Measurement of Bose--Einstein correlations with first CMS data

Bose--Einstein correlations between identical particles are measured using samples of proton-proton collisions at 0.9 and 2.36 TeV centre-of-mass energy, recorded by the CMS experiment at the CERN Large Hadron Collider. The signal is observed in the form of an enhancement of pairs of same sign charged particles with small relative momentum. A significant increase of the size of the correlated particle emission region with the particle multiplicity in the event is observed.