scholarly journals B decay anomalies at LHCb

2018 ◽  
Vol 175 ◽  
pp. 01004
Author(s):  
Arantza Oyanguren
Keyword(s):  
Standard Model ◽  
B Meson ◽  
Neutral Current ◽  
New Physics ◽  
Lhcb Collaboration ◽  
Beyond The Standard Model ◽  
Clear Tendency ◽  
The Standard Model ◽  
Model Predictions ◽  
Lepton Flavour

The LHCb collaboration has provided a plethora of precise measurements of flavour observables in the last years. In the B meson sector some of these results show consistent deviations from Standard Model predictions with a clear tendency to specific New Physics scenarios. B decay anomalies are found in particular related to lepton flavour universality tests and angular observables in Flavour-Changing-Neutral-Current transitions. I review here the LHCb measurements and their experimental caveats. Results from Lattice are crucial in the coming years to verify if these anomalies are explained by QCD effects or if they are unambiguous hints of physics beyond the Standard Model.

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.

CP ASYMMETRIES IN B0DECAYS BEYOND THE STANDARD MODEL

1991 ◽  
Vol 06 (08) ◽  
pp. 1253-1266 ◽  
Author(s):  
CLAUDIO O. DIB ◽  
DAVID LONDON ◽  
YOSEF NIR
Keyword(s):  
Standard Model ◽  
New Physics ◽  
The Other ◽  
Beyond The Standard Model ◽  
Neutral Currents ◽  
Flavor Changing ◽  
The Standard Model ◽  
Model Predictions ◽  
The Many ◽  
Cp Asymmetries

Of the many ingredients of the Standard Model that are relevant to the analysis of CP asymmetries in B0 decays, some are likely to hold even beyond the Standard Model while others are sensitive to new physics. Consequently, certain predictions are maintained while others may show dramatic deviations from the Standard Model. Many classes of models may show clear signatures when the asymmetries are measured: four quark generations, Z-mediated flavor-changing neutral currents, supersymmetry and “real superweak” models. On the other hand, models of left-right symmetry and multi-Higgs sectors with natural flavor conservation are unlikely to modify the Standard Model predictions.

scholarly journals Naturalising the third family hypercharge model for neutral current $$B{-}\hbox {anomalies}$$

2019 ◽  
Vol 79 (11) ◽  
Author(s):  
B. C. Allanach ◽  
Joe Davighi
Keyword(s):  
Gauge Symmetry ◽  
Standard Model ◽  
Neutral Current ◽  
Beyond The Standard Model ◽  
Yukawa Couplings ◽  
The Third ◽  
Standard Model Contribution ◽  
The Standard Model ◽  
Model Predictions ◽  
Flavour Violation

Abstract We consider a deformation of the Third Family Hypercharge Model, which arguably makes the model more natural. Additional non-zero charges of the spontaneously broken, family-dependent $$U(1)_F$$U(1)F gauge symmetry are assigned to the second family leptons, and the third family leptons’ charges are deformed away from their hypercharges in such a way that the $$U(1)_F$$U(1)F gauge symmetry remains anomaly-free. Second family $$U(1)_F$$U(1)F lepton charges allow a $$Z^\prime $$Z′ coupling to muons without having to assume large charged lepton mixing, which risks violating tight lepton flavour violation bounds. In this deformed version, only the bottom and top Yukawa couplings are generated at the renormalisable level, whereas the tauon Yukawa coupling is absent. The $$Z^\prime $$Z′ mediates a beyond the Standard Model contribution to an effective $$({\bar{b}} s) (\bar{\mu }\mu )$$(b¯s)(μ¯μ) vertex in the combination $$C_9=-9C_{10}$$C9=-9C10 and is able to fit the apparent discrepancy between Standard Model predictions in flavour changing neutral-current $$B-$$B-meson decays and their measurements, whilst simultaneously avoiding current constraints from direct $$Z^\prime $$Z′ searches and other measurements, when $$0.8~\text {TeV}< M_{Z^\prime } < 12.5 ~\text {TeV}$$0.8TeV<MZ′<12.5TeV.

scholarly journals BEYOND THE STANDARD MODEL WITH B AND K PHYSICS

2004 ◽  
Vol 19 (06) ◽  
pp. 907-917 ◽  
Author(s):  
Y. GROSSMAN
Keyword(s):  
Standard Model ◽  
Extra Dimension ◽  
Flavor Physics ◽  
New Physics ◽  
Beyond The Standard Model ◽  
The Standard Model ◽  
Model Predictions ◽  
Physics Model ◽  
K Physics

In the first part of the talk the flavor physics input to models beyond the Standard Model is described. One specific example of such a new physics model is given: a model with bulk fermions in one non-factorizable extra dimension. In the second part of the talk we discuss several observables that are sensitive to new physics. We explain what type of new physics can produce deviations from the Standard Model predictions in each of these observables.

B MESON RADIATIVE EFFECTIVE NEUTRAL CURRENT ("PENGUIN") TRANSITION RATES

2010 ◽  
Vol 25 (27) ◽  
pp. 2289-2303
Author(s):  
BRUCE A. SCHUMM
Keyword(s):  
Standard Model ◽  
B Meson ◽  
Neutral Current ◽  
New Physics ◽  
Transition Rates ◽  
Penguin Decays ◽  
The Standard Model ◽  
Coupling Parameters ◽  
Meson Mixing ◽  
Better Than

B meson radiative effective neutral current ("penguin") decays rates, including the b → sγ and b → dγ transitions, represent one of the most powerful indirect constraints on new physics scenarios. Approaches to the measurements of the b → sγ width are presented, and the combined result is compared to its Standard-Model expectation. Various approaches to studying the b → dγ transition involve a comparison to corresponding b → sγ processes, and are presented in terms of the extracted ratio of CKM coupling parameters |Vtd/Vts|, which is precisely constrained within the context of the Standard Model by measurements of B meson mixing. The relative accuracy of experimental constraints on radiative penguin transition rates are better than ±7% for b → sγ and ±20% for b → dγ/b → sγ. The implications of the increasingly precise complementary constraint on |Vtd/Vts| that arises from the measurement radiative penguin decay widths may not yet be fully appreciated. There is significant potential for the improvement of these constraints in both the near (particularly for b → sγ) and longer terms.

scholarly journals DIRECT CP ASYMMETRY IN INCLUSIVE RARE B-DECAYS IN 2HDM

2001 ◽  
Vol 16 (23) ◽  
pp. 3805-3822 ◽  
Author(s):  
H. H. ASATRYAN ◽  
H. M. ASATRIAN ◽  
G. K. YEGHIYAN ◽  
G. K. SAVVIDY
Keyword(s):  
Cp Violation ◽  
Standard Model ◽  
Higgs Doublet ◽  
New Physics ◽  
Beyond The Standard Model ◽  
Renormalization Scale ◽  
Cp Asymmetry ◽  
Rate Asymmetry ◽  
The Standard Model ◽  
Model Predictions

The direct CP asymmetry in the inclusive B → Xdγ and B → Xde+e-decays is investigated in the two-Higgs doublet extension of the Standard Model (2HDM). The investigation is performed in the lowest nonvanishing order of the perturbation theory using the existing restrictions on the 2HDM parameters space. It is shown that the direct CP asymmetry in the B → Xdγ decay can deviate significantly from the Standard Model predictions. In the presence of only one source of CP violation (the CKM matrix weak phase) aCP(B → Xdγ) can have the sign opposite to that in the SM. The new source of CP violation can make |aCP(B → Xdγ)| arbitrary small (unlike the SM case) and hence unmeasurable. Quantitatively, the obtained results suffer from the uncertainty of the choice of renormalization scale. As for the B → Xde+e-rate asymmetry, its renormalization scale dependence in the lowest nonvanishing order does not allow to conclude if this quantity is efficient for testing new physics beyond the Standard Model.

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 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 Flavour Anomalies in a U(1) SUSY Extension of the SM

Symmetry ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 191
Author(s):  
Alexander Bednyakov ◽  
Alfiia Mukhaeva
Keyword(s):  
Standard Model ◽  
Parameter Space ◽  
Gauge Boson ◽  
New Physics ◽  
Low Energy ◽  
Effective Theory ◽  
The Standard Model ◽  
Meson Mixing ◽  
Additional Anomaly ◽  
Lepton Flavour

Flavour anomalies have attracted a lot of attention over recent years as they provide unique hints for possible New Physics. Here, we consider a supersymmetric (SUSY) extension of the Standard Model (SM) with an additional anomaly-free gauge U(1) group. The key feature of our model is the particular choice of non-universal charges to the gauge boson Z′, which not only allows a relaxation of the flavour discrepancies but, contrary to previous studies, can reproduce the SM mixing matrices both in the quark and lepton sectors. We pay special attention to the latter and explicitly enumerate all parameters relevant for our calculation in the low-energy effective theory. We find regions in the parameter space that satisfy experimental constraints on meson mixing and LHC Z′ searches and can alleviate the flavour anomalies. In addition, we also discuss the predictions for lepton-flavour violating decays B+→K+μτ and B+→K+eτ.

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