First Measurement of Bose-Einstein Correlations in Proton-Proton Collisions at √s=0.9 and 2.36 TeV at the LHC.

In particle collisions, the space-time structure of the hadronization source can be studied using measurements of Bose–Einstein correlations (BEC) between pairs of identical bosons. Boson interferometry at the Large Hadron Collider provides a powerful tool to investigate the space-time structure of the particle emission source on femtometric length scales at different center-of-mass energies and with different initial states, using the same detector. This article reports the first measurement of BEC parameters in pp collisions at 0.9 and 2.36 TeV with the CMS detector. The signal is observed in the form of an enhancement of pairs of same-sign charged particles with small relative four-momentum. The size of the correlated particle emission region is seen to increase significantly with the particle multiplicity of the event.