Monday, April 13, 2015

A (Probably) Final Tevatron Top Quark Mass Measurement

The final Tevatron mass measurement for the top quark is 174.34±0.64 GeV.  This is the most accurate single measurement of this fundamental standard model mass parameter to date.

This compares to the latest top quark mass estimate from ATLAS of 172.99 +/- 0.91 GeV. The latest combined mass estimate of the top quark (excluding the latest top quark mass measurement estimate from ATLAS) is 173.34 +/- 0.76 GeV.

The Tevatron measurement pulls the LHC estimates to a higher value, which is a good fit for some theoretical expectations for it. The overlap of the combined one sigma experimentally measured ranges for the top quark mass at Tevatron and the LHC is 173.70 to 174.10 GeV with an average of 173.90 GeV.  Weighting the Tevatron results slightly more heavily than the LHC combined result since it has a smaller margin of error, only slightly increases the average since the margins of error are still quite similar.

The expected value of the top mass from the formula that the sum of the square of each of the fundamental particle masses equals the square of the Higgs vaccum expectation value, given the state of the art Higgs boson mass measurement (using a global fit value of 80.376 GeV for the W boson rather than the PDG value) is 173.73 GeV (173.39 to 174.07 GeV within the plus or minus one sigma band of the current Higgs boson measurement).

If the the sum of the square of the boson masses equals the sum of the square of the fermion masses the implied top quark mass is 174.03 GeV if pole masses of the quarks are used, and 174.05 GeV if MS masses at typical scales are used.

The experimental measurements are perfectly consistent with any of these theoretical expectations.


Alejandro Rivero said...

There is too many possible relationships between masses in the electroweak sector, it is amazing. And at the same time, discouraging, if we are still to expect some new particle from Run II.

Alejandro Rivero said...

Point is, if wished to have some place for two extra H+, H- higgses, any easy formula will be forcefully more complicated. Well, if they had been exactly next to the H0 we could have had:

3*80.385^2+3*91.1876^2+3*125.09^2)= 3 * top^2

Blaming to the number of colours. Next opportunity is to fix the charged higgses at the vacuum scale, using

sqrt(3*80.385^2+3*91.1876^2+125.09^2+2*244.88^2)/sqrt(3) =

and then claim

3*MW^2+ 3*MZ^2 + MH^2 + 2*Mh^2 = 2* 3 Mt^2