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”.
Since monday the last of a string of summer High Energy Physics (HEP) conferences is unwinding in Beijing, SUSY-12 and before that in Melbourne ICHEP-2012. Some results with leading contributions from the Stockholm HEP group figure high in the topics of discussion. Finally ATLAS physicists can breathe a little bit, with most results out for now. The Higgs boson discovery got a lot of attention, and this is great because it is not every day that there is a discovery of that magnitude, but there is an other important reason: simply said, the existence of the Higgs boson is at the basis of much of the research being carried out at Stockholm University and in ATLAS.
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).
The ATLAS experiment has almost completed the analysis of the first 2 inverse femtobarns(*) of data provided by the Large Hadron Collider (LHC) until July this year.
On the forefront of the search for the Higgs boson, ATLAS and CMS, two of the LHC experiments aimed at measuring the Higgs boson signal, did not detect any signal excess so far.
From a particle physicist point of view the search for dark matter is just the search for yet another exotic particle. But the search for a possible dark matter candidate in particle physics experiments has definitely a special place on a par with the search for the famous Higgs boson.