9th Plenary Workshop of the Muon g-2 Theory Initiative

Aug 3, 2026, 8:30 AM → Aug 7, 2026, 5:00 PM America/New_York

GS117 and GS119 (Department of Physics, University of Connecticut)

Thomas Blum (UConn), Luchang Jin (UCONN)

Workshop website (this website): https://indico.phys.uconn.edu/e/muon-g-2-2026

The 9th Plenary Workshop of the Muon g-2 Theory Initiative hosted by the University of Connecticut (UCONN) will be held on August 3-7, 2026. The aim of the workshop is to work towards reducing the total error on the Standard Model value of muon anomalous magnetic moment to the level of the Fermilab experiment (124 ppb) and resolve discrepancies between lattice QCD and data-driven approaches for the hadronic vacuum polarization contribution which dominates the total theoretical uncertainty. This series of workshops began with the formation of the theory initiative in 2017. The first plenary workshop was held near Fermilab in St. Charles, Illinois, in June 2017 and last year's was at the Irène Joliot-Curie Lab (Paris-Saclay) in Bures-sur-Yvette, France, in September 2025. More details and a complete list of workshops can be found on the Muon g-2 Theory Initiative website (follow the above link).

 

Financial support for early career researchers

There is limited support available for early career attendees. If you are an early career researcher (e.g., graduate student) needing financial support to attend the workshop, please email the local organizers with Subject "Application for financial support" (thomas.blum@uconn.edu and ljin.luchang@gmail.com). The email should include your current position, institution, and advisor and should briefly describe your current research and whether you have submitted an abstract, or not. The deadline for requests is 06/30/2026.

Important dates

• Registration and abstract submission deadline: 05/29/2026
• Early career support request deadline: 06/30/2026
• Workshop: Aug 3 - Aug 7, 2026

dinner 2.jpeg

dinner 3.jpeg

dinner 4.jpeg

The hikers

Workshop Group Photo

Workshop Poster.pptx

Mon, August 3

8:30 AM → 9:20 AM Registration + Coffee + Snack

9:20 AM → 9:30 AM Welcome

welcome-slides.pdf

9:30 AM → 10:20 AM Experimental inputs HVP

Convener: Riccardo Aliberti (JGU Mainz)

9:30 AM Exp inputs HVP CMD2/3 by Vanya Logashenko

Speaker: Ivan Logashenko (BINP)

Logashenko_CMD_TI_2026_08.pdf

9:50 AM e+e- -> pi+pi- generation using KKMC

Events from the $e^+e^- \to \mu^+\mu^-$ process are cleanly identifiable at the Belle II experiment. To simulate the $e^+e^- \to \pi^+\pi^-$ process, angular distributions from a final state of two spin-1/2 particles can be reweighted to a final state of two pseudoscalar particles using the KK2F Monte Carlo generator. Variations in photon radiation, evaluated using the Collins-Soper and Mustraal frames, account for the leading systematic uncertainty in the process. Higher-order bremsstrahlung corrections are specifically studied, and their implementation is validated.

Speaker: Swagato Banerjee (University of Louisville)

EE2PiPi.pdf

10:20 AM → 10:50 AM Coffee break

10:50 AM → 11:50 AM Experimental inputs HVP

Convener: Swagato Banerjee (University of Louisville)

10:50 AM Exp inputs HVP from KLOE

Speaker: Lorenzo Punzi (Scuola Normale Superiore and INFN Pisa)

TI_03_08_26.pdf

11:20 AM Exp inputs HVP from BESIII

Speaker: Riccardo Aliberti (JGU Mainz)

Muon_g-2_general_workshop_2026.pdf

11:50 AM → 12:05 PM Exp input HVP Discussion

Conveners: Achim Denig (JGU and HIM Mainz), Thomas Teubner (University of Liverpool)

12:05 PM → 1:35 PM Lunch

1:35 PM → 2:20 PM Exp input HVP Discussion

Conveners: Achim Denig (JGU and HIM Mainz), Thomas Teubner (University of Liverpool)

2:20 PM → 3:15 PM MC, radiative corrections

Convener: Maarten Golterman (San Francisco State University)

2:20 PM Overview on radiative corrections and Monte Carlo codes: an update on the RadioMonteCarlow2 activities

The development of precise event generators for $e^+$ $e^-$ colliders
and a thorough assessment of the uncertainties associated with the
Monte Carlo simulations are the essential ingredients for sound estimates
of the muon anomalous magnetic moment with the data-driven approach.
A general overview of the RadioMonteCarLow 2 effort is presented with an
update on recent developments.

Speaker: Fulvio Piccinini (INFN Pavia and GGI Arcetri)

piccinini.pdf

2:50 PM McMule update

With McMule, fully differential predictions for the radiative process $e^+e^-\to\mu^+\mu^-\gamma$ including NNLO initial-state corrections are now available.

Furthermore, we also calculate $e^+e^-\to\pi^+\pi^-\gamma$ at NLO by applying form-factor scalar QED wherever it is physically justified. By considering additional contributions, we gain insights into the associated theory uncertainty.

I will present selected results for RadioMonteCarLow2 scenarios, highlight the main challenges and underlying methods, and outline the path forward.

Speaker: Sophie Kollatzsch (PSI / UZH)

mcmule-TI9.pdf

3:15 PM → 3:45 PM Coffee break

3:45 PM → 4:45 PM MC, radiative corrections

Convener: Carleton DeTar (University of Utah)

3:45 PM High-precision Monte Carlo predictions for radiative return with BabaYaga@NLO

To resolve the tension between lattice QCD and data-driven evaluations of the hadronic
vacuum polarization contribution to the muon anomaly $a_\mu$, precise cross-section measurements
of the dominant $\pi^+\pi^-$ channel are highly relevant. The radiative return process
$e^+e^- \to \pi^+\pi^-\gamma$ at flavor factories is essential for extracting this
cross section below $2\,\mathrm{GeV}$, requiring tight control over theoretical systematic uncertainties.

To this end, we present the first calculation of QED
next-to-leading order (NLO) corrections to radiative pion and muon pair production in
$e^+e^-$ annihilation, matched to a QED Parton Shower (PS) algorithm for fully exclusive
simulations, achieving NLOPS accuracy. For the dipion channel, we go beyond the
factorized approach (FxsQED) to evaluate structure-dependent corrections by
including the pion form factor in the one-loop
amplitudes according to different formulations. These developments are implemented in a new version of the
BabaYaga@NLO event generator, and we present the corresponding
phenomenological results for $e^+e^- \to X^+X^-\gamma$ ($X=\mu,\pi$) in different experimental scenarios from 1 GeV to 10 GeV.

Speaker: Marco Ghilardi (University of Pavia-INFN Section of Pavia)

BabaYaga_radiative_Talk_TI2026-2.pdf

4:15 PM Phokhara beyond NLO -- an update

In this talk, we present recent progress in extending PHOKHARA beyond NLO precision. First, we report new results for the pion-pair channel, incorporating the Generalised Vector Dominance Model as an improvement over the usual point-like treatment of pions. We then present the implementation of soft-photon resummation and discuss ongoing work on additional next-to-next-to-leading-order (NNLO) corrections.

Speaker: William Torres Bobadilla (University of Liverpool)

TorresBobadilla.pdf

4:45 PM → 5:15 PM MC RC Discussion

Conveners: Thomas Teubner (University of Liverpool), Achim Denig (JGU and HIM Mainz)

5:15 PM → 5:30 PM Break

5:30 PM → 8:00 PM Reception & poster

5:30 PM Dark Photon Search at BESIII using Initial State Radiation

Speaker: Maurice Anderson (Johannes Gutenberg University Mainz)

01 Poster_Prelim_Anderson_DarkPhoton.pdf

5:50 PM Towards the hadronic light-by-light contribution to the muon g−2 with C∗boundary conditions

Speaker: Khai Phan (ETH Zurich)

Khai Phan poster_gm2_2026.pdf

Tue, August 4

9:00 AM → 9:50 AM Dispersion HVP

Convener: Davide Giusti (Forschungszentrum Jülich)

9:00 AM Hadronic Vacuum Polarisation Contributions to Muon g-2: KNTW Update

Significant tensions impede dispersive evaluations of hadronic vacuum polarisation (HVP) contributions to the muon anomalous magnetic moment $a_\mu$. I will give a progress update discussing improvements to the still blinded KNTW (Keshavarzi-Nomura-Teubner-Wright) HVP analysis procedure, the results from which will form a critical component of future $a_\mu$ evaluations.

Speaker: Aidan Wright (University of Liverpool)

AWright_TI9_KNTW_Dispersive (10).pdf

9:30 AM Data-driven HVP in a_\mu, a_e and muonic atoms

Speakers: Bogdan Malaescu (LPNHE, CNRS), Vladimir Pascalutsa

Pascalutsa_TheoryInit_9Plenary_Aug4_2026.pdf

9:50 AM → 10:20 AM Coffee break

10:20 AM → 10:45 AM Dispersion HVP

Convener: Steven Gottlieb (Indiana University)

10:20 AM The pion vector form factor with explicit inelasticities

Speaker: Leon Heuser (HISKP, University of Bonn)

Heuser_VFF.pdf

10:45 AM → 11:50 AM Disp HVP Discussion

Conveners: Martin Hoferichter (University of Bern), Thomas Leplumey (LLR / Ecole Polytechnique), Peter Stoffer (UZH and PSI)

Slides_HVP_final.pdf

11:50 AM → 12:30 PM MC RC Discussion

Conveners: Thomas Teubner (University of Liverpool), Achim Denig (JGU and HIM Mainz)

12:30 PM → 2:00 PM Lunch

2:00 PM → 2:25 PM Tau decay exp

Convener: Maarten Golterman (San Francisco State University)

2:00 PM Tau decay measurements at BESIII and super tau-charm factory

According to the conserved vector current theorem, the tau lepton decays could be utilized to calculate the hadronic vacuum polarization (HVP) contribution to the muon anomaly. For example, the decay rate of tau -> 2pi nu is related to the cross section of e+e- -> pi+pi- which gives the dominant contribution to the HVP at low energies. Operating in the tau–charm energy region and having accumulated large data samples, BESIII offers excellent opportunities for precision measurements of various tau decays. In addition, the super tau-charm factory (STCF) is expected to produce massive tau leptons, which enables an improved measurement of tau decays. In this presentation, we will introduce the current plan and status of tau decay measurement at BESIII. discussed, the potential of tau decay study at STCF will also be presented.

Speaker: Christoph Florian Redmer (JGU Mainz)

CFR260804.pdf

2:25 PM → 3:25 PM Tau and IB corrections

Convener: Marina Krstic Marinkovic (ETH Zurich)

2:25 PM RBC/UKQCD results

Speaker: Mattia Bruno (Univesita' di Milano-Bicocca)

uconn-bruno.pdf

2:55 PM Comparison of the hadronic vacuum polarization between hadronic $\tau$-decay data and the lattice

We compare the isospin-one hadronic vacuum polarization (HVP) obtained from isospin-symmetric lattice QCD with that obtained from a dispersive representation employing inclusive hadronic $\tau$ decay data corrected for isospin breaking. We consider the subtracted HVP evaluated at momenta ranging from $0.5$ GeV$^2$ to $12$~GeV$^2$, together with the light-quark-connected HVP contribution to the muon anomalous magnetic moment and the short-, intermediate- and long-distance RBC/UKQCD window components thereof. Contributions from hadronic invariant masses above the $\tau$ mass are evaluated using perturbative QCD. We also consider dispersive determinations using $\tau$ data only for contributions from two-pion, or two-pion and four-pion, modes, and evaluating the remaining contributions using exclusive-mode $e^+e^-\to\mbox{hadrons}$ cross sections up to about 2 GeV. We find generally good agreement between lattice and $\tau$-based results, but we find some discrepancies between $\tau$-based and $e^+e^-$-based four-pion spectral distributions.

Speaker: Maarten Golterman (San Francisco State University)

tau_lattice_Golterman.pdf

3:25 PM → 3:55 PM Coffee break

3:55 PM → 5:00 PM Tau and IB corrections

Convener: Shaun Lahert (University of Utah)

3:55 PM Bern group results

Speaker: Martin Hoferichter (University of Bern)

Slides_hoferichter_tau.pdf

4:15 PM Short distance contribtions

Speaker: Vincenzo Cirigliano (University of Washington)

tau-2026-cirigliano.pdf

4:40 PM Isospin breaking in rho parameters

Speaker: Gabriel Lopez Castro (Departamento de Fisica, Cinvestav, Mexico)

TI-GLC-4Aug-sm.pdf

5:00 PM → 6:00 PM Tau and IB Discussion: complete calculation of IB corrections

Convener: Maarten Golterman (San Francisco State University)

5:00 PM Tau isospin breaking discussion

Speaker: Mattia Bruno (Università di Milano-Bicocca)

discussion.pdf

Wed, August 5

9:00 AM → 10:00 AM Muon g-2 experiments

Convener: Siyuan Li (Johannes Gutenberg-Universität Mainz (JGU))

9:00 AM Experiment Update J-PARC

Speaker: Takashi Yamanaka (Kyushu University)

J-PARC_g2_9thTheoryInitiative_260805.pdf

9:30 AM BSM searches with the Fermilab Muon g-2 Experiment

With the publication of our final result on $a_{\mu}$, the collaboration is focussing on three Beyond the Standard Model (BSM) searches. They are searches for a muon EDM, an Ultralight Scalar DM, and violation of CPT and Lorentz Invariance. These analyses are built upon the $a_{\mu}$ data products and are nearing completion. I will review the physics signatures, the systematic errors, and our expected sensitivity using the Run 2/3 dataset.

Speaker: Hogan Nguyen (Fermilab)

g-2 BSM physics theory workshop with Fermilab template.key

10:00 AM → 10:30 AM Coffee break

10:30 AM → 12:30 PM Lattice HVP

Convener: Steven Gottlieb (Indiana University)

10:30 AM The Muon g-2 HVP contribution from the BMW/DMZ collaboration

We present a complete calculation of the hadronic vacuum polarization contribution to the muon magnetic anomaly reaching the sub-5‰ precision level. Our result, recently published in Nature, constitues an unprecedented validation of the Standard Model, at the given accuracy, in explaining the experimental measurement world average of $a_\mu$, agreeing with the latter at 0.5 standard deviations.
Several intermediate quantities used as benchmarks for lattice calculations, the so-called Euclidean time-distance windows, will be addressed in the talk.

Speaker: Bálint Tóth (University of Wuppertal)

tothb_uconn25.pdf

11:00 AM Update on $a_\mu^\text{HVP, isoQCD}$ from the ETM collaboration

In this talk we review the status of the lattice calculation of the Hadronic Vacuum Polarization (HVP) contribution to $a_\mu=(g-2)_\mu$ from the ETM collaboration.
Our result includes the effects of the $u,d,s,c$ quarks in the isospin-symmetric limit of QCD. Our ensembles are generated with $N_f=2+1+1$ dynamical flavors through Wilson-clover twisted mass fermions, and our correlators are tuned at physical point to permille precision.

Speaker: Simone Romiti (University of Bern)

main.pdf

11:30 AM Lattice HVP from FNAL/HPQCD/MILC

Speaker: Shaun Lahert (University of Utah)

g_2workshop_conn_ShaunLahert.pdf

12:00 PM Mainz status update

We present the Mainz update on the determination of the hadronic vacuum polarization contribution to the muon $g-2$. We discuss ongoing improvements to our dataset and ensemble set aimed at better constraining the chiral–continuum extrapolation, as well as our efforts toward a complete estimate of isospin-breaking effects. In addition, we report on our progress in the determination of satellite observables relevant to the anomalous magnetic moment.

Speaker: Arnau Beltran (JGU Mainz)

HVPMainz.pdf

12:30 PM → 2:00 PM Lunch & SC members meeting

2:00 PM → 3:30 PM Lattice HVP

Convener: Bálint Tóth (University of Wuppertal)

2:00 PM Lattice HVP from RBC/UKQCD

Speaker: Julian Parrino (Universität Regensburg)

gm2_2026_Parrino.pdf

2:30 PM Lattice HVP with RC*

Speaker: Marina Krstic Marinkovic (ETH Zurich)

Marinkovic_UConn_080526_v3.pdf

3:00 PM Lattice HVP from Aubin et al.

Speaker: Vaishakhi Moningi (University of Connecitcut)

9th_plenary_g_2.pdf

3:30 PM → 4:00 PM Coffee break

4:00 PM → 4:15 PM Lattice HVP

Convener: Bálint Tóth (University of Wuppertal)

4:00 PM PACS Collaboration for Muon g-2 Precision Physics

I will report on the launch of the lattice QCD project by the PACS Collaboration (PACSc) for muon g-2 precision physics in collaboration with the J-PARC experiments. Using the Fugaku supercomputer, the PACSc has generated PACS10 gauge ensembles by adopting the stout-smeared O(a) improved Wilson-clover quark action and the Iwasaki gauge action at the physical pion/kaon masses on the lattice with the spatial extent of 10 fm for lattice spacings 0.09 fm (128^4), 0.06 fm (160^4), and 0.04 fm (256^4). The flavor contents are Nf=2+1 and Nf=2+1+1. This opens a new possibility to calculate hadronic contributions to the muon g-2 and related quantities with precision required by the J-PARC and FNAL measurements. I will how the motivation, strategy, and the roadmap. As a first step, the PACSc focuses on the pion form factor and its comparison with results by data-deiven approaches, with the goal of clarifying the origin of tensions reported in the muon g-2.

Speaker: Kohtaroh Miura (University of Tsukuba)

kohtaroh_miura.pdf

4:15 PM → 5:15 PM Lattice HVP short talks

Convener: Urs Wenger (University of Bern)

4:15 PM The lattice scale setting procedure in the BMW/DMZ muon (g-2) calculation

The lattice scale setting already represents, and will increasingly become in the future, one of the leading sources of uncertainty in first-principles calculations of the HVP contribution to $(g_\mu-2)$.
In this talk, I will discuss the procedure adopted in the BMW/DMZ collaboration calculation, which currently provides the most precise Standard Model determination of the muon anomalous magnetic moment at the frontier of sub-5‰ precision. To this end, the pion decay constant was employed, and achieving the desired precision target required controlling the radiative corrections to its leptonic decay on the lattice.

Speaker: Davide Giusti (Forschungszentrum Jülich)

Giusti_gm2TI26-1.pdf

4:30 PM Improved calculational setup for isospin-breaking corrections to the HVP contribution

Isospin-breaking corrections to the hadronic vacuum polarisation
contribution to the muon g-2 dominate the error of recent lattice
calculations. It is therefore crucial to reduce the uncertainties
coming from these contributions to reach the overall target
precision. I will present preliminary results from a new calculational
setup that improves the statistical precision for constant numerical
cost. Additionally, contributions coming from disconnected diagrams,
on which only very few lattice calculations exist, can now be computed
with reasonable numerical effort.

Speaker: Sebastian Lahrtz

Talk_G2_UConn_2026.pdf

4:45 PM Improved estimators for the HVP

Speaker: Christoph Lehner (University of Regensburg)

lehner.pdf

5:00 PM Spurion Matching of HVP and HLbL Diagrams

Chiral perturbation theory ($\chi$PT) is the effective field theory (EFT) of QCD at low energies and is routinely used to complement lattice QCD analyses. EFT matching can be used to relate objects, such as operators and correlators, in the UV theory (QCD) to those in the IR EFT ($\chi$PT). In this talk, we present a charge matrix spurion analysis to match diagrams with external vector currents utilizing QED isospin structure. The diagrams considered are relevant for QED corrections to the hadronic vacuum polarization for muon $g-2$.

Speaker: Jake Sitison (University of Colorado Boulder)

Sitison_SpurionMatching_gm2_2026.pdf

5:15 PM → 6:15 PM Lat HVP Discussions

Convener: Christoph Lehner (University of Regensburg)

5:15 PM Lattice HVP discussions

Speaker: Christoph Lehner (University of Regensburg)

discussion.pdf

Thu, August 6

9:00 AM → 9:20 AM Experimental inputs HVP

Convener: Mattia Bruno (Univesita' di Milano-Bicocca)

9:00 AM Status of the Experimental Inputs for HVP by SND

New results of the $e^+e^- \to \pi^+\pi^-$ and $e^+e^- \to \pi^+\pi^-\pi^0$ cross section measurements, performed by SND collaboration.

Speaker: Andrey Kupich (BINP)

GM2W2026.pdf

9:20 AM → 9:45 AM MUonE

Convener: Christian Zimmermann (University of Kentucky)

9:20 AM Status and plans for MUonE experiment

Speaker: Riccardo Nunzio Pilato (University of Liverpool)

MUonE_TI2026_RP.pdf

9:45 AM → 10:15 AM Coffee break

10:15 AM → 10:45 AM Connections

Convener: Riccardo Aliberti (JGU Mainz)

10:15 AM The running of the electroweak gauge couplings from first principles

Precision measurements provide a powerful probe of physics beyond the Standard Model, but their sensitivity is often limited by our ability to control hadronic effects. In this talk, I will focus on the hadronic contribution to the running of the electroweak gauge couplings, with particular emphasis on $\Delta\alpha_{\mathrm{had}}^{(5)}(M_Z^2)$.

I will present a recent high-precision lattice QCD determination of the hadronic vacuum polarization in the Euclidean region, reaching sub-percent precision and confirming tensions at space-like virtualities with data-driven estimates based on $e^+e^-$ cross sections. By combining the lattice calculation with the Euclidean split technique, we obtain a precise determination of the running of $\alpha$ up to the $Z$-pole and assess its implications for global electroweak fits. I will conclude with an outlook on further improvements and on the precision targets set by the FCC-ee program.

Speaker: Alessandro Conigli (JGU Mainz)

AConigli_uconn.pdf

10:45 AM → 11:15 AM Connections Discussion: Towards a consensus evaluation of Delta alpha_had(M_Z)?

Conveners: Hartmut Wittig, Martin Hoferichter (University of Bern)

Slides_Delta_alpha.pdf

11:15 AM → 12:30 PM Lattice HLbL

Convener: Julian Parrino (Universität Regensburg)

11:15 AM Update on the calculation of the long-distance $\pi^0$ exchange part of the hadronic light-by-light (HLbL) contribution to muon g-2 from RBC-UKQCD.

We will provide an update to the RBC-UKQCD collaborations on the lattice calculation of the position-space, long-distance $\pi^0$ exchange part of the HLbL contribution to the anomalous magnetic moment of the muon. We will present the results of the calculation from 48I and 64I gauge-field ensembles at $a^{-1}=1.73$ GeV and $a^{-1}=2.359$ GeV, respectively. Additionally, we will present the comparison of the above results with the model calculations of the $\pi^0$ exchange contribution and the long-distance part of the pion-pole contribution, both based on the Lowest Meson Dominance (LMD) model for the $\pi^0$ transition form factor.

Speaker: Anton Shcherbakov (UCONN)

Lattice_conference_presentation_2026 (2).pdf

11:45 AM Mainz update on the HLbL

We present an update to the Mainz effort on the HLbL contribution to the muon $(g-2)$. We extended the number of ensembles for the calculation of the pion transition from factor $\mathcal{F}_{\pi^0 \gamma^* \gamma^*}$. This especially includes the disconnected diagrams. The form factor is the main ingredient in the calculation of the pion-pole contribution to the HLbL.
We will also show a new approach for the direct lattice calculation of the HLbL contribution. It changes the order of integration of the usual method in order to increase the number of simultaneous sums over the four internal vertices from two to three.

Speaker: Domink Erb (Johannes Gutenberg University Mainz)

Dominik_Erb_g-2_2026.pdf

12:15 PM Towards hadronic light-by-light contribution to the muon g-2 with C* boundary conditions

Within the RC* programme, we are working towards an independent lattice calculation of the hadronic light-by-light (HLbL) contribution to the muon $g$-2, with $C^\star$ boundary conditions using openQxD. As a proof of concept, we compute the analogous leptonic light-by-light contribution in quenched QED at large coupling, benchmarked against the perturbative Laporta–Remiddi result, and present a preliminary analysis on the coarsest of several ensembles. We discuss the signal-to-noise problem in this approach and its implications for the planned computation in full QCD+QED.

Speaker: Khai Phan (ETH Zurich)

gm2workshop_talk.pdf

12:30 PM → 2:00 PM Lunch

2:00 PM → 3:00 PM Lattice HLbL

Convener: Mattia Bruno (Univesita' di Milano-Bicocca)

2:00 PM The hadronic light-by-light contribution to the muon $g-2$ using staggered fermions

We calculate the hadronic light-by-light scattering contribution to the anomalous magnetic moment of the muon using staggered fermions at the physical point. This is done by evaluating four-point functions in position space using a method based on the idea by the Mainz group, which is adapted to staggered fermions. Our calculation is carried out for several physical volumes and lattice spacings which allows us to perform the continuum limit. We include contributions by light, strange and charm quarks. Finite volume effects are corrected for by considering pseudoscalar pole contributions.

Speaker: Christian Zimmermann (University of Kentucky)

zimmermann.pdf

2:30 PM HLbL contributions from twisted-mass lattice QCD

We present results for the hadronic light-by-light (HLbL) contribution from lattice-QCD calculations based on ETMC's Nf​=2+1+1 Wilson-clover twisted-mass ensembles at the physical point. These include continuum extrapolations for the strange- and charm-quark connected contributions and results for the light-quark connected and 2+2 disconnected contributions at two lattice spacings.

Speaker: Urs Wenger (University of Bern)

g-2TI_workshop_Storrs2026_wenger.pdf

3:00 PM → 3:30 PM Lat HLbL Discussion

Conveners: Thomas Blum (UConn), Luchang Jin (UCONN)

note.pdf

pion-pole-disconnected.pdf

simone-urs.pdf

3:30 PM → 4:00 PM Coffee break

4:00 PM → 7:00 PM Excursion

7:00 PM → 9:00 PM Workshop Dinner

Fri, August 7

9:00 AM → 10:00 AM Experimental input HLbL

Convener: Alessandro Conigli (JGU Mainz)

9:00 AM Experimental input for hadronic light-by-light from JLab

Slides from the Confinement meeting can be found here

Speaker: Liping Gan

9:30 AM Experimental Inputs for Hadronic Light-by-Light Scattering from the BESIII Collaboration

Data-driven evaluations of the hadronic light-by-light contribution to the muon anomalous magnetic moment rely critically on precise experimental inputs. This talk presents recent and ongoing measurements from the BESIII experiment specifically targeted to constrain these theoretical frameworks. Utilizing the large $e^+e^-$ datasets collected at the BEPCII collider, we extract single- and double-virtual transition form factors of pseudoscalar, scalar, tensor, and axial states. We emphasize the systematic challenges in the phenomenologically crucial low- to intermediate-$Q^2$ regime. Results of the two-photon production of pseudoscalar states and preliminary results of the two-photon production of pion pairs will be presented along with an outlook on ongoing measurements.

Speaker: Max Lellmann (JGU Mainz)

280708_g-2_theory_init_HLBL_BESIII.pdf

10:00 AM → 10:30 AM Coffee break

10:30 AM → 11:45 AM Dispersive HLbL

Conveners: Carleton DeTar (University of Utah), Martin Hoferichter (University of Bern)

Roundtable_HLbL_final.pdf

11:45 AM → 12:35 PM a_e session

Convener: Christian Zimmermann (University of Kentucky)

11:45 AM Report from MITP alpha workshop

Speaker: Hartmut Wittig

UConn_gm2_alpha.pdf

12:15 PM On HVP contribution to $g-2$ of the muon versus the electron

We study a linear combination of $a_e$ and $a_\mu$ that utilizes the strong correlation between the hadronic contributions to both anomalous magnetic moments. This subtracted observable potentially reduces the uncertainties associated with higher energy contributions, and may help address the current discrepancy between lattice and data-driven evaluations, through improved measurements of $a_e$ and the fine-structure constant.

Speaker: Siyuan Li (Johannes Gutenberg-Universität Mainz (JGU))

SLi_g_2_UCONN_a_u_e.pdf

12:35 PM → 2:00 PM Lunch

2:00 PM → 2:30 PM Implications for NP

Convener: Swagato Banerjee (University of Louisville)

2:00 PM Muon g-2 and the Status of Physics Beyond the Standard Model

In the past decades, the muon g-2 has attracted a lot of attention as a powerful probe
of physics beyond the Standard Model. However, in light of the updated SM value and
final result of the Fermilab measurement, its impact on a wide range of BSM scenarios
has to be reevaluated.
In this talk I discuss how g-2 connects to a number of complementary observables
relevant in searches for new physics, and give an overview of the status for several
well motivated extensions of the Standard Model, emphasising the difference between
the WP20 and WP25 results.

Speaker: Kilian Möhling (TU Dresden, Institut für Kern- und Teilchen Physik)

UConn-moehling.pdf

2:30 PM → 2:45 PM Implications for NP Discussion

2:45 PM → 3:45 PM TI future plans Discussion

Convener: Aida El-Khadra (University of Illinois Urbana-Champaign)

Final_Day_UConn2026_final (1).pdf