Measurements of Bose-Einstein correlations with the ATLAS detector

This report summarizes studies of Bose-Einstein Correlations (BEC) for pairs of like-sign charged particles measured in the kinematic range $p_T > 100$~MeV and $|\eta| < 2.5$ in $pp$ collisions at $\sqrt{s} = 0.9$ and $7$~TeV with the ATLAS detector at LHC. The integrated luminosities are approximately 7~$\mu$b$^{-1}$, 190~$\mu$b$^{-1}$ and 12.4~nb$^{-1}$ for 0.9 and 7~TeV minimum-bias and 7~TeV high-multiplicity data samples, respectively. The multiplicity dependence of BEC parameters characterizing the correlation strength and the correlation source size are investigated for charged-particle multiplicities of up to 240. A saturation effect in the multiplicity dependence of the correlation source size parameter is observed using the high-multiplicity 7 TeV data sample. The dependence of the BEC parameters on the average transverse momentum of the particle pair is also investigated. ATLAS results are compared to other experiments at the same and lower centre-of-mass energies, where possible.