GPU-implemented tracking in a COMET drift chamber

Abstract

Track finding with GPU-implemented fourth order Runge-Kutta (RK) method is investigated to track electrons from muon decay in the COMET drift chamber. In the COMET drift chamber, about 30-40 % of signal events are composed of multiple turns where the right hit assignments to each turn partition are significant in the track finding. Scanning all possible track seeds can resolve the hit-to-track assignment problem with a high robustness about the noise hits, but requires a huge computational cost because of two reasons: 1) The adaptive RK method to propagate the electron track needs small global errors, corresponding to small step sizes. 2) Initial track seeds (θ, z, px, py, pz) have broad uncertainties, so many initial seeds should be tried and compared. In this presentation, these problems of massive computations are mitigated with 1) the parallel computing of RK track propagation, which assigns each track to each GPU block unit, 2) a better initial guess on the track seeds using the Hough transform and the geometrical property of the cylindrical drift chamber.