Time-of-flight detector

A time-of-flight (TOF) detector is a particle detector which can discriminate between a lighter and a heavier elementary particle of same momentum using their time of flight between two scintillators. The first of the scintillators activates a clock upon being hit while the other stops the clock upon being hit. If the two masses are denoted by $$m_1$$and $$ m_2$$ and have velocities $$v_1$$ and $$v_2$$ then the time of flight difference is given by
 * $$\Delta t = L\left(\frac{1}{v_1}-\frac{1}{v_2}\right)\approx \frac{Lc}{2p^2}(m_1^2-m_2^2)$$

where $$L$$ is the distance between the scintillators. The approximation is in the relativistic limit at momentum $$p$$ and $$c$$ denotes the speed of light in vacuum.