Results on two-particle angular correlations for charged particles produced in $pp$ collisions at a center-of-mass energy of 13 TeV are presented. The data were taken with the CMS detector at the LHC and correspond to an integrated luminosity of about $270{\mathrm{nb}}^{-1}$. The correlations are studied over a broad range of pseudorapidity ($|\eta |<2.4$) and over the full azimuth ($\varphi$) as a function of charged particle multiplicity and transverse momentum ($p_{\mathrm{T}}$). In high-multiplicity events, a long-range ($|\mathrm{\Delta }\eta |>2.0$), near-side ($\mathrm{\Delta }\varphi \approx 0$) structure emerges in the two-particle $\mathrm{\Delta }\eta$–$\mathrm{\Delta }\varphi$ correlation functions. The magnitude of the correlation exhibits a pronounced maximum in the range $1.0<p_{\mathrm{T}}<2.0\mathrm{GeV}/c$ and an approximately linear increase with the charged particle multiplicity, with an overall correlation strength similar to that found in earlier $pp$ data at $\sqrt{s}=7\mathrm{TeV}$. The present measurement extends the study of near-side long-range correlations up to charged particle multiplicities $N_{\mathrm{ch}}\sim 180$, a region so far unexplored in $pp$ collisions. The observed long-range correlations are compared to those seen in $pp$, $p\mathrm{Pb}$, and PbPb collisions at lower collision energies.

• Received 11 October 2015

DOI:https://doi.org/10.1103/PhysRevLett.116.172302

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© 2016 CERN, for the CMS Collaboration