Abstract
The paper presents studies of Bose–Einstein Correlations (BEC) for pairs of like-sign charged particles measured in the kinematic range p_mathrm{T}> 100 MeV and |eta |< 2.5 in proton collisions at centre-of-mass energies of 0.9 and 7 TeV with the ATLAS detector at the CERN Large Hadron Collider. The integrated luminosities are approximately 7 upmu b^{-1}, 190 upmu b^{-1} and 12.4 nb^{-1} for 0.9 TeV, 7 TeV minimum-bias and 7 TeV high-multiplicity data samples, respectively. The multiplicity dependence of the 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.
Highlights
Particle correlations play an important role in the understanding of multiparticle production
In nucleus– nucleus collisions the dependence of the particle emitter size on the transverse momentum is explained as a “collective flow”, which generates a characteristic fall-off of the emitter size with increasing transverse momentum [36,37,38] while strong space–time momentum–energy correlations may offer an explanation in more “elementary” leptonic and hadronic systems [6,7,9,30,31,32,35] where Bose–Einstein correlations (BEC) measurements serve as a test of different models [30,31,32,39,40,41,42,43,44,45,46]
The innermost part of the ATLAS detector is the inner detector (ID), which has full coverage in φ and covers the pseudorapidity range |η| < 2.5.1 It consists of a silicon pixel detector (Pixel), a silicon microstrip detector (SCT) and a transition radiation tracker (TRT)
Summary
Particle correlations play an important role in the understanding of multiparticle production. The size of the source emitting the correlated particles has been observed to increase with particle multiplicity This can be understood as arising from the increase in the initial geometrical region of overlap of the colliding objects [22]: a large overlap implies a large multiplicity. While this dependence is natural in nucleus–nucleus collisions, the increase of size with multiplicity has been observed in hadronic and leptonic interactions. The results are compared to measurements at the same or lower energies
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