Measurement of quarkonium production at forward rapidity in pp collisions at $\sqrt{s}$= 7 TeV

Abstract

The inclusive production cross sections at forward rapidity of J/$\psi$, $\psi$(2S), ${\rm Y}$(1S) and ${\rm Y}$(2S) are measured in pp collisions at $\sqrt{s}=7$ TeV with the ALICE detector at the LHC. The analysis is based in a data sample corresponding to an integrated luminosity of 1.35 pb${}^{-1}$. Quarkonia are reconstructed in the dimuon-decay channel and the signal yields are evaluated by fitting the ${\mu }^{+}{\mu }^{-}$ invariant mass distributions. The differential production cross sections are measured as a function of the transverse momentum $p_{\mathrm{T}}$ and rapidity $y$, over the ranges $0<p_{\mathrm{T}}<20$ GeV/$c$ for J/$\psi$, $0<p_{\mathrm{T}}<12$ GeV/$c$ for all other resonances and for $2.5<y<4$. The measured cross sections integrated over $p_{\mathrm{T}}$ and $y$, and assuming unpolarized quarkonia, are: ${\sigma }_{J/\psi }=6.69\pm 0.04\pm 0.63$ $\mu$b, ${\sigma }_{{\psi }^{\prime }}=1.13\pm 0.07\pm 0.14$ $\mu$b, ${\sigma }_{{\rm Y}(1S)}=54.2\pm 5.0\pm 6.7$ nb and ${\sigma }_{{\rm Y}(2S)}=18.4\pm 3.7\pm 2.2$ nb, where the first uncertainty is statistical and the second one is systematic. The results are compared to measurements performed by other LHC experiments and to theoretical models.

arXiv comment28 pages, 9 captioned figures, 6 tables, authors from page 23, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/552