Probing triaxial deformation of atomic nuclei in high-energy heavy ion collisions

Jiangyong Jia

doi:10.1103/PhysRevC.105.044905

paper

Probing triaxial deformation of atomic nuclei in high-energy heavy ion collisions

arXiv:2109.00604 · doi:10.1103/PhysRevC.105.044905

Abstract

Most atomic nuclei are deformed with a quadrupole shape described by its overall strength $β_{2}$ and triaxiality $γ$ . The deformation can be accessed in high-energy heavy-ion collisions by measuring the collective flow response of the produced quark-gluon plasma to the eccentricity $ε_{2}$ and the density gradient $d_{⊥}$ in the initial state. Using analytical estimate and a Glauber model, I show that the variances, $⟨ ε_{2}^{2} ⟩$ or $⟨(δ d_{⊥} / d_{⊥})^{2} ⟩$ , and skewnesses, $⟨ ε_{2}^{2} δ d_{⊥} / d_{⊥} ⟩$ or $⟨(δ d_{⊥} / d_{⊥})^{3} ⟩$ , have a simple analytical form of $a^{'} + b^{'} β_{2}^{2}$ and $a^{'} + (b^{'} + c^{'} cos (3 γ)) β_{2}^{3}$ , respectively. From these, I constructed several normalized skewnesses to isolate the $γ$ dependence from that of $β_{2}$ , and show that the correlations between any normalized skewness and any variance can constrain simultaneously the $β_{2}$ and $γ$ . Assuming a linear relation with elliptic flow $v_{2}$ and mean-transverse momentum $[p_{T}]$ of final state particles, similar conclusions are also expected for the variances and skewnesses of $v_{2}$ and $[p_{T}]$ . Our findings motivate a dedicated system scan of high-energy heavy ion collisions to measure triaxiality of atomic nuclei. This is better done by collisions of prolate, $cos (3 γ) = 1$ , and oblate nuclei, $cos (3 γ) = - 1$ , with well known $β_{2}$ values to calibrate the coefficients $b^{'}$ and $c^{'}$ , followed by collisions of species of interest especially those with known $β_{2}$ but unknown $γ$ . The results demonstrate the unique opportunities offered by high-energy collisions as a tool to perform interdisciplinary nuclear physics studies.

arXiv comment20 pages, 14 figures, plus 3 appendix, published version

Probing triaxial deformation of atomic nuclei in high-energy heavy ion collisions

Abstract

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