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 Towards a Higgs mass determination in asymptotically safe gravity with a dark portal

2021 ◽  
Vol 2021 (10) ◽  
Author(s):  
Astrid Eichhorn ◽  
Martin Pauly ◽  
Shouryya Ray
Keyword(s):  
Standard Model ◽  
Top Quark ◽  
Quark Mass ◽  
Higgs Mass ◽  
Beyond The Standard Model ◽  
Top Quark Mass ◽  
Dark Sector ◽  
Central Value ◽  
The Standard Model ◽  
Higgs Portal

Abstract There are indications that an asymptotically safe UV completion of the Standard Model with gravity could constrain the Higgs self-coupling, resulting in a prediction of the Higgs mass close to the vacuum stability bound in the Standard Model. The predicted value depends on the top quark mass and comes out somewhat higher than the experimental value if the current central value for the top quark mass is assumed. Beyond the Standard Model, the predicted value also depends on dark fields coupled through a Higgs portal. Here we study the Higgs self-coupling in a toy model of the Standard Model with quantum gravity that we extend by a dark scalar and fermion. Within the approximations used in [1], there is a single free parameter in the asymptotically safe dark sector, as a function of which the predicted (toy model) Higgs mass can be lowered due to mixing effects if the dark sector undergoes spontaneous symmetry breaking.

CAN WE RELATE TIME-REVERSAL VIOLATION TO NEW PHYSICS PROCESSES IN WEAK HADRONIC DECAYS?

2013 ◽  
Vol 22 (03) ◽  
pp. 1330006 ◽  
Author(s):  
Z. J. AJALTOUNI ◽  
E. DI SALVO
Keyword(s):  
Experimental Data ◽  
Cp Violation ◽  
Standard Model ◽  
Time Reversal ◽  
Review Paper ◽  
New Physics ◽  
Hadronic Decays ◽  
Beyond The Standard Model ◽  
Weak Decays ◽  
The Standard Model

This review paper stresses the possible connection between time-reversal violation and new physics processes beyond the standard model. In particular, this violation is proposed as an alternative to CP violation in the search for such unkown processes. Emphasis is put on the weak decays of heavy hadrons, especially beauty ones. Specific methods for extracting useful parameters from experimental data are elaborated in order to test TR symmetry. These methods could be used successfully in the analysis of the LHC data.

scholarly journals THE LIMITS OF CUSTODIAL SYMMETRY

2010 ◽  
Vol 25 (27n28) ◽  
pp. 5082-5096
Author(s):  
R. SEKHAR CHIVUKULA ◽  
ROSHAN FOADI ◽  
ELIZABETH H. SIMMONS ◽  
STEFANO DI CHIARA
Keyword(s):  
Standard Model ◽  
Top Quark ◽  
Quark Mass ◽  
Electroweak Symmetry ◽  
Top Quark Mass ◽  
Particle Content ◽  
Dirac Mass ◽  
The Standard Model ◽  
Custodial Symmetry ◽  
Weak Doublet

We introduce a toy model implementing the proposal of using a custodial symmetry to protect the [Formula: see text] coupling from large corrections. This "doublet-extended standard model" adds a weak doublet of fermions (including a heavy partner of the top quark) to the particle content of the standard model in order to implement an O(4) × U(1)X ~ SU(2)L × SU(2)R × PLR × U(1)X symmetry in the top-quark mass generating sector. This symmetry is softly broken to the gauged SU(2)L × U(1)Y electroweak symmetry by a Dirac mass M for the new doublet; adjusting the value of M allows us to explore the range of possibilities between the O(4)-symmetric (M → 0) and standard-model-like (M → ∞) limits.

scholarly journals $\bar{B}\rightarrow X_s\gamma$ in the μνSSM

2014 ◽  
Vol 29 (38) ◽  
pp. 1450196 ◽  
Author(s):  
Hai-Bin Zhang ◽  
Guo-Hui Luo ◽  
Tai-Fu Feng ◽  
Shu-Min Zhao ◽  
Tie-Jun Gao ◽  
...  
Keyword(s):  
Experimental Data ◽  
Standard Model ◽  
Rare Decay ◽  
New Physics ◽  
Majorana Neutrino ◽  
Decay Process ◽  
Neutrino Masses ◽  
Beyond The Standard Model ◽  
Seesaw Mechanism ◽  
The Standard Model

The μνSSM, one of supersymmetric extensions beyond the Standard Model, introduces three singlet right-handed neutrino superfields to solve the μ problem and can generate three tiny Majorana neutrino masses through the seesaw mechanism. In this paper, we investigate the rare decay process [Formula: see text] in the μνSSM, under a minimal flavor violating assumption for the soft breaking terms. Constrained by the SM-like Higgs with mass around 125 GeV, the numerical results show that the new physics can fit the experimental data for [Formula: see text] and further constrain the parameter space.

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.

CP-ODD PHENOMENA DUE TO FINITE WIDTH EFFECTS OF THE TOP QUARK

1991 ◽  
Vol 06 (21) ◽  
pp. 1933-1942 ◽  
Author(s):  
MAREK NOWAKOWSKI ◽  
APOSTOLOS PILAFTSIS
Keyword(s):  
Standard Model ◽  
Top Quark ◽  
Quark Mass ◽  
Quark Propagator ◽  
Upper Bounds ◽  
Coupling Constants ◽  
Charged Current ◽  
Finite Width ◽  
Top Quark Mass ◽  
The Standard Model

Strong experimental indications exist that the top quark mass in the Standard Model (SM) exceeds the mass of the W gauge boson. Since this opens the decay mode t → Wb a suitable regularization of the top quark propagator in the s-channel is required in many tree reactions. As in the Z0 case this regularization essentially results in an. additional imaginary contribution (iΓtmt) to the propagator. This absorptive phase can combine with complex coupling constants of the charged current sector to give rise to new CP violating effects. Theoretical upper bounds for the size of these CP-odd signals are estimated in various extensions of the SM such as: the four generation SM, left-right symmetric models and models with two or three Higgs doublets.

NEW BOUNDS ON THE HIGGS SECTOR OF MINIMAL SUSY

1990 ◽  
Vol 05 (16) ◽  
pp. 1259-1264 ◽  
Author(s):  
JORGE L. LOPEZ ◽  
D.V. NANOPOULOS
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Top Quark ◽  
Quark Mass ◽  
Higgs Mass ◽  
Higgs Sector ◽  
Boson Mass ◽  
Top Quark Mass ◽  
Supersymmetric Extension ◽  
The Standard Model

We examine the Higgs sector of the minimal supersymmetric extension of the standard model. The requirement of perturbative unification combined with the recent LEP data on Higgs boson searches, excludes substantial regions of parameter space. We find that only 0.42 ≤ tan β≲0.76 and tan β≳1.30 are the allowed values for tan β=υ2/υ1. We also determine the absolute lower bound on the lightest Higgs mass to be ≈8 GeV. We conclude that improved lower bounds on the top quark mass and/or the standard model Higgs boson mass will impose yet more stringent constraints on the model. These results clearly favor tan β>1, in agreement with N=1 supergravity or superstring-inspired models.

scholarly journals Disentangling QCD and new physics in D → πℓ+ℓ−

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Aoife Bharucha ◽  
Diogo Boito ◽  
Cédric Méaux
Keyword(s):  
Standard Model ◽  
Branching Ratio ◽  
Branching Ratios ◽  
New Physics ◽  
Operator Product ◽  
Beyond The Standard Model ◽  
Spectral Functions ◽  
The Standard Model ◽  
Model Independent ◽  
Weak Annihilation

Abstract In this paper we consider the decay D+ → π+ℓ+ℓ−, addressing in particular the resonance contributions as well as the relatively large contributions from the weak annihilation diagrams. For the weak annihilation diagrams we include known results from QCD factorisation at low q2 and at high q2, adapting the existing calculation for B decays in the Operator Product Expansion. The hadronic resonance contributions are obtained through a dispersion relation, modelling the spectral functions as towers of Regge-like resonances in each channel, as suggested by Shifman, imposing the partonic behaviour in the deep Euclidean. The parameters of the model are extracted using e+e− → (hadrons) and τ → (hadrons) + ντ data as well as the branching ratios for the resonant decays D+ → π+R(R → ℓ+ℓ−), with R = ρ, ω, and ϕ. We perform a thorough error analysis, and present our results for the Standard Model differential branching ratio as a function of q2. Focusing then on the observables FH and AFB, we consider the sensitivity of this channel to effects of physics beyond the Standard Model, both in a model independent way and for the case of leptoquarks.

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