# Why is there still disagreement over the mass of the bottom (or beauty) quark, but none of the others?

Wikipedia (among other places) lists two values for the alleged mass of the B quark, 4.18 and 4.65 GeV.

Only one of the two possible masses listed has a link to another Wiki page explaining the theoretical framework behind it.

Is there a good reason for the continuing confusion?

• A link to at least one of the "other places" would have been polite. Normally I just edit obviously missing links into the post, but on mobile that is kind of a hassle.
– rob
Jun 21 at 21:34

Looking at the wiki article, the difference in the mass values depends on the mathematical model used to derive from the data the value of the bottom quark mass.

One of the values links to this model

In quantum field theory, the minimal subtraction scheme, or MS scheme, is a particular renormalization scheme used to absorb the infinities that arise in perturbative calculations beyond leading order, introduced independently by Gerard 't Hooft and Steven Weinberg in 1973.1 The MS scheme consists of absorbing only the divergent part of the radiative corrections into the counterterms.

The other value does not have a page linked for the model of the calculation but says: 1S scheme. I cannot find any calculations in this scheme.

The latest paper uses the MS scheme.

We present a new measurement of the bottom quark mass in the MS¯ scheme at the renormalization scale of the Higgs boson mass from measurements of Higgs boson decay rates at the LHC: $$mb(mH)=2.60+0.36−0.31 GeV.$$

An active proof that quark masses depend on the model and the assumptions used in the model for the given data.

The mass here

The masses should not be taken too seriously, because the confinement of quarks implies that we cannot isolate them to measure their masses in a direct way. The masses must be implied indirectly from scattering experiments. The numbers in the table are very different from numbers previously quoted and are based on the July 2010 summary in Journal of Physics G, Review of Particle Physics, Particle Data Group. A summary can be found on the LBL site.

• Note that, in the proud tradition of physicists giving things names that are impossible to type, there is a difference between "minimal subtraction" $\mathit{MS}$ and "modified minimal subtraction" $\overline{\mathit{MS}}$, pronounced em-ess-bar.
– rob
Jun 22 at 4:29
• @rob thanks for the correction. Yes, I cannot put a bar :( Jun 22 at 4:58