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" Evidence of Spin-Orbital Angular Momentum Interactions in Relativistic Heavy-Ion Collisions. "
Acharya, SAdamová, DAdler, AAdolfsson, JAggarwal, MMAglieri Rinella, GAgnello, MAgrawal, NAhammed, ZAhmad, SAhn, SUAkindinov, AAl-Turany, MAlam, SNAlbuquerque, DSDAleksandrov, DAlessandro, BAlfanda, HMAlfaro Molina, RAli, BAli, YAlici, AAlkin, AAlme, JAlt, TAltenkamper, Let al.
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AL
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| Record Number
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901905
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LA1hd0g19d
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| Title & Author
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Evidence of Spin-Orbital Angular Momentum Interactions in Relativistic Heavy-Ion Collisions. [Article]\ Acharya, SAdamová, DAdler, AAdolfsson, JAggarwal, MMAglieri Rinella, GAgnello, MAgrawal, NAhammed, ZAhmad, SAhn, SUAkindinov, AAl-Turany, MAlam, SNAlbuquerque, DSDAleksandrov, DAlessandro, BAlfanda, HMAlfaro Molina, RAli, BAli, YAlici, AAlkin, AAlme, JAlt, TAltenkamper, Let al.
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2020
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Lawrence Berkeley National Laboratory
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| Abstract
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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.
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