Indirect determination of the Higgs mass through electroweak radiative corrections (original) (raw)
Related papers
Physical Review Letters, 2004
We present a complete calculation of the contributions to the effective leptonic weak mixing angle, sin 2 lept eff , generated by closed fermion loops at the two-loop level of the electroweak interactions. This quantity is the source of the most stringent bound on the mass M H of the standard model Higgs boson. The size of the corrections with respect to known partial results varies between ÿ4 10 ÿ5 and ÿ8 10 ÿ5 for a realistic range of M H from 100 to 300 GeV. This translates into a shift of the predicted (from sin 2 lept eff alone) central value of M H by 19 GeV, to be compared with the shift induced by a recent change in the measured top quark mass which amounts to 36 GeV.
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 .
Physical Review D, 1995
We present analytic results for the two-loop leading heavy top quark contributions as required for precise predictions of electroweak observables. The Higgs boson mass is kept arbitrary. We discuss a set of recurrence relations for diagrams with three masses at zero momentum, which allow one to reduce the calculation to a few master integrals. Simple analytic expressions are obtained for the p parameter and for the Zbb vertex. Results are presented for the on-shell and the MS definition of the top quark mass. We explicitly discuss and verify the validity of Ward-Takahashi identities and check that the use of an anticommuting p5 preserves the latter.
Consequences of Recent Electroweak Data and W-mass for the Top 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.
Higgs couplings and precision electroweak data
Journal of High Energy Physics, 2013
In light of the discovery of a Higgs-like particle at the LHC, we revisit the status of the precision electroweak data, focusing on two discrepant observables: 1) the long-standing 2.4σ deviation in the forward-backward asymmetry of the bottom quark A b F B , and 2) the 2.3σ deviation in R b , the ratio of the Z → bb partial width to the inclusive hadronic width, which is now in tension after a recent calculation including new two-loop electroweak corrections. We consider possible resolutions of these discrepancies. Taking the data at face value, the most compelling scenario is that new physics directly affects A b F B and R b , bringing the prediction into accord with the measured values. We propose a modified 'Beautiful Mirrors' scenario which contains new vector-like quarks that mix with the b quark, modifying the Zbb vertex and thus correcting A b F B and R b . We show that this scenario can lead to modifications to the production rates of the Higgs boson in certain channels, and in particular a sizable enhancement in the diphoton channel. We also describe additional collider tests of this scenario.
One-loop electroweak factorizable correctionsfor the Higgsstrahlung at a linear collider
The European Physical Journal C, 2005
We present standard model predictions for the four-fermion reaction e + e − → µ + µ −b b being one of the best detection channels of a low mass Higgs boson produced through the Higgsstrahlung mechanism at a linear collider. We include leading virtual and real QED corrections due to initial state radiation and a modification of the Higgs-bb Yukawa coupling, caused by the running of the b-quark mass, for e + e − → µ + µ −b b. The complete O(α) electroweak corrections to the Z-Higgs production and to the Z boson decay width, as well as remaining QCD and EW corrections to the Higgs decay width, as can be calculated with a program HDECAY, are taken into account in the double pole approximation.
Electroweak radiative corrections and the W boson mass at hadron colliders
2003
At present and future hadron colliders, the precision physics program started in the past will be continued. In particular, a precise determination of the W boson mass will be carried out. This requires the calculation of the radiative corrections and their implementation in Monte Carlo event generators for data analysis. In this talk, the status of the calculation of the order α electroweak radiative corrections is reviewed and a study of the impact of higher order QED corrections on the W boson mass is presented.
Two-loop electroweak fermionic corrections to
Nuclear Physics B, 2009
We present the first calculation of the two-loop electroweak fermionic correction to the flavour-dependent effective weak-mixing angle for bottom quarks, sin 2 θ bb eff. For the evaluation of the missing two-loop vertex diagrams, two methods are employed, one based on a semi-numerical Bernstein-Tkachov algorithm and the second on asymptotic expansions in the large top-quark mass. A third method based on dispersion relations is used for checking the basic loop integrals. We find that for small Higgs-boson mass values, M H ∝ 100 GeV, the correction is sizable, of order O(10 −4).