Variations on Photon Vacuum Polarization

Jegerlehner, F.

doi:10.1051/epjconf/201921801003

Cited by 56 publications

(71 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…It can be divided into a leptonic and a hadronic part, ∆α = ∆α lept + ∆α rad . ∆α lept has been computed to three-loop order [59], whereas ∆α had contains non-perturbative hadronic contributions, which are commonly extracted from data [60][61][62]. We neglect the light fermion masses m f , f = t, everywhere besides in ∆α and (at leading power) in the radiator functions…”

Section: )mentioning

confidence: 99%

Electroweak pseudo-observables and Z-boson form factors at two-loop accuracy

Dubovyk

Freitas

Gluza

et al. 2019

J. High Energ. Phys.

View full text Add to dashboard Cite

We present Standard Model predictions for the complete set of phenomenologically relevant electroweak precision pseudo-observables related to the Zboson: the leptonic and bottom-quark effective weak mixing angles sin 2 θ eff , sin 2 θ b eff , the Z-boson partial decay widths Γ f , where f indicates any charged lepton, neutrino and quark flavor (except for the top quark), as well as the total Z decay width Γ Z , the branching ratios R , R c , R b , and the hadronic cross section σ 0 had . The input parameters are the masses M Z , M H and m t , and the couplings α s , α. The scheme dependence due to the choice of M W or its alternative G µ as a last input parameter is also discussed. Recent substantial technical progress in the calculation of Minkowskian massive higher-order Feynman integrals allows the calculation of the complete electroweak two-loop radiative corrections to all the observables mentioned. QCD contributions are included appropriately. Results are provided in terms of simple and convenient parameterization formulae whose coefficients have been determined from the full numerical multi-loop calculation. The size of the missing electroweak three-loop or QCD higher-order corrections is estimated. We briefly comment on the prospects for their calculation. Finally, direct predictions for the Zf f vector and axial-vector form-factors are given, including a discussion of separate order-by-order contributions.

show abstract

Section: )mentioning

confidence: 99%

Electroweak pseudo-observables and Z-boson form factors at two-loop accuracy

Dubovyk

Freitas

Gluza

et al. 2019

J. High Energ. Phys.

View full text Add to dashboard Cite

show abstract

“…a 1 σ increase. See also the results presented in Table 3 of [129] where a ρ 0 − γ mixing shift of 2.74 × 10 −10 on the I=1 component at LO has been reported as a difference between LQCD data and the phenomenological dispersive approach.The upgraded result for δa µ [ππ] ργ is based on an actualized data compilation, with mixing correction applied to the full vector form-factor and including NLO corrections.…”

Section: Dispersive Vs Lqcd Methods : Additional Systematicsmentioning

confidence: 94%

$${\hbox {BHLS}}_2$$, a new breaking of the HLS model and its phenomenology

2020

View full text Add to dashboard Cite

Previous studies have shown that the Hidden Local Symmetry (HLS) Model, supplied with appropriate symmetry breaking mechanisms, provides an Effective Lagrangian (BHLS) able to encompass a large number of processes within a unified framework. This allowed to design a global fit procedure which provides a fair simultaneous description of the e + e − annihilation into 6 final states (π + π − , π 0 γ, ηγ, π + π − π 0 , K + K − , K L K S ), the dipion spectrum in the τ decay and some more light meson decay partial widths. In this paper, additional breaking schemes are defined which improve the BHLS working and extend its scope so as to absorb spacelike processes within a new framework (BHLS 2 ). The phenomenology previously explored with BHLS is fully revisited in the BHLS 2 context with special emphasis on the φ mass region using all available data samples. It is shown that BHLS 2 addresses perfectly the close spacelike region covered by NA7 and Fermilab data; it is also shown that the recent Lattice QCD (LQCD) information on the pion form factor are accurately predicted by the BHLS 2 fit functions derived from fits to only annihilation data. The contribution to the muon anomalous magnetic moment a th 1 The e + e − → η ′ γ channel has been considered in [25,26] and found to contributes to a had µ at the 10 −12 level only and can thus be safely discarded.As clear in Equations (8), BKY breaks the symmetry of the HLS Model in the very definition of its Lagrangian. This is quite legitimate and strongly validated by its remarkable description of a considerable amount of data [25,26,27]. Nevertheless, it is of interest to explore other possibilities to improve the description of the data in some specific mass regions and, then, reduce or cancel out the additional systematic uncertainties reported in [27].Let us focus on Equation (4) which defines the original HLS covariant derivative :

show abstract

“…with the uncertainty in the last digits in parentheses. The hadronic and weak contributions a hadronic = 1.693 (11) × 10 −12 (11) a weak = 0.03053 (23) × 10 −12 (12) have been estimated with their uncertainties [9].…”

Section: Testing the Standard Model's Most Precise Predictionmentioning

confidence: 99%

Towards an Improved Test of the Standard Model’s Most Precise Prediction

Gabrielse

Fayer

Myers

et al. 2019

Atoms

View full text Add to dashboard Cite

The electron and positron magnetic moments are the most precise prediction of the standard model of particle physics. The most accurate measurement of a property of an elementary particle has been made to test this result. A new experimental method is now being employed in an attempt to improve the measurement accuracy by an order of magnitude. Positrons from a "student source" now suffice for the experiment. Progress toward a new measurement is summarized.

show abstract

Variations on Photon Vacuum Polarization

Cited by 56 publications

References 28 publications

Electroweak pseudo-observables and Z-boson form factors at two-loop accuracy

Electroweak pseudo-observables and Z-boson form factors at two-loop accuracy

$${\hbox {BHLS}}_2$$, a new breaking of the HLS model and its phenomenology

Towards an Improved Test of the Standard Model’s Most Precise Prediction

Contact Info

Product

Resources

About