# How we differentiate between bosons and fermions?

1. Nov 11, 2015

### MAKK

if we have two particle then how we differentiate between boson and fermion ,any experiment that differentiate them?

2. Nov 11, 2015

### PWiz

Fermions have half-integer spins (they follow the Pauli exclusion principle), whereas bosons always have integer spins.

3. Nov 11, 2015

### MAKK

i knw but wht exp that differentiate them??

4. Nov 11, 2015

### e.bar.goum

There's more than one possibility, but the most famous example would be the Stern–Gerlach experiment. Here's a more detailed description.

Another way (as you would do in particle physics collisions) would to look at the decay of the particle. The spin and parity will affect the various decay probabilities.

5. Nov 11, 2015

### Staff: Mentor

Decay probabilities are rarely used, they depend on too many other things. Just the possibility of a decay channel is sufficient to classify the particle. Finding its actual spin value is then done by angular analysis of the decay products.

In case we suddenly forget all spin values:
Electrons have to be fermions, otherwise all electrons in atoms would occupy the lowest energy state and there would be no chemistry.
Protons and neutrons have to be fermions, otherwise the nuclide chart would look completely different (e. g. more stable large elements).
The decay of a fermion always leads to an odd number of fermions, the decay of a boson always leads to an even number.
In beta decays, neutrons decay to proton+electron+neutrino, therefore the neutrino has to be a fermion. It also follows that the W has to be a boson.
Electron+positron, both fermions, can annihilate to two and three photons, therefore the photon has to be a boson.
Quarks can radiate gluons, which looks like "quark -> quark+gluon", therefore the gluon has to be a boson. The same is true for Z, W, photons and Higgs.
Three valence quarks make up a proton or neutron, therefore quarks have to be fermions.
The Higgs can decay to two photons, therefore it has to be a boson.

6. Nov 12, 2015

### MathematicalPhysicist

I read in I think it was Rudolf Haag's Local Quantum Physics, that there was a paper by someone that suggested a different sorting of particles, instead of bosons and fermions.

Yeah, it's on page 35, instead of Bose-Fermi statistics there has been suggested a para-statistics which have been suggested by H.S Green in his paper from 1953 called "A generalized method of field quantization ".(http://journals.aps.org/pr/pdf/10.1103/PhysRev.90.270 [Broken]).

The boson/fermion distinction is deduced from this generalized method, I am not sure if this paper is legitimate, since we'd be learning it in university graduate or undergraduate courses if it were.

Last edited by a moderator: May 7, 2017
7. Nov 21, 2015

### A. Neumaier

Parastatistics is a perfectly respectable concept. It can also account for the substructure of mesons and baryons but was later displaced by QCD which gave a more powerful machinery to work with.