Hints of a Higgs Boson?

26 July 2011

The Oxford Particle Physics group is playing a key role in the search for the Higgs Boson at the Large Hadron Collider. The most recent search results were presented by the ATLAS collaboration at the European Physical Society meeting in Grenoble. These intriguing results show an excess of events that would be consistent with decays of Higgs bosons to pairs of W particles. In the Standard Model of particle physics the Higgs boson is an excitation in the field that endows the fundamental particles with their masses. The (up to 2.8-sigma) excess in the approximate mass range 130-150 GeV* is still far from conclusive, but may be the first hints of direct evidence for this elusive particle. Other possible values for the mass of the Higgs boson itself in the ranges 155 GeV to 190 GeV and 295 GeV to 450 GeV have been excluded at the 95% confidence level.

A central component in identifying the electrons and muons produced in W boson decays is the ATLAS semiconductor tracker barrel, which was originally assembled by the Oxford group in the Denys Wilkinson Building before transportation to CERN.

As well as the hardware operations, the group has made central contributions to other aspects of the analysis, including the Monte Carlo simulations [Claire Gwenlan is the ATLAS Monte Carlo convenor] and kinematic reconstruction (Barr et al.). Oxford physicists are also working to increase the sensitivity of the search in the decay to W-boson pairs by maximizing the theoretical information used in the search (previously demonstrated by Chris Hays and others for the CDF collaboration). Updated results are expected at the next major physics conference at the end of August.