Particle Physics & Beyond the Standard Model
Higgs precision, the muon g-2 saga, neutrino masses and oscillations, flavor anomalies and collider searches for new physics.
Particle Physics & Beyond the Standard Model: State of the Field (October 2026)
This dossier covers the muon anomalous magnetic moment and the hadronic inputs that limit its Standard Model prediction, lepton flavor and flavor-anomaly tests, neutrino mass measurements and direct searches for light or long-lived new states. The main takeaway is that the 2025 Fermilab result has sharpened the muon g-2 test, while hadronic vacuum polarization remains the dominant uncertainty and no confirmed new-physics signal is established in the sources reviewed.
Most influential
- Measurement of the Positive Muon Anomalous Magnetic Moment to 0.46 ppm
We present the first results of the Fermilab Muon g-2 Experiment for the positive muon magnetic anomaly $a_μ\equiv (g_μ-2)/2$. The anomaly is determined from the precision measurements of two angular frequencies. Intensity variation of high-energy positrons from muon decays directly encodes the difference frequency $ω_a$ between the spin-precession and cyclo…
Article1,273 citationsarXiv:2104.03281doi:10.1103/physrevlett.126.141801 - The anomalous magnetic moment of the muon in the Standard Model
We review the present status of the Standard Model calculation of the anomalous magnetic moment of the muon. This is performed in a perturbative expansion in the fine-structure constant $α$ and is broken down into pure QED, electroweak, and hadronic contributions. The pure QED contribution is by far the largest and has been evaluated up to and including $\ma…
Article1,204 citationsarXiv:2006.04822doi:10.1016/j.physrep.2020.07.006 - The anomalous magnetic moment of the muon in the Standard ModelArticle1,134 citationsdoi:10.5167/uzh-191493
- Leading hadronic contribution to the muon magnetic moment from lattice QCDArticle893 citationsdoi:10.1038/s41586-021-03418-1
- Muon g − 2 and α ( M Z 2 ) : A new data-based analysis
This work presents a complete re-evaluation of the hadronic vacuum polarisation contributions to the anomalous magnetic moment of the muon, $a_μ^{\rm had, \, VP}$ and the hadronic contributions to the effective QED coupling at the mass of the $Z$ boson, $Δα_{\rm had}(M_Z^2)$, from the combination of $e^+e^-\rightarrow {\rm hadrons}$ cross section data. Focus…
Article694 citationsarXiv:1802.02995doi:10.1103/physrevd.97.114025 - A new evaluation of the hadronic vacuum polarisation contributions to the muon anomalous magnetic moment and to $$\varvec{\alpha }({{\varvec{m}}}_{{\varvec{Z}}}^2)$$
We reevaluate the hadronic vacuum polarisation contributions to the muon magnetic anomaly and to the running of the electromagnetic coupling constant at the $Z$-boson mass. We include newest $e^+e^- \to$ hadrons cross-section data together with a phenomenological fit of the threshold region in the evaluation of the dispersion integrals. The precision in the …
Article508 citationsarXiv:1908.00921doi:10.1140/epjc/s10052-020-7792-2 - Hadronic contribution to the muon anomalous magnetic moment to next-to-next-to-leading order
We compute the next-to-next-to-leading order hadronic contribution to the muon anomalous magnetic moment originating from the photon vacuum polarization. The corresponding three-loop kernel functions are calculated using asymptotic expansion techniques which lead to analytic expressions. Our final result, $a_μ^{\rm had,NNLO} = 1.24 \pm 0.01 \times 10^{-10}$,…
Article519 citationsarXiv:1403.6400doi:10.1016/j.physletb.2014.05.043 - Search for a Dark Photon in e + e − Collisions at BaBar
Dark sectors charged under a new Abelian force have recently received much attention in the context of dark matter models. These models introduce a light new mediator, the so-called dark photon (A'), connecting the dark sector to the Standard Model. We present a search for a dark photon in the reaction e+e- -> gamma A', A'-> e+e-, mu+mu- using 514 fb-1 of da…
Article516 citationsarXiv:1406.2980doi:10.1103/physrevlett.113.201801 - A call for new physics: The muon anomalous magnetic moment and lepton flavor violation
We review how the muon anomalous magnetic moment ($g-2$) and the quest for lepton flavor violation are intimately correlated. Indeed the decay $μ\to e γ$ is induced by the same amplitude for different choices of in- and outgoing leptons. In this work, we try to address some intriguing questions such as: Which hierarchy in the charged lepton sector one should…
Article508 citationsarXiv:1610.06587doi:10.1016/j.physrep.2017.12.001 - Measurement of the Positive Muon Anomalous Magnetic Moment to 0.20 ppm
We present a new measurement of the positive muon magnetic anomaly, a_{μ}≡(g_{μ}-2)/2, from the Fermilab Muon g-2 Experiment using data collected in 2019 and 2020. We have analyzed more than 4 times the number of positrons from muon decay than in our previous result from 2018 data. The systematic error is reduced by more than a factor of 2 due to better runn…
Abstract excerpt by D. P. Aguillard et al., CC-BY, https://doi.org/10.1103/physrevlett.131.161802; truncated.
Article368 citationsdoi:10.1103/physrevlett.131.161802 - Hadronic Light-by-Light Scattering Contribution to the Muon Anomalous Magnetic Moment from Lattice QCD
We report the first result for the hadronic light-by-light scattering contribution to the muon anomalous magnetic moment with all errors systematically controlled. Several ensembles using 2+1 flavors of physical mass Möbius domain-wall fermions, generated by the RBC/UKQCD collaborations, are employed to take the continuum and infinite volume limits of finite…
Article418 citationsarXiv:1911.08123doi:10.1103/physrevlett.124.132002 - Remarks on higher-order hadronic corrections to the muon g−2
Recently, it was shown that insertions of hadronic vacuum polarization at O(alpha^4) generate non-negligible effects in the calculation of the anomalous magnetic moment of the muon. This result raises the question if other hadronic diagrams at this order might become relevant for the next round of g-2 measurements as well. In this note we show that a potenti…
Article444 citationsarXiv:1403.7512doi:10.1016/j.physletb.2014.06.012 - Short-distance constraints for the HLbL contribution to the muon anomalous magnetic moment
We derive short-distance constraints for the hadronic light-by-light contribution (HLbL) to the anomalous magnetic moment of the muon in the kinematic region where the three virtual momenta are all large. We include the external soft photon via an external field leading to a well-defined Operator Product Expansion. We establish that the perturbative quark lo…
Article377 citationsarXiv:1908.03331doi:10.1016/j.physletb.2019.134994 - Calculation of the Hadronic Vacuum Polarization Contribution to the Muon Anomalous Magnetic Moment
We present a first-principles lattice QCD+QED calculation at physical pion mass of the leading-order hadronic vacuum polarization contribution to the muon anomalous magnetic moment. The total contribution of up, down, strange, and charm quarks including QED and strong isospin breaking effects is found to be $a_μ^{\rm HVP~LO}=715.4(16.3)(9.2) \times 10^{-10}$…
Article377 citationsarXiv:1801.07224doi:10.1103/physrevlett.121.022003 - Combined explanations of ( g − 2 ) μ , e and implications for a large muon EDM
With the long-standing tension between experiment and Standard-Model (SM) prediction in the anomalous magnetic moment of the muon, $a_μ=(g-2)_μ/2$, at the level of 3-4$σ$, it is natural to ask if there could be a sizable effect in the electric dipole moment (EDM) $d_μ$ as well. In this context it has often been argued that in UV complete models the electron …
Article306 citationsarXiv:1807.11484doi:10.1103/physrevd.98.113002
Newest work
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