{rho}{sup 0} photoproduction in ultraperipheral relativistic heavy ion collisions at {radical}(s{sub NN})=200 GeV

Journal Article · Sat Mar 15 04:00:00 EDT 2008 · Physical Review. C, Nuclear Physics

DOI:https://doi.org/10.1103/PHYSREVC.77.034910· OSTI ID:21189859

Abelev, B I; Barannikova, O; Betts, R R; Callner, J; Garcia-Solis, E; Hofman, D J; Hollis, R S; Iordanova, A; Suarez, M C ^[1]; Aggarwal, M M; Bhati, A K; Kumar, A; Pruthi, N K; Sharma, M ^[2]; Ahammed, Z; Chattopadhyay, S; Mazumdar, M R. Dutta; Ganti, M S; Ghosh, P; Mohanty, B ^[3]

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1. University of Illinois at Chicago, Chicago, Illinois 60607 (United States)
2. Panjab University, Chandigarh 160014 (India)
3. Variable Energy Cyclotron Centre, Kolkata 700064 (India)

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}{sup 0} and direct {pi}{sup +}{pi}{sup -} photoproduction in ultraperipheral relativistic heavy ion collisions at {radical}(s{sub NN})=200 GeV. We observe both exclusive photoproduction and photoproduction accompanied by mutual Coulomb excitation. We find a coherent cross section of {sigma}(AuAu{yields}Au*Au*{rho}{sup 0})=530{+-}19(stat.){+-}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}{sup 0} transverse momentum spectrum (p{sub T}{sup 2}) is fit by a double exponential curve including both coherent and incoherent coupling to the target nucleus; we find {sigma}{sub inc}/{sigma}{sub coh}=0.29{+-}0.03(stat.){+-}0.08(syst.). The ratio of direct {pi}{sup +}{pi}{sup -} to {rho}{sup 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}{sup 0} spin helicity matrix elements agree within errors with the expected s-channel helicity conservation.

• OSTI ID: 21189859
• Journal Information: Physical Review. C, Nuclear Physics, Journal Name: Physical Review. C, Nuclear Physics Journal Issue: 3 Vol. 77; ISSN 0556-2813; ISSN PRVCAN
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
COLLISIONS
COULOMB EXCITATION
COUPLING
CROSS SECTIONS
DIPOLES
ELECTROMAGNETIC FIELDS
ERRORS
GEV RANGE 100-1000
GOLD IONS
HEAVY ION REACTIONS
HEAVY IONS
HELICITY
HERA STORAGE RING
MATRIX ELEMENTS
NUCLEI
PHOTONS
PHOTOPRODUCTION
PIONS MINUS
PIONS PLUS
RELATIVISTIC RANGE
S CHANNEL
SPECTRA
SPIN
TRANSVERSE MOMENTUM