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The role of momentum dependent dressing functions and vector meson dominance in hadronic light-by-light contributions to the muon g-2  [PDF]
Tobias Goecke,Christian S. Fischer,Richard Williams
Physics , 2012, DOI: 10.1103/PhysRevD.87.034013
Abstract: We present a refined calculation of the quark-loop contribution to hadronic light-by-light scatter- ing that focuses upon the impact of the transverse components of the quark-photon vertex. These structures are compared and contrasted with those found within the extended NJL-models. We discuss similarities and differences between the two approaches and further clarify the important role of momentum dependent dressing functions. As expected we find that the transverse structures of the quark-photon vertex lead to a suppression of the quark-loop contribution to the anomalous magnetic moment of the muon. However, we find evidence that this suppression is overestimated within models with simple approximations for the quark-photon interaction.
Hadronic Contributions to the Muon Lifetime  [PDF]
Timo van Ritbergen,Robin G. Stuart
Physics , 1998, DOI: 10.1016/S0370-2693(98)00895-8
Abstract: Hadronic corrections to the muon lifetime are calculated in the Fermi theory in the presence of QED using dispersion relations. The result, after convolution of hadron data with the calculated perturbative kernel is Delta Gamma_had = -Gamma_0(alpha/pi)^2(0.042) where Gamma_0 is the tree-level width. The results are also used to obtain the corrections to the muon lifetime coming from virtual muon and tau loops Delta Gamma_muon = Gamma_0(alpha/pi)^2[(16987/576)-(85/36)zeta(2)-(64/3)zeta(3)] = -Gamma_0(alpha/pi)^2(0.0364333) Delta Gamma_tau = -Gamma_0(alpha/pi)^2)(0.00058)
Electroweak Hadronic Contributions to the muon g-2  [PDF]
M. Knecht,S. Peris,M. Perrottet,E. de Rafael
Physics , 2002, DOI: 10.1088/1126-6708/2002/11/003
Abstract: We reanalyze the two-loop electroweak hadronic contributions to the muon g-2 that may be enhanced by large logarithms. The present evaluation is improved over those already existing in the literature by the implementation of the current algebra Ward identities and the inclusion of the correct short-distance QCD behaviour of the relevant hadronic Green's function.
Hadronic Contributions to the Muon $g-2$ and Low-Energy QCD  [PDF]
Eduardo de Rafael
Physics , 1993, DOI: 10.1016/0370-2693(94)91114-2
Abstract: The contributions to the muon anomalous magnetic moment from hadronic vacuum polarization and from hadronic light-by-light scattering are reexamined within the frame work of chiral perturbation theory; the $1/N_c$-expansion; and the extended Nambu Jona-Lasinio model of low-energy QCD.
Study of the hadronic contributions to the running of the QED coupling and the weak mixing angle  [PDF]
Anthony Francis,Vera Gülpers,Gregorio Herdoíza,Hanno Horch,Benjamin J?ger,Harvey B. Meyer,Hartmut Wittig
Physics , 2015,
Abstract: The electromagnetic coupling receives significant contributions to its running from non-perturbative QCD effects. We present an update of a lattice QCD study of the Adler function and of its application to the determination of the running of the QED coupling. We perform a high-statistics computation with two flavours of O$(a)$ improved Wilson fermions in a large range of momentum transfer $Q^2$. The running of the electromagnetic coupling, including contributions from $u$, $d$, $s$ and $c$ valence quarks, is compared to phenomenological determinations at intermediate $Q^2$ values. An extension of this study to the determination of the hadronic contributions to the running of the weak mixing angle is also described.
Hadronic Contributions to the Muon Anomaly in the Constituent Chiral Quark Model  [PDF]
David Greynat,Eduardo de Rafael
Physics , 2012, DOI: 10.1007/JHEP07(2012)020
Abstract: The hadronic contributions to the anomalous magnetic moment of the muon which are relevant for the confrontation between theory and experiment at the present level of accuracy, are evaluated within the same framework: the constituent chiral quark model. This includes the contributions from the dominant hadronic vacuum polarization as well as from the next--to--leading order hadronic vacuum polarization, the contributions from the hadronic light-by-light scattering, and the contributions from the electroweak hadronic $Z\gamma\gamma$ vertex. They are all evaluated as a function of only one free parameter: the constituent quark mass. We also comment on the comparison between our results and other phenomenological evaluations.
Leading hadronic contributions to the running of the electroweak coupling constants from lattice QCD  [PDF]
Florian Burger,Karl Jansen,Marcus Petschlies,Grit Pientka
Physics , 2015, DOI: 10.1007/JHEP11(2015)215
Abstract: The quark-connected leading-order hadronic contributions to the running of the electromagnetic fine structure constant, $\alpha_{\rm QED}$, and the weak mixing angle, $\theta_W$, are determined by a four-flavour lattice QCD computation with twisted mass fermions. Full agreement of the results with a phenomenological analysis is observed with an even comparable statistical uncertainty. We show that the uncertainty of the lattice calculation is dominated by systematic effects which then leads to significantly larger errors than obtained by the phenomenological analysis.
Holographic calculation of hadronic contributions to muon g-2  [PDF]
Deog Ki Hong,Doyoun Kim,Shinya Matsuzaki
Physics , 2009, DOI: 10.1103/PhysRevD.81.073005
Abstract: Using the gauge/gravity duality, we compute the leading order hadronic (HLO) contribution to the anomalous magnetic moment of muon, amu(HLO). Holographic renormalization is used to obtain a finite vacuum polarization. We find amu(HLO) =470.5 x 10^{-10} in AdS/QCD with two light flavors, which is compared with the currently revised BABAR data estimated from e^+ e^- -> pi^+ pi^- events, amu(HLO)[pipi]=(514.1 +- 3.8) x 10^{-10}.
Hadronic Light by Light Contributions to the Muon Anomalous Magnetic Moment With Physical Pions  [PDF]
Luchang Jin,Thomas Blum,Norman Christ,Masashi Hayakawa,Taku Izubuchi,Christoph Lehner
Physics , 2015,
Abstract: The current measurement of muonic $g - 2$ disagrees with the theoretical calculation by about 3 standard deviations. Hadronic vacuum polarization (HVP) and hadronic light by light (HLbL) are the two types of processes that contribute most to the theoretical uncertainty. The current value for HLbL is still given by models. I will describe results from a first-principles lattice calculation with a 139 MeV pion in a box of 5.5 fm extent. Our current numerical strategies, including noise reduction techniques, evaluating the HLbL amplitude at zero external momentum transfer, and important remaining challenges, in particular those associated with finite volume effects, will be discussed.
Model-independent parametrization of the hadronic vacuum polarization and g-2 for the muon on the lattice  [PDF]
Christopher Aubin,Thomas Blum,Maarten Golterman,Santiago Peris
Physics , 2012, DOI: 10.1103/PhysRevD.86.054509
Abstract: The leading hadronic contribution to the muon anomalous magnetic moment is given by a weighted integral over euclidean momentum of the hadronic vacuum polarization. This integral is dominated by momenta of order the muon mass. Since the finite volume in lattice QCD makes it difficult to compute the vacuum polarization at a large number of low momenta with high statistics (combined with the fact that one cannot compute it at zero momentum), a parametrization of the vacuum polarization is required to extrapolate the data. A much used functional form is based on vector meson dominance, which introduces model dependence into the lattice computation of the magnetic moment. Here we introduce a model-independent extrapolation method, and present a few first tests of this new method.
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