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

Understand

Most atomic nuclei are deformed with a quadrupole shape described by its overall strength $\beta_2$ and triaxiality $\gamma$.

• 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 $\varepsilon_2$ and the density gradient $d_{\perp}$ in the initial state.
• Using analytical estimate and a Glauber model, I show that the variances, $\langle\varepsilon_2^2\rangle$ or $\langle(\delta d_{\perp}/d_{\perp})^2\rangle$, and skewnesses, $\langle\varepsilon_2^2\delta d_{\perp}/d_{\perp}\rangle$ or $\langle(\delta d_{\perp}/d_{\perp})^3\rangle$, have a simple analytical form of $a'+b'\beta_2^2$ and $a'+(b'+c'\cos(3\gamma))\beta_2^3$, respectively.
• From these, I constructed several normalized skewnesses to isolate the $\gamma$ dependence from that of $\beta_2$, and show that the correlations between any normalized skewness and any variance can constrain simultaneously the $\beta_2$ and $\gamma$.