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We investigate restrictions on the hadronic contribution to the muon $(g-2)$ factor and to the pion electromagnetic formfactor from the analytical properties of the pion formfactor and the experimental data of the pion formfactor in the…

High Energy Physics - Phenomenology · Physics 2007-05-23 B. V. Geshkenbein

We review the recent progress made with regard to the hadronic light-by-light (HLbL) contribution to the Standard Model prediction of the muon anomalous magnetic moment and how well this compares with predictions from holographic QCD…

High Energy Physics - Phenomenology · Physics 2026-04-17 Anton Rebhan , Luigi Cappiello , Josef Leutgeb , Jonas Mager

We calculate the pion transition form factor ${\cal F}_{\pi^0\gamma^*\gamma^*}(q_1^2,q_2^2)$, which describe the interaction of an on-shell pion with two off-shell photons, using lattice QCD simulations with two degenerate flavors of…

High Energy Physics - Lattice · Physics 2016-12-07 Antoine Gérardin , Harvey B. Meyer , Andreas Nyffeler

We correct the error in the sign of the pseudoscalar pole contribution to the muon g-2, which dominates the O(alpha^3) hadronic light-by-light scattering effect. The error originates from our oversight of a feature of the algebraic…

High Energy Physics - Phenomenology · Physics 2016-09-06 Masashi Hayakawa , Toichiro Kinoshita

Hadronic light-by-light scattering in the anomalous magnetic moment of the muon $a_\mu$ is one of two hadronic effects limiting the precision of the Standard Model prediction for this precision observable, and hence the new-physics…

High Energy Physics - Lattice · Physics 2018-11-21 Nils Asmussen , Antoine Gérardin , Andreas Nyffeler , Harvey B. Meyer

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…

High Energy Physics - Phenomenology · Physics 2013-03-14 Tobias Goecke , Christian S. Fischer , Richard Williams

We summarize our results for hadronic contributions to the anomalous magnetic moment of the muon ($a_\mu$), the one from hadronic vacuum-polarisation (HVP) and the light-by-light scattering contribution (LBL), obtained from the…

High Energy Physics - Phenomenology · Physics 2015-06-03 Tobias Goecke , Christian S. Fischer , Richard Williams

We report preliminary results for the hadronic light-by-light scattering contribution to the muon anomalous magnetic moment. Several ensembles using 2+1 flavors of M\"obius domain-wall fermions, generated by the RBC/UKQCD collaborations,…

High Energy Physics - Lattice · Physics 2019-07-02 Thomas Blum , Norman Christ , Masashi Hayakawa , Taku Izubuchi , Luchang Jin , Chulwoo Jung , Christoph Lehner

We report on our ongoing project to determine the leading-order hadronic vacuum polarisation contribution to the muon $g-2$, using ensembles with $N_f=2+1$ flavours of O($a$) improved Wilson quarks generated by the CLS effort, with pion…

High Energy Physics - Lattice · Physics 2018-12-11 Antoine Gérardin , Tim Harris , Georg von Hippel , Ben Hörz , Harvey Meyer , Daniel Mohler , Konstantin Ottnad , Hartmut Wittig

Hadronic light-by-light (HLbL) scattering defines one of the critical contributions in the Standard-Model prediction of the anomalous magnetic moment of the muon. In this Letter, we present a complete evaluation using a dispersive…

High Energy Physics - Phenomenology · Physics 2025-02-13 Martin Hoferichter , Peter Stoffer , Maximilian Zillinger

One of the most promising quantities for the search of signatures of physics beyond the Standard Model is the anomalous magnetic moment $g-2$ of the muon, where a comparison of the experimental result with the Standard Model estimate yields…

High Energy Physics - Lattice · Physics 2020-02-03 Vera Gülpers

In our previous work, the connected and leading disconnected hadronic light-by-light contributions to the muon anomalous magnetic moment (g - 2) have been computed using lattice QCD ensembles corresponding to physical pion mass generated by…

High Energy Physics - Lattice · Physics 2017-08-30 Thomas Blum , Norman Christ , Masashi Hayakawa , Taku Izubuchi , Luchang Jin , Chulwoo Jung , Christoph Lehner

With the recent interest in the measured and standard model values of the muon anomalous magnetic moment, a_mu, some confusion has arisen concerning our knowledge of the hadronic contribution to a_mu. In the dispersion integral approach to…

High Energy Physics - Phenomenology · Physics 2007-05-23 William J. Marciano , B. Lee Roberts

We calculate the double-virtual $\eta \rightarrow \gamma^* \gamma^*$ transition form factor $\mathcal{F}_{\eta \to \gamma^* \gamma^*}(q_1^2,q_2^2)$ from first principles using a lattice QCD simulation with $N_f=2+1+1$ quark flavors at the…

We use recently evaluated radiative and nonperturbative corrections to production of heavy quarks by a vector current to give very precise theoretical calculations of the high energy ($t^{1/2}\geq \sqrt{2}$ GeV) imaginary part of the photon…

High Energy Physics - Phenomenology · Physics 2007-05-23 K. Adel , F. J. Ynduráin

A key ingredient in the evaluation of hadronic light-by-light (HLbL) scattering in the anomalous magnetic moment of the muon $(g-2)_\mu$ concerns short-distance constraints (SDCs) that follow from QCD by means of the operator product…

High Energy Physics - Phenomenology · Physics 2020-03-16 Gilberto Colangelo , Franziska Hagelstein , Martin Hoferichter , Laetitia Laub , Peter Stoffer

The contribution of pseudoscalar pole diagrams to the hadronic light-by-light corrections of order alpha^3 E_F to the ground state hyperfine splitting in hydrogenic atom is calculated in the pseudoscalar pole terms approximation. The vector…

High Energy Physics - Phenomenology · Physics 2009-11-07 R. N. Faustov , A. P. Martynenko

The leading order hadronic contribution to the muon g-2, $a_{\mu}^{HAD}$, is determined entirely from theory using an approach based on Cauchy's theorem in the complex squared energy s-plane. This is possible after fitting the integration…

High Energy Physics - Phenomenology · Physics 2015-05-28 S. Bodenstein , C. A. Dominguez , K. Schilcher

There are indications that hadronic loops in some electroweak observables are almost saturated by parton level effects. Taking this as the hypothesis for this work, we propose a genuine parton level estimate of the hadronic light-by-light…

High Energy Physics - Phenomenology · Physics 2009-11-11 Jens Erler , Genaro Toledo Sanchez

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…

High Energy Physics - Lattice · Physics 2015-11-18 Luchang Jin , Thomas Blum , Norman Christ , Masashi Hayakawa , Taku Izubuchi , Christoph Lehner