scholarly journals CONSTRAINING NEW MODELS WITH PRECISION ELECTROWEAK DATA

2006 ◽  
Vol 21 (19n20) ◽  
pp. 4045-4070 ◽  
Author(s):  
MU-CHUN CHEN ◽  
SALLY DAWSON ◽  
TADAS KRUPOVNICKAS
Keyword(s):  
Top Quark ◽  
New Physics ◽  
Tree Level ◽  
Symmetric Model ◽  
Top Quark Mass ◽  
Precision Data ◽  
The Standard Model ◽  
The One ◽  
Electroweak Precision ◽  
Electroweak Precision Data

Electroweak precision data have been extensively used to constrain models containing physics beyond that of the Standard Model (SM). When the model contains Higgs scalars in representations other than singlets or doublets, and hence ρ≠1 at tree-level, a correct renormalization scheme requires more inputs than the three commonly used for the SM case. In such cases, the one-loop electroweak results cannot be split into a SM contribution plus a piece which vanishes as the scale of new physics becomes much larger than MW. We illustrate our results by presenting the dependence of MW on the top-quark mass in a model with a Higgs triplet and in the SU (2)L × SU (2)R left–right symmetric model. In these models, the allowed range for the lightest neutral Higgs mass can be as large as a few TeV.

scholarly journals THE TOP PRIORITY: PRECISION ELECTROWEAK PHYSICS FROM LOW TO HIGH ENERGY

2004 ◽  
Vol 19 (06) ◽  
pp. 808-820 ◽  
Author(s):  
P. GAMBINO
Keyword(s):  
Precise Measurement ◽  
High Energy ◽  
New Physics ◽  
Precision Data ◽  
The Standard Model ◽  
B Quark ◽  
Electroweak Precision ◽  
Top Mass ◽  
Electroweak Precision Data

Overall, the Standard Model describes electroweak precision data rather well. There are however a few areas of tension (charged current universality, NuTeV, (g-2)μ, b quark asymmetries), which I review critically, emphasizing recent theoretical and experimental progress. I also summarize what precision data tell us about the Higgs boson and new physics scenarios. In this context, the role of a precise measurement of the top mass is crucial.

ONE LOOP-INDUCED WZH COUPLING IN THE TWO HIGGS DOUBLET MODEL

1989 ◽  
Vol 04 (28) ◽  
pp. 2757-2766 ◽  
Author(s):  
THOMAS G. RIZZO
Keyword(s):  
Standard Model ◽  
Higgs Doublet ◽  
New Physics ◽  
Tree Level ◽  
Beyond The Standard Model ◽  
The Standard Model ◽  
Charged Higgs ◽  
Doublet Model ◽  
The One ◽  
Two Higgs Doublet Model

Although absent at the tree level in models with only doublet and singlet Higgs representations, the WZH coupling can be induced at the one-loop level. We examine the size of this induced coupling in the two Higgs doublet model due to fermion as well as Higgs/gauge boson loops. Such couplings could provide a new mechanism for charged Higgs production at colliders and are ‘backgrounds’ to new physics beyond the Standard Model. We find, however, that these couplings are very weak for all regions of the parameter space explored.

scholarly journals RADIATIVE DECAY ZH→γAH IN THE LITTLE HIGGS MODEL WITH T-PARITY

2011 ◽  
Vol 26 (32) ◽  
pp. 5349-5368 ◽  
Author(s):  
I. CORTÉS-MALDONADO ◽  
G. TAVARES-VELASCO
Keyword(s):  
Radiative Decay ◽  
Branching Ratio ◽  
Small Region ◽  
Higgs Model ◽  
Tree Level ◽  
Little Higgs ◽  
Precision Data ◽  
The One ◽  
Three Body ◽  
Electroweak Precision

In the little Higgs model with T-parity (LHTM), the only tree-level kinematically allowed two-body decay of the ZH boson can be the ZH→AHH decay and thus one-loop induced two-body decays may have a significant rate. We study the ZH→γAH decay, which is induced at the one-loop level by a fermion triangle and is interesting as it depends on the mechanism of anomaly cancelation of the model. All the relevant two- and three-body decays of the ZH gauge boson arising at the tree-level are also calculated. We considered a small region of the parameter space where f is still allowed to be as low as 500 GeV by electroweak precision data. We analyzed the scenario of a Higgs with a mass of 120 GeV. We found that the ZH→γAH branching ratio can be of the order of a tree-level three-body decay and may be at the reach of detection at the LHC for f close to 500 GeV, but it may be difficult to detect for f = 1 TeV . There is also an scenario where the Higgs boson has an intermediate mass such that the ZH→AHH decay is closed, the ZH→γAH gets considerably enhanced and the chances of detection get a large boost.

scholarly journals Quark-flavor-changing Higgs decays from a universal extra dimension

2020 ◽  
Vol 35 (24) ◽  
pp. 2050141
Author(s):  
Carlos M. Farrera ◽  
Alejandro Granados-González ◽  
Héctor Novales-Sánchez ◽  
J. Jesús Toscano
Keyword(s):  
Standard Model ◽  
Extra Dimension ◽  
New Physics ◽  
Tree Level ◽  
Universal Extra Dimension ◽  
Loop Level ◽  
Flavor Changing ◽  
The Standard Model ◽  
The One ◽  
Kaluza Klein

Kaluza–Klein fields characterizing, from a four-dimensional viewpoint, the presence of compact universal extra dimensions would alter low-energy observables through effects determined by some compactification scale, [Formula: see text], since the one-loop level, thus being particularly relevant for physical phenomena forbidden at tree level by the Standard Model. This paper explores, for the case of one universal extra dimension, such new-physics contributions to Higgs decays [Formula: see text], into pairs of quarks with different flavors, a sort of decay process which, in the Standard Model, strictly occurs at the loop level. Finite results, decoupling as [Formula: see text], are calculated. Approximate short expressions, valid for large compactification scales, are provided. We estimate that Kaluza–Klein contributions lie below predictions from the Standard Model, being about 2 to 3 orders of magnitude smaller for compactification scales within [Formula: see text].

scholarly journals HIGGS MASS IN THE STANDARD MODEL FROM COUPLING CONSTANT REDUCTION

2002 ◽  
Vol 17 (03) ◽  
pp. 335-346 ◽  
Author(s):  
B. ANANTHANARAYAN ◽  
J. PASUPATHY
Keyword(s):  
Renormalization Group ◽  
Standard Model ◽  
Top Quark ◽  
Higgs Mass ◽  
Gauge Coupling ◽  
Renormalization Scale ◽  
Coupling Constant ◽  
Top Quark Mass ◽  
The Standard Model ◽  
The One

Plausible interrelations between parameters of the standard model are studied. The empirical value of the top quark mass, when used in the renormalization group equations, suggests that the ratio of the color SU(3) gauge coupling g3, and the top coupling gt is independent of the renormalization scale. On the other hand, the variety of top-condensate models suggests that the Higgs self-coupling λ is proportional to [Formula: see text]. Invoking the requirement that the ratio [Formula: see text] is independent of the renormalization scale t, fixes the Higgs mass. The pole mass of the Higgs (which differs from the renormalization group mass by a few percent) is found to be ~ 154 GeV for the one-loop equations and ~ 148 GeV for the two-loop equations.

THE STANDARD MODEL WITH THREE GENERATIONS: CLOSING IN ON THE TOP QUARK MASS

1989 ◽  
Vol 04 (04) ◽  
pp. 753-768 ◽  
Author(s):  
F. HALZEN ◽  
C. S. KIM ◽  
S. PAKVASA
Keyword(s):  
Experimental Data ◽  
Standard Model ◽  
Top Quark ◽  
Quark Mass ◽  
New Physics ◽  
Experimental Information ◽  
Beyond The Standard Model ◽  
Top Quark Mass ◽  
Three Generations ◽  
The Standard Model

Within the standard model with three generations we fit the top quark mass mt by combining experimental information of [Formula: see text] and [Formula: see text] mixing, CP-violation in K decay and the ratio Γ(W)/Γ(Z) extracted from [Formula: see text] collider data. We conclude that [Formula: see text] where the "systematic error" associated with theoretical ambiguities in performing the calculations is likely to be significantly larger than the quoted 10 GeV error associated with input parameters and experimental data. The anticipated value essentially guarantees the discovery of the top quark by existing experiments. Failure to discover it should force us to reconsider generally accepted calculational procedures before it signals new physics beyond the standard model. We discuss this in some detail.

scholarly journals EWPD in the SMEFT to dimension eight

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Tyler Corbett ◽  
Andreas Helset ◽  
Adam Martin ◽  
Michael Trott
Keyword(s):  
Effective Field ◽  
Precision Data ◽  
Data Set ◽  
The Standard Model ◽  
Electroweak Precision ◽  
The Impact ◽  
First Time ◽  
Geometric Formulation ◽  
Electroweak Precision Data ◽  
Theory Error

Abstract We calculate the $$ \mathcal{O}\left({\left\langle {H}^{\dagger }H\right\rangle}^2/{\Lambda}^4\right) $$ O H † H 2 / Λ 4 corrections to LEP electroweak precision data using the geometric formulation of the Standard Model Effective Field Theory (SMEFT). We report our results in simple-to-use interpolation tables that allow the interpretation of this data set to dimension eight for the first time. We demonstrate the impact of these previously unknown terms in the case of a general analysis in the SMEFT, and also in the cases of two distinct models matched to dimension eight. Neglecting such dimension-eight corrections to LEP observables introduces a theoretical error in SMEFT studies. We report some preliminary studies defining such a theory error, explicitly demonstrating the effect of previously unknown dimension-eight SMEFT corrections on LEP observables.

scholarly journals TOP QUARK PHYSICS

2008 ◽  
Vol 23 (27n28) ◽  
pp. 4421-4433 ◽  
Author(s):  
◽  
ERICH W. VARNES
Keyword(s):  
Top Quark ◽  
Production Cross ◽  
New Physics ◽  
Recent Measurement ◽  
Top Quark Mass ◽  
Text Production ◽  
Single Top ◽  
The Standard Model ◽  
Top Quark Production ◽  
Quark Production

A review is presented of the current experimental status of the top quark sector of the Standard Model. The measurements summarized include searches for electroweak single top production, the latest results on the [Formula: see text] production cross-section, and searches for new physics in top quark production and decay. In addition, the recent measurement of the top quark mass to a precision of 0.7% is highlighted.

scholarly journals Mixed EW-QCD leading fermionic three-loop corrections at $$ \mathcal{O} $$(αsα2) to electroweak precision observables

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Lisong Chen ◽  
Ayres Freitas
Keyword(s):  
Top Quark ◽  
Z Boson ◽  
W Boson ◽  
Boson Mass ◽  
Top Quark Mass ◽  
Weak Mixing Angle ◽  
Mixing Angle ◽  
The Standard Model ◽  
Precision Observables ◽  
Electroweak Precision

Abstract Measurements of electroweak precision observables at future electron-position colliders, such as the CEPC, FCC-ee, and ILC, will be sensitive to physics at multi-TeV scales. To achieve this sensitivity, precise predictions for the Standard Model expectations of these observables are needed, including corrections at the three- and four-loop level. In this article, results are presented for the calculation of a subset of three-loop mixed electroweak-QCD corrections, stemming from diagrams with a gluon exchange and two closed fermion loops. The numerical impact of these corrections is illustrated for a number of applications: the prediction of the W-boson mass from the Fermi constant, the effective weak mixing angle, and the partial and total widths of the Z boson. Two alternative renormalization schemes for the top-quark mass are considered, on-shell and $$ \overline{\mathrm{MS}} $$ MS ¯ .

scholarly journals Leading Weak Corrections to the Production of Heavy Top Quarks at Hadron Colliders

1997 ◽  
Vol 12 (07) ◽  
pp. 1341-1372 ◽  
Author(s):  
Chung Kao ◽  
G. A. Ladinsky ◽  
C.-P. Yuan
Keyword(s):  
Higgs Boson ◽  
Parity Violation ◽  
Top Quark ◽  
Top Quarks ◽  
New Physics ◽  
Threshold Region ◽  
Hadron Colliders ◽  
Top Quark Mass ◽  
Quark Pairs ◽  
The Standard Model

We calculate the leading weak corrections at [Formula: see text] to the QCD production of heavy top quark pairs via [Formula: see text] at hadron colliders and compare them with the complete one-loop weak corrections. We find that these corrections dominate the threshold region for a heavy top quark if the Higgs boson is light. For a heavy Higgs boson, these corrections are generally small. The chromo-anapole form factor of the top quark and effects of parity violation are studied in the Standard Model (SM). The parity violation effect in [Formula: see text] from the SM weak corrections is found to be very small, so any observation of large parity violation in this process would indicate new physics. The polarization of the [Formula: see text] pairs is also discussed, including the effect that this has on proposed techniques for measuring the top quark mass.

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