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Title: Nucleon axial radius and muonic hydrogen—a new analysis and review

Abstract

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, r$$_{A}^{2}$$ (z exp:) = 0.46(22) fm 2, 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, Λ$$_{singlet}^{MuCap}$$ = 715:6(7:4) s -1, to update the induced pseudoscalar nucleon coupling $$\overline{g}$$$_{P}^{MuCap}$$ = 8.23(83) derived from experiment, and $$\overline{g}$$$_{P}^{theory}$$ = 8.25(25) predicted by chiral perturbation theory. Accounting for correlated errors this implies $$\overline{g}$$$_{P}^{theory}$$ =$$\overline{g}$$$_{P}^{MuCap}$$ = 1:00(8), confirming theory at the 8% level. If instead, the predicted expression for $$\overline{g}$$$_{P}^{theory}$$ is employed as input, then the capture rate alone determines r$$_{A}^{2}$$ (μH) = 0.46(24) fm 2, or together with the independent z expansion neutrino scattering result, a weighted average r$$_{A}^{2}$$ (ave:) = 0.46(16) fm 2. Sources of theoretical uncertainty are critically examined and potential experimental improvements are described that can reduce the capture rate error by about a factor of 3. Muonic hydrogen can thus provide a precise and independent r$$_{A}^{2}$$ value which may be compared with other determinations, such as ongoing lattice gauge theory calculations. The importance of an improved r2A determination for phenomenology is illustrated by considering the impact on critical neutrino-nucleus cross sections at neutrino oscillation experiments. $$\overline{g}$$

Authors:
ORCiD logo [1]; ORCiD logo [2];  [3];  [4]
  1. Univ. of Kentucky, Lexington, KY (United States); Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Perimeter Inst. for Theoretical Physics, Waterloo, ON (Canada)
  2. Univ. of Washington, Seattle, WA (United States)
  3. Brookhaven National Lab. (BNL), Upton, NY (United States)
  4. New York Univ. (NYU), NY (United States)
Publication Date:
Research Org.:
Brookhaven National Lab. (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1469794
Report Number(s):
BNL-209035-2018-JAAM
Journal ID: ISSN 0034-4885
Grant/Contract Number:  
SC0012704
Resource Type:
Accepted Manuscript
Journal Name:
Reports on Progress in Physics
Additional Journal Information:
Journal Volume: 81; Journal Issue: 9; Journal ID: ISSN 0034-4885
Publisher:
IOP Publishing
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; neutrino; anomalies; oscillation; probe; chiral; axial; vector; particle physics; QCD; radius; hydrogen; nucleon

Citation Formats

Hill, Richard J., Kammel, Peter, Marciano, William J., and Sirlin, Alberto. Nucleon axial radius and muonic hydrogen—a new analysis and review. United States: N. p., 2018. Web. doi:10.1088/1361-6633/aac190.
Hill, Richard J., Kammel, Peter, Marciano, William J., & Sirlin, Alberto. Nucleon axial radius and muonic hydrogen—a new analysis and review. United States. doi:10.1088/1361-6633/aac190.
Hill, Richard J., Kammel, Peter, Marciano, William J., and Sirlin, Alberto. Tue . "Nucleon axial radius and muonic hydrogen—a new analysis and review". United States. doi:10.1088/1361-6633/aac190. https://www.osti.gov/servlets/purl/1469794.
@article{osti_1469794,
title = {Nucleon axial radius and muonic hydrogen—a new analysis and review},
author = {Hill, Richard J. and Kammel, Peter and Marciano, William J. and Sirlin, Alberto},
abstractNote = {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, r$_{A}^{2}$ (z exp:) = 0.46(22) fm2, 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, Λ$_{singlet}^{MuCap}$ = 715:6(7:4) s-1, to update the induced pseudoscalar nucleon coupling $\overline{g}$$_{P}^{MuCap}$ = 8.23(83) derived from experiment, and $\overline{g}$$_{P}^{theory}$ = 8.25(25) predicted by chiral perturbation theory. Accounting for correlated errors this implies $\overline{g}$$_{P}^{theory}$ =$\overline{g}$$_{P}^{MuCap}$ = 1:00(8), confirming theory at the 8% level. If instead, the predicted expression for $\overline{g}$$_{P}^{theory}$ is employed as input, then the capture rate alone determines r$_{A}^{2}$ (μH) = 0.46(24) fm2, or together with the independent z expansion neutrino scattering result, a weighted average r$_{A}^{2}$ (ave:) = 0.46(16) fm2. 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 r$_{A}^{2}$ value which may be compared with other determinations, such as ongoing lattice gauge theory calculations. The importance of an improved r2A determination for phenomenology is illustrated by considering the impact on critical neutrino-nucleus cross sections at neutrino oscillation experiments. $\overline{g}$},
doi = {10.1088/1361-6633/aac190},
journal = {Reports on Progress in Physics},
number = 9,
volume = 81,
place = {United States},
year = {2018},
month = {5}
}

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