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| Format: | Preprint |
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2026
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| Online Access: | https://arxiv.org/abs/2606.02414 |
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| _version_ | 1866913180351987712 |
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| author | Lu, Xingjian Shi, Shuzhe |
| author_facet | Lu, Xingjian Shi, Shuzhe |
| contents | Correlations in the phase-space distribution of partons play an important role in the initial stage of relativistic heavy-ion collisions, where the matter is dense and far from equilibrium. Photons produced in the hot medium, which predominantly originate from two-parton initial states, are sensitive to two-particle correlations in the phase-space distribution. In this work, we study how pair correlations in non-equilibrium QCD matter affect in-medium photon production. We decompose the two-particle distribution as $\mathcal F_{ab}=f_a f_b+g_{ab}$, where $g_{ab}$ is the pair correlation. Focusing on the $2\to2$ quark--antiquark annihilation and Compton channels, we compute the leading-logarithmic photon spectrum by expanding the single-particle distribution and pair correlation in a spectral basis, thereby accommodating a broad class of two-particle distributions. For a rotationally invariant medium, we find that relative-angle modes of the pair correlation generate sign-changing modifications to the photon spectrum, with magnitudes that can be comparable to the factorized contribution. Thus, photon spectra, although single-particle observables, can measure the momentum correlations of the emitting medium and therefore probe the early-time hydrodynamization. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2606_02414 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Probing Pair Correlations in QCD Matter with Photon Spectra Lu, Xingjian Shi, Shuzhe High Energy Physics - Phenomenology Nuclear Theory Correlations in the phase-space distribution of partons play an important role in the initial stage of relativistic heavy-ion collisions, where the matter is dense and far from equilibrium. Photons produced in the hot medium, which predominantly originate from two-parton initial states, are sensitive to two-particle correlations in the phase-space distribution. In this work, we study how pair correlations in non-equilibrium QCD matter affect in-medium photon production. We decompose the two-particle distribution as $\mathcal F_{ab}=f_a f_b+g_{ab}$, where $g_{ab}$ is the pair correlation. Focusing on the $2\to2$ quark--antiquark annihilation and Compton channels, we compute the leading-logarithmic photon spectrum by expanding the single-particle distribution and pair correlation in a spectral basis, thereby accommodating a broad class of two-particle distributions. For a rotationally invariant medium, we find that relative-angle modes of the pair correlation generate sign-changing modifications to the photon spectrum, with magnitudes that can be comparable to the factorized contribution. Thus, photon spectra, although single-particle observables, can measure the momentum correlations of the emitting medium and therefore probe the early-time hydrodynamization. |
| title | Probing Pair Correlations in QCD Matter with Photon Spectra |
| topic | High Energy Physics - Phenomenology Nuclear Theory |
| url | https://arxiv.org/abs/2606.02414 |