Elliptic flow coefficients from transverse momentum conservation

We calculate the $k$-particle $\left(k=2,4,6,8\right)$ azimuthal cumulants resulting from the conservation of transverse momentum. We find that $c_2\left\{k\right\}>0$ and, depending on the transverse momenta, $c_2\left\{k\right\}$ can reach substantial values even for a relatively large number of particles. The impact of our results on the understanding of the onset of collectivity in small systems is emphasized.

Figure 1

(a) The multiparticle azimuthal cumulants ${\left(c_2\left\{2\right\}\right)}^{1/2},{\left(c_2\left\{4\right\}\right)}^{1/4},{(c_2\left\{6\right\}/4)}^{1/6}$, and ${(c_2\left\{8\right\}/33)}^{1/8}$ as a function of the number of particles, $N$. (b) ${\left(c_2\left\{2\right\}\right)}^{1/2}$ as function of transverse momentum, $p$, for different values of $N=20,50$, and 100.