Defining Occupancy

The occupancy measures the number of particles per a detector cell for an event. For the CLAS12 drift chamber, there are 112 wires on each layer, with 12 layers within a region, giving 1344 cells. The registering of a "hit" takes a finite time in which the detector and its associated electronics are not able to register an additional signal if it occurs. This time window is known as the "dead time" during which only limited events are registered. Since the events are simulated outside the dead time constraints of the DC, we can factor in the number of event windows that occur by dividing the dead time window per region by the time that would have been required to produce the number of incident electrons given a known current.

DC occupancy [math]\equiv \frac{N_{hits}}{N_{evt}}\frac{\Delta t}{t_{sim}}\frac{1}{112}\frac{1}{12}[/math]

where

[math]N_{hits}\equiv [/math]The number of DC wires intersected by primary and secondary events throughout the drift chamber in Region 1

[math]N_{evt} \equiv \phi \times Prob(interacting)[/math]

[math]\phi \equiv [/math] Number of incident particles on the face of drift chamber per cm[math]^2[/math]

[math]\Delta t \equiv [/math] 250 ns: The time needed for events to be read by the electronics within Region 1

[math]t_{sim} \equiv [/math] Time of simulation = [math]\frac{N_{incident}}{I}[/math]