skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Model dependence of the {gamma}Z dispersion correction to the parity-violating asymmetry in elastic ep scattering

Abstract

We analyze the dispersion correction to elastic parity violating electron-proton scattering due to {gamma}Z exchange. In particular, we explore the theoretical uncertainties associated with modeling contributions of hadronic intermediate states. Taking into account constraints from low- and high-energy, parity-conserving electroproduction measurements, choosing different models for contributions from the nonresonant processes, and performing the corresponding flavor rotations to obtain the electroweak amplitude, we arrive at an estimate of the uncertainty in the total contribution to the parity-violating asymmetry. At the kinematics of the Q-Weak experiment, we obtain a correction to the asymmetry equivalent to a shift in the proton weak charge of (0.0054{+-}0.0020). This should be compared to the value of the proton's weak charge of Q{sub W}{sup p}=0.0713{+-}0.0008 that includes Standard Model contributions at tree level and one-loop radiative corrections. Therefore, we obtain a new Standard Model prediction for the parity-violating asymmetry in the kinematics of the Q-Weak experiment of (0.0767{+-}0.0008{+-}0.0020{sub {gamma}Z}). The latter error leads to a relative uncertainty of 2.8% in the determination of the proton's weak charge and is dominated by the uncertainty in the isospin structure of the inclusive cross section. We argue that future parity-violating inelastic ep asymmetry measurements at low to moderate Q{sup 2}more » and W{sup 2} could be exploited to reduce the uncertainty associated with the dispersion correction. Because the corresponding shift and error bar decrease monotonically with decreasing beam energy, a determination of the proton's weak charge with a lower-energy experiment or measurements of ''isotope ratios'' in atomic parity violation could provide a useful cross-check on any implications for physics beyond the Standard Model derived from the Q-Weak measurement.« less

Authors:
;  [1];  [2]
  1. Center for Exploration of Energy and Matter, Physics Department, Indiana University, Bloomington, Indiana 47403 (United States)
  2. Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States) and Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, California 91125 (United States)
Publication Date:
OSTI Identifier:
21596619
Resource Type:
Journal Article
Journal Name:
Physical Review. C, Nuclear Physics
Additional Journal Information:
Journal Volume: 84; Journal Issue: 1; Other Information: DOI: 10.1103/PhysRevC.84.015502; (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0556-2813
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ASYMMETRY; CROSS SECTIONS; DISPERSIONS; ELASTIC SCATTERING; ELECTRON-PROTON INTERACTIONS; ELECTROPRODUCTION; FLAVOR MODEL; INTERMEDIATE STATE; ISOSPIN; ISOTOPE RATIO; PARITY; PROTONS; RADIATIVE CORRECTIONS; SCATTERING; SIMULATION; STANDARD MODEL; BARYONS; BASIC INTERACTIONS; COMPOSITE MODELS; CORRECTIONS; DIMENSIONLESS NUMBERS; ELECTROMAGNETIC INTERACTIONS; ELECTRON-NUCLEON INTERACTIONS; ELEMENTARY PARTICLES; FERMIONS; FIELD THEORIES; GRAND UNIFIED THEORY; HADRONS; INTERACTIONS; LEPTON-BARYON INTERACTIONS; LEPTON-HADRON INTERACTIONS; LEPTON-NUCLEON INTERACTIONS; MATHEMATICAL MODELS; NUCLEONS; PARTICLE INTERACTIONS; PARTICLE MODELS; PARTICLE PRODUCTION; PARTICLE PROPERTIES; QUANTUM FIELD THEORY; QUARK MODEL; UNIFIED GAUGE MODELS

Citation Formats

Gorchtein, Mikhail, Horowitz, C. J., and Ramsey-Musolf, Michael J. Model dependence of the {gamma}Z dispersion correction to the parity-violating asymmetry in elastic ep scattering. United States: N. p., 2011. Web. doi:10.1103/PHYSREVC.84.015502.
Gorchtein, Mikhail, Horowitz, C. J., & Ramsey-Musolf, Michael J. Model dependence of the {gamma}Z dispersion correction to the parity-violating asymmetry in elastic ep scattering. United States. doi:10.1103/PHYSREVC.84.015502.
Gorchtein, Mikhail, Horowitz, C. J., and Ramsey-Musolf, Michael J. Fri . "Model dependence of the {gamma}Z dispersion correction to the parity-violating asymmetry in elastic ep scattering". United States. doi:10.1103/PHYSREVC.84.015502.
@article{osti_21596619,
title = {Model dependence of the {gamma}Z dispersion correction to the parity-violating asymmetry in elastic ep scattering},
author = {Gorchtein, Mikhail and Horowitz, C. J. and Ramsey-Musolf, Michael J.},
abstractNote = {We analyze the dispersion correction to elastic parity violating electron-proton scattering due to {gamma}Z exchange. In particular, we explore the theoretical uncertainties associated with modeling contributions of hadronic intermediate states. Taking into account constraints from low- and high-energy, parity-conserving electroproduction measurements, choosing different models for contributions from the nonresonant processes, and performing the corresponding flavor rotations to obtain the electroweak amplitude, we arrive at an estimate of the uncertainty in the total contribution to the parity-violating asymmetry. At the kinematics of the Q-Weak experiment, we obtain a correction to the asymmetry equivalent to a shift in the proton weak charge of (0.0054{+-}0.0020). This should be compared to the value of the proton's weak charge of Q{sub W}{sup p}=0.0713{+-}0.0008 that includes Standard Model contributions at tree level and one-loop radiative corrections. Therefore, we obtain a new Standard Model prediction for the parity-violating asymmetry in the kinematics of the Q-Weak experiment of (0.0767{+-}0.0008{+-}0.0020{sub {gamma}Z}). The latter error leads to a relative uncertainty of 2.8% in the determination of the proton's weak charge and is dominated by the uncertainty in the isospin structure of the inclusive cross section. We argue that future parity-violating inelastic ep asymmetry measurements at low to moderate Q{sup 2} and W{sup 2} could be exploited to reduce the uncertainty associated with the dispersion correction. Because the corresponding shift and error bar decrease monotonically with decreasing beam energy, a determination of the proton's weak charge with a lower-energy experiment or measurements of ''isotope ratios'' in atomic parity violation could provide a useful cross-check on any implications for physics beyond the Standard Model derived from the Q-Weak measurement.},
doi = {10.1103/PHYSREVC.84.015502},
journal = {Physical Review. C, Nuclear Physics},
issn = {0556-2813},
number = 1,
volume = 84,
place = {United States},
year = {2011},
month = {7}
}