Large Hadron Collider: Will Higgs Boson finally be registered?

Physicists, operating Large Hadron Collider's CMS detecting facility, recently registered production of two Z-bosons, which can be an evidence of a «heavy» variety of Higgs boson. CMS is a Compact Muon Solenoid facility, a general-purpose detector, designed for studying different aspects of proton collisions at 14 teraelectronvolt, the center-of-mass energy of the LHC particle accelerator.

During of the experiment on October 10, 2010, CMS facility has detected production of four mu-mesons (muons). Preliminary results of the reconstruction allowed researchers to explain this phenomenon as a candidate event for production of two neutral gauge Z-bosons. Z-bosons and W-bosons are elementary particles, which were predicted by the Standard Model of modern theory of elementary particles, and their existence was already proved. Higgs boson is still a hypothetic particle, which discovery would be a real success for followers of the Standard Model of mentioned theory. This particle is responsible for masses of all other elementary particles. However, particle physics is still unable to surely say, whether Higgs boson, which is the last missing element of this theory, exists or not.

Physicists all over the world currently discuss two possibilities of Higgs boson existence: “light” and “heavy” varieties. “Light” Higgs, weighing between 135 and 200 gigaelectronvolt should split into pair of W-bosons, and when Higgs boson’s mass equals or exceeds 200 gigaelectronvolt, it splits into pairs of Z-bosons, which in their turn “give birth” to pairs of electrons or muons.

What the Compact Muon Solenoid has actually detected, was production of four muons. Scientists admit that this event per se cannot be a direct evidence of Higgs boon production, because four muons can appear due to many other reasons. However, production of four muons is the first event of the type, which can finally prove that Higgs really exists.

In order to positively talk about Higgs boson’s existence in some kind of weight range, researchers should detect a large number of events, similar to the one described and analyze how masses of “newborn” particles are distributed. Experiments, performed by physicists in 1980s on the Large Electron–Positron Collider (LEP), which was the largest particle accelerator before Large Hadron Collider, also built in CERN, showed that Higgs boson cannot be found in weight range smaller that 114 gigaelectronvolt. Mass of 100 gigaelectronvolt corresponds to about 107 protons.

This summer physicists from Fermi National Accelerator Laboratory (Fermilab), where experiments on Tevatron, a circular particle accelerator, are performed, have eliminated a possibility of Higgs boson’s existence in the weight range from 158 to 175 gigaelectronvolt. About one year before, in November 2009, researchers from the same lab, located in Batavia near Chicago, IL, showed that evasive Higgs boson couldn’t exist between 163 and 166 gigaelectronvolt.


LHC: Possible Evidence of Higgs Boson Registered