Hall D Calorimeter

Calorimeters (also called shower counters) are detectors  used in nuclear physics to measure the energy, E,  of a high-energy particle. The particle enters the detector, interacts with the active material, and creates a shower of secondary particles. The energy of the secondary particles is, in effect, summed to give the energy of the primary, incident particle.

Other detectors track the particle (before it enters the calorimeter) and its track, through a magnetic field, gives the particle's momentum p and charge. From the relativistic relationship between energy, mass, and momentum, E²=p²c²+m²c⁴, where c is the speed of light,  the mass of the particle, m,  is determined. The mass and the charge uniquely identify the particle--e.g, hey, that was a proton! This particle identification (PID as we call it) is vital part of the data analysis.

Here is a picture of a new calorimeter being developed here at Jefferson Lab for our new Hall D experimental hall and suite of detectors.