Scattering amplitudes from Euclidean Lattice QCD (I)

• Stephen Sharpe (U. of Washington, Seattle)

Room: SC353

The muon anomalous magnetic moment: a high-precision probe of the Standard Model (I)

• Laurent Lellouch (Aix-Marseille U.)

Room: SC353 The Muon g−2 Experiment at Fermi National Accelerator Laboratory has concluded its six-year data-taking campaign with a measurement of the muon's anomalous magnetic moment, a_μ, at a precision of 0.127 parts per million. Because a_μ arises entirely from quantum fluctuations, it is sensitive to all the particles and interactions of the Standard Model, as well as to possible new degrees of freedom that are too heavy or too weakly coupled to be produced directly. To fully exploit this sensitivity, however, a theoretical prediction of comparable accuracy is required. In this course, I will first explain why lepton anomalous magnetic moments, particularly the muon's, are such effective probes of fundamental physics, and describe how a_μ is measured, from producing polarized muons to extracting their anomalous spin-precession frequency in a storage ring. I will then review the Standard Model prediction: the QED contributions, now known to five loops; the electroweak corrections; and the hadronic contributions, which dominate the theoretical uncertainty. After discussing the dispersive, data-driven determination of the leading-order hadronic vacuum polarization contribution and the tensions that have emerged among the underlying e⁺e⁻ → hadrons measurements, I will give a brief introduction to lattice QCD. I will then present a hybrid calculation of this contribution, in which about 96% is computed from first principles on the lattice and the small remainder is obtained from e⁺e⁻ → hadrons data. Combined with all other Standard Model contributions, this result yields a prediction that agrees with experiment within one standard deviation, thereby testing the Standard Model at the level of 0.4 parts per billion on the muon magnetic moment, g_μ=2(1+ a_μ). I will conclude with the open questions that remain and the prospects for further progress on both the experimental and theoretical fronts.

Lattice calculation for QCD strong coupling

• Isabella Leone Zimmel (U. of Valencia)

Room: SC353

Lattice QCD and neutrinoless double beta decay (I)

• Andre Walker-Loud (LBNL)

Room: SC353

Study of symmetries from N_f = 2 and N_f = 2+1 finite femperature QCD using mobius domain wall fermions

• David Ward (National Taiwan U.)

Room: SC353

Heavy-meson mixing and lifetimes via gradient flow

• Antonio Rago (U. of Odense)

Room: SC353

Higher moments of parton distributions from lattice QCD with gradient flow

• Jangho Kim (Seoul National University)

Room: SC353

Lattice QCD and neutrinoless double beta decay (II)

• Andre Walker-Loud (LBNL)

Room: SC353

Scattering amplitudes from Euclidean Lattice QCD (II)

• Stephen Sharpe (U. of Washington, Seattle)

Room: SC353

Moments of pion and kaon light-cone distribution amplitudes from dynamical lattice QCD using the heavy-quark operator product expansion

• S.-P. Alex Chang (National Yang Ming Chiao Tung University)

Room: SC353

Spectral bounds in multi-hadron spectroscopy

• William Detmold (Massachusetts Institute of Technology)

Room: SC353

The Collins-Soper kernel from a vacuum soft function

• Wayne Morris (National Yang Ming Chiao Tung University)

Room: SC353

The muon anomalous magnetic moment: a high-precision probe of the Standard Model (II)

• Laurent Lellouch (Aix-Marseille U.)

Room: SC353 The Muon g−2 Experiment at Fermi National Accelerator Laboratory has concluded its six-year data-taking campaign with a measurement of the muon's anomalous magnetic moment, a_μ, at a precision of 0.127 parts per million. Because a_μ arises entirely from quantum fluctuations, it is sensitive to all the particles and interactions of the Standard Model, as well as to possible new degrees of freedom that are too heavy or too weakly coupled to be produced directly. To fully exploit this sensitivity, however, a theoretical prediction of comparable accuracy is required. In this course, I will first explain why lepton anomalous magnetic moments, particularly the muon's, are such effective probes of fundamental physics, and describe how a_μ is measured, from producing polarized muons to extracting their anomalous spin-precession frequency in a storage ring. I will then review the Standard Model prediction: the QED contributions, now known to five loops; the electroweak corrections; and the hadronic contributions, which dominate the theoretical uncertainty. After discussing the dispersive, data-driven determination of the leading-order hadronic vacuum polarization contribution and the tensions that have emerged among the underlying e⁺e⁻ → hadrons measurements, I will give a brief introduction to lattice QCD. I will then present a hybrid calculation of this contribution, in which about 96% is computed from first principles on the lattice and the small remainder is obtained from e⁺e⁻ → hadrons data. Combined with all other Standard Model contributions, this result yields a prediction that agrees with experiment within one standard deviation, thereby testing the Standard Model at the level of 0.4 parts per billion on the muon magnetic moment, g_μ=2(1+ a_μ). I will conclude with the open questions that remain and the prospects for further progress on both the experimental and theoretical fronts.

Tuning a relativistic heavy-quark action using machine learning

• Thamirys de Oliveira (National Yang Ming Chiao Tung University)

Room: SC353

Hadronic vacuum polarization to three loops in chiral perturbation theory

• Laurent Lellouch (Aix-Marseille U.)

Room: SC353 At low virtualities, hadronic vacuum polarization (HVP) limits the precision of key Standard Model tests, notably the muon anomalous magnetic moment and the running of the electromagnetic coupling. Chiral perturbation theory constrains its functional form in this regime and provides the framework for computing finite-volume effects in lattice QCD. In this seminar, I will present a three-loop (N³LO) calculation of HVP in two-flavor chiral perturbation theory, the only second three-loop computation in this effective theory. Integration-by-parts reduction expresses the amplitude in terms of eleven three-loop master integrals, six of which are elliptic functions of the photon virtuality. Five of these are new, and all are related to the equal-mass three-loop sunset integral. I will explain how Tarasov's dimensional shift separates their divergences from their elliptic content. I will also show that renormalizability requires relations among master integrals that do not follow from integration by parts: Schouten relations, which hold only in fixed integer dimension. Differential equations then reduce the most complicated integrals to one-dimensional integrals over the sunset, enabling fast, high-precision evaluation for arbitrary complex virtualities. In the resulting amplitude, the elliptic part contains no free parameters and gives the leading contribution to the four-pion cut. I will conclude with prospects for phenomenology and for finite-volume corrections to lattice calculations.

Progress in determining multiparticle amplitudes from Lattice QCD

• Stephen Sharpe (U. of Washington, Seattle)

Room: SC353

Lattice QCD calculations of two-nucleons at light pion mass and connecting to EFT

• Andre Walker-Loud (LBNL)

Room: SC353

Parton physics from Hamiltonian lattice gauge theory with tensor networks

• Manuel Schneider (National Yang Ming Chiao Tung University)

Room: SC353