Editing LHCb experiment (section)

=== Rare decays ===
Rare decays are the decay modes harshly suppressed in the Standard Model, which makes them sensitive to potential effects from yet unknown physics mechanisms.

In 2014, LHCb and [[Compact Muon Solenoid|CMS]] experiments published a joint paper in [[Nature (journal)|Nature]] announcing the discovery of the very rare decay <math>\mathrm{B}^0_{\rm s} \to \mu^+\mu^-</math>, rate of which was found close to the Standard Model predictions.<ref>{{Cite journal|last1=Khachatryan|first1=V.|last2=Sirunyan|first2=A.M.|last3=Tumasyan|first3=A.|last4=Adam|first4=W.|last5=Bergauer|first5=T.|last6=Dragicevic|first6=M.|last7=Erö|first7=J.|last8=Friedl|first8=M.|last9=Frühwirth|first9=R.|last10=Ghete|first10=V.M.|last11=Hartl|first11=C.|date=June 2015|title=Observation of the rare B s 0 → μ + μ − decay from the combined analysis of CMS and LHCb data|journal=Nature|language=en|volume=522|issue=7554|pages=68–72|doi=10.1038/nature14474|pmid=26047778|s2cid=4394036|issn=1476-4687|doi-access=free|hdl=2445/195036|hdl-access=free}}</ref> This measurement has harshly limited the possible parameter space of supersymmetry theories, which have predicted a large enhancement in rate. Since then, LHCb has published several papers with more precise measurements in this decay mode.

Anomalies were found in several rare decays of B mesons. The most famous example in the so-called <math>\mathrm{P}_5^'</math> angular observable was found in the decay <math>\mathrm{B}^0 \to \mathrm{K}^{*0} \mu^+\mu^-</math>, where the deviation between the data and theoretical prediction has persisted for years.<ref>{{Cite web|title=New LHCb analysis still sees previous intriguing results|url=https://home.cern/news/news/physics/new-lhcb-analysis-still-sees-previous-intriguing-results|access-date=2021-03-21|website=CERN|language=en}}</ref> The decay rates of several rare decays also differ from the theoretical predictions, though the latter have sizeable uncertainties.