Determining particle spin in collision experiments

In summary, high energy physicists can determine the spin of a particle that decays before reaching the silicon detectors by analyzing the angular distribution of their decay products with respect to a chosen frame, such as Gottfried-Jackson, Collins-Soper, or Helicity. This does not require spin polarization, but rather a non-equally populated density matrix. Other methods for measuring spin include identifying the factor 1/(2s+1) in the cross section and comparing the spin of a particle to that of other particles in a decay process.
  • #1
JustinLevy
895
1
How can high energy physicists determine the spin of a particle that decays before even reaching the silicon detectors?

For example if a new particle turned out to have spin 3/2, how would it be distinguished from a spin 1, spin 1/2, or spin 0 particle?
 
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  • #2
Usually by the angular distribution of their decay products.
 
  • #3
Angular distribution with respect to what?

And since the spin can't be known for each particle, wouldn't this require the production of the particle to be spin polarized?
 
  • #4
Pick your favorite frame. The literature is full of them: Gottfried-Jackson (yes, that Jackson), Collins-Soper, Helicity.

It does not require polarization. It requires that the density matrix not be equally populated, which is similar but less restrictive.
 
  • #5
There are number of ways of measuring spin, besides polarization.
The spin of the neutrino was 'measured' to be 1/2 because the other three particles in
neutron decay had spin 1/2.
Some spins are measure by recognizing the factor 1/(2s+1) in the cross section.
... and so on.
 

1. What is particle spin and why is it important in collision experiments?

Particle spin is an intrinsic property of subatomic particles such as electrons and protons, which determines their angular momentum. In collision experiments, the spin of particles can provide important information about their internal structure and interactions.

2. How do scientists determine the spin of particles in collision experiments?

Scientists use a variety of techniques to determine the spin of particles in collision experiments. These include measuring the deflection of particles in a magnetic field and analyzing the particles' decay products.

3. Can particles have a fractional spin?

Yes, particles can have a fractional spin, meaning they have a spin that is not a whole number. This is known as a “spinor” or “half-integer” spin, and is commonly observed in particles such as electrons and quarks.

4. How does the spin of particles affect the outcome of a collision experiment?

The spin of particles can affect the outcome of a collision experiment in several ways. For instance, particles with different spin states may interact differently, and the spin of a particle can also determine the direction and energy of the particles it decays into.

5. What are some potential applications of determining particle spin in collision experiments?

Determining particle spin in collision experiments can have a wide range of applications, including understanding the fundamental properties of matter, studying the behavior of particles in extreme conditions, and developing new technologies such as quantum computing.

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