October 1, 2000
Including contributions of scale-dependent vacuum expectation values, we derive new analytic formulas and obtain substantially different numerical predictions for the running masses of quarks and charged-leptons at higher scales in the SM, 2HDM and MSSM. These formulas exhibit significantly different behaviours with respect to their dependence on gauge and Yukawa couplings than those derived earlier. At one-loop level the masses of the first two generations are found to be independent of Yukawa couplings of the third generation in all the three effective theories in the small mixing limit. Analytic formulas are also obtained for running $\tan\beta(\mu)$ in 2HDM and MSSM. Other numerical analyses include study of the third generation masses at high scales as functions of low-energy values of $\tan\beta$ and SUSY scale $M_S=M_Z-10^4$ GeV.
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February 17, 1999
Including contributions of scale-dependent vacuum expectation values of Higgs scalars, we derive new one-loop formulas analytically for running quark-lepton masses at higher scales in MSSM. Apart from the gauge-coupling dependence being different from earlier formulas, the third-generation- Yukawa-coupling effects are absent in the masses of the first two generations. While predicting the masses and $\tan\beta$ numerically, we also include two-loop effects.
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Updated values of running quark and lepton masses at GUT (Grand unified theories) scales are important for fermion mass model building, and to calculate neutrino masses, in GUTs . We present their values at GUT scales, in SM, MSSM and 2HDM theories, using the latest values of running quark and lepton masses.
December 23, 2009
Masses of heavy Standard Model fermions (top-quark, bottom-quark, and tau-lepton) play an important role in the analysis of theories beyond the SM. They serve as low-energy input and reduce the parameter space of such theories. In this paper Minimal supersymmetric extension of the SM is considered and two-loop relations between known SM values of fermion masses and running parameters of the MSSM are studied within the effective theory approach. Both b-quark and tau-lepton hav...
January 21, 1993
Relations among fermion masses and mixing angles at the scale of grand unification are modified at lower energies by renormalization group running induced by gauge and Yukawa couplings. In supersymmetric theories, the $b$ quark and $\tau$ lepton Yukawa couplings, as well as the $t$ quark coupling, may cause significant running if $\tan \beta$, the ratio of Higgs field expectation values, is large. We present approximate analytic expressions for the scaling factors for fermion...
January 18, 2007
Taking the dominant couplings in the standard model to be the quartic scalar coupling, the Yukawa coupling of the top quark, and the SU(3) gauge coupling, we consider their associated running couplings to one loop order. Despite the non-linear nature of the differential equations governing these functions, we show that they can be solved exactly. The nature of these solutions is discussed and their singularity structure is examined. It is shown that for a sufficiently small H...
March 28, 1995
In various unified extensions of the Minimal Supersymmetric Standard Model, the Yukawa couplings of the third generation are predicted to be of the same order. As a result, low energy measured mass ratios, require large ratios of the standard model Higgs vacuum expectation values, corresponding to a large value of the parameter $tan\beta$. We present analytic solutions for the Yukawa couplings and the Higgs and third generation squark masses, in the case of large top and bott...
December 10, 2007
Reliable values of quark and lepton masses are important for model building at a fundamental energy scale, such as the Fermi scale M_Z \approx 91.2 GeV and the would-be GUT scale \Lambda_GUT \sim 2 \times 10^16 GeV. Using the latest data given by the Particle Data Group, we update the running quark and charged-lepton masses at a number of interesting energy scales below and above M_Z. In particular, we take into account the possible new physics scale (\mu \sim 1 TeV) to be ex...
September 10, 2020
The precise values of the running quark and lepton masses $m^{}_f(\mu)$, which are defined in the modified minimal subtraction scheme ($\overline{\rm MS}$) with $\mu$ being the renormalization scale and the subscript $f$ referring to all the charged fermions in the Standard Model (SM), are very useful for the model building of fermion masses and flavor mixing and for the precision calculations in the SM or its new-physics extensions. In this paper, we calculate the running fe...
April 4, 2008
We investigate the effect of supersymmetric (SUSY) threshold corrections on the values of the running quark and charged lepton masses at the GUT scale within the large $\tan\beta$ regime of the MSSM. In addition to the typically dominant SUSY QCD contributions for the quarks, we also include the electroweak contributions for quarks and leptons and show that they can have significant effects. We provide the GUT scale ranges of quark and charged lepton Yukawa couplings as well ...
December 8, 2006
Running of gauge couplings in the MSSM from a unified value at high energies leads to a successful prediction of the weak mixing angle. Supersymmetric models at the TeV scale may contain further hints of high scale physics, such as the pattern of superpartner masses when evolved from the TeV scale to a high scale using the renormalization group. This running is traditionally assumed to be independent of effects in the hidden sector. In this paper we re-examine this assumption...