scholarly journals Branching ratios, forward-backward asymmetries, and angular distributions ofB→K2*l+l−in the standard model and two new physics scenarios

2011 ◽  
Vol 83 (3) ◽  
Author(s):  
Run-Hui Li ◽  
Cai-Dian Lü ◽  
Wei Wang
Keyword(s):  
Standard Model ◽  
Branching Ratios ◽  
New Physics ◽  
Angular Distributions ◽  
The Standard Model

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 Study of the Υ(1S) → DP decays

2021 ◽  
pp. 2150061
Author(s):  
Yueling Yang ◽  
Mingfei Duan ◽  
Junliang Lu ◽  
Jinshu Huang ◽  
Junfeng Sun
Keyword(s):  
Standard Model ◽  
Perturbative Qcd ◽  
Branching Ratios ◽  
New Physics ◽  
High Luminosity ◽  
Weak Decays ◽  
The Standard Model

Inspired by the potential prospects of high-luminosity dedicated colliders and the high enthusiasms in searching for new physics in the flavor sector at the intensity frontier, the [Formula: see text], [Formula: see text] and [Formula: see text] weak decays are studied with the perturbative QCD approach. It is found within the standard model that the branching ratios for the concerned processes are tiny, about [Formula: see text], and far beyond the detective ability of current experiments unless there exists some significant enhancements from a novel interaction.

Study of B̄s → ϕμ+μ− decays in the G(211) model and vector leptoquark model

2017 ◽  
Vol 32 (25) ◽  
pp. 1750155 ◽  
Author(s):  
Shuai-Wei Wang
Keyword(s):  
Standard Model ◽  
Large Deviation ◽  
Branching Fraction ◽  
New Physics ◽  
Decay Process ◽  
Angular Distributions ◽  
The Standard Model ◽  
Lepton Polarization ◽  
Text Model

We study [Formula: see text] decay in the [Formula: see text] model and vector leptoquark model, respectively. We consider the effects of these two new physics (NP) models on some measured physical observables of this decay process, such as the differential branching fraction and the angular distributions. We find that the large deviation of the differential branching fraction between the measurement and the Standard Model (SM) prediction can be explained in these two NP models. However, we found that not all observables of the double-lepton polarization asymmetries are sensitive to the contributions of these NP models.

scholarly journals Anomalies in b→s Transitions and Dark Matter

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Avelino Vicente
Keyword(s):  
Dark Matter ◽  
Standard Model ◽  
Particle Physics ◽  
Branching Ratios ◽  
New Physics ◽  
Lhcb Collaboration ◽  
Lepton Flavor ◽  
The Standard Model ◽  
Predicted Values ◽  
The Universe

Since 2013, the LHCb collaboration has reported on the measurement of several observables associated with b→s transitions, finding various deviations from their predicted values in the Standard Model. These include a set of deviations in branching ratios and angular observables, as well as in the observables RK and RK⁎, specially built to test the possible violation of Lepton Flavor Universality. Even though these tantalizing hints are not conclusive yet, the b→s anomalies have gained considerable attention in the flavor community. Here we review new physics models that address these anomalies and explore their possible connection to the dark matter of the Universe. After discussing some of the ideas introduced in these works and classifying the proposed models, two selected examples are presented in detail in order to illustrate the potential interplay between these two areas of current particle physics.

scholarly journals U-SPIN TESTS OF THE STANDARD MODEL AND NEW PHYSICS

2008 ◽  
Vol 23 (16) ◽  
pp. 1175-1185 ◽  
Author(s):  
MAKIKO NAGASHIMA ◽  
ALEJANDRO SZYNKMAN ◽  
DAVID LONDON
Keyword(s):  
Standard Model ◽  
Branching Ratios ◽  
New Physics ◽  
The Standard Model ◽  
Cp Asymmetries

Within the standard model, a relation involving branching ratios and direct CP asymmetries holds for the B-decay pairs that are related by U-spin. The violation of this relation indicates new physics (NP). In this paper, we assume that the NP affects only the ΔS = 1 decays, and show that the NP operators are generally the same as those appearing in B → πK decays. The fit to the latest B → πK data shows that only one NP operator is sizeable. As a consequence, the relation is expected to be violated for only one decay pair: [Formula: see text] and [Formula: see text].

Lepton flavor violating decays in model

2019 ◽  
Vol 97 (12) ◽  
pp. 1270-1276
Author(s):  
P. Nayek ◽  
P. Maji ◽  
S. Sahoo
Keyword(s):  
Standard Model ◽  
Neutral Current ◽  
Branching Ratios ◽  
New Physics ◽  
Beyond The Standard Model ◽  
Lepton Flavor ◽  
Flavor Changing ◽  
The Standard Model ◽  
Flavor Changing Neutral Current ◽  
Text Model

Motivated by the hints of lepton flavor violating (LFV) decays, we study Bd,s → μτ, Bs,d → τe, and τ– → e– + e+ + e– decays in [Formula: see text] model. These LFV decays present interesting patterns that may reveal the shape of new physics beyond the standard model. Considering the effect of both Z- and [Formula: see text]-mediated flavor-changing neutral current we calculate the branching ratios for these decays. We find the branching ratios [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text].

scholarly journals Probing for new physics with rare charm baryon (Λc, Ξc, Ωc) decays

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Marcel Golz ◽  
Gudrun Hiller ◽  
Tom Magorsch
Keyword(s):  
Standard Model ◽  
Branching Ratios ◽  
New Physics ◽  
Cp Asymmetry ◽  
Vector Coupling ◽  
Lepton Flavor ◽  
The Standard Model ◽  
Charm Baryon ◽  
Order Of Magnitude ◽  
Rare Charm

Abstract We analyze rare charm baryon decays within the standard model and beyond. We identify all null test observables in unpolarized Λc→ pℓ+ℓ−, ℓ = e, μ decays, and study the new physics sensitivities. We find that the longitudinal dilepton polarization fraction FL is sensitive to electromagnetic dipole couplings $$ {C}_7^{\left(\prime \right)} $$ C 7 ′ , and to the right-handed 4-fermion vector coupling $$ {C}_9^{\left(\prime \right)} $$ C 9 ′ . The forward-backward asymmetry, AFB, due to the GIM-suppression a standard model null test already, probes the left-handed axialvector 4-fermion coupling C10; its CP–asymmetry, $$ {A}_{\mathrm{FB}}^{\mathrm{CP}} $$ A FB CP probes CP-violating phases in C10. Physics beyond the standard model can induce branching ratios of dineutrino modes Λc→ pν$$ \overline{\nu} $$ ν ¯ up to a few times 10−5, and one order of magnitude smaller if lepton flavor universality is assumed, while standard model rates are negligible. Charged lepton flavor violation allows for striking signals into e±μ∓ final states, up to 10−6 branching ratios model-independently, and up to order 10−8 in leptoquark models. Related three-body baryon decays Ξc→ Σℓℓ, Ξc→ Λℓℓ and Ωc→ Ξℓℓ offer similar opportunities to test the standard model with |∆c| = |∆u| = 1 transitions.

scholarly journals Study of the rare decays Bs,d∗→ l+l− in Z′ model

2017 ◽  
Vol 32 (14) ◽  
pp. 1750075 ◽  
Author(s):  
Debika Banerjee ◽  
Priya Maji ◽  
Sukadev Sahoo
Keyword(s):  
Gauge Symmetry ◽  
Standard Model ◽  
Rare Decays ◽  
Branching Ratio ◽  
Branching Ratios ◽  
New Physics ◽  
Leptonic Decays ◽  
The Standard Model ◽  
Text Model ◽  
Vector Formula

The rare decays [Formula: see text] are important to probe the flavor sector of the standard model and to search new physics beyond the SM. Unlike pseudoscalar [Formula: see text] meson, the leptonic decays of vector [Formula: see text] mesons are not chirally suppressed which compensates for their short lifetimes, and results in significant branching ratios. In this paper, we estimate the branching ratios of [Formula: see text][Formula: see text] rare decays in [Formula: see text] model which is an extension of the SM with an extra [Formula: see text] gauge symmetry. We find that the branching ratios are increased from their corresponding standard model values and vary with the mass of [Formula: see text] boson. The lower the mass of [Formula: see text] boson, the higher is the branching ratio.

scholarly journals Standard Model prediction of the Bc lifetime

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Jason Aebischer ◽  
Benjamín Grinstein
Keyword(s):  
Standard Model ◽  
Model Prediction ◽  
Strange Quark ◽  
Standard Model Prediction ◽  
New Physics ◽  
Operator Product ◽  
Special Focus ◽  
Third Order ◽  
Clear Cut ◽  
The Standard Model

Abstract Applying an operator product expansion approach we update the Standard Model prediction of the Bc lifetime from over 20 years ago. The non-perturbative velocity expansion is carried out up to third order in the relative velocity of the heavy quarks. The scheme dependence is studied using three different mass schemes for the $$ \overline{b} $$ b ¯ and c quarks, resulting in three different values consistent with each other and with experiment. Special focus has been laid on renormalon cancellation in the computation. Uncertainties resulting from scale dependence, neglecting the strange quark mass, non-perturbative matrix elements and parametric uncertainties are discussed in detail. The resulting uncertainties are still rather large compared to the experimental ones, and therefore do not allow for clear-cut conclusions concerning New Physics effects in the Bc decay.

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