I New QCD Parameter Determinations

ohwilleke
Gold Member
Messages
2,647
Reaction score
1,605
TL;DR Summary
A pair of new papers make precision determinations of the quark masses and the strong force coupling constant using the renormalization group summed perturbation theory (RGSPT). The values are close to previous estimates, but there is some tension in the strange quark mass determination.
A pair of new papers (here and here) make precision determinations of the quark masses and the strong force coupling constant using the renormalization group summed perturbation theory (RGSPT). For comparison purposes, I have followed each value with the Particle Data Group (PDG) value, and then the 2021 Flavor Lattice Averaging Group (FLAG) value.

α(s)(n(f)=5)(M(Z)) = 0.1171(7)
<----> 0.1179(9) <----> 0.1184(8).

m_b(MS mass pole mass) = 4174.3(9.5) MeV
<----> 4180-20+30 MeV <----> 4203(11) MeV

m_c(MS mass pole mass) = 1281.1(3.8) MeV
<----> 1270(20) MeV <----> 1278(13) MeV

m_s(2 GeV) = 104.34-4.21+4.23 MeV
<----> 93.4-3.4+8.6 MeV <----> 93.44(68) MeV

m_d(2 GeV) = 4.21-0.45+0.48 MeV
<----> 4.67-0.17+0.48 MeV <----> 4.70(5) MeV

m_u(2 GeV) = 2.00-0.40+0.33 MeV
<----> 2.16-0.26+0.49 MeV <----> 2.14(8) MeV

Can anyone explain, at an educated layman's "intermediate" level, why the strange quark mass value in this method has more tension than the other parameters do with previously estimated values?

My gut intuition is that the tension is due to insufficient consideration of non-perturbative effects by RGSPT, which turns out to be maximal for the strange quark, but I don't have a well substantiated basis for that hypothesis.
 
Last edited:
Physics news on Phys.org
what does

<---->mean?
 
malawi_glenn said:
what does

<---->mean?
I'm merely using it as a way to visually distinguish between the values from each of the three sources for each parameter, while connecting all three values to the definition of the parameter described (which would ideally all appear on the same line).

If you use of comma or semi-colon, they tend to visually blend into each other to my tired middle aged bifocal wearing eyes.

If you you separate lines for each entry, it gets harder to read the post as a whole, since it has six more lines.
 
tableworksfinetoo
the<---->isgarbage

personallyIthink
thelackof
## \LaTeX ##formationis

evenmore
hurtfulto

eyes
 
  • Haha
Likes ohwilleke and Vanadium 50
Toponium is a hadron which is the bound state of a valance top quark and a valance antitop quark. Oversimplified presentations often state that top quarks don't form hadrons, because they decay to bottom quarks extremely rapidly after they are created, leaving no time to form a hadron. And, the vast majority of the time, this is true. But, the lifetime of a top quark is only an average lifetime. Sometimes it decays faster and sometimes it decays slower. In the highly improbable case that...
I'm following this paper by Kitaev on SL(2,R) representations and I'm having a problem in the normalization of the continuous eigenfunctions (eqs. (67)-(70)), which satisfy \langle f_s | f_{s'} \rangle = \int_{0}^{1} \frac{2}{(1-u)^2} f_s(u)^* f_{s'}(u) \, du. \tag{67} The singular contribution of the integral arises at the endpoint u=1 of the integral, and in the limit u \to 1, the function f_s(u) takes on the form f_s(u) \approx a_s (1-u)^{1/2 + i s} + a_s^* (1-u)^{1/2 - i s}. \tag{70}...

Similar threads

Back
Top