J/psi Production as a Function of Charged Particle Multiplicity in pp Collisions at √s = 7 TeV

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7 TeV
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The ALICE collaboration reports the measurement of inclusive J/psi
yield as a function of charged particle pseudorapidity density
dNch/deta in pp collisions at sqrt{s} = 7 TeV at the LHC.  J/psi
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-.  An approximately linear increase of the J/psi yields normalized to their event average (dNJ/psi/dy)/<dNJ/psi/dy> with
(dNch/deta)/<dNch/deta> is observed in both rapidity
ranges, where dNch/deta is measured within |eta| < 1 and pt >
0.  In the highest multiplicity interval with <dNch/deta(bin}> = 24.1, corresponding to
four times the minimum bias multiplicity, an enhancement relative to
the minimum bias J/psi yield by a factor of about 5 at 2.5 < y < 4
(8 at |y| < 0.9) is observed.