Skip to main content
eScholarship
Open Access Publications from the University of California

UCLA

UCLA Previously Published Works bannerUCLA

Coherent diffractive photoproduction of ρ0 mesons on gold nuclei at 200 GeV/nucleon-pair at the Relativistic Heavy Ion Collider

  • Author(s): Adamczyk, L
  • Adkins, JK
  • Agakishiev, G
  • Aggarwal, MM
  • Ahammed, Z
  • Ajitanand, NN
  • Alekseev, I
  • Anderson, DM
  • Aoyama, R
  • Aparin, A
  • Arkhipkin, D
  • Aschenauer, EC
  • Ashraf, MU
  • Attri, A
  • Averichev, GS
  • Bai, X
  • Bairathi, V
  • Behera, A
  • Bellwied, R
  • Bhasin, A
  • Bhati, AK
  • Bhattarai, P
  • Bielcik, J
  • Bielcikova, J
  • Bland, LC
  • Bordyuzhin, IG
  • Bouchet, J
  • Brandenburg, JD
  • Brandin, AV
  • Brown, D
  • Bunzarov, I
  • Butterworth, J
  • Caines, H
  • Calderón De La Barca Sánchez, M
  • Campbell, JM
  • Cebra, D
  • Chakaberia, I
  • Chaloupka, P
  • Chang, Z
  • Chankova-Bunzarova, N
  • Chatterjee, A
  • Chattopadhyay, S
  • Chen, X
  • Chen, JH
  • Chen, X
  • Cheng, J
  • Cherney, M
  • Christie, W
  • Contin, G
  • Crawford, HJ
  • Das, S
  • De Silva, LC
  • Debbe, RR
  • Dedovich, TG
  • Deng, J
  • Derevschikov, AA
  • Didenko, L
  • Dilks, C
  • Dong, X
  • Drachenberg, JL
  • Draper, JE
  • Dunkelberger, LE
  • Dunlop, JC
  • Efimov, LG
  • Elsey, N
  • Engelage, J
  • Eppley, G
  • Esha, R
  • Esumi, S
  • Evdokimov, O
  • Ewigleben, J
  • Eyser, O
  • Fatemi, R
  • Fazio, S
  • Federic, P
  • Federicova, P
  • Fedorisin, J
  • Feng, Z
  • Filip, P
  • Finch, E
  • Fisyak, Y
  • Flores, CE
  • Fulek, L
  • Gagliardi, CA
  • Garand, D
  • Geurts, F
  • Gibson, A
  • Girard, M
  • Grosnick, D
  • Gunarathne, DS
  • Guo, Y
  • Gupta, A
  • Gupta, S
  • Guryn, W
  • Hamad, AI
  • Hamed, A
  • Harlenderova, A
  • Harris, JW
  • He, L
  • Heppelmann, S
  • et al.
Abstract

The STAR Collaboration reports on the photoproduction of π+π- pairs in gold-gold collisions at a center-of-mass energy of 200 GeV/nucleon-pair. These pion pairs are produced when a nearly real photon emitted by one ion scatters from the other ion. We fit the π+π- invariant-mass spectrum with a combination of ρ0 and ω resonances and a direct π+π- continuum. This is the first observation of the ω in ultraperipheral collisions, and the first measurement of ρ-ω interference at energies where photoproduction is dominated by Pomeron exchange. The ω amplitude is consistent with the measured γp→ωp cross section, a classical Glauber calculation, and the ω→π+π- branching ratio. The ω phase angle is similar to that observed at much lower energies, showing that the ρ-ω phase difference does not depend significantly on photon energy. The ρ0 differential cross section dσ/dt exhibits a clear diffraction pattern, compatible with scattering from a gold nucleus, with two minima visible. The positions of the diffractive minima agree better with the predictions of a quantum Glauber calculation that does not include nuclear shadowing than with a calculation that does include shadowing.

Many UC-authored scholarly publications are freely available on this site because of the UC's open access policies. Let us know how this access is important for you.

Main Content
Current View