We present the first measurement at the LHC of exclusive J/psi photoproduction off protons, in ultraperipheral proton-lead collisions at root s(NN) = 5.02 TeV. Events are selected with a dimuon pair produced either in the rapidity interval, in the laboratory frame, 2.5 < y < 4 (p-Pb) or -3.6 < y < -2.6 (Pb-p), and no other particles observed in the ALICE acceptance. The measured cross sections sigma(gamma + p -> J/psi + p) are 33.2 +/- 2.2(stat) +/- 3.2(syst) +/- 0.7(theor) nb in p-Pb and 284 +/- 36(stat)(-32)(+27)(syst) +/- 26(theor) nb in Pb-p collisions. We measure this process up to about 700 GeV in the gamma p center of mass, which is a factor of two larger than the highest energy studied at HERA. The data are consistent with a power law dependence of the J/psi photoproduction cross section in gamma p energies from about 20 to 700 GeV, or equivalently, from Bjorken x scaling variable between similar to 2 x 10(-2) and similar to 2 x 10(-5), thus indicating no significant change in the gluon density behavior of the proton between HERA and LHC energies.

Exclusive J/psi Photoproduction off Protons in Ultraperipheral p-Pb Collisions at root s(NN)=5.02 TeV / Abelev, B., Adam, J., Adamova, D., Aggarwal, M.M., Rinella, G.A., Agnello, M., Agostinelli, A., Agrawal, N., Ahammed, Z., Ahmad, N., Ahmed, I., Ahn, S.U., Ahn, S.A., Aimo, I., Aiola, S., Ajaz, M., Akindinov, A., Alam, S.N., Aleksandrov, D., Alessandro, B., et al.. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - STAMPA. - 113:23(2014). [10.1103/PhysRevLett.113.232504]

Exclusive J/psi Photoproduction off Protons in Ultraperipheral p-Pb Collisions at root s(NN)=5.02 TeV

Cunqueiro, L.;MEDDI, Franco;
2014

Abstract

We present the first measurement at the LHC of exclusive J/psi photoproduction off protons, in ultraperipheral proton-lead collisions at root s(NN) = 5.02 TeV. Events are selected with a dimuon pair produced either in the rapidity interval, in the laboratory frame, 2.5 < y < 4 (p-Pb) or -3.6 < y < -2.6 (Pb-p), and no other particles observed in the ALICE acceptance. The measured cross sections sigma(gamma + p -> J/psi + p) are 33.2 +/- 2.2(stat) +/- 3.2(syst) +/- 0.7(theor) nb in p-Pb and 284 +/- 36(stat)(-32)(+27)(syst) +/- 26(theor) nb in Pb-p collisions. We measure this process up to about 700 GeV in the gamma p center of mass, which is a factor of two larger than the highest energy studied at HERA. The data are consistent with a power law dependence of the J/psi photoproduction cross section in gamma p energies from about 20 to 700 GeV, or equivalently, from Bjorken x scaling variable between similar to 2 x 10(-2) and similar to 2 x 10(-5), thus indicating no significant change in the gluon density behavior of the proton between HERA and LHC energies.
2014
quarkonia, ultra-peripheral collisions, heavy-ion collisions
01 Pubblicazione su rivista::01a Articolo in rivista
Exclusive J/psi Photoproduction off Protons in Ultraperipheral p-Pb Collisions at root s(NN)=5.02 TeV / Abelev, B., Adam, J., Adamova, D., Aggarwal, M.M., Rinella, G.A., Agnello, M., Agostinelli, A., Agrawal, N., Ahammed, Z., Ahmad, N., Ahmed, I., Ahn, S.U., Ahn, S.A., Aimo, I., Aiola, S., Ajaz, M., Akindinov, A., Alam, S.N., Aleksandrov, D., Alessandro, B., et al.. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - STAMPA. - 113:23(2014). [10.1103/PhysRevLett.113.232504]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/837026
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