Image 1: A candidate Bs → μμ event recorded in the CMS detector in 2012, produced in proton-proton collisions at 8 TeV. (Ultra-high-resolution image below, Image 5.)
Image 2: History of searches for decays of Bs and B0 to pairs of muons at current and past colliders, showing an improvement of four orders of magnitude.
Image 3: The di-muon mass distribution. The purple and red curves show the B0 and Bs signals, respectively, while the dashed line, and the green and black shapes show three different types of background. The solid curve shows the sum of the fit components.
Image 4: Two-dimensional contours showing the significance for the Bs → μμ and B0 → μμ measurements. The insets show the one-dimentional projections where the curve minimum is the best-fit value for the decay rates and the intersection with zero on the X-axis shows the significance of the measurement.
Image 5: Ultra-high-resolution image of a candidate Bs → μμ event recorded in the CMS detector in 2012, produced in proton-proton collisions at 8 TeV.
CMS Experiment, CERN
13 May 2015 UPDATE 2: The CMS data used in the result below have been analysed together with LHCb's data to obtain a combined result that is now published in Nature. Including all of the data taken by both experiments at 7 and 8 TeV in 2011 and 2012 respectively, the joint observation of a Bs decay to two muons has a significance of 6.2 σ, while the probability of a Bs to decay to two muons is measured to be approximately 2.8 parts per billion. The paper is available at: http://dx.doi.org/10.1038/nature14474 The CERN press release is available at: http://press.web.cern.ch/press-releases/2015/05/cms-and-lhcb-experiments...