Particle Identification by Time of Flight in ND280 detector for T2K experiment

The T2K experiment in Japan is an experiment that studies the oscillation of muon neutrinos over a large distance. Accurate identification of the flavor of neutrino interactions—specifically, distinguishing between muons and other particles such as protons produced in the detector—is crucial for the experiment’s success. The ND280 near detector is responsible for this particle identification (PID). While the primary PID method in ND280 is based on energy loss per unit length ($\frac{dE}{dx}$), this approach becomes ineffective at momenta around 1.5 GeV, where the energy loss distributions for muons and protons overlap. To address this, time-of-flight (TOF) measurements can be used: by measuring the time a particle takes to traverse the detector, its velocity (β) can be determined. Since particles of different masses have different velocities at the same momentum,
combining TOF with dE/dx information allows for improved separation of particle species.