scholarly journals Alleviating the B̄ → Dτντ and B̄ → D∗τντ puzzle in the MSSM

2019 ◽  
Vol 34 (32) ◽  
pp. 1950209
Author(s):  
Dris Boubaa ◽  
Shaaban Khalil ◽  
Stefano Moretti
Keyword(s):  
Standard Model ◽  
Branching Ratios ◽  
Current Data ◽  
The Standard Model ◽  
Model Predictions ◽  
Theoretical Predictions ◽  
Sneutrino Mass ◽  
Sizeable Increase

We show that Supersymmetric effects driven by penguin contributions to the [Formula: see text] transition are able to account simultaneously for a sizeable increase of both branching ratios of [Formula: see text] and [Formula: see text] with respect to the Standard Model predictions, thereby approaching their experimentally measured values. We emphasize that a light chargino and neutralino, with masses less than 300 GeV, in addition to a large stau/sneutrino mass and a large [Formula: see text], are essential for enhancing the effect of the lepton penguin [Formula: see text], which is responsible for the improved theoretical predictions with respect to current data.

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.

B anomalies with unparticles

2021 ◽  
Vol 36 (30) ◽  
Author(s):  
Jong-Phil Lee
Keyword(s):  
Experimental Data ◽  
Standard Model ◽  
Branching Ratio ◽  
Branching Ratios ◽  
The Standard Model ◽  
Model Predictions ◽  
Best Fit

We analyze the [Formula: see text] anomalies associated with the [Formula: see text] decays in the unparticle model. The fraction of the branching ratios [Formula: see text] and other parameters related to the polarization are fitted to the experimental data by minimizing [Formula: see text]. The best-fit values are [Formula: see text] and [Formula: see text] which are still larger than the standard model predictions. We find that our results safely render the branching ratio [Formula: see text] below [Formula: see text].

scholarly journals RARE BARYONIC DECAYS Λb → Λl+l- IN THE TTM MODEL

2013 ◽  
Vol 28 (17) ◽  
pp. 1350075 ◽  
Author(s):  
YAN-LI WEN ◽  
CHONG-XING YUE ◽  
JIAO ZHANG
Keyword(s):  
Standard Model ◽  
Parameter Space ◽  
Rare Decays ◽  
Form Factors ◽  
Branching Ratios ◽  
Wide Range ◽  
The Standard Model ◽  
Model Predictions ◽  
Order Of Magnitude ◽  
Transversal Polarization

In the framework of the top triangle moose model, we analyze the rare decays Λb → Λl+l-(l = e, μ, τ) by using the form factors calculated in full QCD. We calculate the contributions of the new particles predicted by this model to observables, such as the branching ratios, forward–backward asymmetry (A FB ) and polarizations related these decay processes. We find that, in wide range of the parameter space, the values of the branching ratios are enhanced by one order of magnitude comparing to the standard model predictions. This model can also produce significant corrections to A FB , normal polarization PN and transversal polarization PT.

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.

scholarly journals Indirect $$ \mathcal{CP} $$ probes of the Higgs-top-quark interaction: current LHC constraints and future opportunities

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Henning Bahl ◽  
Philip Bechtle ◽  
Sven Heinemeyer ◽  
Judith Katzy ◽  
Tobias Klingl ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Top Quark ◽  
Decay Channel ◽  
New Physics ◽  
Current Data ◽  
Quark Interaction ◽  
The Standard Model ◽  
Vector Bosons ◽  
Selection Of

Abstract The $$ \mathcal{CP} $$ CP structure of the Higgs boson in its coupling to the particles of the Standard Model is amongst the most important Higgs boson properties which have not yet been constrained with high precision. In this study, all relevant inclusive and differential Higgs boson measurements from the ATLAS and CMS experiments are used to constrain the $$ \mathcal{CP} $$ CP -nature of the top-Yukawa interaction. The model dependence of the constraints is studied by successively allowing for new physics contributions to the couplings of the Higgs boson to massive vector bosons, to photons, and to gluons. In the most general case, we find that the current data still permits a significant $$ \mathcal{CP} $$ CP -odd component in the top-Yukawa coupling. Furthermore, we explore the prospects to further constrain the $$ \mathcal{CP} $$ CP properties of this coupling with future LHC data by determining tH production rates independently from possible accompanying variations of the $$ t\overline{t}H $$ t t ¯ H rate. This is achieved via a careful selection of discriminating observables. At the HL-LHC, we find that evidence for tH production at the Standard Model rate can be achieved in the Higgs to diphoton decay channel alone.

TeV Scale B – L Phenomenology at LHC

2007 ◽  
Vol 22 (31) ◽  
pp. 5889-5908 ◽  
Author(s):  
M. Abbas ◽  
W. Emam ◽  
S. Khalil ◽  
M. Shalaby
Keyword(s):  
Standard Model ◽  
Gauge Boson ◽  
Cross Sections ◽  
Branching Ratios ◽  
Higgs Production ◽  
Neutrino Masses ◽  
Natural Explanation ◽  
The Standard Model ◽  
The Cross

We present the phenomenology of the low scale U(1)B–L extension of the standard model and its implications at LHC. We show that this model provides a natural explanation for the presence of three right-handed neutrinos and can naturally account the observed neutrino masses and mixing. We study the decay and production of the extra gauge boson and the SM singlet scalar (heavy Higgs) predicted in this type of models. We find that the cross sections of the SM-like Higgs production are reduced by ~ 20% – 30%, while its decay branching ratios remain intact. The extra Higgs has relatively small cross sections and the branching ratios of Z′ → l+l− are of order ~ 20% compared to ~ 3% of the SM results.

scholarly journals Charming loops in exclusive rare FCNC B-decays

2019 ◽  
Vol 222 ◽  
pp. 01007 ◽  
Author(s):  
Dmitri Melikhov
Keyword(s):  
Standard Model ◽  
Gain Control ◽  
New Physics ◽  
Beyond The Standard Model ◽  
Reliable Control ◽  
B Decays ◽  
Flavour Changing Neutral Currents ◽  
Neutral Currents ◽  
The Standard Model ◽  
Theoretical Predictions

Rare B-decays induced by flavour-changing neutral currents (FCNC) is one of the promising candidates for probing physics beyond the Standard model. However, for identifying potential new physics from the data, reliable control over QCD contributions is necessary. We focus on one of such QCD contributions – the charming loops – that potentially can lead to difficulties in disentangling new physics effects from the observable and discuss the possibility to gain control over theoretical predictions for charming loops.

CP VIOLATION IN THE B SYSTEM—A STATISTICAL ANALYSIS

1990 ◽  
Vol 05 (05) ◽  
pp. 337-347
Author(s):  
DAVID LONDON
Keyword(s):  
Statistical Analysis ◽  
Cp Violation ◽  
Standard Model ◽  
Probability Distributions ◽  
New Physics ◽  
Hadronic Decay ◽  
System A ◽  
The Standard Model ◽  
Model Predictions ◽  
Cp Asymmetries

The standard model predictions for CP violating hadronic decay asymmetries are presented in the form of probability distributions. From these distributions, it can be easily seen what the most likely values of these quantities are, which measurements would clearly be signs of new physics, and which values of the CP asymmetries would most constrain the parameters of the standard model.

CHARM MIXING AND CP VIOLATION AT B-FACTORIES

2014 ◽  
Vol 35 ◽  
pp. 1460413
Author(s):  
GIANLUIGI CIBINETTO ◽  
Keyword(s):  
Cp Violation ◽  
Standard Model ◽  
New Physics ◽  
Ratio Analysis ◽  
Charm Meson ◽  
Final State ◽  
Charm Decays ◽  
Decay Modes ◽  
The Standard Model ◽  
Model Predictions

CP violation in charm decays is expected to be very small in the Standard Model, at the level of 0.1% or less. A sizable excess of CP violation with respect to the Standard Model predictions could be a signature of new physics. We report on recent searches for CP violation in charm meson decays at BABAR and Belle experiments. In particular we report a lifetime ratio analysis of D0 → K+K−, π+π− with respect to D0 → K−π+ decays, which is sensitive to [Formula: see text] mixing and CP violation. We report also on searches for CPV in the 3-body D+ → K+K−π+ decay and for decay modes with a [Formula: see text] in the final state, such as [Formula: see text].

scholarly journals η′K PUZZLE OF B MESON DECAYS AND NEW PHYSICS EFFECTS IN THE TC2 MODEL

2001 ◽  
Vol 16 (07) ◽  
pp. 441-455 ◽  
Author(s):  
ZHENJUN XIAO ◽  
WENJUN LI ◽  
GONGRU LU ◽  
LIBO GUO
Keyword(s):  
Standard Model ◽  
B Meson ◽  
New Physics ◽  
Decay Rates ◽  
Low Energy ◽  
Effective Hamiltonian ◽  
B Meson Decays ◽  
The Standard Model ◽  
Model Predictions ◽  
Input Parameters

Using the low energy effective Hamiltonian with the generalized factorization, we calculate the new physics contributions to B→π+π-, Kπ and Kη′ in the topcolor-assisted-technicolor (TC2) model, and compare the results with the available data. By using [Formula: see text] preferred by the CLEO data of B→π+π-decay, we find that the new physics enhancements to B→ Kη′ decays are significant in size, ~ 50% with respect to the standard model predictions, insensitive to the variations of input parameters and hence provide a simple and plausible new physics interpretation for the observed unexpectedly large B→ Kη′ decay rates.

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