As the year 2013 is now nearing its end, it is time to recapitulate the main events of the year from the OKC perspective. If I temporarily put on my Nobel hat (being the scientific secretary of the Nobel Committee for Physics) the main event from the Stockholm horizon is without doubt the Nobel Prize to Francois Englert and Peter Higgs for their almost 50-year old prediction from the early 1960’s that was so spectacularly confirmed by the ATLAS and CMS experiments at CERN’s LHC accelerator last year.
Today’s Nobel Prize awarded jointly to François Englert and Peter W. Higgs “for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERN’s Large Hadron Collider”.
Oscar Stål is one of the OKC fellows working at the Cosmology, Particle astrophysics and String theory group (CoPS) since August 2012. He is doing his second postdoc and his filed of interest is particle physics phenomenology. He is Swedish and studied both as undergraduate and for his PhD at Uppsala University, before moving to Hamburg.
Today the ATLAS and CMS experiments have reported the observation of a strong excess of proton-proton collision events compatible with the Higgs boson.
The observed excess is obtained by combining 5 channels in the case of CMS to reach a level of 4.9 sigma of statistical significance. ATLAS has presented so far the result from two channels and observes an excess of 5 sigma. The number of events and the type of decays observed are both compatible with the standard model Higgs boson with a mass of about 125 GeV, and given the statistical significance of both ATLAS and CMS observations this can no longer be a statistical fluctuation. So today we have the discovery of a new particle.
CERN has announced that the two experiments leading the search for the Higgs boson, ATLAS and CMS will update their results concerning the search for the Higgs boson tomorrow on July 4th.
Last December the ATLAS and CMS experiments reported they excluded a Higgs boson in the mass range above 130 GeV and up to 500 GeV and observed a modest excess of collisions compatible with a Higgs boson at about 125 GeV, but with a low statistical significance.
Today the ATLAS and CMS experiments at CERN’s Large Hadron Collider (LHC) have presented the results of the analysis of all their most recent data. One tricky thing about the Higgs boson is that we do not know what is its mass, and so one needs to look for it in all its possible decay channels. ATLAS and CMS show that there is no Higgs boson with a mass above about 130 GeV and below 115 GeV (it could still be heavier than about 500 GeV but this is not favored by the theory).