Effect of Finite Granularity of Detector on Anisotropy Coefficients

Over the last one decade, elliptic flow in ultrarelativistic heavy ion collisions has become an important probe of the dynamics of the system [1]. The elliptic flow manifests itself as an anisotropy in the azimuthal distributions of transverse momentum of the emitted particles. The azimuthal distributions are expanded in a Fourier series where the coefficients of expansion are the measures of different orders of anisotropy [2]. Large number of experiments have measured the elliptic flow of different particle species in different kinematic domains for a variety of colliding systems and a range of center of mass energies [3, 4, 5, 6, 7, 8, 9]. These measurements have provided new perspectives attempting to explain the observed mass dependence of the elliptic flow [10]. In experiments where pT is not measured, the anisotropy coefficients are determined from the azimuthal distribution of the number of particles. Detectors in some experiments measure the distribution of hits. Anisotropy coefficients describing distribution of hits is expected to be smaller than coefficients describing disribution of particles; v n < vn and there is need to determine an appropriate correction factor to obtain vn from the measured values of v hits n . In the present work, we obtain an approximate expression for the ratio v hits n vn , and corroborate the results with simulation results.