The ALICE experiment at the LHC has studied inclusive J/ψ production at central and forward rapidities in pp collisions at √s = 7 TeV. In this Letter, we report on the first results obtained detecting the J/ψ through its dilepton decay into e+e− and μ+μ− pairs in the rapidity range |y| < 0.9 and 2.5 < y < 4, respectively, and with acceptance down to zero pT . 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/ψ) = 249 ± 27 (stat.) ± 20 (syst.); the corresponding figures in the dimuon channel are L(int) = 15.6 nb−1 and N(J/ψ) = 1924 ± 77 (stat.) ± 144 (syst.). The measured
production cross sections are σ(J/ψ)(|y| < 0.9) = 10.7 ± 1.2 (stat.) ± 1.7 (syst.) +1.6 −2.3 (syst.pol.) μb, and σ(J/ψ) (2.5 < y < 4) = 6.31 ± 0.25 (stat.) ± 0.80 (syst.) +0.95 −1.96 (syst.pol.) μb. The differential cross sections, in transverse momentum and rapidity, of the J/ψ were also measured.
