# Particle Physics & Beyond the Standard Model Domain: Fundamental & Quantum Physics · 236 papers indexed · newest 2026-10-29 Higgs precision, the muon g-2 saga, neutrino masses and oscillations, flavor anomalies and collider searches for new physics. Key concepts: muon g-2, Higgs boson, neutrino oscillation, beyond the Standard Model, lepton flavor, new physics, LHC search ## Research dossier (premium) **Particle Physics & Beyond the Standard Model: State of the Field (October 2026)** (v1, updated 2026-10-30; 4,477 words, 60 sources, 30 evidence-mapped claims) 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. - Preview (free): https://space-kitty.com/api/v1/dossiers/particle-physics-bsm/preview - Full dossier ($0.20 via x402): https://space-kitty.com/api/v1/dossiers/particle-physics-bsm - Research pack ($0.20): https://space-kitty.com/api/v1/topics/particle-physics-bsm/pack ## Most influential - **[Measurement of the Positive Muon Anomalous Magnetic Moment to 0.46 ppm](https://space-kitty.com/papers/arxiv:2104.03281)**. B. Abi, T. Albahri, S. Al-Kilani et al. · 2021 · Physical Review Letters (arXiv:2104.03281 · doi:10.1103/physrevlett.126.141801 · 1,273 citations). Source: > 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 cyclotron frequencies for polarized muons in a magnetic storage ring. The storage ring magnetic field is measured using nuclear magnetic resonance probes calibrated in terms of the equivalent proton spin precession frequency ${\\tildeω'^{}\_p}$ in… - **[The anomalous magnetic moment of the muon in the Standard Model](https://space-kitty.com/papers/arxiv:2006.04822)**. T. Aoyama, Nils Asmussen, M. Benayoun et al. · 2020 · Physics Reports (arXiv:2006.04822 · doi:10.1016/j.physrep.2020.07.006 · 1,204 citations). Source: > 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 $\\mathcal{O}(α^5)$ with negligible numerical uncertainty. The electroweak contribution is suppressed by $(m\_μ/M\_W)^2$ and only shows up at the level of the seventh significant digit. It has been evaluated up to two loops and is known to better … - **[The anomalous magnetic moment of the muon in the Standard Model](https://space-kitty.com/papers/doi:10.5167/uzh-191493)**. Andreas Crivellin, Nils Asmussen, M. Benayoun et al. · 2020 · LA Referencia (Red Federada de Repositorios Institucionales de Publicaciones Científicas) (doi:10.5167/uzh-191493 · 1,134 citations). Source: - **[Leading hadronic contribution to the muon magnetic moment from lattice QCD](https://space-kitty.com/papers/doi:10.1038/s41586-021-03418-1)**. Sz. Borsányi, Z. Fodor, Jana N. Guenther et al. · 2021 · Nature (doi:10.1038/s41586-021-03418-1 · 893 citations). Source: - **[Muon g − 2 and α ( M Z 2 ) : A new data-based analysis](https://space-kitty.com/papers/arxiv:1802.02995)**. A. Keshavarzi, Daisuke Nomura B, T. Teubner · 2018 · Physical review. D/Physical review. D. (arXiv:1802.02995 · doi:10.1103/physrevd.97.114025 · 694 citations). Source: > 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 has been placed on the development of a new data combination method, which fully incorporates all correlated statistical and systematic uncertainties in a bias free approach. All available $e^+e^-\\rightarrow {\\rm hadrons}$ cross section da… - **[A new evaluation of the hadronic vacuum polarisation contributions to the muon anomalous magnetic moment and to $$\\varvec{\\alpha }({{\\varvec{m}}}\_{{\\varvec{Z}}}^2)$$](https://space-kitty.com/papers/arxiv:1908.00921)**. Michel Davier A, Andreas Höcker, B. Malaescu et al. · 2020 · The European Physical Journal C (arXiv:1908.00921 · doi:10.1140/epjc/s10052-020-7792-2 · 508 citations). Source: > 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 individual datasets cannot be fully exploited due to discrepancies that lead to additional systematic uncertainty in particular between BABAR and KLOE data in the dominant $π^+π^-$ channel. For the muon $(g-2)/2$, we find for the lowest-ord… - **[Hadronic contribution to the muon anomalous magnetic moment to next-to-next-to-leading order](https://space-kitty.com/papers/arxiv:1403.6400)**. Alexander Kurz, Tao Liu, Peter Marquard et al. · 2014 · Physics Letters B (arXiv:1403.6400 · doi:10.1016/j.physletb.2014.05.043 · 519 citations). Source: > 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, $a\_μ^{\\rm had,NNLO} = 1.24 \\pm 0.01 \\times 10^{-10}$, has the same order of magnitude as the current uncertainty of the leading order hadronic contribution and should thus be included in future analyses. - **[Search for a Dark Photon in e + e − Collisions at BaBar](https://space-kitty.com/papers/arxiv:1406.2980)**. J. P. Lees, Vincent Poireau, V. Tisserand et al. · 2014 · Physical Review Letters (arXiv:1406.2980 · doi:10.1103/physrevlett.113.201801 · 516 citations). Source: > 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 data collected with the BABAR detector. We do not observe a significant signal and we set 90% confidence level upper limits on the mixing strength between the photon and dark photon at the level of 10^-4 - 10^-3 for dark photon masses in the … - **[A call for new physics: The muon anomalous magnetic moment and lepton flavor violation](https://space-kitty.com/papers/arxiv:1610.06587)**. M. Lindner, Moritz Platscher, Farinaldo S. Queiroz · 2018 · Physics Reports (arXiv:1610.06587 · doi:10.1016/j.physrep.2017.12.001 · 508 citations). Source: > 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 have in order to reconcile possible signals coming simultaneously from $g-2$ and lepton flavor violation? What can we learn if the $g-2$ anomaly is confirmed by the upcoming flagship experiments at FERMILAB and J-PARC, and no signal is see… - **[Measurement of the Positive Muon Anomalous Magnetic Moment to 0.20 ppm](https://space-kitty.com/papers/doi:10.1103/physrevlett.131.161802)**. D. P. Aguillard, T. Albahri, D. H. Allspach et al. · 2023 · Physical Review Letters (doi:10.1103/physrevlett.131.161802 · 368 citations). Source: > 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 running conditions, a more stable beam, and improved knowledge of the magnetic field weighted by the muon distribution, ω\[over ˜\]\_{p}^{'}, and of the anomalous precession frequency corrected for beam dynamics effects, ω\_{a}. From the ratio ω\_{a… > _Abstract excerpt by D. P. Aguillard et al., CC-BY, https://doi.org/10.1103/physrevlett.131.161802; truncated._ - **[Hadronic Light-by-Light Scattering Contribution to the Muon Anomalous Magnetic Moment from Lattice QCD](https://space-kitty.com/papers/arxiv:1911.08123)**. Thomas Blum, Norman H. Christ, Masashi Hayakawa et al. · 2020 · Physical Review Letters (arXiv:1911.08123 · doi:10.1103/physrevlett.124.132002 · 418 citations). Source: > 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 volume lattice QED+QCD. We find $a\_μ^{\\rm HLbL} = 7.87(3.06)\_\\text{stat}(1.77)\_\\text{sys}\\times 10^{-10}$. Our value is consistent with previous model results and leaves little room for this notoriously difficult hadronic contribution to e… - **[Remarks on higher-order hadronic corrections to the muon g−2](https://space-kitty.com/papers/arxiv:1403.7512)**. Gilberto Colangelo A, Martin Hoferichter, Andreas Nyffeler C et al. · 2014 · Physics Letters B (arXiv:1403.7512 · doi:10.1016/j.physletb.2014.06.012 · 444 citations). Source: > 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 potentially enhanced such contribution, hadronic light-by-light scattering in combination with electron vacuum polarization, is already sufficiently suppressed. - **[Short-distance constraints for the HLbL contribution to the muon anomalous magnetic moment](https://space-kitty.com/papers/arxiv:1908.03331)**. Johan Bijnens, Nils Hermansson–Truedsson, Antonio Rodríguez–Sánchez · 2019 · Physics Letters B (arXiv:1908.03331 · doi:10.1016/j.physletb.2019.134994 · 377 citations). Source: > 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 loop gives the leading contribution in a well defined expansion. We compute the first nonzero power correction. It is related to to the magnetic susceptibility of the QCD vacuum. The results can be used as model-independent short-distance con… - **[Calculation of the Hadronic Vacuum Polarization Contribution to the Muon Anomalous Magnetic Moment](https://space-kitty.com/papers/arxiv:1801.07224)**. Thomas Blum, P. A. Boyle, Vera Gülpers et al. · 2018 · Physical Review Letters (arXiv:1801.07224 · doi:10.1103/physrevlett.121.022003 · 377 citations). Source: > 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 $a\_μ^{\\rm HVP~LO}=715.4(16.3)(9.2) \\times 10^{-10}$, where the first error is statistical and the second is systematic. By supplementing lattice data for very short and long distances with experimental R-ratio data using the compilation of Ref. \[1\], we significantly improve the precision of… - **[Combined explanations of ( g − 2 ) μ , e and implications for a large muon EDM](https://space-kitty.com/papers/arxiv:1807.11484)**. Andreas Crivellin, Martin Hoferichter, P. Schmidt-Wellenburg · 2018 · Physical review. D/Physical review. D. (arXiv:1807.11484 · doi:10.1103/physrevd.98.113002 · 306 citations). Source: > 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 EDM, which is very precisely measured, excludes a large effect in $d\_μ$. However, the recently observed 2.5$σ$ tension in $a\_e=(g-2)\_e/2$, if confirmed, requires that the muon and electron sectors effectively decouple to avoid constraints f… ## Newest - **[Neutron Optical Constraints on Exotic Parity-odd Interactions between Neutrons and Nucleons](https://space-kitty.com/papers/arxiv:2610.39333)**. V. Kurmangaliyeva, O. Agyl-Mussapar, S. Amangeldinova et al. · 2026 (arXiv:2610.39333). Source: - **[Searching for axion-like particles with space-based optical lattice clock networks](https://space-kitty.com/papers/arxiv:2610.39725)**. Yu-Song Cao, Nick Houston, YanXia Liu et al. · 2026 (arXiv:2610.39725). Source: - **[Two-loop QCD contribution to the quark-initiated production of a top-antitop quark pair and a Higgs boson at the LHC](https://space-kitty.com/papers/arxiv:2610.40266)**. Xiang Chen, Massimiliano Grazzini, Stefan Kallweit · 2026 (arXiv:2610.40266). Source: - **[Probabilistic Energy-Based Neural Networks for Uncertainty-Aware Collider Data Analyses](https://space-kitty.com/papers/arxiv:2610.40268)**. Raymundo Ramos, Ahmed Hammad, Amit Chakraborty et al. · 2026 (arXiv:2610.40268). Source: - **[FCC-μe: High Energy, High Luminosity Muon-Electron Collider & Neutrino Factory at CERN](https://space-kitty.com/papers/arxiv:2610.40451)**. K. Piotrzkowski · 2026 (arXiv:2610.40451). Source: - **[Probing Charged Higgs Bosons through $H^\\pm \\to W^\\pm A$ Decay in the Type-I Two-Higgs Doublet Model](https://space-kitty.com/papers/arxiv:2610.36780)**. Abdesslam Arhrib, Mohamed Krab, Tanmoy Mondal et al. · 2026 (arXiv:2610.36780). Source: - **[Constraining New Physics by Studying Single Top Quark Production](https://space-kitty.com/papers/arxiv:2610.37039)**. Maryam Roknabadi, Saeid Paktinat Mehdiabadi, Seyed Mohammad Reza Tabatabaei · 2026 (arXiv:2610.37039). Source: - **[Probing new $C\\!P$-violating sources in $Λ\_b\\toΛ\_c\\ell^-\\barν\_\\ell$](https://space-kitty.com/papers/arxiv:2610.37106)**. Dong-Hao Li, Meng-Chao Gao, Qin Qin et al. · 2026 (arXiv:2610.37106). Source: - **[Searches for new particle physics by methods of classical and neutrino astronomy](https://space-kitty.com/papers/arxiv:2610.37198)**. Sergey Troitsky · 2026 (arXiv:2610.37198). Source: - **[Search for Neutrino-Produced Long-Lived Particles Using the SBND Cosmic Ray Tagger Beam Telescope](https://space-kitty.com/papers/arxiv:2610.37555)**. R. Acciarri, L. Aliaga-Soplin, D. Andrade Aldana et al. · 2026 (arXiv:2610.37555). Source: --- Space Kitty Archive · https://space-kitty.com · API: https://space-kitty.com/api/v1 · MCP: https://space-kitty.com/mcp · Premium: $0.20/request via x402 (Base Sepolia (testnet)). Metadata: arXiv (CC0), OpenAlex (CC0), Europe PMC (CC BY/CC0 works), ClinicalTrials.gov.