The Top Quark Mass From ATLAS 13 TeV Data

A summary and review of ATLAS 13 TeV data at the Large Hadron Collider (LHC) from a talk presented at a recent conference, explains this direct measurement of the top quark mass from fully leptonic decays. It notes that: "this top-mass extraction turns out to be the most precise single measurement from the reconstruction of the top-decay products, i.e. m(t) = 174.41 ± 0.39 (stat.) ± 0.66 (syst.) ± 0.25 (recoil)." Combining all three sources of uncertainty in quadrature, this is 174.41 ± 0.81 GeV. The brief paper recaps an earlier disclosure of this measurement published on June 5, 2023.

This top quark mass is at the high end of recent top quark measurements. The Particle Data Group value is 172.57 ± 0.29 GeV (determined by inflating uncertainty estimates by a factor of 1.5 because they otherwise wouldn't all be reasonably consistent). But this result, which is included in the PDG world average, is still consistent with the world average as it is just 1.2 sigma above the PDG value.

This result is close to the Tevatron combined measurement from 2016 of 174.30 ± 0.64 GeV. But seven CMS experiment measurements (and one different ATLAS measurement from 2019) over the time period from 2016 to 2023 measure values ranging from 171.77 ± 0.37 GeV to 173.06 ± 0.84 GeV which drag down the world average.

A determination of the top quark pole mass from cross-section measurements is close to the world average from direct measurements and is competitive in precision. The world average top quark pole mass from cross-section measurements is 172.4 ± 0.7 GeV.

The inverse error average weighted average top quark mass from direct measurements and cross-section measurements combined (which is arguably more robust) is 172.52 GeV, with an uncertainty of a bit less than ± 0.29 GeV (probably something like ± 0.25 GeV).

I suspect that the true value is probably about 173 GeV.