Abstract
Exclusive {{{uprho _{}^{}} _{}^{}}{{left( {770}right) }{}_{}^{}}} ^{0} photoproduction is measured for the first time in ultraperipheral pPb collisions at sqrt{smash [b]{s_{_{mathrm {NN}}}}} = 5.02,text {Te}text {V} with the CMS detector. The cross section sigma ({upgamma _{}^{}} mathrm{p}rightarrow {{{uprho _{}^{}} _{}^{}}{{left( {770}right) }{}_{}^{}}} ^{0}mathrm{p}) is 11.0 pm 1.4,text {(stat)} pm 1.0,text {(syst)} mu b at langle W_{{upgamma _{}^{}} mathrm{p}}rangle = 92.6,text {Ge}text {V} for photon–proton centre-of-mass energies W_{{upgamma _{}^{}} mathrm{p}} between 29 and 213,text {Ge}text {V} . The differential cross section mathrm {d}sigma /mathrm {d}|t | is measured in the interval 0.025< |t | < 1,text {Ge}text {V} ^{2} as a function of W_{{upgamma _{}^{}} mathrm{p}}, where t is the squared four-momentum transfer at the proton vertex. The results are compared with previous measurements and theoretical predictions. The measured cross section sigma ({upgamma _{}^{}} mathrm{p}rightarrow {{{uprho _{}^{}} _{}^{}}{{left( {770}right) }{}_{}^{}}} ^{0}mathrm{p}) has a power-law dependence on the photon–proton centre-of-mass, consistent with electron–proton collision measurements performed at HERA. The W_{{upgamma _{}^{}} mathrm{p}} dependence of the exponential slope of the differential cross section mathrm {d}sigma /mathrm {d}|t | is also measured.
Highlights
The main background sources are listed below.– Nonresonant π+π− production
Within the solenoid volume are a silicon pixel and strip tracker, a lead tungsten crystal electromagnetic calorimeter (ECAL), and a brass and scintillator hadron calorimeter (HCAL), each composed of a barrel and two endcap sections
The CMS Collaboration has made the first measurement of exclusive ρ (770)0 photop√roduction off protons in ultraperipheral pPb collisions at s = 5.02 TeV
Summary
[5,6,7,8,9,10]. 5.02 TeV at the LHC, the ALICE Collaboration has measured the exclusive photoproduction of J/ψ(1S) mesons in the centre-of-mass energy interval 20 < Wγ p < 700 GeV [11,12]. 5.02 TeV at the LHC, the ALICE Collaboration has measured the exclusive photoproduction of J/ψ(1S) mesons in the centre-of-mass energy interval 20 < Wγ p < 700 GeV [11,12]. Exclusive photoproduction of ρ (770)0 mesons was first studied in fixed-target experiments at Wγ p values up to 20 GeV [15,16]. Exclusive photoproduction of ρ (770)0 mesons has been studied by the STAR Collaboration in ultraperipheral AuAu collisions at the BNL RHIC collider [21,22,23], and by the ALICE Collaboration in PbPb collisions [24]. The Glauber approach reproduces the measured cross sections well at lower energies.
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