PX156 - K5 - detectors

collider detectors are onion-like with different types of sub detectors with different types of subdetectors doing different things to 'reconstruct' particles coming from a collision

tracker

detects and tracks charged particles close to the interaction point
many type of trackers
all are built in layers around the beam pipe to trace particles coming out

calorimeter

energy measurement

electromagnetic calorimeter (ECAL)

measures electron and photon energies from how they move through material
electrons: in a field of an atom in a material, it scatters, radiating in a photon
photons: pair-production
in a detector, an electromagnetic shower of $e^{-} / e^{+} / γ$ is created
$γ$ can be detected in light detectors

hadronic calorimeters (HCAL)

same thing a ECAL for hadrons
instead of just $e^{-} / e^{+} / γ$ , there are also other hadrons in the shower

probability of survival

calorimeters are designed around specific length scales that define the shower development
EM showers: probability that an electron or photon survives to a distance, $x$ , inside a material as:

P_{e} (x) = \exp (- \frac{x}{x_{0}})

where, $x_{0} =$ reiteration length, property of a material

hadronic showers: probability of a hadron to survive a distance, $x$ , inside a material as:

P_{h} (x) = \exp (- \frac{x}{λ_{I}})

where, $λ_{x} =$ 'nuclear reiteration length', material dependent

material	$x_{0} (c m)$	$λ_{I} (c m)$
water	$3.6$	$83$
iron	$1.8$	$17$
lead	$0.5$	$17$