scholarly journals Solving the electron and muon $$g-2$$ anomalies in $$Z'$$ models

2021 ◽  
Vol 81 (12) ◽  
Author(s):  
Arushi Bodas ◽  
Rupert Coy ◽  
Simon J. D. King
Keyword(s):  
Standard Model ◽  
Higgs Doublet ◽  
Neutrino Scattering ◽  
Narrow Region ◽  
Independent Analysis ◽  
The Standard Model ◽  
Doublet Model ◽  
Model Independent ◽  
Charged Leptons ◽  
Gauge Structure

AbstractWe consider simultaneous explanations of the electron and muon $$g-2$$ g - 2 anomalies through a single $$Z'$$ Z ′ of a $$U(1)'$$ U ( 1 ) ′ extension to the Standard Model (SM). We first perform a model-independent analysis of the viable flavour-dependent $$Z'$$ Z ′ couplings to leptons, which are subject to various strict experimental constraints. We show that only a narrow region of parameter space with an MeV-scale $$Z'$$ Z ′ can account for the two anomalies. Following the conclusions of this analysis, we then explore the ability of different classes of $$Z'$$ Z ′ models to realise these couplings, including the SM$$+U(1)'$$ + U ( 1 ) ′ , the N-Higgs Doublet Model$$+U(1)'$$ + U ( 1 ) ′ , and a Froggatt–Nielsen style scenario. In each case, the necessary combination of couplings cannot be obtained, owing to additional relations between the $$Z'$$ Z ′ couplings to charged leptons and neutrinos induced by the gauge structure, and to the stringency of neutrino scattering bounds. Hence, we conclude that no $$U(1)'$$ U ( 1 ) ′ extension can resolve both anomalies unless other new fields are also introduced. While most of our study assumes the Caesium $$(g-2)_e$$ ( g - 2 ) e measurement, our findings in fact also hold in the case of the Rubidium measurement, despite the tension between the two.

scholarly journals The dark phases of the N2HDM

2020 ◽  
Vol 2020 (8) ◽  
Author(s):  
Isabell Engeln ◽  
Pedro Ferreira ◽  
M. Margarete Mühlleitner ◽  
Rui Santos ◽  
Jonas Wittbrodt
Keyword(s):  
Dark Matter ◽  
Large Hadron Collider ◽  
Standard Model ◽  
Hadron Collider ◽  
Higgs Doublet ◽  
Tree Level ◽  
Vacuum Structure ◽  
The Standard Model ◽  
Doublet Model ◽  
Specific Phase

Abstract We discuss the dark phases of the Next-to-2-Higgs Doublet model. The model is an extension of the Standard Model with an extra doublet and an extra singlet that has four distinct CP-conserving phases, three of which provide dark matter candidates. We discuss in detail the vacuum structure of the different phases and the issue of stability at tree-level of each phase. Taking into account the most relevant experimental and theoretical constraints, we found that there are combinations of measurements at the Large Hadron Collider that could single out a specific phase. The measurement of h125 → γγ together with the discovery of a new scalar with specific rates to τ+τ− or γγ could exclude some phases and point to a specific phase.

scholarly journals Testing lepton flavour universality with (semi)-leptonic $$\varvec{D_{(s)}}$$ decays

2020 ◽  
Vol 80 (2) ◽  
Author(s):  
Robert Fleischer ◽  
Ruben Jaarsma ◽  
Gabriël Koole
Keyword(s):  
Standard Model ◽  
Branching Ratios ◽  
Current Data ◽  
Leptonic Decays ◽  
Independent Analysis ◽  
The Standard Model ◽  
Model Independent ◽  
Pseudo Scalar ◽  
The Impact ◽  
Lepton Flavour

Abstract Data in B-meson decays indicate violations of lepton flavour universality, thereby raising the question about such phenomena in the charm sector. We perform a model-independent analysis of NP contributions in (semi)-leptonic decays of $$D_{(s)}$$D(s) mesons which originate from $$c \rightarrow d \bar{{\ell }} \nu _l$$c→dℓ¯νl and $$c \rightarrow s \bar{{\ell }} \nu _{\ell }$$c→sℓ¯νℓ charged-current interactions. Starting from the most general low-energy effective Hamiltonian containing four-fermion operators and the corresponding short-distance coefficients, we explore the impact of new (pseudo)-scalar, vector and tensor operators and constrain their effects through the interplay with current data. We pay special attention to the elements $$|V_{cd}|$$|Vcd| and $$|V_{cs}|$$|Vcs| of the Cabibbo–Kobayashi–Maskawa matrix and extract them from the $$D_{(s)}$$D(s) decays in the presence of possible NP decay contributions, comparing them with determinations utilizing unitarity. We find a picture in agreement with the Standard Model within the current uncertainties. Using the results from our analysis, we make also predictions for leptonic $$D_{(s)}^+ \rightarrow e^+ \nu _e$$D(s)+→e+νe modes which could be hugely enhanced with respect to their tiny Standard Model branching ratios. It will be interesting to apply our strategy at the future high-precision frontier.

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 A model-independent analysis of $$b{\rightarrow }s\mu ^{+}\mu ^{-}$$transitions with GAMBIT ’s FlavBit

2021 ◽  
Vol 81 (12) ◽  
Author(s):  
Jihyun Bhom ◽  
Marcin Chrzaszcz ◽  
Farvah Mahmoudi ◽  
Markus T. Prim ◽  
Pat Scott ◽  
...  
Keyword(s):  
Standard Model ◽  
Neutral Current ◽  
Current Data ◽  
Operator Product ◽  
Beyond The Standard Model ◽  
Vector Coupling ◽  
Independent Analysis ◽  
The Standard Model ◽  
Model Independent ◽  
Best Fit

AbstractThe search for flavour-changing neutral current effects in B-meson decays is a powerful probe of physics beyond the Standard Model. Deviations from SM behaviour are often quantified by extracting the preferred values of the Wilson coefficients of an operator product expansion. We use the module of the package to perform a simultaneous global fit of the Wilson coefficients $$C_7$$ C 7 , $$C_9$$ C 9 , and $$C_{10}$$ C 10 using a combination of all current data on $$b{\rightarrow }s\mu ^{+}\mu ^{-}$$ b → s μ + μ -  transitions. We further extend previous analyses by accounting for the correlated theoretical uncertainties at each point in the Wilson coefficient parameter space, rather than deriving the uncertainties from a Standard Model calculation. We find that the best fit deviates from the SM value with a significance of 6.6$$\sigma $$ σ . The largest deviation is associated with a vector coupling of muons to b and s quarks.

scholarly journals Grand Unified Origin of Gauge Interactions and Families Replication in the Standard Model

Universe ◽  
2021 ◽  
Vol 7 (12) ◽  
pp. 461
Author(s):  
António P. Morais ◽  
Roman Pasechnik ◽  
Werner Porod
Keyword(s):  
Standard Model ◽  
Higgs Doublet ◽  
New Physics ◽  
Effective Field ◽  
Tree Level ◽  
Emergent Properties ◽  
Grand Unified Theory ◽  
Yukawa Couplings ◽  
The Standard Model ◽  
Doublet Model

The tremendous phenomenological success of the Standard Model (SM) suggests that its flavor structure and gauge interactions may not be arbitrary but should have a fundamental first-principle explanation. In this work, we explore how the basic distinctive properties of the SM dynamically emerge from a unified New Physics framework tying together both flavor physics and Grand Unified Theory (GUT) concepts. This framework is suggested by a novel anomaly-free supersymmetric chiral E6×SU(2)F×U(1)F GUT containing the SM. Among the most appealing emergent properties of this theory is the Higgs-matter unification with a highly-constrained massless chiral sector featuring two universal Yukawa couplings close to the GUT scale. At the electroweak scale, the minimal SM-like effective field theory limit of this GUT represents a specific flavored three-Higgs doublet model consistent with the observed large hierarchies in the quark mass spectra and mixing already at tree level.

scholarly journals Direct CP violation in $$D^+ \rightarrow K^0({\bar{K}}^0) \pi ^+$$ decays as a probe for new physics

2020 ◽  
Vol 80 (7) ◽  
Author(s):  
David Delepine ◽  
Gaber Faisel ◽  
Carlos A. Ramirez
Keyword(s):  
Cp Violation ◽  
Standard Model ◽  
Parameter Space ◽  
Higgs Doublet ◽  
New Physics ◽  
Cp Asymmetry ◽  
The Standard Model ◽  
Doublet Model ◽  
Two Higgs Doublet Model ◽  
Cp Asymmetries

Abstract In this paper we investigate CP violation in charged decays of D meson. Particularly, we study the direct CP asymmetry of the Cabibbo favored non-leptonic $$D^+ \rightarrow {\bar{K}}^0 \pi ^+$$D+→K¯0π+ and the doubly Cabibbo-suppressed decay mode $$D^+ \rightarrow K^0 \pi ^+$$D+→K0π+ within standard model, two Higgs doublet model with generic Yukawa structure and left right symmetric models. In the standard model, we first derive the contributions from box and di-penguin diagrams contributing to their amplitudes which are relevant to the generation of the weak phases essential for non-vanishing direct CP violation. Then, we show that the generated phases are so tiny leading to null direct CP asymmetries of both decay modes. Regarding the two Higgs doublet model with generic Yukawa structure, after taking into account all constraints on the parameter space of the model, we show that the weak phases of the amplitudes can be enhanced compared to the standard model ones. However, the enhancement is still not enough to have sizable direct CP asymmetries. Finally, within left right symmetric models, we find that $$|A^{SM+LR}_{CP} (D^+ \rightarrow {\bar{K}}^0 \pi ^+)|\lesssim \mathcal {O}(10^{-3})$$|ACPSM+LR(D+→K¯0π+)|≲O(10-3) after respecting all relevant constraints on the parameter space of the model.

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