Observation of a ridge correlation structure in high multiplicity pp collisions with CMS

May 23, 2011, 3:00 PM
20m
Rotonde de l'Europe (Imperial Palace)

Rotonde de l'Europe

Imperial Palace

Parallel Correlations and fluctuations Correlations and fluctuations

Speaker

Dragos Velicanu (MIT)

Description

Results on two-particle angular correlations are presented in proton-proton collisions at center of mass energies of 0.9, 2.36, 2.76 and 7 TeV, over a broad range of pseudorapidity and azimuthal angle. In very high multiplicity events at 7 TeV, a pronounced structure emerges in the two-dimensional correlation function for particle pairs with intermediate $p_T$ of 1-3 GeV/c, in the kinematic region 2.0 $< |\Delta\eta| <$ 4.8 and small \Delta\Phi. This structure, which has not been observed in pp collisions before, is similar to what is known as the "ridge" in heavy ion collisions. It is not predicted by commonly used proton-proton Monte Carlo models and is not seen in lower multiplicity pp collisions. Updated studies of this new effect as a function of particle transverse momentum, rapidity and event characteristics are shown and discussed in comparison to various model calculations.

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