Resonance (particle Physics)
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Resonance Particle Physics

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 particles, which include a variety of bosons, quarks and hadrons (such as nucleons, delta baryons or upsilon mesons) and their excitations. In common usage, "resonance" only describes particles with very short lifetimes, mostly high-energy hadrons existing for or less.[1]

The width of the resonance (Γ) is related to the mean lifetime (τ) of the particle (or its excited state) by the relation

${\displaystyle \Gamma ={\frac {\hbar }{\tau }}}$

where h is the Planck constant and ${\displaystyle {\hbar }={\frac {h}{2\pi }}}$.

Thus, the lifetime of a particle is the direct inverse of the particle's resonance width. For example, the charged pion has the second-longest lifetime of any meson, at .[2] 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.[3]

## References

1. ^ Dudley, Chris. "What is a Resonance Particle?". Retrieved 2017.
2. ^ K.A. Olive et al. (Particle Data Group) (2016): Particle listings -
π±
3. ^ K.A. Olive et al. (Particle Data Group) (2016): Particle listings -
ρ

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