This paper presents studies of Bose-Einstein correlations (BEC) in proton-proton collisions at a centre-of-mass energy of 13 TeV, using data from the ATLAS detector at the CERN Large Hadron Collider. Data were collected in a special low-luminosity configuration with a minimum-bias trigger and a high-multiplicity track trigger, accumulating integrated luminosities of 151 mu b(-1) and 8.4 nb(-1), respectively. The BEC are measured for pairs of like-sign charged particles, each with vertical bar eta vertical bar < 2.5, for two kinematic ranges: the first with particle pr > 100 MeV and the second with particle pr > 500 MeV. The BEC parameters, characterizing the source radius and particle correlation strength, are investigated as functions of charged-particle multiplicity (up to 300) and average transverse momentum of the pair (up to 1.5 GeV). The double-differential dependence on charged-particle multiplicity and average transverse momentum of the pair is also studied. The BEC radius is found to be independent of the charged-particle multiplicity for high charged-particle multiplicity (above 100), confirming a previous observation at lower energy. This saturation occurs independent of the transverse momentum of the pair.

Two-particle Bose-Einstein correlations in pp collisions at root s=13 TeV measured with the ATLAS detector at the LHC

Alberghi, GL;Bellagamba, L;Bindi, M;Boscherini, D;Cabras, G;Caforio, D;DeCastro, S;Di Sipio, R;Fabbri, L;Franchini, M;Gabrielli, A;Giacobbe, B;Macchiolo, A;Massa, L;Polini, A;