scholarly journals Revisiting the flavor violating decays of the Tau and Mu leptons in the Standard Model with massive neutrinos

2019 ◽  
Author(s):  
Gerardo Hernández-Tomé
Keyword(s):  
Standard Model ◽  
Leptonic Decays ◽  
The Standard Model ◽  
Massive Neutrinos ◽  
Charged Leptons ◽  
Previous Prediction ◽  
Good Agreement ◽  
Made In

The flavor violating leptonic decays of the \tauτ and \muμ leptons into three lighter charged leptons are revisited in the framework the Standard Model with massive neutrinos. In contrast to the previous prediction, we have found strongly suppressed rates for the \tau^-\to \mu^- \ell^+ \ell^-τ−→μ−ℓ+ℓ− (\ell=\mu, eℓ=μ,e) decays. Our results are in good agreement with the approximation of neglecting masses and momenta of the external particles in the loop integrals made in the first computation for the \mu^- \to e^-e^+ e^-μ−→e−e+e− decay.

scholarly journals Long-distance QCD effects in FCNC B → γl+l- decays

2018 ◽  
Vol 192 ◽  
pp. 00031 ◽  
Author(s):  
Anastasiia Kozachuk ◽  
Dmitri Melikhov ◽  
Nikolai Nikitin
Keyword(s):  
Standard Model ◽  
Recent Work ◽  
Flavour Changing Neutral Currents ◽  
Neutral Currents ◽  
Long Distance ◽  
Leptonic Decays ◽  
The Standard Model

This presentation reviews the main results of our recent work [1] on rare radiative leptonic decays Bd,s → γμ+μ- and Bd,s → γe+e- induced by flavour-changing neutral currents (FCNC) in the Standard Model.

scholarly journals One Loop Corrections to Decay \(\tau\rightarrow \mu\gamma\) in Economical 3-3-1 Model

2015 ◽  
Vol 25 (2) ◽  
pp. 113
Author(s):  
Truong Trong Thuc ◽  
Le Tho Hue ◽  
Dinh Phan Khoi ◽  
Nguyen Thanh Phong
Keyword(s):  
Standard Model ◽  
New Physics ◽  
Beyond The Standard Model ◽  
Lepton Flavor ◽  
Unitary Gauge ◽  
The Standard Model ◽  
Charged Leptons

Lepton flavor violating (cLFV) decays of charged leptons such as \(\tau\rightarrow \mu\gamma\), \(\tau\rightarrow e\gamma\), \(\mu\rightarrow e\gamma\),..., are now the subjects of experiments as signals of new Physics beyond the Standard Model (SM). In the limit of the unitary gauge, we prove that contributions from one loop corrections to the above decays are very small in the framework of the economical 3-3-1 model.

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.

scholarly journals THE UNIT OF ELECTRIC CHARGE AND THE MASS HIERARCHY OF HEAVY PARTICLES

2007 ◽  
Vol 22 (38) ◽  
pp. 2909-2916
Author(s):  
G. LÓPEZ CASTRO ◽  
J. PESTIEAU
Keyword(s):  
Standard Model ◽  
Mass Hierarchy ◽  
Empirical Formulas ◽  
Heavy Particles ◽  
The Standard Model ◽  
Experimental Values ◽  
The One ◽  
Simple Ratio ◽  
The Masses ◽  
Good Agreement

We propose some empirical formulas relating the masses of the heaviest particles in the standard model (the W, Z, H bosons and the t quark) to the charge of the positron e and the Higgs condensate v. The relations for the masses of gauge bosons mW = (1+e)v/4 and [Formula: see text] are in good agreement with experimental values. By requiring the electroweak standard model to be free from quadratic divergences at the one-loop level, we find: [Formula: see text] and [Formula: see text], or the very simple ratio (mt/mH)2 = e.

scholarly journals Beyond the Standard Model at LEP

1991 ◽  
Vol 336 (1642) ◽  
pp. 247-259 ◽  
Keyword(s):  
Dark Matter ◽  
Standard Model ◽  
Beyond The Standard Model ◽  
Grand Unified Theories ◽  
The Standard Model ◽  
Unified Theories ◽  
Massive Neutrinos ◽  
Supersymmetric Particles ◽  
The Universe

LEP data constrain severely many proposed extensions of the Standard Model. These include: massive neutrinos, which are now largely excluded as candidates for the dark matter of the Universe; supersymmetric particles, the lightest of which would still constitute detectable dark matter; technicolour, of which many favoured versions are now excluded by precision electroweak measurements; and grand unified theories, of which LEP data favour supersymmetric versions.

S-Z POWER SPECTRA

2008 ◽  
Vol 23 (17n20) ◽  
pp. 1498-1505 ◽  
Author(s):  
YOEL REPHAELI ◽  
SHARON SADEH
Keyword(s):  
Standard Model ◽  
Dark Energy Model ◽  
Density Fluctuation ◽  
Power Spectra ◽  
Observational Evidence ◽  
Clusters Of Galaxies ◽  
The Standard Model ◽  
Non Gaussian ◽  
Cluster Abundance ◽  
Good Agreement

There is some observational evidence for earlier evolution of clusters of galaxies than predicted in the standard ΛCDM model with a Gaussian primordial density fluctuation field, and a low value for the mass variance parameter (σ8). Particularly difficult in this model is the interpretation of possible excess CMB anisotropy on cluster scales as due to the Sunyaev-Zeldovich (S-Z) effect. We have calculated S-Z power spectra in the standard model, and in two alternative models which predict higher cluster abundance - a model with non-Gaussian PDF, and an early dark energy model. As anticipated, the levels of S-Z power in the latter two models are significantly higher than in the standard model, and in good agreement with current measurements of CMB anisotropy at high multipole values. Our results provide a sufficient basis for testing the viability of the three models by future high quality measurements of cluster abundance and the anisotropy induced by the S-Z effect.

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