Particle identification in detectors

[ghery]

Hello:

Can anyone please tell me how do they identify the particles in the detectors?+, for instance, how do you know if an electron is an electron and not a muon or some other negative charged particle in a detector (without using magnetic fields)?

[humanino]

for instance, how do you know if an electron is an electron and not a muon or some other negative charged particle in a detector (without using magnetic fields)?I do not know why you would like not to use a magnetic field : it is very convenient to measure the ratio charge/momentum. Anyway, muons and electrons will give different Cerenkov light (you will need to choose the medium optical index in advance, according to the range in momentum you are interested in). If your muon is slow enough you may be able to measure the time of flight accurately enough to distinguish with an electron. Also, they produce different electromagnetic interactions in heavy material at a given incident energy (the showering process for muons in calorimeters requires much more energy than for electrons).

[Bob S]

Hi ghery-
A high energy electron going into a 20-radiation-length lead-scintillator calorimeter sandwich would lose all its energy and stop. A muon of the same energy would lose only about 2 MeV per gram per cm-squared of material (Bethe-Bloch de/dx). Many years ago, I used time of flight (with 1-ns time resolution) to separate muons and pions in a low-momentum beam.
Bob S

[Bob_for_short]

...(without using magnetic fields)?

Two fast charged particles of the same velocity make the same ionisation traces so using some magnetic filed and other things to distinguish the particle masses and charges is important.

[ghery]

When I wrote "without using magnetic fields" what I really meant was if there was any other way to distinguish for example the velocity of a charged particle besides the use of magnetic fields?

[Bob S]

Hi ghery-
Lead-scintillator detectors can discriminate between electrons (electromagnetic showers) muons (minimum ionizing track) and mesons and hadrons (hadronic showers). Energy can be estimated for electromagnetic and hadronic showers.
Cerenkov counters (mentioned above) can measure the Cerenkov light angle (Cerenkov ring detectors) to select the particle velocity. Varying the pressure in high-pressure gas Cerenkov detectors has been used to identify particles by varying the threshold particle velocity.
Electric fields, often in Wien filters, have been used as velocity detectors. See
http://en.wikipedia.org/wiki/Wien_filter
Particle time-of-flight (mentioned above) between two plastic scintillators or Cerenkov radiators on photomultiplier tubes has been used to select particle velocities.
Bob S