Gluonic hot spot initial conditions in heavy-ion collisions

Predictions and postdictions for relativistic lead and oxygen collisions with Trajectum

“…We furthermore show three variations obtained by setting the number of constituents to n c = 1 as well as rescaling σ fluct by a factor √ 3. We note that 2 and 3 correlate very well with v 2 {2} and v 3 {2}, respectively [10,13,66]. We hence see that while the influence of σ fluct is moderate over the complete centrality range (left panel) the contribution becomes relatively important in ultracentral collisions (middle and right panels) because of the small absolute magnitude of 2 and 3 in ultracentral collisions.…”

“…We remark that both [29] and [8,36] have an excellent description of the 0-5% centrality class of both v 2 {2} and v 3 {2} so we regard it as likely that they will also describe the ultracentral centrality classes. The good fit of the Magma model [63] however likely does not survive a full hydrodynamic simulation [13].…”

“…These collisions hence probe a special part of heavy ion collision physics, and have been historically difficult to describe accurately. A relatively famous example is the v 2 -v 3 -ultracentral puzzle, which states that it is difficult to simultaneously describe both v 2 and v 3 in the 0-1% centrality class [13,[62][63][64], but also for mean transverse momentum there are theoretical predictions [65]. The interesting observation in the latter work is that for extremely ultracentral collisions (0-0.01% centrality) the size of the plasma is limited by the radius of the colliding nucleus and the increase in multiplicity is solely sourced by an upward fluctuation in the initial temperature.…”

“…There are multiple outstanding grand questions in the field of heavy ion collisions [3], which range from the lim-its of hydrodynamics to the behavior of energetic quarks and gluons as a function of energy scale and coupling constant. Crucial questions are the nature of the prehydrodynamic phase (both its lifetime and dynamics [5]), the initial shape of the energy deposited by the colliding nuclei [13], the behavior of hydrodynamics when viscous corrections are (too?) large [14] or even if hydrodynamics can still make sense if only a few dozen particles per unit rapidity are produced.…”

Correlation between initial spatial anisotropy and final momentum anisotropies in relativistic heavy ion collisions

“…Models based on relativistic hydrodynamics can be useful to estimate the initial states and the space time evolution of the matter which cannot be probed experimentally [1][2][3][4][5][6][7][8][9][10][11]. Several groups have studied the correlation between ε n and v n earlier [1,10,[12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. It has been shown in different studies that the p T , beam energy, collision centrality all play important role in the determination of the final momentum anisotropy [13,[27][28][29][30][31].…”