Evidence of Spin-Orbital Angular Momentum Interactions in Relativistic Heavy-Ion Collisions



Acharya, S, Adamova, D, Adler, A, Adolfsson, J, Aggarwal, MM, Rinella, G Aglieri, Agnello, M, Agrawal, N, Ahammed, Z, Ahmad, S
et al (show 987 more authors) (2020) Evidence of Spin-Orbital Angular Momentum Interactions in Relativistic Heavy-Ion Collisions. PHYSICAL REVIEW LETTERS, 125 (1). 012301-.

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Abstract

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 (sqrt[s_{NN}]) 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 3σ and 2σ, respectively. No significant spin alignment is observed for the K_{S}^{0} meson (spin=0) in Pb-Pb collisions and for the vector mesons in pp 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.

Item Type: Article
Uncontrolled Keywords: ALICE Collaboration
Depositing User: Symplectic Admin
Date Deposited: 11 Aug 2020 07:23
Last Modified: 18 Jan 2023 23:37
DOI: 10.1103/PhysRevLett.125.012301
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3097036