Observation of enhanced long-range elliptic anisotropies inside high-multiplicity jets in pp collisions at $\sqrt{s}$ = 13 TeV

Abstract

A search for partonic collective effects inside jets produced in proton-proton collisions is performed via correlation measurements of charged constituents using the CMS detector at the CERN LHC. The analysis uses data collected at a center-of-mass energy of $\sqrt{s}$ = 13 TeV, corresponding to an integrated luminosity of 138 fb${}^{-1}$. Jets are reconstructed with the anti-$k_{\mathrm{T}}$ algorithm with a distance parameter of 0.8 and are required to have transverse momentum greater than 550 GeV and pseudorapidity $|\eta |$ $<$ 1.6. Two-particle correlations among the charged constituents within the jets are studied as functions of the particles' azimuthal angle and pseudorapidity separations ($\Delta {\varphi }^{\ast }$ and $\Delta {\eta }^{\ast }$) in a jet coordinate basis, where constituents' ${\eta }^{\ast }$, ${\varphi }^{\ast }$ are defined relative to the direction of the jet. The correlation functions are studied in classes of in-jet charged-particle multiplicity up to $N_{\text{ch}}^{\mathrm{j}}$ $\approx$ 100. Fourier harmonics are extracted from long-range azimuthal correlation functions to characterize azimuthal anisotropy for $|\Delta {\eta }^{\ast }|$ $>$ 2. For low-$N_{\text{ch}}^{\mathrm{j}}$, the long-range elliptic anisotropic harmonic, $v_2^{\ast }$, is observed to decrease with $N_{\text{ch}}^{\mathrm{j}}$. This trend is well described by Monte Carlo event generators. However, a rising trend for $v_2^{\ast }$ emerges at $N_{\text{ch}}^{\mathrm{j}}$ $\gtrsim$ 80, hinting at a possible onset of collective behavior, which is not reproduced by the models tested. This observation yields new insights into the dynamics of parton fragmentation processes in the vacuum.

Replaced with the published version. Added the journal reference and the DOI. All the figures and tables can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/HIN-21-013 (CMS Public Pages)

References in corpus (61)

• The anti-k_t jet clustering algorithm
• A Brief Introduction to PYTHIA 8.1
• FastJet user manual
• Event Generation with Sherpa 2.2
• Particle-flow reconstruction and global event description with the CMS detector
• Observation of Long-Range Near-Side Angular Correlations in Proton-Proton Collisions at the LHC
• Elliptic flow of charged particles in Pb-Pb collisions at 2.76 TeV
• Heavy Ion Collisions: The Big Picture, and the Big Questions
• The CMS trigger system
• Description and performance of track and primary-vertex reconstruction with the CMS tracker
• Long-range angular correlations on the near and away side in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV
• Observation of long-range near-side angular correlations in proton-lead collisions at the LHC
• Jet energy scale and resolution in the CMS experiment in pp collisions at 8 TeV
• Observation of Associated Near-side and Away-side Long-range Correlations in sqrt(s_NN)=5.02 TeV Proton-lead Collisions with the ATLAS Detector
• Performance of the CMS muon detector and muon reconstruction with proton-proton collisions at $\sqrt{s}=$ 13 TeV
• Distributions of Charged Hadrons Associated with High Transverse Momentum Particles in pp and Au+Au Collisions at sqrt(s_NN)=200 GeV
• Multiplicity and transverse-momentum dependence of two- and four-particle correlations in pPb and PbPb collisions
• Measurement of the azimuthal anisotropy for charged particle production in sqrt(s_NN) = 2.76 TeV lead-lead collisions with the ATLAS detector
• First Results from Pb+Pb collisions at the LHC
• Evidence for collectivity in pp collisions at the LHC
• Flow analysis from multiparticle azimuthal correlations
• Towards Jetography
• Extraction and validation of a new set of CMS PYTHIA8 tunes from underlying-event measurements
• Pileup Per Particle Identification
• Long-range angular correlations of $\pi$, K and p in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV
• Observation of long-range elliptic anisotropies in $\sqrt{s}=$13 and 2.76 TeV $pp$ collisions with the ATLAS detector
• Performance of the CMS Level-1 trigger in proton-proton collisions at $\sqrt{s}=$ 13 TeV
• Creating small circular, elliptical, and triangular droplets of quark-gluon plasma
• Long range rapidity correlations and jet production in high energy nuclear collisions
• Electron and photon reconstruction and identification with the CMS experiment at the CERN LHC
• Evidence for collective multi-particle correlations in pPb collisions
• Centrality dependence of dihadron correlations and azimuthal anisotropy harmonics in PbPb collisions at sqrt(s[NN]) = 2.76 TeV
• Performance of missing transverse momentum reconstruction in proton-proton collisions at $\sqrt{s}=$ 13 TeV using the CMS detector
• High transverse momentum triggered correlations over a large pseudorapidity acceptance in Au+Au collisions at sqrt(s_NN)=200 GeV
• Novel Collective Phenomena in High-Energy Proton-Proton and Proton-Nucleus Collisions
• Charged-particle nuclear modification factors in PbPb and pPb collisions at sqrt(s[NN]) = 5.02 TeV
• A modified cluster-hadronization model
• Measurement of long-range near-side two-particle angular correlations in pp collisions at sqrt(s) = 13 TeV
• Performance of reconstruction and identification of $\tau$ leptons decaying to hadrons and ${\nu }_{\tau }$ in pp collisions at $\sqrt{s}=$ 13 TeV
• Pileup mitigation at CMS in 13 TeV data
• Measurements of elliptic and triangular flow in high-multiplicity ${}^3$He$+$Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV
• Long-range and short-range dihadron angular correlations in central PbPb collisions at a nucleon-nucleon center of mass energy of 2.76 TeV
• Measurement of multi-particle azimuthal correlations in $pp$, $p$+Pb and low-multiplicity Pb+Pb collisions with the ATLAS detector
• Studies of azimuthal dihadron correlations in ultra-central PbPb collisions at sqrt(s[NN]) = 2.76 TeV
• Long-range two-particle correlations of strange hadrons with charged particles in pPb and PbPb collisions at LHC energies
• Long-range pseudorapidity dihadron correlations in $d$+Au collisions at $\sqrt{s_{\mathrm{NN}}}=200$ GeV
• System size dependence of cluster properties from two-particle angular correlations in Cu+Cu and Au+Au collisions at $\sqrt{s_{{}_{NN}}}$ = 200 GeV
• Measurements of long-range near-side angular correlations in $\sqrt{s_{\text{NN}}}=5$TeV proton-lead collisions in the forward region
• Measurement of multi-particle azimuthal correlations with the subevent cumulant method in $pp$ and $p$+Pb collisions with the ATLAS detector at the LHC
• Estimates of hadron azimuthal anisotropy from multiparton interactions in proton-proton collisions at sqrt(s) = 14 TeV
• Measurements of multiparticle correlations in $d$$+$Au collisions at 200, 62.4, 39, and 19.6 GeV and $p$$+$Au collisions at 200 GeV and implications for collective behavior
• Two-particle azimuthal correlations in photonuclear ultraperipheral Pb+Pb collisions at 5.02 TeV with ATLAS
• Measurements of two-particle correlations in $e^{+}{e}^{-}$ collisions at 91 GeV with ALEPH archived data
• Nuclear like effects in proton-proton collisions at high energy
• Two-particle azimuthal correlations as a probe of collective behaviour in deep inelastic $\text{ep}$ scattering at HERA
• Novel observables for exploring QCD collective evolution and quantum entanglement within individual jets
• Energy evolution of the moments of the hadron distribution in QCD jets including NNLL resummation and NLO running-coupling corrections
• Two-particle azimuthal correlations in $\gamma$p interactions using pPb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 8.16 TeV
• Long-range near-side correlation in $e^{+}{e}^{-}$ Collisions at 183-209 GeV with ALEPH Archived Data
• Azimuthal correlations in photoproduction and deep inelastic $\mathbf{ep}$ scattering at HERA
• Measurement of Two-Particle Correlations of Hadrons in $e^{+}{e}^{-}$ Collisions at Belle

Cited by in corpus (11)

• Thermodynamical string fragmentation and string density effects in jets
• Search for nuclear modifications of B${}^{+}$ meson production in pPb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 8.16 TeV
• Soft QCD Physics at the LHC: highlights and opportunities
• Flattenicity as "centrality" estimator in p-Pb collisions simulated with PYTHIA 8.312 Angantyr
• Exploring hidden sectors with two-particle angular correlations at future $e^{+}{e}^{-}$ colliders
• Universality of scaled particle spectra in ultrarelativistic heavy-ion collisions
• Impact of soft QCD effects over intrajet azimuthal anisotropies
• Understanding the medium-like effects in the jet-like yield in pp and p-Pb collisions using event generators
• System size and event shape dependence of particle-identified balance functions in proton-proton collisions at $\sqrt{s}=13$ TeV using PYTHIA 8 and EPOS models
• Finite $V_{2\Delta }$ puzzle in low-multiplicity pp collisions from ultra-long-range azimuthal correlations in the string-shoving model
• Two-particle number and transverse momentum balance function with event topology in pp collisions at $\sqrt{s}=13$ TeV