The potential of discrimination methods in a high pressure xenon TPC for   the search of the neutrinoless double-beta decay of Xe-136
  In the search for the neutrinoless double beta decay of $^{136}$Xe, a high pressure xenon time projection chamber (HPXe-TPC) has two advantages over liquid xenon TPCs: a better energy resolution and the access to topological features, which may provide extra discrimination from background events. The PandaX-III experiment has recently proposed a 200 kg HPXe-TPC based on Micromegas readout planes, to be located at the Jinping Underground Laboratory in China. Its detection concept is based on two results obtained within the T-REX project: Micromegas readouts can be built with extremely low levels of radioactivity; and the operation in xenon-trimethylamine at 10 bar in realistic experimental conditions has proven an energy resolution of 3% FWHM at the region of interest. In this work, two discrimination methods are applied to simulated signal and background data in a generic 200 kg HPXe-TPC, based on two well-known algorithms of graph theory: the identification of connections and the search for the longest path. Rejection factors greater than 100 are obtained for small pixel sizes and a signal efficiency of 40%. Moreover, a new observable (the blob charge density) rejects better surface contaminations, which makes the use of a trigger signal ($T_0$) not imperative in this experiment. 
F.J. Iguaz, F. Aznar, J.F. Castel, S. Cebrian, T. Dafni, J. Galan,   J.G. Garza, I.G. Irastorza, G. Luzon, H. Mirallas and E...
physics.ins-det hep-ex