# J/psi Production as a Function of Charged Particle Multiplicity in pp Collisions at sqrt{s} = 7 TeV

The ALICE collaboration reports the measurement of the inclusive $\jpsi$ yield as a function of charged particle pseudorapidity density d$N_\rm{ch}$/d$\eta$ in pp collisions at $\sqrt{s}$ = 7 TeV at the LHC. $\jpsi$ particles are detected for $\pt$ > 0, in the rapidity interval |y| < 0.9 via decay into e$^+$e$^-$, and in the interval 2.5 < y < 4.0 via decay into $\mu^{+}\mu^{-}$ pairs. An approximately linear increase of the $\jpsi$ yields normalized to their event average (d$N_{\jpsi}/$d$y$)/$\langle$d$N_{\jpsi}/$d$y\rangle$ with d$N_\rm{ch}$/d$\eta$/$\langle$d$N_{ch}/$d$\eta \rangle$ is observed in both rapidity ranges, where d$N_\rm{ch}$/d$\eta$ is measured within |$\eta$| < 1 and $\pt$ > 0. In the highest multiplicity interval with $\langle$d$N_\rm{ch}$/d$\eta \rangle ({\rm {bin}})$ = 24.1, corresponding to four times the minimum bias multiplicity density, an enhancement relative to the minimum bias $\jpsi$ yield by a factor of about 5 at 2.5 < $y$ < 4 (8 at |$y$| < 0.9) is observed.

Figures

## Figure 4

 Relative $\jpsi$ yield d$N_{\jpsi}/$d$y$ as a function of relative charged particle multiplicity densities around mid-rapidity d$N_\rm{ch}$/d$\eta$ as calculated with PYTHIA 6.4 in the Perugia 2011 tune. Shown are results for directly produced $\jpsi$ in hard scatterings via the NRQCD framework at forward rapidities ($2.5 < y < 4$) and at mid-rapidity ($|y|< 0.9$)