) is fit by a double exponential curve including both coherent and incoherent coupling to the target nucleus; we find sigma_{inc}/sigma_{coh} = 0.29 pm 0.03 (stat.) pm 0.08 (syst.). The ratio of direct pi^+pi^- to rho^0 production is comparable to that observed in gamma p collisions at HERA, and appears to be independent of photon energy. Finally, the measured rho^0 spin helicity matrix elements agree within errors with the expected s-channel helicity conservation.
ISSN:2469-9985
2469-9993
DOI:10.1103/PhysRevC.77.034910