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Adamová, D.; Agrawal, N.; Andrei, C.; Andronic, A.; Appelshäuser, H.; Augustinus, A.; Bagnasco, S.; Bell Hechavarria, A. D. C.; Bencedi, G.; Beole, S.; Bhatt, H.; Bielčík, J.; Biro, G.; Boi, S.; Bombara, M.; Botta, E.; Braun-Munzinger, P.; Budnikov, D.; Buxton, J. T.; Camerini, P.; Capon, A. A.; Castillo Castellanos, J.; Chattopadhyay, S.; Chibante Barroso, V.; Cosentino, M. R.; de Cuveland, J.; Fantoni, A.; Ferretti, A.; Fionda, F. M.; Foka, P.; Galvan, C. D.; Gianotti, P.; González-Zamora, P.; Hadjidakis, C.; Hetland, K. F.; Hohlweger, B.; Innocenti, G. M.; Jadlovska, S.; Jusko, A.; Karasu Uysal, A.; Karavicheva, T.; Karpechev, E.; Kirsch, S.; Kollegger, T.; Kondratyeva, N.; Krüger, M.; Kuijer, P. G.; Kumar, L.; Kwon, J. Y.; Li, X.; Lietava, R.; Majka, R. D.; Malzacher, P.; Marín, A.; Martinengo, P.; Masera, M.; Mastroserio, A.; Meddi, F.; Mohanty, B.; Munhoz, M. G.; Nattrass, C.; Nayak, T. K.; Oliver, M. H.; Otwinowski, J.; Peitzmann, T.; Peskov, V.; Pillot, P.; Putschke, J.; Rak, J.; Raniwala, R.; Ravasenga, I.; Rehman, A.; Reidt, F.; Rossi, A.; Sas, M. H. P.; Scapparone, E.; Schaefer, B.; Schmidt, C.; Schwarz, K.; Šefčík, M.; Senyukov, S.; Shahoyan, R.; Shirinkin, S.; Siddhanta, S.; Snellman, T. W.; Stankus, P.; Taillepied, G.; Tarzila, M. G.; Thoresen, F.; Torres, S. R.; Trifiro, A.; Trzaska, W. H.; Vande Vyvre, P.; Varga, Z.; Vasiliev, A.; Vilakazi, Z.; Weber, M.; Wessels, J. P.; Yalcin, S.; Yang, S.
Physical review letters, 07/2020, Letnik: 125, Številka: 1Journal Article
The first evidence of spin alignment of vector mesons ( K*0 and ϕ ) in heavy-ion collisions at the Large Hadron Collider (LHC) is reported. The spin density matrix element ρ 00 is measured at midrapidity ( | y | < 0.5 ) in Pb-Pb collisions at a center-of-mass energy ( √sNN ) of 2.76 TeV with the ALICE detector. ρ 00 values are found to be less than 1/3 (1/3 implies no spin alignment) at low transverse momentum ( p T < 2 GeV / c ) for K*0 and ϕ at a level of 3 σ and 2 σ , respectively. No significant spin alignment is observed for the K0S meson ( spin = 0 ) in Pb-Pb collisions and for the vector mesons in p p collisions. The measured spin alignment is unexpectedly large but qualitatively consistent with the expectation from models which attribute it to a polarization of quarks in the presence of angular momentum in heavy-ion collisions and a subsequent hadronization by the process of recombination.
