scholarly journals THEORY OF THE τ LEPTON ANOMALOUS MAGNETIC MOMENT

2007 ◽  
Vol 22 (03) ◽  
pp. 159-179 ◽  
Author(s):  
S. EIDELMAN ◽  
M. PASSERA
Keyword(s):  
Standard Model ◽  
Model Prediction ◽  
Magnetic Moment ◽  
Anomalous Magnetic Moment ◽  
Standard Model Prediction ◽  
Low Energy ◽  
Leading Order ◽  
The Standard Model

This paper reviews and updates the Standard Model prediction of the τ lepton g-2. Updated QED and electroweak contributions are presented, together with new values of the leading-order hadronic term, based on the recent low energy e+ e- data from BaBar, CMD-2, KLOE and SND, and hadronic light-by-light contribution. The total prediction is confronted to the available experimental bounds on the τ lepton anomaly, and prospects for its future measurements are briefly discussed.

scholarly journals Hadronic light-by-light scattering in the anomalous magnetic moment of the muon

2019 ◽  
Author(s):  
Nils Asmussen ◽  
Antoine Gerardin ◽  
Andreas Nyffeler ◽  
Harvey B. Meyer
Keyword(s):  
Light Scattering ◽  
Standard Model ◽  
Model Prediction ◽  
Magnetic Moment ◽  
Anomalous Magnetic Moment ◽  
Recent Progress ◽  
Standard Model Prediction ◽  
New Physics ◽  
The Standard Model ◽  
Discovery Potential

Hadronic light-by-light scattering in the anomalous magnetic moment of the muon a_\muaμ is one of two hadronic effects limiting the precision of the Standard Model prediction for this precision observable, and hence the new-physics discovery potential of direct experimental determinations of a_\muaμ. In this contribution, I report on recent progress in the calculation of this effect achieved both via dispersive and lattice QCD methods.

scholarly journals The new $$(g-2)_\mu $$ result and the $$\mu \nu $$SSM

2021 ◽  
Vol 81 (9) ◽  
Author(s):  
Sven Heinemeyer ◽  
Essodjolo Kpatcha ◽  
Iñaki Lara ◽  
Daniel E. López-Fogliani ◽  
Carlos Muñoz ◽  
...  
Keyword(s):  
Standard Model ◽  
Model Prediction ◽  
Magnetic Moment ◽  
Anomalous Magnetic Moment ◽  
Alternative Model ◽  
Standard Model Prediction ◽  
Experimental Result ◽  
Link Type ◽  
The Standard Model ◽  
Electroweak Sector

AbstractThe $$\mu \nu \mathrm {SSM}$$ μ ν SSM is a highly predictive alternative model to the MSSM. In particular, the electroweak sector of the model can explain the longstanding discrepancy between the experimental result for the anomalous magnetic moment of the muon, $$(g-2)_\mu $$ ( g - 2 ) μ , and its Standard Model prediction, while being in agreement with all other theoretical and experimental constraints. The recently published MUON G-2 result is within $${0.8}\,\sigma $$ 0.8 σ in agreement with the older BNL result on $$(g-2)_\mu $$ ( g - 2 ) μ . The combined result was announced as $$a_\mu ^{\mathrm{exp}} = (11 659 {206.1}\pm {4.1}) \times 10^{-10}$$ a μ exp = ( 11659 206.1 ± 4.1 ) × 10 - 10 , yielding a new deviation from the Standard Model prediction of $$\Delta a_\mu = ({25.1}\pm {5.9}) \times 10^{-10}$$ Δ a μ = ( 25.1 ± 5.9 ) × 10 - 10 , corresponding to $${4.2}\,\sigma $$ 4.2 σ . Using this improved bound we update the analysis in the $$\mu \nu \mathrm {SSM}$$ μ ν SSM as presented in Kpatcha et al. (Eur Phys J C 81(2):154. arXiv:1912.04163 [hep-ph], 2021) and set new limits on the allowed parameters space of the electroweak sector of the model. We conclude that significant regions of the model can explain the new $$(g-2)_\mu $$ ( g - 2 ) μ data.

scholarly journals Probing new physics scenarios of muon g − 2 via J/ψ decay at BESIII

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Gorazd Cvetič ◽  
C. S. Kim ◽  
Donghun Lee ◽  
Dibyakrupa Sahoo
Keyword(s):  
Model Prediction ◽  
Magnetic Moment ◽  
Experimental Measurement ◽  
Anomalous Magnetic Moment ◽  
Numerical Study ◽  
Standard Model Prediction ◽  
Vector Boson ◽  
New Physics ◽  
Muon Anomalous Magnetic Moment ◽  
The Standard Model

Abstract The disagreement between the standard model prediction and the experimental measurement of muon anomalous magnetic moment can be alleviated by invoking an additional particle which is either a vector boson (X1) or a scalar (X0). This new particle, with the mass mX ≲ 2mμ, can be searched for in the decay J/ψ → μ−μ+X, where X is missing. Our numerical study shows that the search is quite feasible at the BESIII experiment in the parameter space allowed by muon g − 2 measurements.

scholarly journals Hadronic Leading Order Contribution to the Muon g-2

2018 ◽  
Vol 179 ◽  
pp. 01016
Author(s):  
Daisuke Nomura
Keyword(s):  
Experimental Data ◽  
Standard Model ◽  
Magnetic Moment ◽  
Anomalous Magnetic Moment ◽  
Leading Order ◽  
Muon Anomalous Magnetic Moment ◽  
Order Contribution ◽  
Quark Contribution ◽  
The Standard Model ◽  
Vacuum Polarisation

We calculate the Standard Model (SM) prediction for the muon anomalous magnetic moment. By using the latest experimental data for e+e- → hadrons as input to dispersive integrals, we obtain the values of the leading order (LO) and the next-to-leading-order (NLO) hadronic vacuum polarisation contributions as ahad, LO VPμ = (693:27 ± 2:46) × 10-10 and ahad, NLO VP μ = (_9.82 ± 0:04) × 1010-10, respectively. When combined with other contributions to the SM prediction, we obtain aμ(SM) = (11659182:05 ± 3.56) × 10-10; which is deviated from the experimental value by Δaμ(exp) _ aμ(SM) = (27.05 ± 7.26) × 10-10. This means that there is a 3.7 σ discrepancy between the experimental value and the SM prediction. We also discuss another closely related quantity, the running QED coupling at the Z-pole, α(M2 Z). By using the same e+e- → hadrons data as input, our result for the 5-flavour quark contribution to the running QED coupling at the Z pole is Δ(5)had(M2 Z) = (276.11 ± 1.11) × 10-4, from which we obtain Δ(M2 Z) = 128.946 ± 0.015.

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.

scholarly journals Leptoquarks in Flavour Physics

2018 ◽  
Vol 179 ◽  
pp. 01015 ◽  
Author(s):  
Dario Müller
Keyword(s):  
Standard Model ◽  
Magnetic Moment ◽  
Anomalous Magnetic Moment ◽  
Z Boson ◽  
New Physics ◽  
Experimental Results ◽  
The Standard Model ◽  
Z Boson Decays ◽  
Flavour Physics ◽  
Lepton Flavour

While the LHC has not directly observed any new particle so far, experimental results from LHCb, BELLE and BABAR point towards the violation of lepton flavour universality in b ⟶ sℓ+ and b ⟶ c-ℓν. In this context, also the discrepancy in the anomalous magnetic moment of the muon can be interpreted as a sign of lepton flavour universality violation. Here we discuss how these hints for new physics can also be explained by introducing leptoquarks as an extension of the Standard Model. Indeed, leptoquarks are good candidates to explain the anomaly in the anomalous magnetic moment of the muon because of an mg/mμ enhanced contribution giving correlated effects in Z boson decays which is particularly interesting in the light of future precision experiments.

Supersymmetric Lepton Flavor Violation, the Muon Anomalous Magnetic Moment, and e- e- Colliders

2003 ◽  
Vol 18 (16) ◽  
pp. 2769-2778
Author(s):  
Graham D. Kribs
Keyword(s):  
Standard Model ◽  
Magnetic Moment ◽  
Anomalous Magnetic Moment ◽  
International Workshop ◽  
Lepton Flavor Violation ◽  
Muon Anomalous Magnetic Moment ◽  
Lepton Flavor ◽  
Flavor Violation ◽  
Central Value ◽  
The Standard Model

I explain the theoretical connection between lepton flavor violation and muon g - 2 in supersymmetry1. Given any central value deviation of muon g - 2 from the standard model that is assumed to be due to weak scale supersymmetry, I show that stringent bounds on lepton flavor violating scalar masses can be extracted. These bounds are essentially independent of supersymmetric parameter space. I then briefly compare this indirect handle on supersymmetric lepton flavor violation with direct observation at a future lepton collider operating in the e- e- mode. This is a summary of a talk given at e- e-01: 4th International Workshop on Electron-Electron Interactions at TeV Energies.

scholarly journals The anomalous magnetic moment of the muon in the Standard Model

2020 ◽  
Vol 887 ◽  
pp. 1-166 ◽  
Author(s):  
T. Aoyama ◽  
N. Asmussen ◽  
M. Benayoun ◽  
J. Bijnens ◽  
T. Blum ◽  
...  
Keyword(s):  
Standard Model ◽  
Magnetic Moment ◽  
Anomalous Magnetic Moment ◽  
The Standard Model
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