Thermal photons as a sensitive probe of $\alpha$-cluster in C+Au collisions at the BNL Relativistic Heavy Ion Collider

Abstract

Different orientations of $\alpha$-clustered carbon nuclei colliding with heavy ions can result in a large variation in the value of anisotropic flow. Thus, photon flow observables from clustered ${}^{12}\mathrm{C}$ and ${}^{197}\mathrm{Au}$ collisions could be a potential probe to study the `direct photon puzzle'. We calculate the transverse momentum spectra and anisotropic flow coefficients ($v_n$) of thermal photons from collisions of triangular $\alpha$-clustered carbon and gold at $\sqrt{s_{\mathrm{NN}}}=200$ GeV at RHIC using a hydrodynamic model framework and compare the results with those obtained from unclustered carbon and gold collisions. The slope of the thermal photon spectra is found to vary moderately for different orientations of collisions. However, we find that the elliptic ($v_2$) and triangular flow ($v_3$) coefficients of direct photons for specific configurations are significantly larger and predominantly formed by the QGP radiation. A strong anti-correlation between initial spatial ellipticity and triangularity is observed in an event-by-event framework of $\alpha$-clustered $\mathrm{C}+\mathrm{Au}$ collisions. These special features provide us an opportunity to detect the exotic nature of cluster structure inside carbon nucleus using the photon probe in the future experiments.

10 pages, 10 figures; final published version

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Cited by in corpus (8)

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• Effects of clustered nuclear geometry on the anisotropic flow in O-O collisions at the LHC within a multiphase transport model framework
• Influence of nuclear structure in relativistic heavy-ion collisions
• Ratio of photon anisotropic flow in relativistic heavy ion collisions
• Mean free path of photons in relativistic heavy ion collisions
• Production and anisotropic flow of thermal photons in collision of $\alpha$-clustered carbon with heavy nuclei at relativistic energies
• $\alpha$ + core structure described with an additional interaction in the nuclear matter saturation region
• Hydrodynamic model of heavy-ion collisions with low momentum components