Disentangling Sources of Momentum Fluctuations in Xe + Xe and Pb + Pb Collisions with the ATLAS Detector

• Published in: Physical review letters 2024-12, Vol.133 (25)
• Main Authors: Abreu, H., Addepalli, S. V., Ahmadov, F., Ashby Pickering, R. A., Baer, T. M., Ballabene, E., Bechtle, P., Bendebba, F., Biglietti, M., Bouquet, R., Brau, J. E., Bruschi, M., Butler, J. M., Cabrera Urbán, S., Carmignani, J., Chatterjee, M., Chubinidze, Z., Cieri, D., Corchia, F. A., Cristoforetti, M., Cueto, A., Cui, H., Dal Santo, D., De Sanctis, U., Duda, D., Duden, E. R., Ezzarqtouni, S., Fellers, D. E., Filthaut, F., Fox, H., Franco, L., Franconi, L., Franklin, M., Gargan, J. M., Gil, D. T., Golling, T., Gorini, B., Gouighri, M., Guilloton, E., Guo, Y., Hill, E., Hitchings, T. G., Introzzi, G., Islam, W., Jones, P., Kawade, K., Klein, S. B., Lahbabi, F. Z., Landgraf, U., Lanza, A., LeBlanc, M., Lee, S. C., Lehmann Miotto, G., Levêque, J., Li, B., Lie, K., Lucio Alves, F. L., Lux, A. B., Lyukova, M. M., Mascione, D., Maurer, J., Mineev, M., Mohapatra, S., Montereali, F., Negrini, M., Nitschke, J-E., Panduro Vazquez, J. G., Parodi, F., Principe Martin, M. A., Procter, T., Robles Manzano, M., Saibel, A., Sandhoff, M., Santi, L., Sawyer, C., Schegelsky, V. A., Seixas, J. M., Shinner, J. D., Shipsey, I. P. J., Siral, I., Skorda, E., Smakhtin, V., Suzuki, H., Sykora, T., Timoshyn, D., Ting, E. X. L., Tsai, M., Tu, Y., Unal, G., Valente, M., Valiente Moreno, E., Van Der Graaf, A., Vu, N. K., Vukotic, I., Wang, Z., Ward, R. J., Wengler, T., Wilbern, D. J., Wilkinson, J. J. H., Yang, H. J.
• Format: Article
• Language: English
• ISSN: 0031-9007
• DOI: 10.1103/PhysRevLett.133.252301

High-energy nuclear collisions create a quark-gluon plasma, whose initial condition and subsequent expansion vary from event to event, impacting the distribution of the eventwise average transverse momentum [ P ( [ p T ] ) ]. Disentangling the contributions from fluctuations in the nuclear overlap size (geometrical component) and other sources at a fixed size (intrinsic component) remains a challenge. This problem is addressed by measuring the mean, variance, and skewness of P ( [ p T ] ) in Pb 208 + Pb 208 and Xe 129 + Xe 129 collisions at s NN = 5.02 and 5.44 TeV, respectively, using the ATLAS detector at the LHC. All observables show distinct features in ultracentral collisions, which are explained by a suppression of the geometrical component as the overlap area reaches its maximum. These results demonstrate a new technique to separate geometrical and intrinsic fluctuations, providing constraints on initial conditions and properties of the quark-gluon plasma, such as the speed of sound. © 2024 CERN, for the ATLAS Collaboration 2024 CERN