View source for Long-lived particle

A '''long-lived particle''' ('''LLP''') is any hypothetical new particle that has a "macroscopic" lifetime, and can e.g. fly a macrocopic distance through a detector before decaying. New particles beyond the standard model might have long lifetimes for several reasons, including approximate [[symmetry|symmetries]] that stabilize the LLP, small couplings between the LLP and lighter states, and suppressed phase space available for decays <ref name="alimena"></ref>. LLP signatures at the [https://en.wikipedia.org/wiki/Large_Hadron_Collider LHC] can include tracks with unusual ionisation and propagation properties; small, localized deposits of energy inside of the calorimeters without associated tracks; stopped particles that decay out of time with collisions; displaced vertices in the inner detector or muon spectrometer; and disappearing, appearing, and kinked tracks <ref name="alimena"></ref>.

== Learn more ==

* Very comprehensive review article <ref name="alimena"></ref>

== References ==
<references>
<ref name="alimena">Juliette Alimena et al.: ''Searching for long-lived particles beyond the Standard Model at the Large Hadron Collider'', [https://doi.org/10.1088/1361-6471/ab4574 J. Phys. G: Nucl. Part. Phys. 47 090501 (2020)], ([https://arxiv.org/abs/1903.04497 arXiv:1903.04497])</ref>
</references>