Is the Higgs boson finally seen at LHC?
Kajari Mazumdar on behalf of TIFR-CMS Group
29 June 2012
The results on the search for the Higgs boson using LHC data of 2011 combined with that of 2012, has been announced at CERN on July 4th, 2012.
Here is the webcast http://webcast.web.cern.ch/webcast
CERN press release : http://press.web.cern.ch/press/PressReleases/Releases2012/PR17.12E.html
The interactions among various elementary particles are described in the theory of the Standard Model based on various symmetry considerations. Though the predictions from this model has been confirmed by many experiments during last 30 years, it lacks the power to predict the masses of the elmentary particles. The mass generation is possible by the so called spontaneous electroweak symmetry breaking which was discussed first by Y.Nambu and taken to earnest by 3 teams of scientists named P.W. Higgs, F. Englert, R. Brout, G.S.Guranlink, C.R. Hagen and T. Kibble during 1960s.
In this cartoon of the Higgs potential, the symmetric position of the smiley corresponds to an energy higher than that of the ground state. When the smiley chooses to go down, the symmetry is broken spontaneously, since it can occupy only a particular position.
The carriers of the weak interaction are supposed to have become massive, and thereby breaking the symmetry, at some epoch during the cooling process of the universe after the big bang while the carrier of the electromagnetic interaction, the photon, continued to be massless. This mechanism also evokes a new elementary particle, yet to be seen in experimentally, famously known as the Higgs boson. Thus to complete our understanding of the origin of mass, it is crucial to find the Higgs boson. Even the mass of the Higgs boson itself is an experimental input to the Standard Model! This particle is being hunted in experiments extensively since last few decades but has remained elusive till now.
The Large Hadron Collider (LHC) machine at CERN has been colliding proton-on-proton at high energies since 2010 with high flux thereby making a situation congenial for production of heavy new particles if they ever existed in nature. The multipurpose experiments CMS and ATLAS have analyzed the huge amount of data collected till June 18, 2012 using grid computing. Scientists from TIFR are collaborating in CMS experiment form early phase of the experiment. CMS experiment has excluded most of the plausible mass range of the Higgs boson by analyzing the data collected during proton-proton operation of LHC in 2011. However the still allowed mass range is the most probable area to find the Higgs boson, as predicted indirectly. This mass range is also the most difficult to handle experimentally. LHC experiments are stretching their limits to pin down the Higgs boson with the data being collected in 2012.
Q & A
Kajari Mazumdar : One of the physics motivation of LHC experiment has been to resolve the puzzle you mention, from the early phase. At the LHC facility, there is a dedicated experiment, LHCb, which is particularly equipped to study in details the processes that leads to CP violation. The amount of difference in the few suitable observables being very small, it requires lot of data and hence time. In addition, CMS and ATLAS experiments are alos on hunt to pin down the sources of CP violation which lead to the domination of matter over antimatter. Scientists are on the job, fully motivated and on fast track, always!