Publication : t10/151

Abstract:
It has been argued that high-multiplicity proton-proton collisions at the LHC may exhibit collective phenomena usually studied in the context of heavy-ion collisions, such as elliptic flow. We study this issue using a Monte Carlo implementation of the dipole cascade model. The eccentricity of the transverse area defined by the spatial distribution of produced gluons is found to be close to 40%, similar to the value in semi-central nucleus-nucleus collisions. The resulting elliptic flow is predicted to be in the range 6-7%, comparable to the value in nucleus-nucleus collisions at RHIC. Experimentally, elliptic flow is inferred from the azimuthal correlation between hadrons, which receives contributions from collective flow, and from various other effects referred to as "nonflow". We present the first prediction for the azimuthal correlation in the absence of flow, and argue that the presence of flow is signaled by an up to 50% reduction of correlations in high-multiplicity events.

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