The CMS experiment reports the first observation of the rare decay of an eta meson to two muons and two electrons. The CMS detector was originally built to discover the Higgs boson and search for heavy particles that could transform our unders…

CMS sets the world’s most stringent limits on B⁰ and B⁰ₛ decays into four muons. After examining the Run 3 dataset collected between 2022 and 2024, the CMS experiment has established the most stringent limits to date on the extremely rare decays of…

  Could there be more particles like the Higgs boson? For the first time, the CMS experiment has searched for the decay of the Higgs boson into two more Higgs-boson-like particles with unequal masses. Some theories suggest that the Higgs boson m…