Speaker
Monika Sharma
(Vanderbilt University (US))
Description
Observation of a long-range near-side two-particle correlation (known as the "Ridge") in high-multiplicity pp and pPb collisions opened up new opportunities of exploring novel QCD dynamics in small collision systems. To further investigate the origin of this phenomenon, new measurements of two-particle correlations with identified $\pi^0$, $K^0_s$ and Lambda trigger particles in 5.02 TeV pPb and 2.76 TeV PbPb collisions are presented. One unique feature of this analysis is the implementation of a high-multiplicity trigger during the 2013 LHC pPb run, which enables the correlation studies to be performed up to a multiplicity range that is comparable to mid-central PbPb collisions at 2.76 TeV. The $K^0_s$ and Lambdas are cleanly reconstructed via their secondary decay vertices over a wide pseudorapidity and transverse momentum range 0.2 $< p_T <$ 6 GeV/c. Neutral pions are reconstructed through the decay channel of two photons in the $p_T$ range of 0.7-5.0 GeV/c. The second-order ($v_2$) and third-order ($v_3$) anisotropy harmonics of $\pi^0$, $K^0_s$ and Lambda are extracted from long-range correlations as a function of particle multiplicity and $p_T$. The wide $p_T$ coverage and rich sample of high multiplicity pPb events allow: (1) a precise examination of the mass ordering effect of $v_n$ at low $p_T$ as predicted by hydrodynamics for a collectively expanding medium; (2) exploration of possible constituent quark number scaling of $v_2$ and $v_3$ between mesons and baryons as was observed in high-energy nucleus-nucleus collisions.
| On behalf of collaboration: | CMS |
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Primary author
Monika Sharma
(Vanderbilt University (US))
