Constituent quark masses and the electroweak standard model

Physical Review D, 2010

An updated global analysis within the Standard Model (SM) of all relevant electroweak precision and Higgs boson search data is presented with special emphasis on the implications for the Higgs boson mass, MH . Included are, in particular, the most recent results on the top quark and W boson masses, updated and significantly shifted constraints on the strong coupling constant, αs, from τ decays and other low energy measurements such as from atomic parity violation and neutrino deep inelastic scattering. The latest results from searches for Higgs production and decay at the Tevatron are incorporated together with the older constraints from LEP 2. I find a trimodal probability distribution for MH with a fairly narrow preferred 90% CL window, 115 GeV ≤ MH ≤ 148 GeV.

Nuclear Physics B-proceedings Supplements, 1998

Significant progress has been made in the determination of the light quark masses, using both lattice QCD and sum rule methods, in the last year. We discuss the different methods and review the status of current results. Finally, we review the calculation of bottom and charm masses.

Zeitschrift f�r Physik C Particles and Fields, 1996

We have examined the electroweak radiative corrections in the LEP precision data in view of the new measurements of M W and m t as well as the recent progress in the higher order radiative corrections. From the minimal χ 2-fit to the experimental Z-decay parameters (with the aid of a modified ZFITTER program), we predict that M W = 80.29(4)(2) GeV where the first error is due to the uncertainty in the fitted m t for a fixed m H and the second error comes from the m H in the range of 60−1000 GeV, which is to be compared with the current world average M W = 80.23(18) GeV. The current world average value of M W and the 1994 LEP data definitely favor nonvanishing electroweak radiative corrections and are consistent with a heavy m t as measured by the recent CDF report but with a heavy Higgs scalar of about 400 GeV within the context of the minimal standard model. The sensitivity of and the errors in the best fit solutions due to the uncertainties in the gluonic coupling α s (M Z) and α(M Z) are also studied carefully. In addition we discuss how the future precision measurements of M W can provide a decisive test for the standard model with radiative corrections and give a profound implication for the measurement of t-quark and Higgs masses.

We critically reexamine the precision tests of the standard model by coupling the current world average value of M W with the recent LEP electroweak data with the aid of a modified ZFITTER program to include the dominant two-loop and QCD-EW mixed terms. The results show a clear evidence of nonvanishing electroweak radiative corrections. The recent CDF m t is a solution of the minimal χ 2-fits to the recent LEP data set and M W = 80.23(18) GeV but with a heavy Higgs scalar, i.e., m t = 179 GeV and m H = 300 GeV. We discuss how sensitive m t and m H are depending on the exact value of M W even within the present uncertainty, as well as on α s and α(M Z). We show how the future improvements on M W can discriminate different values of m t and m H from the electroweak data and provide a crucial and decisive test for the standard model.

The European physical journal. C, Particles and fields

Properties of the Higgs boson with mass near 125[Formula: see text] are measured in proton-proton collisions with the CMS experiment at the LHC. Comprehensive sets of production and decay measurements are combined. The decay channels include [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] pairs. The data samples were collected in 2011 and 2012 and correspond to integrated luminosities of up to 5.1[Formula: see text] at 7[Formula: see text] and up to 19.7[Formula: see text] at 8[Formula: see text]. From the high-resolution [Formula: see text] and [Formula: see text] channels, the mass of the Higgs boson is determined to be [Formula: see text]. For this mass value, the event yields obtained in the different analyses tagging specific decay channels and production mechanisms are consistent with those expected for the standard model Higgs boson. The combined best-fit signal relative to the standard model exp...

Physics Letters B, 1984

The phenomenological predictions of Fritzsch-type quark mass matrices and their implications on the underlying structure of particle physics beyond the standard model are considered. Using a recent analysis on the K-M mixing matrix from the b-quark lifetime etc., R b =-r(b ---, uev-")/r(b ~ cev-') is predicted to be in the range 1.44 × 10 -3 ,; R b ~; 1.87 X 10 -2 , while the present upper bound on R b is 5 X 10 -2 . For B K = 0.33, obtained by Donoghue et al. using current algebra and the measured zX/" = 3/2 contribution to k ---, ~r~r, the physical (=-constituent) mass of the t-quark (for A~--~ = 100 MeV) is predicted to be (73.5 + 8.5) GeV and so the t-quark will not be found in PETRA and LEP experiments. For the same value of B K, our predictions on the value OfRb, I Vcbl, and the CP violating phase 8' in the K-M mixing matrix are 0.79 × 10 -z ~; R b ,; 1.01 X 10 -2, 0.066 ,; IVcbl ~ 0.070, 85.6 ° ,; 8' ~ 97.4 °, and are subject to future experiments. Our predicted value of 8' (which is independent of experimental input from CP violating phenomena) is in good agreement with the CP violation strength parameter Re e and strongly supports the validity of the Fritzsch form of quark mass matrices. It is conjeetured that the underlying structure of particle physics is such that the two fundamental phases, o and ~', that appear in the weak charged current mixing matrix, are equal to -~r/2, corresponding to maximal CP violation in the weak interaction sector. This, together with the predicted value of the t-quark mass, can be used as a guide in future model building (o = r = -n/2 can be achieved by the phases of the VEVs of complex Higgs fields). The dependence of our results on the quark mass ratios is considered and a large mass scale for light quarks (u, d, s) is shown to be inconsistent with the Fritzsch form of quark mass matrices. Measurement of the value of R b at CLEO and CUSB and improved determination of I Vcb[ will be the best tests of the validity of Fritzsch-type quark mass matrices in the near future.

2002

We discuss the experimental and theoretical uncertainties on precision electroweak observables and their relationship to the indirect constraints on the Higgs boson mass, M H , in the Standard Model (SM). The critical experimental measurements (M W , sin 2 θ eff , m t , ...) are evaluated in terms of their present uncertainties and their prospects for improved precision at future colliders, and their contribution to the constraints on M H . In addition, the current uncertainties of the theoretical predictions for M W and sin 2 θ eff due to missing higher order corrections are estimated and expectations and necessary theoretical improvements for future colliders are explored. The constraints from rare B decays are also discussed. Analysis of the present experimental and theoretical precisions yield a current upper bound on M H of ∼ 200 GeV. Including anticipated improvements corresponding to the prospective situation at future colliders (Tevatron Run II, LHC, LC/GigaZ), we find a relative precision of about 25% to 8% (or better) is achievable in the indirect determination of M H .

Physics Letters B, 2003

We present a new QCD sum rule with high sensitivity to the continuum regions of charm and bottom quark pair production. Combining this sum rule with existing ones yields very stable results for the MS quark masses,mc(mc) andm b (m b ). We introduce a phenomenological parametrization of the continuum interpolating smoothly between the pseudoscalar threshold and asymptotic quark regions. Comparison of our approach with recent BES data allows for a robust theoretical error estimate. The parametric uncertainty due to αs is reduced by performing a simultaneous fit to the most precise sum rules and other high precision observables. This includes a new evaluation of the lifetime of the τ lepton, ττ , serving as a strong constraint on αs. Our results aremc(mc) = 1.289 +0.040 −0.045 GeV, m b (m b ) = 4.207 +0.030 −0.031 GeV (with a correlation of 29%), and αs(MZ)[ττ ] = 0.1221 +0.0026 −0.0023 .

Physical Review D, 2000

The 1999 precision electroweak data from LEP and SLC persist in showing some slight discrepancies from the assumed standard model, mostly regarding b and c quarks. We show how their mixing with exotic heavy quarks could result in a more consistent fit of all the data, including two unconventional interpretations of the top quark.

Properties of the Higgs boson with mass near 125 GeV are measured in proton-proton collisions with the CMS experiment at the LHC. Comprehensive sets of production and decay measurements are combined. The decay channels include γ γ , ZZ, WW, τ τ , bb, and μμ pairs. The data samples were collected in 2011 and 2012 and correspond to integrated luminosities of up to 5.1 fb −1 at 7 TeV and up to 19.7 fb −1 at 8 TeV. From the high-resolution γ γ and ZZ channels, the mass of the Higgs boson is determined to be 125.02 +0.26 −0.27 (stat) +0.14 −0.15 (syst) GeV. For this mass value, the event yields obtained in the different analyses tagging specific decay channels and production mechanisms are consistent with those expected for the standard model Higgs boson. The combined best-fit signal relative to the standard model expectation is 1.00 ± 0.09 (stat) +0.08 −0.07 (theo) ± 0.07 (syst) at the measured mass. The couplings of the Higgs boson are probed for deviations in magnitude from the standard model predictions in multiple ways, including searches for invisible and undetected decays. No significant deviations are found.