arXiv subjects

George A. Parker

Publications and source records attributed to George A. Parker.

6 recordsLinked to original sources

arXiv2026

A LENS on DUNE-PRISM: Characterizing a Neutrino Beam with Off-Axis Measurements

Upcoming precision long-baseline neutrino oscillation experiments will be severely limited by the large systematic uncertainties associated with neutrino flux predictions and neutrino--nucleus cross sections. A promising remedy is the PRISM (Precision Reaction Independent Spectrum Measurement) technique, whereby the near detector measures the neutrino spectrum at different angles with respect to the beam axis. These measurements are then linearly combined into a prediction of the oscillated neutrino flux at the far detector. This prediction is data-driven, but still dependent on some theoretical knowledge about the neutrino flux. In this paper, we study to what extent off-axis measurements themselves can be used to directly constrain neutrino flux models. In particular, we use them to extract separately the fluxes and spectra of different meson species in the beam. We call this measurement LENS (Lateral Extraction of Neutrino Spectra). Second, we demonstrate how the thus improved flux model helps to further constrain the far detector flux prediction, thereby ultimately improving oscillation measurements.

hep-ph↗

arXiv2026

Pinpointing the Mechanism of Neutrinoless Weak Decays with Positrons

Neutrinoless double beta decay is the flagship laboratory probe of a Majorana contribution to the neutrino mass. However, besides the standard mass mechanism other higher- dimensional lepton number-violating interactions can enter, or even dominate, this process. The corresponding positron-emitting neutrinoless modes, such as electron capture or double-positron emission, have long been considered out of reach experimentally, due to their naturally smaller rates. Recently, innovative detector technologies as used in the proposed NuDoubt++ experiment are changing the game. In this work, we explore how a positron- and electron-mode detector can be complementary in the search for new physics. Assuming an observation of neutrinoless double beta decay, we predict the expected discovery half-life for the positron-modes. Using half-life ratios, especially between the double beta and electron capture modes, we demonstrate how underlying long-range interactions can be distinguished, in particular to identify a purely right-handed leptonic current.

hep-ph↗

arXiv2026

Visible Neutrino Decay As An Open Quantum System

Decays of heavier neutrino mass eigenstates into lighter ones, while very slow in the Standard Model, can be significantly enhanced in scenarios with more than three neutrino flavours, or in models with new ultra-light particles such as Majorons. A full theoretical description is challenging due to the intricate interplay between oscillations and decay, interference between different decay channels, and the possibility of multi-step decay cascades. In this paper, we develop a fully general description of arbitrarily complex systems of oscillating and decaying neutrinos using methods from the theory of open quantum systems. Notably, we demonstrate how such systems can be implemented using the Lindblad master equation, the Liouvillian superoperator, as well as Kraus operators. The last two methods eschew the need for solving a differential equation, thereby showing superior numerical performance.

hep-ph↗

arXiv2025

Vanishing Acts: Quantifying Black Hole Formation with the DSNB Signal

The diffuse supernova neutrino background (DSNB) created by stellar core-collapses throughout cosmic history is on the verge of discovery, with SK-Gd showing early deviations from the background expectation and JUNO starting to take data. However, the interpretation of early DSNB data will face significant challenges due to degeneracies between astrophysical parameters and uncertainties in supernova neutrino modeling. We explore how complementary astronomical observations can break these degeneracies and, in this context, we investigate whether early DSNB observations can constrain invisible supernovae, which have no optical emission but are powerful neutrino sources before being swallowed by a forming black hole. Leveraging the differences in the spectra between invisible and visible supernovae, we estimate the sensitivity of 1) detecting the existence of invisible supernovae, and 2) determining the fraction of invisible supernovae. Finally, we discuss how these conclusions depend on the spectral parameters of the black hole-forming component.

astro-ph.HE↗

arXiv2025

Neutrino Theory in the Precision Era

This document summarises discussions on future directions in theoretical neutrino physics, which are the outcome of a neutrino theory workshop held at CERN in February 2025. The starting point is the realisation that neutrino physics offers unique opportunities to address some of the most fundamental questions in physics. This motivates a vigorous experimental programme which the theory community fully supports. \textbf{A strong effort in theoretical neutrino physics is paramount to optimally take advantage of upcoming neutrino experiments and to explore the synergies with other areas of particle, astroparticle, and nuclear physics, as well as cosmology.} Progress on the theory side has the potential to significantly boost the physics reach of experiments, as well as go well beyond their original scope. Strong collaboration between theory and experiment is essential in the precision era. To foster such collaboration, \textbf{we propose to establish a CERN Neutrino Physics Centre.} Taking inspiration from the highly successful LHC Physics Center at Fermilab, the CERN Neutrino Physics Centre would be the European hub of the neutrino community, covering experimental and theoretical activities.

hep-ph↗

arXiv2024

Looping Around Neutrino Charge Radius at Ultra-Near Reactor Experiments

We scrutinize the potential of upcoming ultra-near reactor neutrino experiments to detect radiative corrections in the elastic neutrino-electron scattering channel, focusing on the JUNO-TAO and CLOUD detectors, which employ advanced scintillator detection technologies. Previous reactor experiments have already constrained the electron neutrino charge radius, which is a neutrino property associated with a certain subset of the total radiative corrections, and have achieved limits that are only about an order of magnitude away from the Standard Model prediction. Our study demonstrates that JUNO-TAO and CLOUD could discover the neutrino charge radius in the near future, considering the established treatment of the charge radius. However, we show that it is necessary to go beyond this standard treatment. By including the complete set of one-loop level radiative corrections, we find a partial cancellation with the charge radius effect, reducing the experimental sensitivity to this quantity. Nevertheless, JUNO-TAO and CLOUD still have the potential to achieve a $5σ$ discovery but over longer timescales within a reasonable operational timeframe.

hep-ph↗