Measurement of isolated-prompt photon$-$hadron correlations in Pb$-$Pb collisions at $\mathbf{\sqrt{\textit{s}_{\rm NN}} = 5.02}$ TeV
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arXiv
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2026
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| _version_ | 1866910188354666496 |
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| author | ALICE Collaboration |
| author_facet | ALICE Collaboration |
| contents | The ALICE Collaboration has measured the azimuthal correlation between trigger isolated-prompt photons and associated charged hadrons in Pb$-$Pb collisions at the CERN LHC, at a centre-of-mass energy per nucleon pair of \snnfive. The trigger isolated-prompt photons are measured in the transverse-momentum range $18< p_{\rm T}^γ < 40$ GeV/$c$ and pseudorapidity range $|η^γ| <0.67$. The isolation selection is based on a charged particle isolation momentum threshold $p_{\rm T}^{\rm iso, ch} = 1.5$ GeV/$c$ within a cone of radius $R=0.2$. The associated charged particles are measured in the transverse-momentum ranges $p_{\rm T}^{\rm h} > 1.8$ GeV/$c$ and pseudorapidity $|η^{\rm h}| <0.9$. The yield D$(z_{\rm T})$ of associated hadrons per trigger, with $z_{\rm T} = p_{\rm T}^{\rm h}/p_{\rm T}^γ$, is measured in three Pb$-$Pb collision centrality classes: central (0$-$30%), semicentral (30$-$50%), and peripheral (50$-$90%). An approximation to the standard $I_{\rm AA}$ is computed from the D$(z_{\rm T})$ conditional yields, using NLO pQCD predictions as pp reference. A strong suppression of this ratio is observed in central collisions compared to peripheral collisions. The result extends to a lower $p_{\rm T}^γ$ relative to those reported in previously published Pb$-$Pb collisions measurements at $\sqrt{s_{\rm NN}}=5.02$ TeV. The measurement is compared to NLO pQCD calculations that include energy loss, and to the CoLBT-hydro model. The results from central collisions are also compared with measurements of jets correlated with isolated-prompt photons and of hadrons correlated with Z$^0$ bosons, both reported by the CMS Collaboration at the LHC, as well as with direct photon$-$hadron correlation measurements reported by the PHENIX and STAR Collaborations at RHIC. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_02342 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Measurement of isolated-prompt photon$-$hadron correlations in Pb$-$Pb collisions at $\mathbf{\sqrt{\textit{s}_{\rm NN}} = 5.02}$ TeV ALICE Collaboration Nuclear Experiment Nuclear Theory The ALICE Collaboration has measured the azimuthal correlation between trigger isolated-prompt photons and associated charged hadrons in Pb$-$Pb collisions at the CERN LHC, at a centre-of-mass energy per nucleon pair of \snnfive. The trigger isolated-prompt photons are measured in the transverse-momentum range $18< p_{\rm T}^γ < 40$ GeV/$c$ and pseudorapidity range $|η^γ| <0.67$. The isolation selection is based on a charged particle isolation momentum threshold $p_{\rm T}^{\rm iso, ch} = 1.5$ GeV/$c$ within a cone of radius $R=0.2$. The associated charged particles are measured in the transverse-momentum ranges $p_{\rm T}^{\rm h} > 1.8$ GeV/$c$ and pseudorapidity $|η^{\rm h}| <0.9$. The yield D$(z_{\rm T})$ of associated hadrons per trigger, with $z_{\rm T} = p_{\rm T}^{\rm h}/p_{\rm T}^γ$, is measured in three Pb$-$Pb collision centrality classes: central (0$-$30%), semicentral (30$-$50%), and peripheral (50$-$90%). An approximation to the standard $I_{\rm AA}$ is computed from the D$(z_{\rm T})$ conditional yields, using NLO pQCD predictions as pp reference. A strong suppression of this ratio is observed in central collisions compared to peripheral collisions. The result extends to a lower $p_{\rm T}^γ$ relative to those reported in previously published Pb$-$Pb collisions measurements at $\sqrt{s_{\rm NN}}=5.02$ TeV. The measurement is compared to NLO pQCD calculations that include energy loss, and to the CoLBT-hydro model. The results from central collisions are also compared with measurements of jets correlated with isolated-prompt photons and of hadrons correlated with Z$^0$ bosons, both reported by the CMS Collaboration at the LHC, as well as with direct photon$-$hadron correlation measurements reported by the PHENIX and STAR Collaborations at RHIC. |
| title | Measurement of isolated-prompt photon$-$hadron correlations in Pb$-$Pb collisions at $\mathbf{\sqrt{\textit{s}_{\rm NN}} = 5.02}$ TeV |
| topic | Nuclear Experiment Nuclear Theory |
| url | https://arxiv.org/abs/2605.02342 |