scholarly journals Holographic QCD and the muon anomalous magnetic moment

2021 ◽  
Vol 81 (11) ◽  
Author(s):  
Josef Leutgeb ◽  
Jonas Mager ◽  
Anton Rebhan
Keyword(s):  
Magnetic Moment ◽  
Anomalous Magnetic Moment ◽  
Short Distance ◽  
Axial Vector ◽  
Distance Constraint ◽  
Vector Mesons ◽  
Goldstone Bosons ◽  
Holographic Qcd ◽  
Scattering Contribution ◽  
Made In

AbstractWe review the recent progress made in using holographic QCD to study hadronic contributions to the anomalous magnetic moment of the muon, in particular the hadronic light-by-light scattering contribution, where the short-distance constraints associated with the axial anomaly are notoriously difficult to satisfy in hadronic models. This requires the summation of an infinite tower of axial vector mesons, which is naturally present in holographic QCD models, and indeed takes care of the longitudinal short-distance constraint due to Melnikov and Vainshtein. Numerically the results of simple hard-wall holographic QCD models point to larger contributions from axial vector mesons than assumed previously, while the predicted contributions from pseudo-Goldstone bosons agree nicely with data-driven approaches.

scholarly journals The LbL contribution to the muon g-2 from the axial-vector mesons exchanges within the nonlocal quark model

2019 ◽  
Vol 212 ◽  
pp. 05001 ◽  
Author(s):  
A.E. Dorokhov ◽  
A.P. Martynenko ◽  
F.A. Martynenko ◽  
A.E. Radzhabov ◽  
A.S. Zhevlakov
Keyword(s):  
Quark Model ◽  
Magnetic Moment ◽  
Anomalous Magnetic Moment ◽  
Axial Vector ◽  
Chiral Quark Model ◽  
Vector Mesons ◽  
Muon Anomalous Magnetic Moment

The light-by-light contribution from the axial-vector (AV) mesons exchanges to the muon anomalous magnetic moment is estimated in the framework of the nonlocal chiral quark model. The preliminary answer for contributions from a1 and f1 mesons to (g − 2)µ is 0.34 · 10−11 and does not support the Melnikov-Vainshtein estimate 2.2 · 10−11.

scholarly journals Electroweak fermion triangle loop contributions to the muon anomalous magnetic moment revisited

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Ken Sasaki
Keyword(s):  
Magnetic Moment ◽  
Top Quark ◽  
Anomalous Magnetic Moment ◽  
Ward Identity ◽  
Axial Vector ◽  
Goldstone Boson ◽  
Muon Anomalous Magnetic Moment ◽  
Feynman Gauge ◽  
Unitary Gauge ◽  
The One

Abstract The contribution to the muon anomalous magnetic moment from the fermion triangle loop diagrams connected to the muon line by a photon and a $Z$ boson is re-analyzed in both the unitary gauge and the ’t Hooft–Feynman gauge. With use of the anomalous axial-vector Ward identity, it is shown that the calculation in the unitary gauge exactly coincides with the one in the ’t Hooft–Feynman gauge. The part which arises from the ordinary axial-vector Ward identity corresponds to the contribution of the neutral Goldstone boson. For the top-quark contribution, the one-parameter integral form is obtained up to the order of $m_\mu^2/m_Z^2$. The results are compared with those obtained by the asymptotic expansion method.

scholarly journals The interplay of transverse degrees of freedom and axial-vector mesons with short-distance constraints in g−2

2021 ◽  
Author(s):  
Pere Masjuan ◽  
Pablo Roig ◽  
Pablo Sanchez Puertas
Keyword(s):  
Short Distance ◽  
Degrees Of Freedom ◽  
Axial Vector ◽  
Form Factors ◽  
Experimental Result ◽  
Special Focus ◽  
Vector Mesons ◽  
Distance Constraints ◽  
The Past

Abstract We revisit well-known short-distance constraints relating the hadronic light-by light Green's function to the〈VVA〉one, that have been a subject of debate over the past years in the context of the muon (g-2). Specifically, we identify a relation among the longitudinal and transverse degrees of freedom that is enforced by the axial anomaly that, by contrast, has not received attention in the past. Such relation allows, among other things, to overcome the problem of basis ambiguities when describing axial-vector mesons transition form factors, but further applications are discussed as well, with special focus on the role of axial-vector mesons in the HLbL contribution to the muon (g-2). Our results should also contribute to a better understanding of the, so far, controversial interplay among short-distance constraints with longitudinal and transverse degrees of freedom, such as axial-vector mesons. This is key to confront the theoretical and experimental result for the muon (g-2) that, currently, exhibits a 4.2σ tension.

scholarly journals Some analytic results for the contribution to the anomalous magnetic moments of leptons due to the polarization of vacuum via lepton loops

2019 ◽  
Vol 222 ◽  
pp. 03007 ◽  
Author(s):  
Olga Solovtsova ◽  
Vasil Lashkevich ◽  
Alexander Sidorov
Keyword(s):  
Magnetic Moment ◽  
Anomalous Magnetic Moment ◽  
Magnetic Moments ◽  
Mass Ratio ◽  
Mass Dependent ◽  
Made In

We present some new exact expressions for the contribution of the mass-dependent three-bubble diagrams to the anomalous magnetic moment of leptons L = e, µ and τ. A comparison with the analytic expansions in terms of the mass ratio mℓ/mL made in the literature, whenever relevant, is discussed.

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