scholarly journals Constraints on coloured scalars from global fits

2021 ◽  
Vol 2021 (10) ◽  
Author(s):  
Otto Eberhardt ◽  
Víctor Miralles ◽  
Antonio Pich
Keyword(s):  
Top Quark ◽  
Scalar Potential ◽  
Higgs Doublet ◽  
Model Parameters ◽  
Simple Extension ◽  
Minimal Flavour Violation ◽  
Yukawa Couplings ◽  
Flavour Violation ◽  
The One ◽  
Potential Parameters

Abstract We consider a simple extension of the electroweak theory, incorporating one SU(2)L doublet of colour-octet scalars with Yukawa couplings satisfying the principle of minimal flavour violation. Using the HEPfit package, we perform a global fit to the available data, including all relevant theoretical constraints, and extract the current bounds on the model parameters. Coloured scalars with masses below 1.05 TeV are already excluded, provided they are not fermiophobic. The mass splittings among the different (charged and CP-even and CP-odd neutral) scalars are restricted to be smaller than 20 GeV. Moreover, for scalar masses smaller than 1.5 TeV, the Yukawa coupling of the coloured scalar multiplet to the top quark cannot exceed the one of the SM Higgs doublet by more than 80%. These conclusions are quite generic and apply in more general frameworks (without fine tunings). The theoretical requirements of perturbative unitarity and vacuum stability enforce relevant constraints on the quartic scalar potential parameters that are not yet experimentally tested.

scholarly journals Fingerprinting the contribution of colored scalars to the $$H^+ W^- Z(\gamma )$$ vertex

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
Nabarun Chakrabarty ◽  
Indrani Chakraborty ◽  
Dilip Kumar Ghosh
Keyword(s):  
Scalar Potential ◽  
Form Factors ◽  
Higgs Doublet ◽  
New Physics ◽  
Model Parameters ◽  
Minimal Flavour Violation ◽  
Color Octet ◽  
Flavour Violation ◽  
Doublet Model ◽  
Two Higgs Doublet Model

AbstractColor-octet scalars arise in various Grand Unification scenarios and also in other models of new physics. They are also postulated for minimal flavour violation. Purely phenomenological imprints of such scalars are therefore worth looking at. Motivated by this, we perform a complete one-loop calculation of the $$H^+ \rightarrow W^+ Z (\gamma )$$ H + → W + Z ( γ ) decay in a two Higgs doublet model augmented by a color-octet $$SU(2)_L$$ S U ( 2 ) L scalar doublet. The computation is conveniently segregated into colorless and colored components. The color-octet part of the amplitude, being scaled by the color-factor, provides an overall enhancement to the form factors. Crucial constraints from perturbative unitarity, positivity of the scalar potential, oblique parameters, Higgs signal strengths and direct search of a charged Higgs and color-octet scalars are folded-in into the analysis. Sensitivity of the loop-induced $$H^+ \rightarrow W^+ Z (\gamma )$$ H + → W + Z ( γ ) vertex to other model parameters is elucidated. Finally, the prospect of observing a loop-induced $$H^+ \rightarrow W^+ Z (\gamma )$$ H + → W + Z ( γ ) interaction at the future hadronic collisions is also discussed.

scholarly journals The framework for a common origin of $$\delta _{\mathrm{CKM}}$$ and $$\delta _{\mathrm{PMNS}}$$

2021 ◽  
Vol 81 (8) ◽  
Author(s):  
Joao M. Alves ◽  
Francisco J. Botella ◽  
Gustavo C. Branco ◽  
Fernando Cornet-Gomez ◽  
Miguel Nebot
Keyword(s):  
Higgs Doublet ◽  
Common Origin ◽  
Tree Level ◽  
Minimal Flavour Violation ◽  
Yukawa Couplings ◽  
Cp Violations ◽  
Flavour Violation ◽  
Two Higgs Doublet Models ◽  
Near Future ◽  
Two Sectors

AbstractWe analyse a possible connection between CP violations in the quark and lepton sectors, parametrised by the CKM and PMNS phases. If one assumes that CP breaking arises from complex Yukawa couplings, both in the quark and lepton sectors, the above connection is not possible in general, since Yukawa couplings in the two sectors have independent flavour structures. We show that both the CKM and PMNS phases can instead be generated by a vacuum phase in a class of two Higgs doublet models, and in this case a connection may be established. This scenario requires the presence of scalar FCNC at tree level, both in the quark and lepton sectors. The appearance of these FCNC is an obstacle and a blessing. An obstacle since one has to analyse which models are able to conform to the strict experimental limits on FCNC, both in the quark and lepton sectors. A blessing, because this class of models is falsifiable since FCNC arise at a level which can be probed experimentally in the near future, specially in the processes $$\mathrm{h}\rightarrow e^\pm \tau ^\mp $$ h → e ± τ ∓ and $$t\rightarrow \mathrm{h}c$$ t → h c . The connection between CP violations in CKM and PMNS is explicitely illustrated in models with Minimal Flavour Violation.

scholarly journals Neutrino masses, vacuum stability and quantum gravity prediction for the mass of the top quark

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Guillem Domènech ◽  
Mark Goodsell ◽  
Christof Wetterich
Keyword(s):  
Quantum Gravity ◽  
Top Quark ◽  
Quark Mass ◽  
Scalar Potential ◽  
Planck Scale ◽  
Neutrino Masses ◽  
Top Quark Mass ◽  
Vacuum Stability ◽  
Intermediate Scale ◽  
Yukawa Couplings

Abstract A general prediction from asymptotically safe quantum gravity is the approximate vanishing of all quartic scalar couplings at the UV fixed point beyond the Planck scale. A vanishing Higgs doublet quartic coupling near the Planck scale translates into a prediction for the ratio between the mass of the Higgs boson MH and the top quark Mt. If only the standard model particles contribute to the running of couplings below the Planck mass, the observed MH∼ 125 GeV results in the prediction for the top quark mass Mt∼ 171 GeV, in agreement with recent measurements. In this work, we study how the asymptotic safety prediction for the top quark mass is affected by possible physics at an intermediate scale. We investigate the effect of an SU(2) triplet scalar and right-handed neutrinos, needed to explain the tiny mass of left-handed neutrinos. For pure seesaw II, with no or very heavy right handed neutrinos, the top mass can increase to Mt ∼ 172.5 GeV for a triplet mass of M∆ ∼ 108GeV. Right handed neutrino masses at an intermediate scale increase the uncertainty of the predictions of Mt due to unknown Yukawa couplings of the right-handed neutrinos and a cubic interaction in the scalar potential. For an appropriate range of Yukawa couplings there is no longer an issue of vacuum stability.

scholarly journals Two-Higgs-doublet models with Minimal Flavour Violation

2010 ◽  
Author(s):  
Maria Valentina Carlucci ◽  
Leonardo Angelini ◽  
Pietro Colangelo ◽  
Fulvia De Fazio ◽  
G. E. Bruno ◽  
...  
Keyword(s):  
Higgs Doublet ◽  
Minimal Flavour Violation ◽  
Flavour Violation ◽  
Two Higgs Doublet Models

scholarly journals Single-top final states as a probe of top-flavoured dark matter models at the LHC

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Monika Blanke ◽  
Priscilla Pani ◽  
Giacomo Polesello ◽  
Giulia Rovelli
Keyword(s):  
Dark Matter ◽  
Top Quark ◽  
Direct Detection ◽  
Final States ◽  
High Luminosity ◽  
Minimal Flavour Violation ◽  
Single Top ◽  
Discovery Potential ◽  
Flavour Violation ◽  
Flavour Physics

Abstract Models incorporating flavoured dark matter provide an elegant solution to the dark matter problem, evading the tight LHC and direct direction constraints on simple WIMP models. In Dark Minimal Flavour Violation, a simple framework of flavoured dark matter with new sources of flavour violation, the constraints from thermal freeze-out, direct detection experiments, and flavour physics create well-defined benchmark scenarios for these models. We study the LHC phenomenology of four such scenarios, focusing on final states where a single top quark is produced accompanied by no jets, one jet from the fragmentation of light quarks or a b-tagged jet. For each of these signatures we develop a realistic LHC analysis, and we show that the proposed analyses would increase the parameter space coverage for the four benchmarks, compared to existing flavour-conserving LHC analyses. Finally we show the projected discovery potential of the considered signatures for the full LHC statistics at 14 TeV, and for the High Luminosity LHC.

scholarly journals Light Higgs searches in $$ t\overline{t}\phi $$ production at the LHC

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Duarte Azevedo ◽  
Rodrigo Capucha ◽  
Emanuel Gouveia ◽  
António Onofre ◽  
Rui Santos
Keyword(s):  
Top Quark ◽  
Mass Range ◽  
Higgs Doublet ◽  
Mass Region ◽  
Reconstruction Method ◽  
Arbitrary Mass ◽  
Quark Pairs ◽  
Yukawa Couplings ◽  
Low Mass ◽  
Mass Reconstruction

Abstract In this paper we propose a new reconstruction method to explore the low mass region in the associated production of top-quark pairs ($$ t\overline{t} $$ t t ¯ ) with a generic scalar boson (ϕ) at the LHC. The new method of mass reconstruction shows an improved resolution of at least a factor of two in the low mass region when compared to previous methods, without the loss of sensitivity of previous analyses. It turns out that it also leads to an improvement of the mass reconstruction of the 125 GeV Higgs for the same production process. We use an effective Lagrangian to describe a scalar with a generic Yukawa coupling to the top quarks. A full phenomenological analysis was performed, using Standard Model background and signal events generated with MadGraph5_aMC@NLO and reconstructed using a kinematic fit. The use of CP-sensitive variables allows then to maximize the distinction between CP-even and CP-odd components of the Yukawa couplings. Confidence Levels (CLs) for the exclusion of ϕ bosons with mixed CP (both CP-even and CP-odd components) were determined as a function of the top Yukawa couplings to the ϕ boson. The mass range analysed starts slightly above the ϒΥ mass up to 40 GeV, although the analysis can be used for an arbitrary mass. If no new light scalar is found, exclusion limits at 95% CL for the absolute value of the CP-even and CP-odd Yukawa are derived. Finally, we analyse how these limits constrain the parameter space of the complex two-Higgs doublet model (C2HDM).

scholarly journals CP-ODD HIGGS BOSON PRODUCTION IN ASSOCIATION WITH NEUTRAL GAUGE BOSON IN HIGH ENERGY e+e- COLLISIONS

1999 ◽  
Vol 14 (30) ◽  
pp. 2093-2107 ◽  
Author(s):  
A. G. AKEROYD ◽  
A. ARHRIB ◽  
M. CAPDEQUI PEYRANÉRE
Keyword(s):  
Higgs Boson ◽  
Gauge Boson ◽  
Cross Sections ◽  
Top Quark ◽  
Higgs Doublet ◽  
High Energy ◽  
Loop Contribution ◽  
Neutral Gauge Boson ◽  
Associated Production ◽  
The One

We study the associated production of a CP-odd Higgs boson A0 with a neutral gauge boson (Z or photon) in high-energy e+e- collisions at the one-loop level in the framework of two Higgs doublet models (THDM). We find that in the small tan β regime, the top quark loop contribution is enhanced leading to significant cross-sections (about a few fb), while in the large tan β regime the cross-section does not attain observable rates.

scholarly journals FLIPPED SU(5), SEESAW SCALE PHYSICS AND DEGENERATE VACUA

2006 ◽  
Vol 21 (14) ◽  
pp. 1151-1160 ◽  
Author(s):  
C. R. DAS ◽  
C. D. FROGGATT ◽  
L. V. LAPERASHVILI ◽  
H. B. NIELSEN
Keyword(s):  
Standard Model ◽  
Effective Potential ◽  
Top Quark ◽  
Multiple Point ◽  
Yukawa Couplings ◽  
Fundamental Scale ◽  
Loop Approximation ◽  
The Standard Model ◽  
Gut Scale ◽  
The One

We investigate the requirement of the existence of two degenerate vacua of the effective potential as a function of the Weinberg–Salam Higgs scalar field norm, as suggested by the multiple point principle, in an extension of the Standard Model including seesaw scale physics. Results are presented from an investigation of an extension of the Standard Model to the gauge symmetry group SU (3)C× SU (2)L× U (1)′×Ũ(1), where U (1)′ and Ũ(1) originate at the seesaw scale M SS , when heavy (right-handed) neutrinos appear. The consequent unification of the group SU (3)C× SU (2)L× U (1)′ into the flipped SU (5) at the GUT scale leads to the group SU (5)×Ũ(1). We assume the position of the second minimum of the effective potential coincides with the fundamental scale, here taken to be the GUT scale. We solve the renormalization group equations in the one-loop approximation and obtain a top-quark mass of 171±3 GeV and a Higgs mass of 129±4 GeV , in the case when the Yukawa couplings of the neutrinos are less than half that of the top quark at the GUT scale.

scholarly journals Top–Bottom Condensation Model: Symmetries and Spectrum of the Induced 2HDM

Symmetry ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1130
Author(s):  
Alexander A. Osipov ◽  
Brigitte Hiller ◽  
Alex H. Blin ◽  
Marcos Sampaio
Keyword(s):  
Top Quark ◽  
Higgs Mass ◽  
Higgs Doublet ◽  
Qualitative Description ◽  
Goldstone Mode ◽  
Common Belief ◽  
Sum Rule ◽  
Composite Models ◽  
Light Scalar ◽  
The One

Here, we use the Schwinger–DeWitt approach to address the four-fermion composite Higgs effective model proposed by Miransky, Tanabashi and Yamawaki (MTY). The surprising benefit of such an approach is that it is possible to ascribe to a SM-type Higgs a quark–antiquark structure of predominantly a b¯b nature with a small t¯t admixture, which in turn yields a Higgs mass compatible with the observed value of 125 GeV. We discuss this result in a detailed and pedagogical way, as it goes against the common belief that this model and akin composite descriptions should predict a Higgs mass-of-order of twice the top quark mass, contrary to empirical evidence. A further aspect of this approach is that it highlights the link of the SU(2)L×U(1)R symmetric four-fermion MTY model interactions of the heavy quark family to a specific two-Higgs-doublet model (2HDM), and the necessity to go beyond the one Higgs doublet to obtain the empirical Higgs mass within composite models. By appropriately fixing the symmetry-defining interaction parameters, we show that the resulting CP-preserving spectrum harbors the following collective states at the electroweak scale ΛEW=246 GeV: a light scalar to which the standard Higgs is associated; a heavier neutral state preconized as the Nambu partner of the standard Higgs within the Nambu sum rule; the expected triplet of Goldstone bosons associated with the longitudinal polarizations of the electroweak massive bosons; and a neutral pseudoscalar state that in the limit of a global U(1)A symmetry would be a Goldstone mode. The anomalous breaking of this axial symmetry is a subleading effect in a large Nc counting scheme, and we discuss how it modifies the leading-order Nambu sum rule result and its relevance for the qualitative description of the spectrum.

scholarly journals ON THE TWO-LOOP DECOUPLING CORRECTIONS TO τ-LEPTON AND b-QUARK RUNNING MASSES IN THE MSSM

2010 ◽  
Vol 25 (12) ◽  
pp. 2437-2456 ◽  
Author(s):  
A. V. BEDNYAKOV
Keyword(s):  
Top Quark ◽  
Bottom Quark ◽  
Higgs Doublet ◽  
Effective Theory ◽  
Theory Approach ◽  
Supersymmetric Extension ◽  
Yukawa Couplings ◽  
Quantum Numbers ◽  
Fermion Masses ◽  
B Quark

Masses of heavy Standard Model (SM) fermions (top-quark, bottom-quark and tau-lepton) play an important role in the analysis of theories beyond the SM. They serve as low-energy input and reduce the parameter space of such theories. In this paper Minimal supersymmetric extension of the SM is considered and two-loop relations between known SM values of fermion masses and running parameters of the MSSM are studied within the effective theory approach. Both b-quark and τ-lepton have the same quantum numbers with respect to SU(2) group and in the MSSM acquire their masses due to interactions with the same Higgs doublet. As a consequence, for large values of tan β parameter corresponding Yukawa couplings also become large and together with tan β can significantly enhance radiative corrections. In the case of b-quark two-loop [Formula: see text] contribution to the relation between running bottom-quark mass in QCD and MSSM is known in literature. This paper is devoted to calculation of the NNLO corrections proportional to Yukawa couplings. For the τ-lepton obtained contribution can be considered as a good approximation to the full two-loop result. For the b-quark numerical analysis given in the paper shows that only the sum of strong and Yukawa corrections can play such a role.

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