Friday, March 21, 2014

Higgs Boson Width Less Than 17.43 MeV

The predicted width of the Standard Model Higgs Boson (another way of describing its mean lifetime - a small number implies a long lifetime, a large number implies a short lifetime) is 4.15 MeV (compared to 1,500 MeV for a top quark and 2,500 MeV for a W boson).

A 4.15 MeV width implies a mean lifetime on the order of 5*10^-22 seconds, about 100 times longer than the typical time scale at which hadronization occurs, for example, but still very ephemeral.

The Higgs boson width is hard to measure directly.  The direct measurement of the width at the LHC limits it to only about 3,000 MeV or less.  But, the CMS experiment at the Large Hadron Collider (LHC) has used some clever data interpretation to determine that the observed Higgs boson width cannot be more than 4.2 times the expected value with 95% confidence (i.e. not more than 17.43 MeV).

This estimate confirms two year old estimates based on comparing the observed cross-sections to the predicted cross-sections of a sampling of particular Higgs boson decays.

This dramatically narrows the range of possible non-Standard Higgs boson decays because more possible decay paths increase the width of a particle.

No comments: