A New Higgs Boson Mass Measurement From CMS

The latest Higgs boson mass measurement from the CMS experiment, in the highly precise diphoton decay channel is 125.78 ± 0.26 GeV, which is 2.3 sigma above the current PDG value and modifies the combined value from CMS to 125.38 ± 0.14 GeV.

This tends to pull up the global average measurement of the Higgs boson mass from its Particle Data Group value of 125.10 ± 0.14 GeV which incorporated a combined value of 125.25 ± 0.20 ± 0.08 from CMS. The PDG used a value of 124.86 ± 0.27 from the ATLAS experiment. Since the new CMS number is very precise, this new measurement receives considerable weight in that determination, and probably pulls the global average up to 125.20 GeV, with a smaller margin of error than the current 0.14 GeV. The ATLAS combined average and the CMS combined average are consistent with each other at roughly the 1.7 sigma level.

A measurement of the Higgs boson mass in the diphoton decay channel

CMS Collaboration

(Submitted on 15 Feb 2020)

A measurement of the mass of the Higgs boson in the diphoton decay channel is presented. This analysis is based on 35.9 fb−1 of proton-proton collision data collected during the 2016 LHC running period, with the CMS detector at a center-of-mass energy of 13 TeV. A refined detector calibration and new analysis techniques have been used to improve the precision of this measurement. The Higgs boson mass is measured to be mH= 125.78±0.26 GeV. This is combined with a measurement of mH already performed in the H→ZZ→4ℓ decay channel using the same data set, giving mH= 125.46±0.16 GeV. This result, when further combined with an earlier measurement of mH using data collected in 2011 and 2012 with the CMS detector, gives a value for the Higgs boson mass of mH= 125.38±0.14 GeV. This is currently the most precise measurement of the mass of the Higgs boson.

Submitted to Phys. Lett. B. All figures and tables can be found at this http URL (CMS Public Pages)

Analysis

First, it is notable that the uncertainty in the Higgs boson mass is now almost down to 1 part per 1,000. This is not bad for a particle just discovered in 2012 that basically only one experimental apparatus in the world has an ability to directly observe.

Among other things, this measurement, together with a recent reanalysis of the top quark mass measurement at D0 make the conclusion that the sum of the square of the fundamental boson masses is greater than the sum of the square of the fundamental fermion masses more significant.

The new Higgs boson global average mass is 4.2 sigma (548 MeV) larger than the value necessary for the sum of the squares of the fundamental boson masses to equal one half of the square of the Higgs vev. The new top quark global average is 3.4 sigma (1,375 MeV) smaller than the value necessary for the sum of squares of the fundamental fermion masses to equal one half of the the square of the Higgs vev.

It isn't clear what significance to attach to this discrepancy in which there is a modest boson heavy bias relative to fermions in the Standard Model mass matrix when viewed in this manner.

But, the discrepancy from the values of the Higgs boson mass and top quark mass from those that would be required to make the sum of the square of the fundamental Standard Model particle masses equal to the square of the Higgs vev is much smaller. If the Higgs boson mass were 1.3 sigma higher (168 MeV, i.e. 125.368 GeV) and the top quark mass were also 1.3 sigma higher (517 MeV, i.e. 173.187 GeV), this relationship, sometimes called the LP & C relationship after the authors of the first paper to suggest the relationship, would be satisfied.