I heard that 'bosons' are particles made from a quark and an anti-quark. Is this true? If it is, then how
come they do not to annihilate each other?
Asked by: Adam
First of all, it is true that a particle that is formed from a quark and an anti-quark is a
boson. But the term 'boson' refers to a much broader class of particles. Quark/anti-quark
bound states are referred to by physicists as 'mesons.' But any particle with integer
intrinsic spin angular momentum is a boson. This includes mesons like pions, gauge
particles like photons and gluons, the hypothesized Higgs scalar, etc.
To answer your second question, quark/anti-quark pairs (mesons) do annihilate one
another! There are no stable mesons that we have ever discovered. Their lifetimes range
from 10^-8 to 10^-16 seconds, but this is long enough for us to detect their presence in
particle accelerator experiments and to measure their properties. Incidently, before the
quark theory was invented to understand the properties of elementary particles the term
'meson' was also applies to muons -- which are not made up of quarks but are
fundamental point particles like the electron. Unfortunately some people still use this
confusedly anachronistic term to refer to muons!
Answered by: Brent Nelson, M.A. Physics, Ph.D. Student, UC Berkeley
'The atomic bomb ... made the prospect of future war unendurable. It has led us up those last few steps to the mountain pass; and beyond there is different country.'