| Abstract: | The ALICE experiment at the LHC has studied inclusive J/psi production at
central and forward rapidities in pp collisions at sqrt(s) = 7 TeV. In this
Letter, we report on the first results obtained detecting the J/psi through its
dilepton decay into e+e- and mu+mu- pairs in the rapidity range |y|<0.9 and
2.5<y<4, respectively, and with acceptance down to zero p_T. In the dielectron
channel the analysis was carried out on a data sample corresponding to an
integrated luminosity L_int = 3.9 nb^-1 and the number of signal events is
N_J/psi=249 pm 27 (stat.) pm 20 (syst.); the corresponding figures in the
dimuon channel are L_int = 15.6 nb ^-1 and N_J/psi = 1924 pm 77 (stat.) pm
144(syst.). The measured production cross sections are sigma_J/psi (|y|<0.9) =
10.7 pm 1.2 (stat.) pm 1.7 (syst.) + 1.6 -2.3 (syst.pol.) mub and
sigma_J/psi (2.5<y<4) = 6.31 pm 0.25 (stat.) pm 0.80 (syst.) +0.95 -1.96
(syst.pol.) mub. The differential cross sections, in transverse momentum and
rapidity, of the J/psi were also measured. |
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