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Hill, Richard J.

Publications and source records attributed to Hill, Richard J..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

All orders factorization and the Coulomb problem

In the limit of large nuclear charge, Z ≫ 1 , or small lepton velocity, β ≪ 1 , Coulomb corrections to nuclear beta decay and related processes are enhanced as Z α / β and become large or even nonperturbative (with α the QED fine structure constant). We provide a constructive demonstration of factorization to all orders in perturbation theory for these processes and compute the all-orders hard and soft functions appearing in the factorization formula. We clarify the relationship between effective field theory amplitudes and historical treatments of beta decay in terms of a Fermi function. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Neutrino Scattering Measurements on Hydrogen and Deuterium: A Snowmass White Paper

Neutrino interaction uncertainties are a limiting factor in current and next-generation experiments probing the fundamental physics of neutrinos, a unique window on physics beyond the Standard Model. Neutrino-nucleon scattering amplitudes are an important part of the neutrino interaction program. However, since all modern neutrino detectors are composed primarily of heavy nuclei, knowledge of elementary neutrino-nucleon amplitudes relies heavily on experiments performed in the 1970s and 1980s, whose statistical and systematic precision are insufficient for current needs. In this white paper, we outline the motivation for attempting measurements on hydrogen and deuterium that would improve this knowledge, and we discuss options for making these measurements either with the DUNE near detector or with a dedicated facility.

Alvarez-Ruso, Luis↗
DOE OSTI2022

Bubble Chamber Detectors with Light Nuclear Targets: A Snowmass 2021 White Paper

Neutrino cross sections are a critical ingredient in experiments that depend on neutrino scattering to reconstruct event kinematics and infer neutrino characteristics, like NOvA and T2K. An opportunity exists to reduce the 5-10% broad uncertainty on neutrino cross sections by producing more measurements of neutrino scattering from light nuclear targets at the relevant energies. Bubble chambers with light nuclear targets would be ideal for these measurements but the most recent device designed for use with an accelerator neutrino source is at least fifty years old. A new bubble chamber with light nuclear targets could be designed by observing how the technology has progressed for use in dark matter experiments and producing smaller modular devices that use more efficient cooling systems. A smaller modular device could also be designed for deployment to all functioning neutrino beams, but an investigation of the proper operating characteristics is necessary to adapt newer detectors to the structure of contemporary neutrino beams.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

QED radiative corrections to neutrino-nucleon elastic scattering

Neutrino oscillation experiments at accelerator energies aim to establish CP violation in the neutrino sector by measuring the energy-dependent rate of $\nu_e$ appearance and $\nu_\mu$ disappearance in a $\nu_\mu$ beam. Extracting the correct oscillation rate demands control over QED radiative corrections at the percent level. Focusing on the critical charged-current neutrino-nucleon scattering process, we show that the cross section factorizes into two pieces. The first piece depends on hadron structure but is universal for $\nu_e$ and $\nu_\mu$, and hence constrained by high-statistics $\nu_\mu$ data. The second piece is nonuniversal and suffers large logarithm enhancements, but is computed to high precision using renormalization group improved perturbation theory. Our results provide a missing ingredient for the robust interpretation of current NOvA and T2K experiments, and can be applied to future experiments such as DUNE and HyperK.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

On the effective theory of neutrino-electron and neutrino-quark interactions

We determine the four Fermi effective theory of neutrino interactions within the Standard Model including one-loop electroweak radiative corrections, in combination with the measured muon lifetime and precision electroweak data. Including two-loop matching and three-loop running corrections, we determine lepton coefficients accounting for all large logarithms through relative order $\cal{O}(\alpha \alpha_s)$ and quark coefficients accounting for all large logarithms through ${\cal{O}}(\alpha)$. We present four-fermion coefficients valid in $n_f=3$ and $n_f=4$ flavor quark theories, as well as in the extreme low-energy limit. We relate the coefficients in this limit to neutrino charge radii governing matter effects via forward neutrino scattering on charged particles.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Nucleon Axial Radius and Muonic Hydrogen — A New Analysis and Review

Weak capture in muonic hydrogen (μH) as a probe of the chiral properties and nucleon structure predictions of quantum chromodynamics (QCD) is reviewed. A recent determination of the axial-vector charge radius squared, , from a model independent z expansion analysis of neutrino-nucleon scattering data is employed in conjunction with the MuCap measurement of the singlet muonic hydrogen capture rate, , to update the induced pseudoscalar nucleon coupling derived from experiment, and predicted by chiral perturbation theory. Accounting for correlated errors this implies , confirming theory at the 8% level. If instead, the predicted expression for is employed as input, then the capture rate alone determines , or together with the independent z expansion neutrino scattering result, a weighted average . Sources of theoretical uncertainty are critically examined and potential experimental improvements are described that can reduce the capture rate error by about a factor of 3. Muonic hydrogen can thus provide a precise and independent value which may be compared with other determinations, such as ongoing lattice gauge theory calculations. The importance of an improved determination for phenomenology is illustrated by considering the impact on critical neutrino-nucleus cross sections at neutrino oscillation experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

From Nucleons to Nuclei: Enabling Discovery for Neutrinos, Dark Matter and More

Neutrino interaction uncertainties are a limiting factor in current and next generation experiments probing the fundamental physics of neutrinos, a unique window on physics beyond the Standard Model. Our understanding of the elementary neutrino-nucleon amplitudes at the heart of the neutrino interaction program relies on experiments from an earlier age whose statistical and systematic precision are insufficient for current needs. The workshop brings together physicists with a diverse range of expertise to discuss the status of neutrino-nucleus scattering and to explore (i) the quantitative impact of better constraints on the elementary amplitudes; (ii) the scientific impact of a new hydrogen or deuterium target experiment; (iii) the optimal design and technical feasibility of a new hydrogen or deuterium target experiment; and (iv) complementary constraints on the elementary amplitudes from other methods. The tools and techniques required for understanding neutrino-nucleus interactions are common to many problems at the interface of particle and nuclear physics. The workshop will discuss new developments and prospects for related topics and new physics searches, including dark matter interactions with the Standard Model and neutrinoless double beta decay.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Nucleon spin-averaged forward virtual Compton tensor at large Q 2

Here, the nucleon spin-averaged forward virtual Compton tensor determines important physical quantities such as electromagnetically-induced mass differences of nucleons, and two-photon exchange contributions in hydrogen spectroscopy. It depends on two kinematic variables: $\nu$, the virtual photon energy in the proton rest frame, and $Q^2$, the photon's invariant four-momentum squared. Using the operator product expansion, we calculate the tensor's large-$Q^2$ behavior for $\nu=0$, including for the first time the full spin-2 contribution and correcting a previous result for the spin-0 contribution. Implications for the proton radius puzzle are discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Review of Experimental and Theoretical Status of the Proton Radius Puzzle

The discrepancy between the measured Lamb shift in muonic hydrogen and expectations from electron-proton scattering and regular hydrogen spectroscopy has become known as the proton radius puzzle, whose most “mundane” resolution requires a > 5σ shift in the value of the fundamental Rydberg constant. I briefly review the status of spectroscopic and scattering measurements, recent theoretical developments, and implications for fundamental physics.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Calculation of the Nucleon Axial Form Factor Using Staggered Lattice QCD

The nucleon axial form factor is a dominant contribution to errors in neutrino oscillation studies. Lattice QCD calculations can help control theory errors by providing first-principles information on nucleon form factors. In these proceedings, we present preliminary results on a blinded calculation of $g_A$ and the axial form factor using HISQ staggered baryons with 2+1+1 flavors of sea quarks. Calculations are done using physical light quark masses and are absolutely normalized. We discuss fitting form factor data with the model-independent $z$ expansion parametrization.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Deuterium target data for precision neutrino-nucleus cross sections

Amplitudes derived from scattering data on elementary targets are basic inputs to neutrino-nucleus cross section predictions. A prominent example is the isovector axial nucleon form factor, F A (q 2 ), which controls charged current signal processes at accelerator-based neutrino oscillation experiments. Previous extractions of F A from neutrino-deuteron scattering data rely on a dipole shape assumption that introduces an unquantified error. A new analysis of world data for neutrino-deuteron scattering is performed using a model-independent, and systematically improvable, representation of F A . A complete error budget for the nucleon isovector axial radius leads to r A 2 = 0.46(22)fm 2 , with a much larger uncertainty than determined in the original analyses. The quasielastic neutrino-neutron cross section is determined as σ(ν μ n → μ - p)| E v =1 GeV = 10.1(0.9)×10 -39 cm 2 . The propagation of nucleon-level constraints and uncertainties to nuclear cross sections is illustrated using MINERvA data and the GENIE event generator. Furthermore, these techniques can be readily extended to other amplitudes and processes.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Extraction of the proton radius from electron-proton scattering data

We perform a new analysis of electron-proton scattering data to determine the proton electric and magnetic radii, enforcing model-independent constraints from form factor analyticity. A wide-ranging study of possible systematic effects is performed. An improved analysis is developed that rebins data taken at identical kinematic settings and avoids a scaling assumption of systematic errors with statistical errors. Employing standard models for radiative corrections, our improved analysis of the 2010 Mainz A1 Collaboration data yields a proton electric radius r E = 0.895(20) fm and magnetic radius r M = 0.776(38) fm. A similar analysis applied to world data (excluding Mainz data) implies r E = 0.916(24) fm and r M = 0.914(35) fm. The Mainz and world values of the charge radius are consistent, and a simple combination yields a value r E = 0.904(15) fm that is 4σ larger than the CREMA Collaboration muonic hydrogen determination. The Mainz and world values of the magnetic radius differ by 2.7σ, and a simple average yields r M = 0.851(26) fm. As a result, the circumstances under which published muonic hydrogen and electron scattering data could be reconciled are discussed, including a possible deficiency in the standard radiative correction model which requires further analysis.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗