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 ρ00 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. ρ00 values are found to be less than 1/3 (1/3 implies no spin alignment) at low transverse momentum (pT<2 GeV/c) for K∗0 and φ at a level of 3σ and 2σ, respectively. No significant spin alignment is observed for the KS0 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.

Acharya S., Adamova D., Adler A., Adolfsson J., Aggarwal M.M., Aglieri Rinella G., et al. (2020). Evidence of Spin-Orbital Angular Momentum Interactions in Relativistic Heavy-Ion Collisions. PHYSICAL REVIEW LETTERS, 125(1), 1-12 [10.1103/PhysRevLett.125.012301].

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

Alici A.;Arcelli S.;Bellini F.;Carnesecchi F.;Cifarelli L.;Colocci M.;Scioli G.;
2020

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 ρ00 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. ρ00 values are found to be less than 1/3 (1/3 implies no spin alignment) at low transverse momentum (pT<2 GeV/c) for K∗0 and φ at a level of 3σ and 2σ, respectively. No significant spin alignment is observed for the KS0 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.
2020
Acharya S., Adamova D., Adler A., Adolfsson J., Aggarwal M.M., Aglieri Rinella G., et al. (2020). Evidence of Spin-Orbital Angular Momentum Interactions in Relativistic Heavy-Ion Collisions. PHYSICAL REVIEW LETTERS, 125(1), 1-12 [10.1103/PhysRevLett.125.012301].
Acharya S.; Adamova D.; Adler A.; Adolfsson J.; Aggarwal M.M.; Aglieri Rinella G.; Agnello M.; Agrawal N.; Ahammed Z.; Ahmad S.; Ahn S.U.; Akindinov A...espandi
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/775720
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