In
particle physics, a resonance is the peak located around a certain energy found in
differential cross sections of
scattering experiments. These peaks are associated with
subatomic particle
In physical sciences, a subatomic particle is a particle that composes an atom. According to the Standard Model of particle physics, a subatomic particle can be either a composite particle, which is composed of other particles (for example, a pr ...
s, which include a variety of
bosons,
quark
A quark () is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. All commonly o ...
s and
hadrons (such as
nucleons,
delta baryons or
upsilon mesons) and their
excitations. In common usage, "resonance" only describes particles with very short
lifetime
Lifetime may refer to:
* Life expectancy, the length of time a person is expected to remain alive
Arts, entertainment, and media
Music
* Lifetime (band), a rock band from New Jersey
* ''Life Time'' (Rollins Band album), by Rollins Band
* ...
s, mostly high-energy hadrons existing for or less.
The
width of the resonance (''Γ'') is related to the
mean lifetime (''τ'') of the particle (or its excited state) by the relation
:
where ''h'' is the
Planck constant and
.
Thus, the lifetime of a particle is the direct
inverse
Inverse or invert may refer to:
Science and mathematics
* Inverse (logic), a type of conditional sentence which is an immediate inference made from another conditional sentence
* Additive inverse (negation), the inverse of a number that, when ad ...
of the particle's resonance width. For example, the charged
pion has the second-longest lifetime of any meson, at . Therefore, its resonance width is very small, about or about 6.11
MHz. Pions are generally not considered as "resonances". The charged
rho meson has a very short lifetime, about . Correspondingly, its resonance width is very large, at 149.1
MeV or about 36
ZHz. This amounts to nearly one-fifth of the particle's
rest mass.
[K.A. Olive ''et al''. (Particle Data Group) (2016)]
Particle listings –
/ref>
See also
* Baryon resonance particles
* Roper resonance
*Giant resonance Giant resonance is a high-frequency collective excitation of atomic nuclei, as a property of many-body quantum systems. In the macroscopic interpretation of such an excitation in terms of an oscillation, the most prominent giant resonance is a colle ...
* Relativistic Breit–Wigner distribution
References
Scattering theory
Particle physics
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