Where can I find the most recent values for the Yukawa couplings in 2023? I currently have access to the values from 2011, but I guess precision has improved over the last decade in measurements.
Edit:
I am interested in the raw values.
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asked Jul 26, 2023 at 18:12
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3$\begingroup$ See the Higgs couplings section of pdglive.lbl.gov/Particle.action?node=S126&init=0 $\endgroup$– AndrewCommented Jul 26, 2023 at 18:18
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$\begingroup$ @Andrew I have checked the website, but I find the top quark Yukawa coupling to be around 0.95 and the bottom quark Yukawa coupling to be around 0.90. This is not correct, since the top quark Yukawa coupling is much bigger than any other Yukawa coupling. I am wrong at interpreting the data in pdglive? $\endgroup$– Independent PhysicsCommented Jul 26, 2023 at 18:26
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3$\begingroup$ You are misreading them! the κ s are ratios of measured over SM-theoretical! $\endgroup$– Cosmas ZachosCommented Jul 26, 2023 at 19:13
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$\begingroup$ @CosmasZachos Then where can I find a list of the precise values? $\endgroup$– Independent PhysicsCommented Jul 26, 2023 at 19:14
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$\begingroup$ The κs, as noted, are defined in here, and specify by how much the coupling of the Higgs boson to a given particle deviates from the SM expectation, $y=\sqrt{2} m/v$, where v=246GeV. So they are perforce all close to 1. You may trivially throw these in all tables of that review provided. Looks like, in practice, they are mostly below 1. You want an answer exemplifying this? $\endgroup$– Cosmas ZachosCommented Jul 26, 2023 at 19:29
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1 Answer
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(11.32) of this pdg overview defines the ratio parameter $\kappa_t=y_t v/m_t$ as the quantity you are seeking in units of the SM expectation in each case/flavor.
So, for example, the measured top yukawa is, e.g. for ATLAS 2022, $$ y_t\equiv \kappa_t m_t/v= 0.95\cdot \frac{172.8}{246}\approx 0.67, $$ etc.
Even though most κs are around 1 for each flavor, indicating the SM works pretty well, the corresponding yukawas scale up as the quark masses.
Edit in response to comments
If you are looking for the formal constant $h_t= y_t \sqrt{2}= 0.95$ defined in (11.3)-(11.6) of the review cited, which is closer to 1, you may retain the silly $\sqrt{2}$ and call $h_t$ the Yukawa coupling. It is purely a matter of normalization. What I am using in the main answer is the actual coupling $y_t$ of the quark to the Higgs scalar H, as specified in WP. These dimensionless constants are mere inputs to the SM, but their origin in an over-arching fundamental theory, perhaps at GUT scales, remains a mystery.
answered Jul 26, 2023 at 22:06
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$\begingroup$ Isn't there a square root of 2 missing in the calculation of the Yukawa couplings? $\endgroup$ Commented Jul 28, 2023 at 8:05
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$\begingroup$ Why isn't the top quark Yukawa coupling almost 1? $\endgroup$ Commented Jul 28, 2023 at 8:24
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$\begingroup$ See edit to answer: sheer trivial convention. It would help if you indicated or suggested why you 'd be interested in these values in the first place. $\endgroup$ Commented Jul 28, 2023 at 14:16
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$\begingroup$ I am studying the fundemental constants of nature, and I want to study Yukawa couplings in the most natural and fundamental values. $\endgroup$ Commented Jul 30, 2023 at 14:36
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$\begingroup$ Not even when measured at low energies and portraited in a non-dimensional way? $\endgroup$ Commented Jul 30, 2023 at 18:24