The ALICE Collaboration has measured inclusive J/psi production in pp collisions at a center of mass energy sqrt(s)=2.76 TeV at the LHC. The results presented in this Letter refer to the rapidity ranges |y|<~0.9 and 2.5<~y<~4 and have been obtained by measuring the electron and muon pair decay channels, respectively. The integrated luminosities for the two channels are L^e_int=1.1 nb^-1 and L^mu_int=19.9 nb^-1, and the corresponding signal statistics are N_J/psi^e+e-=59 +/- 14 and N_J/psi^mu+mu-=1364 +/- 53. We present dsigma_J/psi/dy for the two rapidity regions under study and, for the forward-y range, d^2sigma_J/psi/dydp_t in the transverse momentum domain 0<~p_t<~8 GeV/c. The results are compared with previously published results at sqrt(s)=7 TeV and with theoretical calculations.
Phys.Lett. B718 (2012) 295, Phys. Lett. B 748 (2015) 472 (erratum)
HEP Data
e-Print: arXiv:1203.3641 | PDF | inSPIRE
CERN-PH-EP-2012-055
Figure 1
Top panel: invariant mass distributions for opposite-sign (OS) andlike-sign (LS) electron pairs ($|y|< 0.9$, all $p_{\rm t}$). The background estimate from the TrkRot method (see text for details) is also shown Bottom panel: the difference of the OSand LS distributions with the normalized MC signal shape superimposed. |  |
Figure 4
Double differential J/$\psi$ production cross section at $\sqrt{s}=2.76$ TeV compared to previous ALICE results at $\sqrt{s}=7$ TeV The vertical error bars represent the statistical errorswhile the boxes correspond to the systematic uncertainties. The systematic uncertainties on luminosity are not included The results are compared with a NLO NRQCD calculation performed in the region $p_{\rm t}>3$ GeV/$c$. |  |
Figure 5
The $\sqrt{s}$-dependence of $\langle p_{\rm t}\rangle$ for inclusive J/$\psi$ production, for various fixed-target and collider experiments. For the ALICE points the error bars represent the quadratic sum of statistical and systematic uncertainties. The points for $\sqrt{s}=7$ TeV have been slightly shifted to improve visibility. |  |
Figure 6
Differential J/$\psi$ production cross section at $\sqrt{s}=2.76$ TeV compared to previous ALICE results at $\sqrt{s}=7$ TeV The vertical error bars represent the statistical errorswhile the boxes correspond to the systematic uncertainties. The systematic uncertainties on luminosity are not included. |  |
