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LHCb: rare particle decays

This dossier follows LHCb results on rare decays and their statistical significance.

Last updated : 1 key moments

Where things stand

The LHCb collaboration announced at CERN on 3 November 2026 a signal consistent with a neutral B meson decaying into two muons. Its 3.2-sigma significance remains below the five-sigma discovery threshold.

LHCb reports evidence of a rare decay at 3.2 sigma

The LHCb collaboration announced at CERN on 3 November 2026 a signal consistent with a neutral B meson decaying into two muons. Its 3.2-sigma significance remains below the five-sigma discovery threshold.

An earlier LHCb VELO detector.
2008 archive; not the current detector. LHCb collaboration, CC BY-SA 4.0; unchanged. — LHCb collaboration / Wikimedia Commons — CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0/ — 2008, sans modification.

Researchers expect this process roughly once in ten billion particles of this type. The analysis combines 2024 and 2025 data with earlier runs from 2011 to 2018.

The result agrees with the Standard Model. It provides a more precise test of that theory without establishing the existence of a new particle. More data will be needed to strengthen the signal.

Sources 3