First measurement of D$^{*+}$ vector spin alignment in Pb$-$Pb collisions at $\mathbf{\sqrt{s_{\rm NN}} = 5.02}$ TeV
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arXiv
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| Format: | Preprint |
| Published: |
2025
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| _version_ | 1866915621950717952 |
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| author | ALICE Collaboration |
| author_facet | ALICE Collaboration |
| contents | 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 $ρ_{00}$ of the diagonal spin-density matrix for prompt D$^{*+}$ mesons with $4<p_{\rm T}<30$ 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 $\sqrt{s_{\rm NN}}=5.02$ TeV. Evidence of spin alignment $ρ_{00}>1/3$ has been found for $p_{\rm T}>15$ 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 ($2.5 < y < 4$). |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2504_00714 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | First measurement of D$^{*+}$ vector spin alignment in Pb$-$Pb collisions at $\mathbf{\sqrt{s_{\rm NN}} = 5.02}$ TeV ALICE Collaboration Nuclear Experiment High Energy Physics - Experiment 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 $ρ_{00}$ of the diagonal spin-density matrix for prompt D$^{*+}$ mesons with $4<p_{\rm T}<30$ 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 $\sqrt{s_{\rm NN}}=5.02$ TeV. Evidence of spin alignment $ρ_{00}>1/3$ has been found for $p_{\rm T}>15$ 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 ($2.5 < y < 4$). |
| title | First measurement of D$^{*+}$ vector spin alignment in Pb$-$Pb collisions at $\mathbf{\sqrt{s_{\rm NN}} = 5.02}$ TeV |
| topic | Nuclear Experiment High Energy Physics - Experiment |
| url | https://arxiv.org/abs/2504.00714 |