I will describe our recent effort on the precise calculation of the radiative correction to semileptonic kaon decays that leads to an improved determination of the CKM matrix element Vus and further sharpens the so-called "Cabibbo angle anomaly".

The anomalies in the electron-positron angular correlations from high-energy decays of 8Be were interpreted by the ATOMKI collaboration as evidence of a new beyond-the-Standard Model boson. A theoretical understanding of the nuclear physics involved is an important step towards verification of this claim. Hence, we investigate proton capture with the ab initio no-core shell model with continuum (NCSMC). The NCSMC describes both bound and unbound states in nuclei in a unified way, with realistic two- and three-nucleon interactions as the only input. This allows simultaneous description of 8Be structure, p+7Li scattering, radiative capture and internal pair creation which can individually be benchmarked against available data. We compare pair correlations to ATOMKI data for different proton energies and examine the effect of proper treatment of the initial scattering state. Further, our technique will be applied to the 12C and 4He systems in which similar anomalies have been reported.

The free neutron decay offers a powerful method to test the Standard Model and search for new physics; for example, the neutron lifetime and decay correlations provide essential inputs for the precise extraction of the CKM matrix element Vud and for the search of exotic currents in charged weak interactions. Carefully comparing the experimental outcomes of different decay correlations even allows us to go beyond the effective field theory description of new physics and probe light degrees of freedom. In this talk I will briefly review the few anomalies we observed in neutron decay experiments and describe several recent improvements in theory for a better analysis of the experimental results.

See slides at address above

Compelling evidence suggests that the Standard Model falls short as a complete theory. Recent experiments have unveiled intriguing deviations from the Standard Model, underscoring the pivotal role of the nuclear precision frontier in our pursuit of physics beyond the Standard Model (BSM). This frontier is centered on meticulously measuring nuclear phenomena, thus demanding advanced theoretical predictions. This presentation will spotlight three BSM searches from three distinct physics sub-fields, all of which can be effectively tackled through nuclear experiments. In Astronomy, we will explore dark matter direct detection with nuclear detectors. In particle physics, we will delve into the quest for charged lepton flavor violation via muon-to-electron conversion. Lastly, in nuclear physics, we will investigate exotic nuclear weak interactions, utilizing beta-decays. For each inquiry, I will elucidate the open question and its origins, demonstrate how it can be approached through low-energy nuclei experiments, highlight key theoretical gaps essential for interpreting these experiments, and present cutting-edge theory developments to address these gaps. Additionally, for the latter search, I will showcase recent discoveries stemming from new measurements and theory, illustrate how novel theoretical frameworks lead to innovative measurement techniques, and present preliminary calculations for upcoming state-of-the-art experiments.

In this talk I will review the status of the extraction of the Standard Model parameter Vud from nuclear beta decays, which provides a powerful tool to search for new physics. Particular emphasis is put on the recent developments of the weak decay form factors, electroweak radiative corrections, and the isospin-symmetry-breaking correction to the Fermi matrix element. I will show how lattice QCD, nuclear ab-initio theory and experiments pave the way for the extraction of Vud at a 0.01% precision.

The precise determination of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements Vud and Vus constitutes an important component of the precision test of the Standard Model (SM) and the search for new physics beyond its coverage. In recent years, there has been a resurgence of interest in these matrix elements due to the emergence of a number of intriguing tensions at the 3-sigma level. In this talk I will discuss our current theoretical understanding of the superallowed nuclear beta decay, which is the main avenue for the Vud extraction.

The precise determination of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements Vud and Vus constitutes an important component of the precision test of Standard Model (SM) and the search for new physics beyond its coverage. In recent years, there has been a resurgence of interest in these matrix elements due to the emergence of a number of intriguing tensions at the 3\(\sigma\) level, which makes them a highlighted research topic in the 2023 NSAC Long Range Plan. In this talk I will review the current status of these matrix elements and provide an outlook.

We compare a new MINERvA measurement of the nucleon axial-vector form factor with lattice-QCD calculations and deuterium bubble-chamber data, provide uncertainty projections for future extractions, and present recent calculations of radiative corrections to charged-current (anti)neutrino-nucleon scattering.

At leading order in weak and electromagnetic couplings, cross sections for (anti)neutrino-nucleon elastic scattering are determined by vector and axial-vector form factors. Radiative corrections in the Standard Model, and potential new physics contributions beyond the Standard Model, generate additional operators with corresponding invariant amplitudes. We provide the definition of these amplitudes and study constraints from existing experimental data. We explore the impact of modern and future cross-section measurements, considering both unpolarized and polarized observables, on constraining these amplitudes and discuss the effects of radiative corrections on the observables of interest.

We develop a new top-down effective field theory approach for radiative corrections to the neutron decay. First, we match the Standard Model to the four-fermion effective field theory. To evaluate radiative corrections at scales of the neutron decay, we perform matching to the heavy-baryon chiral perturbation theory. For the vector coupling constant, we find an agreement with the traditional current-algebra approach at the one-loop level, improve on the resummation of next-to-leading logarithms, and provide an updated extraction of the Vud matrix element.

In this talk I will review the status of the Standard Model theory of neutron beta decay. Particular emphasis is put on the recent developments of the inner''™ andouter'' electroweak radiative corrections, and the isospin-symmetry-breaking correction to the Fermi matrix element. The use of dispersion relation, lattice Quantum Chromodynamics and effective field theory framework allows for high-precision theory calculations at the level of \(10^{-4}\), turning neutron beta decay into a powerful tool to search for new physics. I offer an outlook to the future improvements.

We study radiative corrections to the neutron beta decay within the top-down effective field theory approach. First, we match the Standard Model to the four-fermion effective field theory specifying the scheme dependence of the Wilson coefficients. To evaluate radiative corrections at scales of the neutron decay, we perform matching to the heavy-baryon chiral perturbation theory for the vector coupling constant. We find an agreement with traditional current-algebra approach at one-loop level and perform detailed evaluation in renormalization-group-improved perturbation theory.

In this talk, I will discuss neutrino sources and neutrino scattering cross sections at various energy scales. I will motivate and describe a few recent precise calculations of radiative corrections to neutrino-induced processes. I will formulate radiative corrections in the top-down effective field theory approach, present elastic neutrino-electron, coherent elastic neutrino-nucleus, inverse muon decay cross sections, neutrino energy spectra from radiative muon, pion, and kaon decays, and quantify the corresponding uncertainties. I will formulate radiative corrections to charged-current elastic neutrino-nucleon scattering in SCET framework and validate the precise relation between electron and muon flavor cross sections for signal events in neutrino oscillation experiments. I will present new permille-to-percent level effect on (anti)neutrino- and electron-nucleus scattering cross sections due to the exchange of photons with a nuclear medium.