scholarly journals Theory Status - Puzzles in B Meson Decays and LFU?

2019 ◽  
Author(s):  
Svjetlana Fajfer
Keyword(s):  
B Meson ◽  
New Physics ◽  
Charged Current ◽  
B Decays ◽  
Muon Anomalous Magnetic Moment ◽  
High Energies ◽  
Effective Lagrangian ◽  
The Standard Model ◽  
Model Predictions ◽  
Decay Widths

Currently B meson puzzles motivate many studies of New Physics due to the observed deviations from the Standard Model predictions. There are two B meson puzzles, R_{D^{(*)}}RD(*) and R_{K^{(*)}}RK(*). The first one denotes the deviations in the decays driven by the charged current in the ratio of the decay widths for B \to D^{(*)} \tau \nuB→D(*)τν and B \to D^{(*)} \mu \nuB→D(*)μν, while the second one is related to the ratio of the decay widths for B \to K^{(*)} \mu^+ \mu^-B→K(*)μ+μ− and B \to K^{(*)} e^+ e^-B→K(*)e+e− transition. Also, the measured muon anomalous magnetic moment differs from the SM predictions. Usually, the effective Lagrangian approach containing New Physics effects is used to analyse R_{D^{(*)}}RD(*) and R_{K^{(*)}}RK(*). Among many models of New Physics, various leptoquark models are suggested to resolve both B meson anomalies. If New Physics is confirmed in B decays a number of processes at low and high energies should confirm its presence.

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.

RARE B AND τ DECAYS AND SEARCHES FOR NEW PHYSICS

2007 ◽  
Vol 22 (30) ◽  
pp. 5433-5442
Author(s):  
R. J. BARLOW
Keyword(s):  
Cp Violation ◽  
Standard Model ◽  
Excellent Agreement ◽  
Rare Decays ◽  
B Mesons ◽  
New Physics ◽  
B Decays ◽  
The Standard Model ◽  
Model Predictions ◽  
Vector Particles

New results on rare decays of B mesons and τ leptons are summarised. Measurement are generally in excellent agreement with the Standard Model predictions, the only exceptions being the polarisation of vector particles in B decays and the non-appearance of CP violation in B ± → K ±π0.

scholarly journals THEORY OF CP VIOLATION IN THE B-MESON SYSTEM

2002 ◽  
Vol 17 (22) ◽  
pp. 2936-2950 ◽  
Author(s):  
MATTHIAS NEUBERT
Keyword(s):  
Cp Violation ◽  
Standard Model ◽  
B Meson ◽  
New Physics ◽  
B Decays ◽  
The Standard Model ◽  
Recent Developments ◽  
Meson System

Recent developments in the theory of CP violation in the B-meson system are reviewed, with focus on the determination of sin 2β from B → J/ψ K decays, its implications for tests of the Standard Model and searches for New Physics, and the determination of γ and α from charmless hadronic B decays.

scholarly journals THE B → ππ, πK PUZZLES: IMPLICATIONS FOR HADRON PHYSICS, NEW PHYSICS AND RARE DECAYS

2006 ◽  
Vol 21 (04) ◽  
pp. 664-671 ◽  
Author(s):  
R. FLEISCHER
Keyword(s):  
B Meson ◽  
New Physics ◽  
Point Of View ◽  
Strong Interactions ◽  
Matrix Elements ◽  
B Decays ◽  
Hadron Physics ◽  
The Standard Model ◽  
Quark Flavour ◽  
Meson System

The B-meson system is an interesting probe for the exploration of strong interactions, the quark-flavour sector of the Standard Model, and the search for new physics. In this programme, non-leptonic B decays, which are particularly challenging from the point of view of QCD, play a key rôle. After discussing strategies to deal with the corresponding hadronic matrix elements of four-quark operators and popular avenues for new physics to manifest itself in B decays, we focus on puzzling patterns in the B-factory data for B → ππ, πK decays; we explore their implications for hadron physics, new physics and rare K and B decays.

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 Is there new physics in B decays?

2007 ◽  
Vol 85 (6) ◽  
pp. 607-612
Author(s):  
A Datta
Keyword(s):  
Standard Model ◽  
B Meson ◽  
Higgs Sector ◽  
Higgs Doublet ◽  
New Physics ◽  
B Decays ◽  
The Standard Model ◽  
Data Points ◽  
Two Higgs Doublet Model ◽  
Extended Higgs Sector

Rare decays of the B meson are sensitive to new physics effects. Several experimental results on these decays have been difficult to understand within the Standard Model (SM) though more precise measurements and a better understanding of SM theory predictions are needed before any firm conclusions can be drawn. In this note we try to understand the present data assuming the presence of new physics. We find that the data points to new physics of an extended Higgs sector and we present a two-Higgs-doublet model with a 2–3 flavor symmetry in the down-type quark sector that can explain the deviations from the Standard Model reported in several rare B decays. PACS Nos.: 11.30.Er, 11.30.Hv, and 13.20.He

scholarly journals Lowering the scale of Pati-Salam breaking through seesaw mixing

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Matthew J. Dolan ◽  
Tomasz P. Dutka ◽  
Raymond R. Volkas
Keyword(s):  
Degrees Of Freedom ◽  
Tree Level ◽  
Charged Current ◽  
Meson Decay ◽  
Neutrino Masses ◽  
Down Quark ◽  
The Standard Model ◽  
Decay Widths ◽  
Left And Right ◽  
Charged Leptons

Abstract We analyse the experimental limits on the breaking scale of Pati-Salam extensions of the Standard Model. These arise from the experimental limits on rare-meson decay processes mediated at tree-level by the vector leptoquark in the model. This leptoquark ordinarily couples to both left- and right-handed SM fermions and therefore the meson decays do not experience a helicity suppression. We find that the current limits vary from $$ \mathcal{O} $$ O (80–2500) TeV depending on the choice of matrix structure appearing in the relevant three-generational charged-current interactions. We extensively analyse scenarios where additional fermionic degrees of freedom are introduced, transforming as complete Pati-Salam multiplets. These can lower the scales of Pati-Salam breaking through mass-mixing within the charged-lepton and down-quark sectors, leading to a helicity suppression of the meson decay widths which constrain Pati-Salam breaking. We find four multiplets with varying degrees of viability for this purpose: an SU(2)L/R bidoublet, a pair of SU(4) decuplets and either an SU(2)L or SU(2)R triplet all of which contain heavy exotic versions of the SM charged leptons. We find that the Pati-Salam limits can be as low as $$ \mathcal{O} $$ O (5–150) TeV with the addition of these four multiplets. We also identify an interesting possible connection between the smallness of the neutrino masses and a helicity suppression of the Pati-Salam limits for three of the four multiplets.

scholarly journals Lattice calculation of the hadronic leading order contribution to the muon g − 2

2020 ◽  
Vol 234 ◽  
pp. 01016
Author(s):  
Hartmut Wittig ◽  
Antoine Gérardin ◽  
Marco Cè ◽  
Georg von Hippel ◽  
Ben Hörz ◽  
...  
Keyword(s):  
Standard Model Prediction ◽  
Detailed Comparison ◽  
New Physics ◽  
Current Status ◽  
Leading Order ◽  
Lattice Calculation ◽  
Muon Anomalous Magnetic Moment ◽  
The Standard Model ◽  
Vacuum Polarisation

The persistent discrepancy of about 3.5 standard deviations between the experimental measurement and the Standard Model prediction for the muon anomalous magnetic moment, aµ, is one of the most promising hints for the possible existence of new physics. Here we report on our lattice QCD calculation of the hadronic vacuum polarisation contribution $ a_\mu ^{{\rm{hvp}}} $, based on gauge ensembles with Nf = 2 + 1 flavours of O(a) improved Wilson quarks. We address the conceptual and numerical challenges that one encounters along the way to a sub-percent determination of the hadronic vacuum polarisation contribution. The current status of lattice calculations of $ a_\mu ^{{\rm{hvp}}} $ is presented by performing a detailed comparison with the results from other groups.

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.

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