Measurement of $J/\psi$ and $\psi (2S)$ Prompt Double-Differential Cross Sections in $pp$ Collisions at $\sqrt{s}=7\mathrm{TeV}$

The double-differential cross sections of promptly produced $J/\psi$ and $\psi (2S)$ mesons are measured in $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$, as a function of transverse momentum $p_T$ and absolute rapidity $|y|$. The analysis uses $J/\psi$ and $\psi (2S)$ dimuon samples collected by the CMS experiment, corresponding to integrated luminosities of 4.55 and $4.90{\mathrm{fb}}^{-1}$, respectively. The results are based on a two-dimensional analysis of the dimuon invariant mass and decay length, and extend to $p_T=120$ and 100 GeV for the $J/\psi$ and $\psi (2S)$, respectively, when integrated over the interval $|y|<1.2$. The ratio of the $\psi (2S)$ to $J/\psi$ cross sections is also reported for $|y|<1.2$, over the range $10<p_T<100\mathrm{GeV}$. These are the highest $p_T$ values for which the cross sections and ratio have been measured.

Figure 1

Projections on the dimuon invariant mass (left) and pseudo-proper-decay-length (right) axes, for the $J/\psi$ (top) and $\psi (2S)$ (bottom) events in the kinematic bins given in the plots. The right panels show dimuons of invariant mass within $\pm 3{\sigma }_{\mathrm{CB}}$ of the pole masses. The curves, identified in the legends, represent the result of the fits described in the text. The vertical bars on the data points show the statistical uncertainties.

Figure 2

The $J/\psi$ and $\psi (2S)$ differential $p_T$ cross sections times the dimuon branching fractions for four rapidity bins and integrated over the range $|y|<1.2$ (scaled up by a factor of 2 for presentation purposes), assuming the unpolarized scenario. The vertical bars show the statistical and systematic uncertainties added in quadrature.

Figure 3

The $J/\psi$ (open symbols) and $\psi (2S)$ (closed symbols) differential (unpolarized) cross sections from this analysis (circles) and from ATLAS (squares) [14, 15]. The vertical bars show the statistical and systematic uncertainties added in quadrature, not including the uncertainties from integrated luminosities and branching fractions, which are indicated by the percentages given in the legend. The curve shows a fit of the $J/\psi$ cross section measured in this analysis to a power-law function, while the band labeled FKLSW represents a calculation of the $\psi (2S)$ cross section using LDMEs determined with lower-$p_T$ LHC data [6].