Hints of the Higgs Boson?

A view along the beam direction of the ATLAS detector. The two high energy clusters of energy in the ATLAS calorimeter, indicated in yellow, result from the two photons. Note that there is no track pointing to the clusters as photons have no charge
A view along the beam direction of the ATLAS detector. The two high energy clusters of energy in the ATLAS calorimeter, indicated in yellow, result from the two photons. Note that there is no track pointing to the clusters as photons have no charge

news item: 12/12/11

Penn has a large group of postdoctoral fellows and graduate students, led by Professors Joseph Kroll, Elliot Lipeles, Evelyn Thomson, and Brig Williams, working on the ATLAS experiment at the LHC in Geneva, Switzerland. A significant fraction of the group, about 10 physicists in all, has been very involved in obtaining the latest results of searches for the Higgs boson, a particle which is predicted to exist in order to explain the origin of mass of elementary particles such as the electron, muon, and quarks.

In two seminars at CERN today, the ATLAS and CMS experiments presented their latest results. The Higgs can decay into several final states with the most promising ones being two photons, WW, and ZZ, where W and Z are the particles responsible for all weak interactions. The ATLAS experiment observes a small excess in all three of these final states. In the photon photon and ZZ final states, the excess occurs at a mass of approximately 126 GeV. For the WW final state, as there are two neutrinos undetected, one can only say that the excess observed is consistent with this mass. The probability that the Standard Model backgrounds would fluctuate to give the observed signals at this mass is estimated to be 2 * 10-4 . However, given that such a fluctuation could occur at many different possible masses, the overall probability of the observation being a background fluctuation is estimated to be ~ 1%.

A view along the beam direction of ATLAS emphasizing the system for detecting muons. The four blue lines indicate the four muons resulting from the decay of two Z particles
A view along the beam direction of ATLAS emphasizing the system for detecting muons. The four blue lines indicate the four muons resulting from the decay of two Z particles

The CMS experiment also sees some excess in the low mass region, notably in the region of 124 GeV and below. ATLAS and CMS combined have now excluded at 95% confidence level the Higgs having a mass outside the narrow range of 116 – 127 GeV.

While the reported results are very exciting, and could be a "first glimpse" of the Higgs boson, the statistical significance of the results from ATLAS and CMS is still considered to be far from what is required for a true discovery. The data expected to be collected in 2012 should allow one to either definitively discover the Higgs , or exclude it.
 

read the article in the December 12, 2011 [ Philadelphia Inquirer ]

see more on the [ ATLAS project ]