Design and Performance of Reaction Plane Detector in PHENIX

Measuring the event anisotropy of nucleus-nucleus collisions is one of the most important methods to investigate the hot dense partonic matter produced at RHIC. Along with the discovery of jet suppression, the observation of large $v_2$ leads to the conclusion that the strongly coupled medium is formed in Au+Au collisions. However, the $v_2$ measurements of rare observables such as electrons, photons, $J\psi$ and high p$_T$ particles are constrained by the low statistics and reaction plane resolution. By installing a new reaction plane detector at PHENIX, the resolution is improved by factor of 2. This enables us to further study the $v_2$ of rare probes and even to extend our view to $v_4$. In the talk the performance of this new detector in this year's run will be discussed.