Observation of Enhanced Long-Range Elliptic Anisotropies Inside High-Multiplicity Jets in pp Collisions at √s=13 TeV

• Published in: Physical review letters Vol. 133; no. 14
• Main Authors: Waltenberger, W., Gianneios, P., Vander Velde, C., Mercadante, P. G., Hadjiiska, R., Bargassa, P., Lohezic, V., Rosowsky, A., Chabert, E. C., Grimault, C., Haeberle, R., Sessini, M. A., Verdier, P., Botta, V., Mausolf, F., Pozdnyakov, A., De Silva, M., Jafari, A., Lange, W., Kyriakis, A., Bhatnagar, V., Kumar, A., Dutta, S., Saha, N. R., Sahu, B., Abbrescia, M., Silvestris, L., Verwilligen, P., Costa, S., Viliani, L., Bacchetta, N., Aimè, C., Spagnolo, P., Obertino, M. M., Hong, J., Lee, K., Beyrouthy, T., Hoorani, H. R., Bunkowski, K., Dordevic, M., Perez Dengra, C., Gonzalez Caballero, I., Hegeman, J., Lange, C., Gurpinar Guler, E., Sunar Cerci, D., Brown, R. M., Holmberg, M. -L., Seez, C., Wardle, N., Bartek, R., Demiragli, Z., Jeon, S., Cutts, D., Kwon, T., Mondal, S., Zhang, W., Calderon De La Barca Sanchez, M., Guiang, J., Letts, J., Barzdukas, A., Reid, M., Dickinson, J., Dutta, I., Merkel, P., Mrenna, S., Spiegel, L., Menendez, N., Rawal, N., Rosenzweig, D., Baarmand, M. M., Merrit, A. H., Oh, G., Neogi, O., Sekhar, S., Salvatico, R., Hadley, N. J., Kellogg, R. G., Lai, Y., Papageorgakis, C., Novak, A., Roland, G., Wyslouch, B., Vagnerini, A., Hay, L., Taliercio, A., Townsend, A., Yates, B. R., Addesa, F. M., Kopp, G., Halkiadakis, E., Karacheban, O., Hussain, A., Lee, S. W., Mankel, A., Chen, Y., Andreev, V., Karneyeu, A., Kirsanov, M., Slabospitskii, S.
• Format: Journal Article
• Language: English
• Published: United States American Physical Society (APS) 30-09-2024
• Subjects: Hadron colliders; NUCLEAR PHYSICS AND RADIATION PHYSICS; Particle correlations & fluctuations; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Quark & gluon jets; Relativistic heavy-ion collisions
• ISSN: 0031-9007

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 $N^j_{ch}$≈100. Fourier harmonics are extracted from long-range azimuthal correlation functions to characterize azimuthal anisotropy for |Δη*|>2. For low-$N^j_{ch}$ jets, the long-range elliptic anisotropic harmonic, $v^*_2$, is observed to decrease with Νj ch. This trend is well described by Monte Carlo event generators. However, a rising trend for $v^*_2$ emerges at $N^j_{ch}$ ≳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.