28 August 2018
A candidate event display for the production of a Higgs boson decaying to two b-quarks (blue cones), in association with a W boson decaying to a muon (red) and a neutrino. The neutrino leaves the detector unseen, and is reconstructed through the missing transverse energy (dashed line).
(Credit: ATLAS Collaboration/CERN)
UK particle physicists are celebrating that the ATLAS and CMS collaborations at CERN’s Large Hadron Collider (LHC) have – at long last – observed the Higgs boson decaying into a pair of bottom (b) quarks. This elusive interaction is predicted to make up almost 60% of the Higgs boson decays. It has taken over seven years to accomplish this observation but it could ultimately provide the first hints of new physics beyond our current theories.
“This observation is a milestone in the exploration of the Higgs boson. It shows that the ATLAS and CMS experiments have achieved deep understanding of their data and a control of backgrounds that surpasses expectations. ATLAS has now observed all couplings of the Higgs boson to the heavy quarks and leptons of the third generation as well as all major production modes,” said Karl Jakobs, spokesperson of the ATLAS collaboration.
“Since the first single-experiment observation of the Higgs boson decay to tau-leptons one year ago, CMS, along with our colleagues in ATLAS, has observed the coupling of the Higgs boson to the heaviest fermions: the tau, the top quark, and now the bottom quark. The superb LHC performance and modern machine-learning techniques allowed us to achieve this result earlier than expected,” said Joel Butler, spokesperson of the CMS collaboration.
With more data, the collaborations will improve the precision of these and other measurements and probe the decay of the Higgs boson into a pair of much-less-massive fermions called muons, always watching for deviations in the data that could point to physics beyond the Standard Model.
A CMS candidate event for the Higgs boson (H) decaying to two bottom quarks (b), in association with a Z boson decaying to an electron (e-) and an antielectron (e+).
UK groups have played critical roles in the analysis of the data over the past seven years. This includes work on the key detector elements, reconstruction algorithms, data collection and cutting-edge analysis techniques. All of which culminated in this historic achievement that marks a crucial step forward in our understanding of the Higgs boson, just six years after the Higgs boson was first detected.
“It’s amazing to see the progress over the last year by each experiment. We can use these processes to characterise the Higgs sector, unravelling the mysteries of the universe,” said Professor Gavin Davies, a physicist at Imperial College London and CMS-UK Principle Investigator.
For Dr Andy Mehta from the University of Liverpool this announcement is the culmination of over seven years work. “We started to think about this search even before the LHC started and it’s wonderful to finally to see this decay.
“Over the last seven years, each new result has built upon the last one, so it is fantastic for all those people who have been involved over the years to finally observe this critical decay. Finding the Higgs in its favoured decay channel was one of the key missing items in our knowledge of the Higgs boson. It opens a new window into our understanding of this intriguing particle and could ultimately provide the first hints of new physics beyond our current theories.”
Images and the full CERN release can be found on the CERN website.