neutrinos

p_branes

Hi guys just had a question. I know about neutrinos and how they act - their being able to pass through matter leaving it as it was but my question was how are what are the basics of neutrinos are they antimatter particles of some particle? Someone please enlighten me, thanks.

suyver

They are a particle: (almost) no mass, no charge, spin 1/2. No electromagnetic or strong interaction, only weak interaction. Typical strength of the interaction: you'd need about 1000 lightyears of lead to have a 50% probability for an interaction between a neutrino and the lead!

On earth they are generated in large numbers in nuclear beta-decay: a neutron becomes a proton and emits an electron and an anti-neutrino.

The Ultimate Neutrino Page.

p_branes

Thanks Suyver, so they are fermions right? I know its off topic but I used to live in Bern as well!

chroot

Since they have half-integral spin, they are fermions.

- Warren

selfAdjoint

And they have antiparticles called antineutrinos. Since neutrinos have no charge, the only way these differ from the nuetrinos is in spin; they have opposite "helicity." It's actually an anineutrino that carries away energy in the weak decay.

p_branes

Oh ok, so what spin does an anti-neutrino have? -1/2?

suyver

No, also 1/2. Negative spins are not possible: only the projection of the spin on a (z) axis can be <0.

p_branes

Oh ok thanks.

kurious

Are antineutrinos antimatter - they don't have electric charge like positrons.I understand that usually charge and parity are considered for determining whether a particle is matter or antimatter.But surely an antineutrino can't be likened to a positron if it doesn't have charge.If antineutrinos are not antimatter then this would explain why there is no difference in arrival times between antineutrinos and neutrinos
which originate from supernovae explosions and would mean that antimatter could still possibly fall upwards in a gravitational field.

chroot

Antineutrinos are definitely antimatter. All particles, even neutral ones, have antiparticles. In some cases however, a particle is its own antiparticle; the photon is this way.

- Warren

LURCH

Since antineutrinos are antimatter, will they annihilate with neutrinos, producing energy?

swansont

They certainly should, but since they interact only via the weak force, their cross-section for interaction would be small.