The New Parameter Determinations
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
Consistency
All of the RGSPT values are consistent at the two sigma level with the Particle Data Group global average measurements, although there is more tension between the strange quark mass estimates (1.14 sigma) than between the other parameter determinations, which are consistent at the sub-one sigma level.
Some of the tensions between the RGSPT values and the FLAG values are more significant: the bottom quark mass discrepancy is just under two sigma. The strange quark discrepancy is 2.56 sigma. The strong force coupling constant tension is 1.22 sigma.
The FLAG values and Particle Data Group global averages are all consistent with each other at the one sigma or less level.
Uncertainties
The uncertainties in the RGSPT values are smaller than in the Particle Data Group global averages, except for the down quark. The up quark uncertainties are roughly comparable overall between the RGSPT values and the Particle Data Group global averages.
The FLAG values have less uncertainty for the light quarks than the RGSPT values, slightly more uncertainty than the RGSPT values for the charm quark mass, the bottom quark mass, and the strong force coupling constant.
The FLAG values all have less uncertainty than the corresponding Particle Data Group global averages.
Why Are These Values Hard To Determine?
The difficulties involved in measuring these parameters almost entirely come down to calculation issues. Quarks other than the top quark always appear either confined in composite hadron particles, or in a quark-gluon plasma which makes localization of free quark masses impossible as a practical matter. Likewise, there are no clean isolated measurements of the strong force coupling constant.
All of these parameters have to be inferred from the properties of hadrons which have been measured directly to vastly greater precision, and then converted with wickedly difficult quantum chromodynamics (QCD) calculations (sometimes with electromagnetic and weak force adjustments), to determine the fundamental parameter values.
3 comments:
There exists a puzzling disagreement between the results for the neutron lifetime obtained in experiments using the beam technique versus those relying on the bottle method.
new BSM physics ?
arXiv:2306.13026 (physics)
[Submitted on 22 Jun 2023]
Methodological Reflections on the MOND/Dark Matter Debate
Patrick M. Duerr (Hebrew University and Oxford University), William J. Wolf (Oxford University)
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The paper re-examines the principal methodological questions, arising in the debate over the cosmological standard model's postulate of Dark Matter vs. rivalling proposals that modify standard (Newtonian and general-relativistic) gravitational theory, the so-called Modified Newtonian Dynamics (MOND) and its subsequent extensions. What to make of such seemingly radical challenges of cosmological orthodoxy? In the first part of our paper, we assess MONDian theories through the lens of key ideas of major 20th century philosophers of science (Popper, Kuhn, Lakatos, and Laudan), thereby rectifying widespread misconceptions and misapplications of these ideas common in the pertinent MOND-related literature. None of these classical methodological frameworks, which render precise and systematise the more intuitive judgements prevalent in the scientific community, yields a favourable verdict on MOND and its successors -- contrary to claims in the MOND-related literature by some of these theories' advocates; the respective theory appraisals are largely damning. Drawing on these insights, the paper's second part zooms in on the most common complaint about MONDian theories, their ad-hocness. We demonstrate how the recent coherentist model of ad-hocness captures, and fleshes out, the underlying -- but too often insufficiently articulated -- hunches underlying this critique. MONDian theories indeed come out as severely ad hoc: they do not cohere well with either theoretical or empirical-factual background knowledge. In fact, as our complementary comparison with the cosmological standard model's Dark Matter postulate shows, with respect to ad-hocness, MONDian theories fare worse than the cosmological standard model.
Comments: forthcoming in Studies in History and Philosophy of Science
Subjects: History and Philosophy of Physics (physics.hist-ph)
Cite as: arXiv:2306.13026 [physics.hist-ph]
Neutron lifetime. "new BSM physics?" Almost all inclusive v. exclusive measurements see this discrepancy, the methods involved have well known sources of systemic error that are often underestimated.
"Methodological Reflections on the MOND/Dark Matter Debate"
So dubious it barely deserves a rebuttal. Citing Popper is a sign you aren't really looking at the evidence.
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