Multiplicity, average transverse momentum, and azimuthal anisotropy in U+U collisions atSNN=200GeV using a multiphase transport model

Abstract

Using a multiphase transport (AMPT) model that includes the implementation of deformed uranium nuclei, we have studied the centrality dependence of the charged particle multiplicity (${N}_{\mathrm{ch}}$, $d{N}_{\mathrm{ch}}/d\ensuremath{\eta}$), average transverse momentum ($\ensuremath{\langle}{p}_{\mathrm{T}}\ensuremath{\rangle}$), eccentricity (${\ensuremath{\varepsilon}}_{2}$), triangularity (${\ensuremath{\varepsilon}}_{3}$), their fluctuations, elliptic flow (${v}_{2}$), and triangular flow (${v}_{3}$) for different configurations of $\mathrm{U}+\mathrm{U}$ collisions at midrapidity for $\sqrt{{s}_{NN}}$ $=$ 200 GeV. The calculations have been done for both the default and string-melting versions of the AMPT model. The results are compared to the corresponding observations from $\mathrm{Au}+\mathrm{Au}$ collisions. We find that for the $\mathrm{U}+\mathrm{U}$ collisions $d{N}_{\mathrm{ch}}/d\ensuremath{\eta}$ at midrapidity is enhanced by about 15$%$--40$%$ depending on the collision and model configuration chosen, compared to $\mathrm{Au}+\mathrm{Au}$ collisions. Within the several configurations studied, the tip-to-tip collisions lead to the largest values of ${N}_{\mathrm{ch}}$, transverse energy (${E}_{\mathrm{T}}$), and $\ensuremath{\langle}{p}_{\mathrm{T}}\ensuremath{\rangle}$. Both $\ensuremath{\langle}{\ensuremath{\varepsilon}}_{2}\ensuremath{\rangle}$ and its fluctuation show a rich centrality dependence, whereas little variation is observed for $\ensuremath{\langle}{\ensuremath{\varepsilon}}_{3}\ensuremath{\rangle}$ and its fluctuations. The $\mathrm{U}+\mathrm{U}$ side-on-side collision configuration provides maximum values of $\ensuremath{\langle}{\ensuremath{\varepsilon}}_{2}\ensuremath{\rangle}$ and minimum values of eccentricity fluctuations, whereas for peripheral collisions and mid-central collisions minimum values of $\ensuremath{\langle}{\ensuremath{\varepsilon}}_{2}\ensuremath{\rangle}$ and the maximum value of eccentricity fluctuations are observed for the body-to-body configuration and the tip-to-tip configuration has a minimum value of $\ensuremath{\langle}{\ensuremath{\varepsilon}}_{2}\ensuremath{\rangle}$ and a maximum value of eccentricity fluctuations for central collisions. The calculated ${v}_{2}$ value closely correlates with the eccentricity in the model. It is smallest for the body-to-body configuration in peripheral and mid-central collisions while it is minimum for the tip-to-tip configuration in central collisions. For peripheral collisions ${v}_{2}$ in $\mathrm{U}+\mathrm{U}$ can be about 40$%$ larger than in $\mathrm{Au}+\mathrm{Au}$ whereas for central collisions it can be a factor of 2 higher depending on the collision configuration. It is also observed that ${v}_{3}$(${p}_{\mathrm{T}}$) is higher for tip-to-tip and body-to-body configurations compared to other systems for the collision centrality studied.