Observation of enhanced long-range elliptic anisotropies inside high-multiplicity jets in pp collisions at √s = 13 TeV
File(s)
Published version
Author(s)
Type
Journal Article
Abstract
A search for collective effects inside jets produced in proton-proton collisions is performed via correlation measurements of charged particles using the CMS detector at the CERN LHC. The analysis uses data collected at a center-of-mass energy of √𝑠 =13 TeV, corresponding to an integrated luminosity of 138 fb−1. Jets are reconstructed with the anti-𝑘T algorithm with a distance parameter of 0.8 and are required to have transverse momentum greater than 550 GeV and pseudorapidity |𝜂jet|<1.6. Two-particle correlations among the charged particles within the jets are studied as functions of the particles’ azimuthal angle and pseudorapidity separations (Δ𝜙* and Δ𝜂*) in a jet coordinate basis, where particles’ 𝜂*, 𝜙* are defined relative to the direction of the jet. The correlation functions are studied in classes of in-jet charged-particle multiplicity up to 𝑁j
ch ≈100. Fourier harmonics are extracted from long-range azimuthal correlation functions to characterize azimuthal anisotropy for |Δ𝜂*| >2. For low-𝑁j
ch jets, the long-range elliptic anisotropic harmonic, 𝑣*
2, is observed to decrease with 𝑁j
ch. This trend is well described by Monte Carlo event generators. However, a rising trend for 𝑣*
2 emerges at 𝑁j
ch ≳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 jet evolution in the vacuum.
ch ≈100. Fourier harmonics are extracted from long-range azimuthal correlation functions to characterize azimuthal anisotropy for |Δ𝜂*| >2. For low-𝑁j
ch jets, the long-range elliptic anisotropic harmonic, 𝑣*
2, is observed to decrease with 𝑁j
ch. This trend is well described by Monte Carlo event generators. However, a rising trend for 𝑣*
2 emerges at 𝑁j
ch ≳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 jet evolution in the vacuum.
Date Issued
2024-10-04
Date Acceptance
2024-08-27
Citation
Physical Review Letters, 2024, 133 (14)
ISSN
0031-9007
Publisher
American Physical Society (APS)
Journal / Book Title
Physical Review Letters
Volume
133
Issue
14
Copyright Statement
© 2024 CERN, for the CMS Collaboration Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.
License URL
Identifier
https://doi.org/10.1103/physrevlett.133.142301
Publication Status
Published
Article Number
142301
Date Publish Online
2024-09-30