C. Giunti (INFN Torino)

Theories beyond the standard model involving a sub-GeV-scale vector $Z_d$ mediator have been largely studied as a possible explanation of the experimental values of the muon and electron anomalous magnetic moments. Motivated by the recent determination of the anomalous muon magnetic moment performed at Fermilab, we derive the constraints on such a model obtained from the magnetic moment determinations and the measurements of the proton and cesium weak charge, $Q_W$, performed at low-energy transfer. In order to do so, we revisit the determination of the cesium $Q_W$ from the atomic parity violation experiment, which depends critically on the value of the average neutron rms radius of $^{133}\text{Cs}$, by determining the latter from a practically model-independent extrapolation from the recent average neutron rms radius of $^{208}\text{Pb}$ performed by the PREX-2 Collaboration. From a combined fit of all the aforementioned experimental results, we obtain rather precise limits on the mass and the kinetic mixing parameter of the $Z_d$ boson, namely $m_{Z_d} = 47{}^{+61}_{-16} \, \mathrm{MeV}$ and $\varepsilon = 2.3{}^{+1.1}_{-0.4} \times 10^{-3}$, when marginalizing over the $Z-Z_d$ mass mixing parameter $\delta$.
Download the slides here

E.J. Chun (Korea Institute for Advanced Study)

The type-X (lepton-specific) 2HDM allows the presence of a light CP-odd Higgs boson at large tanbeta which can explain the muon g-2 anomaly The model can be extended with an even lighter singlet boson contributing to the muon g-2. We first identify the parameter region consistent with the recent FNAL data while avoiding various experimental constraints, in particular, coming from the lepton universality. Then, we discuss the discovery potential of such a light pseudoscalar at lepton and proton colliders.
Download the slides here

L. Calibbi (Nankai University)

We systematically build and discuss a class of models with minimal field content that can simultaneously provide: (i) a thermal Dark Matter (DM) candidate; (ii) large loop contributions to $b\to s\ell\ell$ processes able to address $R_K$ and the other $B$ anomalies; (iii) a natural solution to the muon $g-2$ discrepancy through chirally-enhanced contributions. We show what are the minimal ingredients and properties necessary to explain both anomalies through loop effects directly involving the DM particles and few other new fields. The general characteristic of this class of models is that the DM phenomenology is controlled by the same parameters that enter the flavour observables. As a consequence, they feature a high degree of correlation among DM, flavour and collider searches and thus an enhanced testability. The new particles are generally heavy enough to evade limits set by LHC searches, but could be in the reach of present and future colliders and direct detection experiments.
Download the slides here

K. Kowalska (National Centre for Nuclear Research Warsaw)

I will discuss a class of simple BSM scenarios that aim at explaining the muon g-2 anomaly and the observed relic density of dark matter. The models involve scalars and VL fermions in various representations of the SU(2) group. The chirality flip in the g-2 loop is driven by the mixing of particles coupled to different chiralities of the muon, which leads to an enhancement of the BSM contribution and allows one to avoid easily the LHC constraints. On the other hand, due to the relatively large number of free parameters in the lagrangian, the parameter space consistent with dark matter and g-2 remains to a large extent unconstrained. Therefore, it is reasonable to look for a UV completion that would increase the predictivity of these scenarios. One option, previously unexplored in this context, is to couple them parametrically to quantum gravity. The presence of the resulting trans-Planckian fixed-point in the system of gauge and Yukawa couplings imposes a set of boundary conditions on the model parameters, which lead to specific low-scale predictions unique for each scenario.
Download the slides here

W. Altmannshofer (UC Santa Cruz)

I will discuss a supersymmetric extension of the Standard Model in which the new physics contributions to the anomalous magnetic moment of the muon can be more than an order of magnitude larger than in the MSSM. The extended electroweak symmetry breaking sector of the model contains additional Higgs bosons and Higgsinos with enhanced couplings to first and second generation fermions. Sleptons with masses in the multi-TeV range can comfortably explain the discrepancy in the anomalous magnetic moment of the muon. I will also discuss additional phenomenological aspects of the model, including flavor changing decays of the tau.
Download the slides here

P. Ferreira (Instituto Politecnico de Lisboa & Universidade de Lisboa)

The recent measurement of the muon g - 2 can be accommodated within the framework of two Higgs doublet models. If one further includes extra fermion content in the form of a generation of vector like leptons, the allowed parameter range that explains the anomaly is further extended. I will show how the muon magnetic moment anomaly can be fitted within these models, under the assumption that the vector-like leptons do not mix with the muon. It is shown that the inclusion of vector-like fermions allows the lepton-specific and muon-specific models to perform much better in fitting the muon g - 2. However, these fits do require the Yukawa coupling between the Higgs and the vector-like leptons to be large, causing potential problems with perturbativity and unitarity.
Download the slides here

H. Baer (University of Oklahoma)

in collaboration with Vernon Barger (University of Wisconsin) and Hasan Serce (University of Oklahoma)

The recent measurement of the muon anomalous magnetic moment $a_\mu\equiv (g-2)_\mu/2$ by the Fermilab Muon g-2 experiment sharpens an earlier discrepancy between theory and the BNL E821 experiment. We examine the predicted $\Delta a_\mu\equiv a_\mu(exp)-a_\mu(th)$ in the context of supersymmetry with low electroweak naturalness (restricting to models which give a plausible explanation for the magnitude of the weak scale). A global analysis including LHC Higgs mass and sparticle search limits points to interpretation within the normal scalar mass hierarchy (NSMH) SUSY model wherein first/second generation matter scalars are much lighter than third generation scalars. We present a benchmark model for a viable NSMH point which is natural, obeys LHC Higgs and sparticle mass constraints and explains the muon magnetic anomaly. Aside from NSMH models, then we find the $(g-2)_\mu$ anomaly cannot be explained within the context of natural SUSY, where a variety of data point to decoupled first/second generation scalars. The situation is worse within the string landscape where first/second generation matter scalars are pulled to values in the 10-50 TeV range. An alternative interpretation for SUSY models with decoupled scalar masses is that perhaps the recent lattice evaluation of the hadronic vacuum polarization could be confirmed which leads to a Standard Model theory-experiment agreement in which case there is no anomaly.
Download the slides here

A. Crivellin (Paul Scherrer Institut & University of Zurich & CERN)

The deviation from the SM prediction in g-2 of the muon can be considered within the larger context of lepton flavour universality violation. The related anomalies include, in addition to g-2 of the muon, b->sll and b->ctaunu processes, the Cabbibo angle anomaly and the CMS measurement of non-resonant di-electrons. After giving an overview of the current situation, I discuss how the anomalies can be explained in terms of new physics.
Download the slides here

F. Jegerlehner (Humboldt University)

I will present a personal view on difficulties in calculating the hadronic contributions to the muon anomaly, with a special focus on the discrepancy between lattice QCD and data-driven dispersive results for the hadronic vacuum polarization.
Download the slides here

L. Darmé (INFN Laboratori Nazionali di Frascati)

Flavourful Feebly-Interacting Particles (FIPs) in the MeV to GeV range have a strong impact on a large variety of precision frontier signatures. We focus in this talk on the current status and prospects of accelerator-based experimental limits and their interplay with the lepton anomalous magnetic momentsmeasurements. In particular, we will tackle the challenging case where the FIP decays mostly into invisible dark sector particles and illustrate the resulting limits with the case of an axion-like particle.
Download the slides here

A. Greljo (University of Bern)

Recent R(K) update from the LHCb experiment at CERN reinforced the tension of B-meson decays into muons. The Muon g-2 experiment at Fermilab strengthened the tension in the muon anomalous magnetic moment. Can muon anomalies be coherently addressed in models beyond the SM, and if so, where else should we look for confirmation? I will discuss extensions of the SM based on 2103.13991 and some work in progress.
Download the slides here

S.C. Park (Yonsei University)

Recently reported anomalies in various B meson decays and also in the anomalous magnetic moment of muon motivate us to consider a particular extension of the standard model incorporating new interactions in lepton and quark sectors simultaneously. Our minimal choice would be leptoquark. In particular, we take vector leptoquark and comprehensively study related observables and see the future perspective of possible tests (2104.06656).
Download the slides here

M. Passera (INFN Padova)

I will discuss the connection of the muon g-2 discrepancy $\Delta a_{\mu}$ to precision electroweak predictions via their common dependence on hadronic vacuum polarization effects. I will also briefly present the recently proposed MUonE experiment at CERN, where fixed-target muon-electron scattering will provide a new direct determination of the leading hadronic contribution to the muon g-2.
Download the slides here

J. Fan (Brown University)

I will review the explanation for the discrepancy between the muon g-2 measurement and the Standard Model prediction, using the loop effects of a heavy axion-like particle. I will then discuss challenges to UV complete this class of explanations.
Download the slides here

D. Cerdeño (Institute for Theoretical Physics UAM-CSIC & Universidad Autonoma de Madrid)

The discrepancy between the measured muon anomalous magnetic moment and the Standard Model prediction might point towards new particle physics models with low-mass mediators that couple to the leptonic sector. In particular, a gauged $U(1)_{L_{\mu}−L_{\tau}}$ stands out for its simplicity, but it is yet indistinguishable from other constructions with a muon-philic vector boson, such as a simplified $U(1)_{L_{\mu}}$ model. In this talk, I will argue that the combined information from future muon fixed target experiments (such as NA64$\mu$), coherent elastic neutrino-nucleus scattering at spallation sources and direct dark matter detection experiments could be used to disentangle these scenarios.
Download the slides here

N. Shah (Wayne State University)

A new measurement of the muon anomalous magnetic moment has been recently reported by the Fermilab Muon g-2 collaboration and shows a $4.2\sigma$ departure from the most precise and reliable calculation of this quantity in the Standard Model. Assuming that this discrepancy is due to new physics, we consider its relation with other potential anomalies, especially in the muon sector, as well as clues from the early universe. We comment on new physics solutions discussed extensively in the literature in the past decades, to finally concentrate on a simple supersymmetric model that also provides a dark matter explanation. We show results for an interesting region of supersymmetric parameter space that can be probed at the high luminosity LHC and future colliders, while leading to values of $(g_{\mu}-2)$ consistent with the Fermilab and Brookhaven $(g_{\mu}-2)$ measurements. Such a parameter region can simultaneously realize a Bino-like dark matter candidate compatible with direct detection constraints for small to moderate values of the Higgsino mass parameter $|\mu|$.
Download the slides here

M. Hoferichter (University of Bern)

I will discuss some aspects of the data-driven evaluation of HVP, including the use of constraints from analyticity and unitarity in the analysis of the experimental data sets and the merging procedure adopted in the white-paper consensus number. In addition, I will comment on the comparison to results from lattice QCD and on future developments to help resolve the current tension.
Download the slides here

T. Teubner (University of Liverpool)

I will introduce the basic ingredients and main features of data-driven evaluations of the HVP contributions to g-2, with emphasis on the methodologies underpinning the global compilations with minimal model-dependence, their differences, and the current status of the input data used in the dispersive approach.
Download the slides here

F. Sannino (Scuola Superiore Meridionale & CP3-Origins & Danish IAS & Università di Napoli Federico II & INFN Napoli)

I will critically present the state-of-the-art of the observed standard model anomalies in flavor physics and in muon g-2 experiment. I will discuss whether the standard model could still be rescued both theoretically and experimentally and whether the anomalies can be considered as serious hints of new physics and what type. In particular I will make the case that the anomalies, especially the g-2 one hint to revived natural models of beyond standard model physics. Looking ahead, I will present possible scenarios of discovery of new physics at colliders and beyond.
Download the slides here

D. Stöckinger (TU Dresden)

We give an overview of g-2 in the general MSSM and describe which parameter regions are viable/promising/excluded in view of LHC constraints, dark matter constraints, and g-2.
Download the slides here