scholarly journals Top quark polarization as a probe of models with extra gauge bosons

2011 ◽  
Vol 83 (11) ◽  
Author(s):  
Edmond L. Berger ◽  
Qing-Hong Cao ◽  
Chuan-Ren Chen ◽  
Hao Zhang
Keyword(s):  
Top Quark ◽  
Gauge Bosons

scholarly journals Non-Universal Gauge Bosons Z′ and Rare Top Decays

2003 ◽  
Vol 18 (31) ◽  
pp. 2187-2193 ◽  
Author(s):  
Chongxing Yue ◽  
Hongjie Zong ◽  
Lanjun Liu
Keyword(s):  
Parameter Space ◽  
Top Quark ◽  
Branching Ratios ◽  
New Method ◽  
Gauge Bosons ◽  
Near Future

We study a new method for detecting non-universal gauge bosons Z′ via considering their effects on rare top decays. We calculate the contributions of the non-universal gauge bosons Z′ predicted by topcolor-assisted technicolor (TC2) models and flavor-universal TC2 models on the rare top decays t → cV (V = g,γ,Z) and t → clilj (li,lj = τ,μ, or e). We show that the branching ratios of these processes can be significantly enhanced. Over a sizeable region of the parameter space, we have Br (t → cg) ~ 10-5 and Br (t → cττ) ~ 10-7, which may approach the observable threshold of near future experiments. Non-universal gauge bosons Z′ may be detected via the rare top decay processes at the top-quark factories such as the CERN LHC.

PREDICTION OF THE TOP QUARK MASS IN A FINITE ELECTROWEAK THEORY

1991 ◽  
Vol 06 (29) ◽  
pp. 2697-2703
Author(s):  
M. CLAYTON ◽  
J. W. MOFFAT
Keyword(s):  
Top Quark ◽  
Quark Mass ◽  
Vacuum Polarization ◽  
Local Scale ◽  
Higgs Mechanism ◽  
Electroweak Theory ◽  
Particle Spectrum ◽  
Top Quark Mass ◽  
Gauge Bosons ◽  
Non Local

A parameter-free prediction of the top quark mass is obtained from the calculation of [Formula: see text] in a finite non-local electroweak theory, in which the W and Z gauge bosons acquire their masses through the lowest order vacuum polarization graphs containing fermion loops. The SU (2)× U (1) gauge symmetry is broken to U (1) em by a symmetry breaking measure factor in the path integral without resorting to a Higgs mechanism. Using the ratio of the W and Z masses obtained from the average of the UAI, UA2 and the CDF experiments, we predict mt=86±33 GeV and the gauge boson non-local scale Λw=523±4 GeV . Using the CDF measured W mass, we find mt=125±40 GeV and Λw=529±6 GeV . The particle spectrum in the model contains the W, Z and photon gauge bosons and the standard three generations of leptons and quarks, including the anticipated top quark.

scholarly journals Global analysis of the top quark couplings to gauge bosons

1994 ◽  
Vol 50 (7) ◽  
pp. 4462-4477 ◽  
Author(s):  
Ehab Malkawi ◽  
C.-P. Yuan
Keyword(s):  
Top Quark ◽  
Global Analysis ◽  
Gauge Bosons

scholarly journals Rare decays of the top quark mediated by Z′ gauge bosons and flavor violation

2020 ◽  
Vol 35 (18) ◽  
pp. 2050153
Author(s):  
J. I. Aranda ◽  
D. Espinosa-Gómez ◽  
J. Montaño ◽  
F. Ramírez-Zavaleta ◽  
E. S. Tututi
Keyword(s):  
Gauge Boson ◽  
Top Quark ◽  
Branching Ratios ◽  
Gauge Bosons ◽  
Flavor Violation ◽  
Gauge Symmetries ◽  
Quark Decays ◽  
The Standard Model ◽  
Order Of Magnitude ◽  
The One

The rare top quark decays mediated by a new neutral massive gauge boson that is predicted in models with extended gauge symmetries are studied. We focus on the processes [Formula: see text] induced at the one loop level, where [Formula: see text], by considering different extended models. It is found that, within a broad range of mass of the new neutral gauge boson, the models predict branching ratios for the decays in study that are competitive with respect to the corresponding branching ratios in the Standard Model (SM). In order to establish bound on our branching ratios, we consider the recent experimental bounds as [Formula: see text], depending on the model, which also impose restrictions on our calculation. Even in this case, the resulting branching ratios are of the same order of magnitude as that predicted by the SM. It should be noted that for the case of two models studied here, since no experimental bound exists to compare with, the results could be important, as they are, in the best of cases, two orders of magnitude larger than the predicted by the SM.

UPPER LIMITS ON THE TOP QUARK MASS IN MODELS WITH NEW GAUGE BOSONS

1990 ◽  
Vol 05 (02) ◽  
pp. 115-123 ◽  
Author(s):  
THOMAS G. RIZZO
Keyword(s):  
Top Quark ◽  
Quark Mass ◽  
Top Quark Mass ◽  
Gauge Bosons ◽  
Gauge Sector ◽  
Upper Limit ◽  
Upper Limits ◽  
The Standard Model ◽  
Lower Limits ◽  
Rule Out

The experimental value of the ρ parameter is used to obtain an upper limit on the top-quark mass (mt) in models with extended gauge sectors. This limit is found to be generally stronger than that obtained from similar considerations in the Standard Model (SM). This bound, however, is shown to depend strongly on the particular extension of the usual SM gauge sector under consideration. Improved experimental lower limits on mt can also be used to rule out large regions of the parameter space of extended electroweak models.

scholarly journals NEW GAUGE BOSONS FROM STRING MODELS

1996 ◽  
Vol 11 (15) ◽  
pp. 1247-1262 ◽  
Author(s):  
MIRJAM CVETIČ ◽  
PAUL LANGACKER
Keyword(s):  
Standard Model ◽  
Supersymmetry Breaking ◽  
Large Class ◽  
Top Quark ◽  
Fine Tuning ◽  
Electroweak Symmetry ◽  
Gauge Bosons ◽  
Exotic Particles ◽  
Yukawa Couplings ◽  
String Models

We address the mass ranges of new neutral gauge bosons and constraints on the accompanying exotic particles as predicted by a class of superstring models. Under certain assumptions about the supersymmetry breaking parameters we show that breaking of an additional U(1)′ symmetry is radiative when the appropriate Yukawa couplings of exotic particles are of order one, analogous to the radiative breaking of the electroweak symmetry in the supersymmetric standard model due to the large top-quark Yukawa coupling. Such large Yukawa couplings occur for a large class of string models. The Z′ and exotic masses are either of [Formula: see text], or of a scale intermediate between the string and electroweak scales. In the former case, [Formula: see text] may be achieved without excessive fine-tuning, and is within future experimental reach.

scholarly journals SMEFT atlas of ∆F = 2 transitions

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Jason Aebischer ◽  
Christoph Bobeth ◽  
Andrzej J. Buras ◽  
Jacky Kumar
Keyword(s):  
Top Quark ◽  
Effective Field ◽  
Effective Theory ◽  
Tree Level ◽  
Gauge Bosons ◽  
Travel Guide ◽  
The Standard Model ◽  
Individual Contributions ◽  
Model Independent ◽  
The Individual

Abstract We present a model-independent anatomy of the ∆F = 2 transitions K0−$$ {\overline{K}}^0 $$ K ¯ 0 , Bs,d−$$ {\overline{B}}_{s,d} $$ B ¯ s , d and D0−$$ {\overline{D}}^0 $$ D ¯ 0 in the context of the Standard Model Effective Field Theory (SMEFT). We present two master formulae for the mixing amplitude [M12]BSM. One in terms of the Wilson coefficients (WCs) of the Low-Energy Effective Theory (LEFT) operators evaluated at the electroweak scale μew and one in terms of the WCs of the SMEFT operators evaluated at the BSM scale Λ. The coefficients $$ {P}_a^{ij} $$ P a ij entering these formulae contain all the information below the scales μew and Λ, respectively. Renormalization group effects from the top-quark Yukawa coupling play the most important role. The collection of the individual contributions of the SMEFT operators to [M12]BSM can be considered as the SMEFT atlas of ∆F = 2 transitions and constitutes a travel guide to such transitions far beyond the scales explored by the LHC. We emphasize that this atlas depends on whether the down-basis or the up-basis for SMEFT operators is considered. We illustrate this technology with tree-level exchanges of heavy gauge bosons (Z′, G′) and corresponding heavy scalars.

NARROW-RESONANCE IN e−e− SCATTERING DUE TO ADDITIONAL GAUGE BOSON

1996 ◽  
Vol 11 (09) ◽  
pp. 1621-1625 ◽  
Author(s):  
PAUL H. FRAMPTON
Keyword(s):  
Standard Model ◽  
Top Quark ◽  
Quark Mass ◽  
Special Role ◽  
Top Quark Mass ◽  
Narrow Resonance ◽  
Gauge Bosons ◽  
The Third ◽  
High Energies ◽  
The Standard Model

It now appears phenomenologically that the third family may be essentially different from the first two. Particularly the high value of the top quark mass suggests a special role. In the standard model all three families are treated similarly [becoming exactly the same at asymptotically high energies] so I need to extend the model to accommodate the goal of a really different third family. In this article I describe one such viable extension, the 331 model which predicts bileptonic gauge bosons.

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