# Correlations between jets and charged particles in PbPb andppcollisionsat $\sqrt{^{s}NN}$ = 2.76TeV - Zurich Open Repository and Archive

CMS Collaboration; Canelli, F; Chiochia, V; Kilminster, B; Robmann, P; et al (2016). Correlations between jets and charged particles in PbPb andppcollisionsat $\sqrt{^{s}NN}$ = 2.76TeV. Journal of High Energy Physics, 1602:1-38.

## Abstract

CThe quark-gluon plasma is studied via medium-induced changes to correlations between jets and charged particles in PbPb collisions compared to pp reference data. This analysis uses data sets from PbPb and pp collisions with integrated luminosi- ties of 166 μb$^{−1}$ and 5.3 pb$^{−1}$, respectively, collected at $\sqrt{^{s}NN}$ = 2.76 TeV. The angular distributions of charged particles are studied as a function of relative pseudorapidity (∆η) and relative azimuthal angle (∆φ) with respect to reconstructed jet directions. Charged particles are correlated with all jets with transverse momentum ($p_{T}$) above 120 GeV, and with the leading and subleading jets (the highest and second-highest in $p_{T}$, respectively) in a selection of back-to-back dijet events. Modifications in PbPb data relative to pp reference data are characterized as a function of PbPb collision centrality and charged particle $p_{T}$. A centrality-dependent excess of low-$p_{T}$ particles is present for all jets studied, and is most pronounced in the most central events. This excess of low-$p_{T}$ particles follows a Gaussian-like distribution around the jet axis, and extends to large relative angles of ∆η ≈ 1 and ∆φ ≈ 1.

## Abstract

CThe quark-gluon plasma is studied via medium-induced changes to correlations between jets and charged particles in PbPb collisions compared to pp reference data. This analysis uses data sets from PbPb and pp collisions with integrated luminosi- ties of 166 μb$^{−1}$ and 5.3 pb$^{−1}$, respectively, collected at $\sqrt{^{s}NN}$ = 2.76 TeV. The angular distributions of charged particles are studied as a function of relative pseudorapidity (∆η) and relative azimuthal angle (∆φ) with respect to reconstructed jet directions. Charged particles are correlated with all jets with transverse momentum ($p_{T}$) above 120 GeV, and with the leading and subleading jets (the highest and second-highest in $p_{T}$, respectively) in a selection of back-to-back dijet events. Modifications in PbPb data relative to pp reference data are characterized as a function of PbPb collision centrality and charged particle $p_{T}$. A centrality-dependent excess of low-$p_{T}$ particles is present for all jets studied, and is most pronounced in the most central events. This excess of low-$p_{T}$ particles follows a Gaussian-like distribution around the jet axis, and extends to large relative angles of ∆η ≈ 1 and ∆φ ≈ 1.

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Item Type: Journal Article, refereed, original work 07 Faculty of Science > Physics Institute 530 Physics English 2016 10 Jan 2017 10:30 10 Jan 2017 10:30 Springer 1029-8479 Publisher DOI. An embargo period may apply. https://doi.org/10.1007/JHEP02(2016)156

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