J/ψ production as a function of charged particle multiplicity in pp collisions at √s =7 TeV

The ALICE Collaboration reports the measurement of the relative J/ψ yield as a function of charged particle pseudorapidity density dNch/dη in pp collisions at √s = 7 TeV at the LHC. J/ψ particles are detected for pt > 0, in the rapidity interval |y| 0. In the highest multiplicity interval with (dNch/dη(bin)) = 24.1, corresponding to four times the minimum bias multiplicity density, an enhancement relative to the minimum bias J/ψ yield by a factor of about 5 at 2.5 <y <4 (8 at |y|