First measurement of D*+ vector meson spin alignment in Pb–Pb collisions at TeV


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Acharya S., Agarwal A., Aglieri Rinella G., Aglietta L., Agnello M., Agrawal N., ...More

Journal of High Energy Physics, vol.2025, no.10, 2025 (SCI-Expanded, Scopus) identifier identifier

  • Publication Type: Article / Article
  • Volume: 2025 Issue: 10
  • Publication Date: 2025
  • Doi Number: 10.1007/jhep10(2025)094
  • Journal Name: Journal of High Energy Physics
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, INSPEC, MathSciNet, zbMATH, Directory of Open Access Journals, Nature Index
  • Keywords: Heavy Ion Experiments, Particle Correlations and Fluctuations, QCD, Quark Gluon Plasma
  • Yıldız Technical University Affiliated: Yes

Abstract

The first measurement of prompt D*+-meson spin alignment in ultrarelativistic heavy-ion collisions with respect to the direction orthogonal to the reaction plane is presented. The spin alignment is quantified by measuring the element ρ00 of the diagonal spin-density matrix for prompt D*+ mesons with 4 < pT< 30 GeV/c in two rapidity intervals, |y| < 0.3 and 0.3 < |y| < 0.8, in central (0–10%) and midcentral (30–50%) Pb–Pb collisions at TeV. Evidence of spin alignment ρ00> 1/3 has been found for pT> 15 GeV/c and 0.3 < |y| < 0.8 with a significance of 3.1σ. The measured spin alignment of prompt D*+ mesons is compared with the one of inclusive J/ψ mesons measured at forward rapidity (2.5 < y < 4).