Particle identification analysis of TREK/E36

The TREK/E36 experiment conducted at J-PARC in Japan aims to test lepton universality by a precise measurement of the ratio of decay widths of the decay channels $K_{e2}$ and $K_{\mu2}$, $R_{K} =\Gamma(K_{e2})/\Gamma(K_{\mu2})$, and to search for exotic $K^+$ decay modes accompanied by light neutral bosons, by utilizing a $K^+$ beam stopped in a scintillating fiber target, a combination a highly segmented CsI(Tl) photon calorimeter covering $75\%$ of $4\pi$, charged-particle tracking detectors, and particle identification systems. Since the $R_{K}$ value is of order $~10^{-5}$, the $e^+$ discrimination from other particles is one of the most important issues. Three independent detection systems: time of flight between TOF1 and TOF2, an aerogel Cherenkov detector (AC), and a lead glass Cherenkov detector (PGC) were used for particle identification (PID). In this talk the status and approach of the PID analysis will be presented.