rho(0) photoproduction in ultraperipheral relativistic heavy ion collisions at root s(NN)=200 GeV
Contribuinte(s) |
UNIVERSIDADE DE SÃO PAULO |
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Data(s) |
18/04/2012
18/04/2012
2008
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Resumo |
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 ultraperipheral relativistic heavy ion collisions at root 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 +/- 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 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 +/- 0.03 (stat.) +/- 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. |
Identificador |
PHYSICAL REVIEW C, v.77, n.3, 2008 0556-2813 http://producao.usp.br/handle/BDPI/15016 10.1103/PhysRevC.77.034910 |
Idioma(s) |
eng |
Publicador |
AMER PHYSICAL SOC |
Relação |
Physical Review C |
Direitos |
restrictedAccess Copyright AMER PHYSICAL SOC |
Palavras-Chave | #TIME PROJECTION CHAMBER #VECTOR-MESON PRODUCTION #DIFFRACTIVE PRODUCTION #PROTON SCATTERING #COMPLEX NUCLEI #PHOTON #HERA #COLLIDERS #ENERGIES #PHYSICS #Physics, Nuclear |
Tipo |
article original article publishedVersion |