Calculations of Di-Hadron Production via Two-Photon Processes in Relativistic Heavy-Ion Collisions

Abstract

Two-photon processes in relativistic heavy-ion collisions have emerged as a critical probe of quantum electrodynamics in ultra-intense electromagnetic fields, with recent focus extending beyond dileptons to hadronic final states. At present, quantitative studies of di-hadron production via two-photon interactions remain scarce. In this work, we employ the Equivalent Photon Approximation and the two-photon fusion measurements from \(e^{+}e^{-}\) collisions to obtain differential cross-section predictions for \(π^{+}π^{-}\), \(K^{+}K^{-}\), and \(p\bar{p}\) pairs produced in ultra-peripheral \(\mathrm{Au{+}Au}\) collisions at \(\sqrt{s_{NN}} = 200\,\text{GeV}\) within the STAR acceptance, as well as in \(\mathrm{Pb{+}Pb}\) collisions at \(\sqrt{s_{NN}} = 5.36\,\text{TeV}\) within typical LHC acceptance. The calculations deliver the unified baseline for light-meson and baryon pairs in this environment, supplying benchmarks for upcoming STAR and LHC measurements and guiding future systematic investigations of hadronic two-photon processes at RHIC and LHC facilities.

Figures (5)

• Figure 1: Two-dimensional distributions of the photon flux as functions of transverse distance $r_{\perp}$ from the nuclear center and photon energy $\omega$, viewed along the beam direction. Calculations are performed using Woods–Saxon nuclear density profiles for (a) $^{197}\mathrm{Au}$ nuclei in Au+Au collisions at $\sqrt{s_{NN}} = 200\,\mathrm{GeV}$ at RHIC, and (b) $^{208}\mathrm{Pb}$ nuclei in Pb+Pb collisions at $\sqrt{s_{NN}} = 5.36\,\mathrm{TeV}$ at the LHC.
• Figure 2: Cross-sections for $\gamma\gamma\to h\bar{h}$ obtained in $e^{+}e^{-}$ collisions: $\pi^{+}\pi^{-}$dipion_fitdikaon_8_dipion_4, $K^{+}K^{-}$dikaon_3_argusdikaon_4_belle2003, and $p\bar{p}$Belle:2005fjiCLEO:1993ahu.
• Figure 3: The production cross sections of dihadron pairs via the two-photon process in $\mathrm{Au{-}Au}$ UPC at $\sqrt{s_{NN}} = 200~\mathrm{GeV}$ within the STAR acceptance (a) and in $\mathrm{Pb{-}Pb}$ UPC at $\sqrt{s_{NN}} = 5.36~\mathrm{TeV}$ within typical acceptance of LHC (b), which are calculated based on fits to experimental data from electron--positron collisions for the $K^+K^-$dikaon_3_argusdikaon_4_belle2003, $\pi^+\pi^-$dipion_fitdipion_7_MRAKII, and $p\bar{p}$Belle:2005fji.
• Figure 4: The normalized transverse momentum ($P^{h\bar{h}}_{T}$) spectra, i.e. $1/\sigma(h\bar{h}) \times d\sigma/dP^{h\bar{h}}_{T}$, of $\pi^{+}\pi^{-}$, $K^{+}K^{-}$, and $p\bar{p}$ pairs produced via the two-photon process in ultra-peripheral $\mathrm{Au{-}Au}$ collisions at $\sqrt{s_{NN}} = 200~\mathrm{GeV}$ within the STAR acceptance (a), and in $\mathrm{Pb{-}Pb}$ collisions at $\sqrt{s_{NN}} = 5.36~\mathrm{TeV}$ within typical acceptance of LHC (b), calculated using Monte Carlo simulations.
• Figure 5: Calculation of the $p\bar{p}$ production cross section via two-photon process in Au+Au UPC collisions at $\sqrt{s_{NN}} = 200~\mathrm{GeV}$, compared with theoretical predictions from Pu et al. ppbar_Pu and Shao et al. ppbar_Shao.