Particle detection during collisions

In summary: I mean to say Pion...how do we detect it?The three pions, two charged and one neutral, have different decay lifetimes and will be detected by the LHC detectors. The charged pion lifetime is about 26 nanoseconds, so with even a minimal time dilation, the charged pions will reach the charged particle detectors at LHC before decaying to a muon and a muon neutrino.
  • #1
humsafar
37
0
I want to know the ways newly created particles are detected during collisions such as in LHC or Fermilab, i.e either they check the EM force, electric charge being observed or other things...
 
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  • #2
There are different methods for different particles.

For example, muon detection in the ATLAS experiment is mostly done with chambers consisting of tubes filled with a gas mixture. If a muon traverses the tube it ionizes some of the gas, which sets off an electrical signal on a high voltage wire running down the center of the tube. The signal is processed at the readout side of the chamber and then sent elsewhere for storage and subsequent analysis.

Of course, a tube only gives you coordinates on two axes (along the beam pathand radially from the beam path). For the third coordinate you rely on triggering mechanisms, which also select which events get recorded.

I suggest you look through LHC's public outreach pages. They're pretty good.

http://public.web.cern.ch/public/en/lhc/lhc-en.html
 
  • #3
humsafar said:
I want to know the ways newly created particles are detected during collisions such as in LHC or Fermilab, i.e either they check the EM force, electric charge being observed or other things...

There are actually only two principles on which people detect elementary particles: by their ionizing effect on matter in one way or another ; or by exciting molecules, atoms, crystals. The particles themselves, their E-fields or whatever are, to my knowledge, almost never directly observed, only their effect on matter. The point is that one single energetic particle can do a lot of ionization or excitation.

When matter gets ionized, charges are set free, and then there can be electrical means to try to see these charges ; when systems get excited, they will de-excite and send out light for instance. Sensitive instruments try to observe these tiny electrical or light signals.

From the characteristics of these signals, one can sometimes also deduce certain parameters of the particle that came by, like its mass.
 
  • #4
But particles like neutrino or neutron are neutral, how do we detect these particles which have no + or - Ion?
 
  • #5
humsafar said:
But particles like neutrino or neutron are neutral, how do we detect these particles which have no + or - Ion?

Well, they have to undergo an interaction which sets into motion a charged particle.
For neutrons, if the neutrons are energetic, then they can collide elastically with a nucleus and set the nucleus in motion (as an ion so there is your moving charged particle). If the neutrons aren't energetic, then you have to use a material which undergoes a nuclear reaction with the neutron, and has end products which are fast charged particles (for instance, U-235 can undergo fission with a slow neutron: the fission products are the charged particles then).
 
  • #6
See
http://pdg.lbl.gov/2009/reviews/rpp2009-rev-particle-detectors-accel.pdf
for information on how to detect newly created particles at accelerator experiments.

Many newly created particles have very short lifetimes, and even with time dilation, they do not reach the detectors before decaying. In this case, the concept of invariant mass [ (mc2)2 = E2 - (pc)2 ] four-momenta is used. By analyzing all the detected decay particles energies and momenta, it is possible to identify the original newly created particle's rest mass and momentum. See

http://en.wikipedia.org/wiki/Invariant_mass

Correcting for missing energy and momentum imbalance from escaping neutrinos and detector inefficiencies is done by careful analysis of all the collision tracks.

Bob S
 
  • #7
OK...just one more thing...how does a particle like Muon which is also electromagnetically zero (like neutron) gets detected...
 
  • #8
humsafar said:
OK...just one more thing...how does a particle like Muon which is also electromagnetically zero (like neutron) gets detected...
The muon and anti-muon are both charged, ± 1 electron charge, and have a mass about 206 times the electron mass. There is no uncharged muon. Both have a decay lifetime of about 2.2 microseconds. Both are easily deflected by the large magnets in the LHC detectors, and leave charged particle tracks in the particle detectors. See

http://pdg.lbl.gov/2009/reviews/rpp2009-rev-particle-detectors-accel.pdf.

Bob S
 
  • #9
He might mean a muon neutrino.
 
  • #10
Sorry...I mean to say Pion...how do we detect it?
 
  • #11
how do we detect pion?
 
  • #12
humsafar said:
how do we detect pion?
There are 3 pions, two charged and one neutral.

The charged pion lifetime is about 26 nanoseconds, so with even a minimal time dilation, the charged pions will reach the charged particle detectors at LHC before decaying to a muon and a muon neutrino.

The neutral pion decays to two gammas in ~8 x 10-17 seconds (plus a 1% branching to a positron and electron), so the detectors in LHC will detect the two decay gammas as electromagnetic cascades. The pi-zero mass, energy, and direction are reconstructed using the invariant mass theorem mentioned in an earlier post. Of course, the LHC detector is simultaneously (within a nanosecond) detecting 100's of other tracks, many of which are probably also pi-zero decays.

Bob S
 
  • #13
Hi, sorry to bump this one, but I have been trying to find some information on how the data received from detectors look throughout the 'analysis phases'. I'm no wiz at maths, so my question is this, I guess:

Are there any layman papers/explanations/exemplifications of a (successful, historical) particle detection process? Starting with some images from any kind of detector, and then explaining what the following analysis was that resulted in the 'eureka! -we have a particle!' ?

I have tried to google this a while now, but couldn't find anything quite down at my level... =)

Thanks a lot!

Regards,
Gnim
 

Related to Particle detection during collisions

1. What is particle detection during collisions?

Particle detection during collisions is the process of detecting and studying the various particles that are produced during high-energy collisions, such as those that occur in particle accelerators. These particles are extremely small and cannot be seen with the naked eye, so specialized detectors are used to identify and measure their properties.

2. Why is particle detection during collisions important?

Particle detection during collisions is important because it allows scientists to study the fundamental building blocks of matter and the forces that govern them. By analyzing the particles produced during collisions, scientists can gain a better understanding of the laws of physics and the nature of the universe.

3. How do scientists detect particles during collisions?

Scientists use a variety of specialized detectors to detect particles during collisions. These detectors include particle trackers, which measure the trajectory of particles, and calorimeters, which measure the energy of particles. Other detectors, such as time-of-flight detectors and Cherenkov detectors, are used to determine the type and identity of particles.

4. What types of particles can be detected during collisions?

A wide range of particles can be detected during collisions, including elementary particles like electrons, protons, and neutrons, as well as more complex particles like mesons and baryons. Scientists have also detected particles that are predicted by theories, such as the Higgs boson, and are constantly searching for new particles that may help to further our understanding of the universe.

5. What can particle detection during collisions tell us about the universe?

Particle detection during collisions can tell us a lot about the universe, including the fundamental forces that govern the behavior of matter, the origins of the universe, and the properties of particles. By studying the particles produced during collisions, scientists can also gain insights into the nature of dark matter and dark energy, which make up the majority of the universe but are still largely unknown.

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