scholarly journals Effective Weak Non-Ieptonic Hamiltonians for Flavour Changing Processes

1982 ◽  
Vol 35 (3) ◽  
pp. 235 ◽  
Author(s):  
Robert DC Miller ◽  
Bruce HJ McKellar
Keyword(s):  
Numerical Analysis ◽  
Effective Theory ◽  
Complete Analysis ◽  
Matrix Formalism ◽  
Minimal Subtraction ◽  
The Standard Model ◽  
Ms Scheme ◽  
Detailed Application ◽  
Theoretical Results ◽  
Theoretical Developments

We present a complete analysis of the W mediated effective weak non-leptonic theory for s, c, b and t flavour changing processes. Calculations are based upon the standard model with n generations. The theory is developed using a matrix formalism which leads to compact theoretical results and a simpler numerical analysis. In our analysis we take account of scheme and effective theory dependence of the QCD parameters. Explicit numerical calculations are performed for effective weak non-leptonic Hamiltonians describing s, c, band t decay, in both the penguin free and penguin generating sectors of the theory, for the modified minimal subtraction (ms) scheme and IX = 0 gauge. Our approach is to display the calculations as a detailed application of the Appelquist-Carazzone decoupling theorem incorporating some of the latest theoretical developments in this area.

scholarly journals Searching for charged lepton flavor violation at ep colliders

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Stefan Antusch ◽  
A. Hammad ◽  
Ahmed Rashed
Keyword(s):  
Standard Model ◽  
Charged Lepton ◽  
Neutral Current ◽  
Effective Theory ◽  
Theory Approach ◽  
Lepton Flavor Violation ◽  
Lepton Flavor ◽  
Flavor Violation ◽  
The Standard Model ◽  
Order Of Magnitude

Abstract We investigate the sensitivity of electron-proton (ep) colliders for charged lepton flavor violation (cLFV) in an effective theory approach, considering a general effective Lagrangian for the conversion of an electron into a muon or a tau via the effective coupling to a neutral gauge boson or a neutral scalar field. For the photon, the Z boson and the Higgs particle of the Standard Model, we present the sensitivities of the LHeC for the coefficients of the effective operators, calculated from an analysis at the reconstructed level. As an example model where such flavor changing neutral current (FCNC) operators are generated at loop level, we consider the extension of the Standard Model by sterile neutrinos. We show that the LHeC could already probe the LFV conversion of an electron into a muon beyond the current experimental bounds, and could reach more than an order of magnitude higher sensitivity than the present limits for LFV conversion of an electron into a tau. We discuss that the high sensitivities are possible because the converted charged lepton is dominantly emitted in the backward direction, enabling an efficient separation of the signal from the background.

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.

scholarly journals Flavor physics: Precision as an avenue to discovery

2020 ◽  
Vol 35 (01) ◽  
pp. 1930018
Author(s):  
Diego Guadagnoli
Keyword(s):  
Cp Violation ◽  
Standard Model ◽  
Flavor Physics ◽  
Standard Model Prediction ◽  
New Physics ◽  
Effective Theory ◽  
Theory Approach ◽  
Long Distance ◽  
The Standard Model ◽  
The Impact

This paper describes the work pursued in the years 2008–2013 on improving the Standard Model prediction of selected flavor-physics observables. The latter includes: (1) [Formula: see text], that quantifies indirect CP violation in the [Formula: see text] system and (2) the very rare decay [Formula: see text], recently measured at the LHC. Concerning point (1), the paper describes our reappraisal of the long-distance contributions to [Formula: see text],[Formula: see text] that have permitted to unveil a potential tension between CP violation in the [Formula: see text]- and [Formula: see text]-system. Concerning point (2), the paper gives a detailed account of various systematic effects pointed out in Ref. 4 and affecting the Standard Model [Formula: see text] decay rate at the level of 10% — hence large enough to be potentially misinterpreted as nonstandard physics, if not properly included. The paper further describes the multifaceted importance of the [Formula: see text] decays as new physics probes, for instance how they compare with [Formula: see text]-peak observables at LEP, following the effective-theory approach of Ref. 5. Both cases (1) and (2) offer clear examples in which the pursuit of precision in Standard Model predictions offered potential avenues to discovery. Finally, this paper describes the impact of the above results on the literature, and what is the further progress to be expected on these and related observables.

scholarly journals Theoretical and experimental investigation of a 1:3 internal resonance in a beam with piezoelectric patches

2020 ◽  
Vol 26 (13-14) ◽  
pp. 1119-1132 ◽  
Author(s):  
Vinciane Guillot ◽  
Arthur Givois ◽  
Mathieu Colin ◽  
Olivier Thomas ◽  
Alireza Ture Savadkoohi ◽  
...  
Keyword(s):  
Harmonic Balance ◽  
Internal Resonance ◽  
Harmonic Balance Method ◽  
Mode Shapes ◽  
Governing Equations ◽  
Internal Resonances ◽  
Thin Beam ◽  
Beam Focusing ◽  
Theoretical Results ◽  
Theoretical Developments

Experimental and theoretical results on the nonlinear dynamics of a homogeneous thin beam equipped with piezoelectric patches, presenting internal resonances, are provided. Two configurations are considered: a unimorph configuration composed of a beam with a single piezoelectric patch and a bimorph configuration with two collocated piezoelectric patches symmetrically glued on the two faces of the beam. The natural frequencies and mode shapes are measured and compared with those obtained by theoretical developments. Ratios of frequencies highlight the realization of 1:2 and 1:3 internal resonances, for both configurations, depending on the position of the piezoelectric patches on the length of the beam. Focusing on the 1:3 internal resonance, the governing equations are solved via a numerical harmonic balance method to find the periodic solutions of the system under harmonic forcing. A homodyne detection method is used experimentally to extract the harmonics of the measured vibration signals, on both configurations, and exchanges of energy between the modes in the 1:3 internal resonance are observed. A qualitative agreement is obtained with the model.

scholarly journals RUNNING MASS OF THE b-QUARK IN QCD AND SUSY QCD

2007 ◽  
Vol 22 (29) ◽  
pp. 5245-5277 ◽  
Author(s):  
A. V. BEDNYAKOV
Keyword(s):  
Numerical Analysis ◽  
Degrees Of Freedom ◽  
Effective Theory ◽  
Supersymmetric Extension ◽  
Heavy Particles ◽  
Advantages And Disadvantages ◽  
The Difference ◽  
B Quark

The running mass of the b-quark defined in [Formula: see text]-scheme is one of the important parameters of SUSY QCD. To find its value, it should be related to some known experimental input. In this paper, the b-quark running mass defined in nonsupersymmetric QCD is chosen for determination of the corresponding parameter in SUSY QCD. The relation between these two quantities is found by considering five-flavor QCD as an effective theory obtained from its supersymmetric extension. A numerical analysis of the calculated two-loop relation and its impact on the MSSM spectrum is discussed. Since for nonsupersymmetric models [Formula: see text]-scheme is more natural than [Formula: see text], we also propose a new procedure that allows one to calculate relations between [Formula: see text]- and [Formula: see text]-parameters. Unphysical ε-scalars that give rise to the difference between the above-mentioned schemes are assumed to be heavy and decoupled in the same way as physical degrees of freedom. By means of this method it is possible to "catch two rabbits," i.e. decouple heavy particles and turn from [Formula: see text] to [Formula: see text], at the same time. An explicit two-loop example of [Formula: see text] transition is given in the context of QCD. The advantages and disadvantages of the method are briefly discussed.

scholarly journals A NUMERICAL TOOLBOX FOR HOMOCLINIC BIFURCATION ANALYSIS

1996 ◽  
Vol 06 (05) ◽  
pp. 867-887 ◽  
Author(s):  
A.R. CHAMPNEYS ◽  
YU. A. KUZNETSOV ◽  
B. SANDSTEDE
Keyword(s):  
Numerical Analysis ◽  
Chemical Kinetics ◽  
Bifurcation Analysis ◽  
Homoclinic Orbit ◽  
Homoclinic Orbits ◽  
Homoclinic Bifurcation ◽  
Codimension Two ◽  
Codimension One ◽  
Homoclinic Bifurcations ◽  
Theoretical Results

This paper presents extensions and improvements of recently developed algorithms for the numerical analysis of orbits homoclinic to equilibria in ODEs and describes the implementation of these algorithms within the standard continuation package AUTO86. This leads to a kind of toolbox, called HOMCONT, for analysing homoclinic bifurcations either as an aid to producing new theoretical results, or to understand dynamics arising from applications. This toolbox allows the continuation of codimension-one homoclinic orbits to hyperbolic or non-hyperbolic equilibria as well as detection and continuation of higher-order homoclinic singularities in more parameters. All known codimension-two cases that involve a unique homoclinic orbit are supported. Two specific example systems from ecology and chemical kinetics are analysed in some detail, allowing the reader to understand how to use the the toolbox for themselves. In the process, new results are also derived on these two particular models.

scholarly journals Systematically Investigating the Structural Variety of Crystalline and Kaleidoscopic Vortex Lattices by Using Laser Beam Arrays

2021 ◽  
Vol 11 (17) ◽  
pp. 8018
Author(s):  
Chengshang Chen ◽  
Yuhan Fang ◽  
Chichen Jang ◽  
Wenchi Chen ◽  
Hui-Chi Lin ◽  
...  
Keyword(s):  
Numerical Calculation ◽  
Numerical Analysis ◽  
Laser Beam ◽  
Vortex Lattice ◽  
Phase Plate ◽  
Lattice Structures ◽  
Vortex Lattices ◽  
Structural Variety ◽  
Theoretical Results ◽  
Spiral Phase

We theoretically demonstrate that a family of vortex-lattice structures can be flexibly generated using a multi-beam interference approach. Numerical calculation presents a variety of crystalline and kaleidoscopic patterns. Based on the numerical analysis, we experimentally realized these structure beams by combining an amplitude mask with multiple apertures and a spiral phase plate. The excellent agreement between the experimental and theoretical results not only validates the presented method, but also manifests the structure of vortex lattices.

scholarly journals Challenges for an axion explanation of the muon g − 2 measurement

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Manuel A. Buen-Abad ◽  
JiJi Fan ◽  
Matthew Reece ◽  
Chen Sun
Keyword(s):  
Decay Constant ◽  
Standard Model Prediction ◽  
New Physics ◽  
Effective Theory ◽  
General Sense ◽  
Weak Scale ◽  
Initial Application ◽  
The Standard Model ◽  
Axion Decay Constant ◽  
Axion Decay

Abstract The discrepancy between the muon g − 2 measurement and the Standard Model prediction points to new physics around or below the weak scale. It is tantalizing to consider the loop effects of a heavy axion (in the general sense, also known as an axion-like particle) coupling to leptons and photons as an explanation for this discrepancy. We provide an updated analysis of the necessary couplings, including two-loop contributions, and find that the new physics operators point to an axion decay constant on the order of 10s of GeV. This poses major problems for such an explanation, as the axion couplings to leptons and photons must be generated at low scales. We outline some possibilities for how such couplings can arise, and find that these scenarios predict new charged matter at or below the weak scale and new scalars can mix with the Higgs boson, raising numerous phenomenological challenges. These scenarios also all predict additional contributions to the muon g−2 itself, calling the initial application of the axion effective theory into question. We conclude that there is little reason to favor an axion explanation of the muon g – 2 measurement relative to other models postulating new weak-scale matter.

scholarly journals Lepton-flavour non-universality of $${\bar{B}}\rightarrow D^*\ell {{\bar{\nu }}}$$ angular distributions in and beyond the Standard Model

2021 ◽  
Vol 81 (11) ◽  
Author(s):  
Christoph Bobeth ◽  
Marzia Bordone ◽  
Nico Gubernari ◽  
Martin Jung ◽  
Danny van Dyk
Keyword(s):  
Experimental Data ◽  
Standard Model ◽  
Effective Theory ◽  
Angular Distributions ◽  
Beyond The Standard Model ◽  
Mass Effects ◽  
Muon Mass ◽  
The Standard Model ◽  
Current Experimental Data ◽  
Lepton Flavour

AbstractWe analyze in detail the angular distributions in $${\bar{B}}\rightarrow D^*\ell {{\bar{\nu }}}$$ B ¯ → D ∗ ℓ ν ¯ decays, with a focus on lepton-flavour non-universality. We investigate the minimal number of angular observables that fully describes current and upcoming datasets, and explore their sensitivity to physics beyond the Standard Model (BSM) in the most general weak effective theory. We apply our findings to the current datasets, extract the non-redundant set of angular observables from the data, and compare to precise SM predictions that include lepton-flavour universality violating mass effects. Our analysis shows that the number of independent angular observables that can be inferred from current experimental data is limited to only four. These are insufficient to extract the full set of relevant BSM parameters. We uncover a $$\sim 4\sigma $$ ∼ 4 σ tension between data and predictions that is hidden in the redundant presentation of the Belle 2018 data on $${\bar{B}}\rightarrow D^*\ell {{\bar{\nu }}}$$ B ¯ → D ∗ ℓ ν ¯ decays. This tension specifically involves observables that probe $$e-\mu $$ e - μ lepton-flavour universality. However, we find inconsistencies in these data, which renders results based on it suspicious. Nevertheless, we discuss which generic BSM scenarios could explain the tension, in the case that the inconsistencies do not affect the data materially. Our findings highlight that $$e-\mu $$ e - μ non-universality in the SM, introduced by the finite muon mass, is already significant in a subset of angular observables with respect to the experimental precision.

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