CGC/saturation approach: re-visiting the problem of odd harmonics in angular correlations

Abstract

In this paper we demonstrate that the selection of events with different multiplicities of produced particles, leads to the violation of the azimuthal angular symmetry, $\varphi \to \pi -\varphi$. We find for LHC and lower energies, that this violation can be so large for the events with multiplicities $n\ge 2\bar{n}$, where $\bar{n}$ is the mean multiplicity, that it leads to almostno suppression of $v_n$, with odd $n$. However, this can only occur if the typical size of the dipole in DIS with a nuclear target is small, or $Q^2>Q_s^2\text{Lb}A,Y_{\min },b\text{Rb}$, where $Q_s$ is the saturation momentum of the nucleus at $Y=Y_{\min }$. In the case of large sizes of dipoles, when $Q^2<Q_s^2\text{Lb}A,Y_{\min },b\text{Rb}$, we show that $v_n=0$ for odd $n$. Hadron-nucleus scattering is discussed.

Comments: 22 pp. 21 figures in eps files