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,r2 A (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,λMuCap singlet = 715.6(7.4)s-1, to update the induced pseudoscalar nucleon coupling gpMuCap = 8.23(83) derived from experiment, and gptheory = 8.25(25) predicted by chiral perturbation theory. Accounting for correlated errors this implies gptheory/ gpMuCap = 1.00(8), confirming theory at the 8% level. If instead, the predicted expression for is employed as input, then the capture rate alone determines r2 A (μH) = 0.46(24)fm2, or r2 A(ave.)=0.46(16)fm2 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.
|Journal||Reports on Progress in Physics|
|State||Published - Jul 30 2018|
Bibliographical noteFunding Information:
We thank M Hoferichter for helpful discussion of the pion-nucleon coupling. We acknowledge the Institute for Nuclear Theory at the University of Washington, where the idea for this review was conceived. RJH thanks TRIUMF for hospitality where a part of this work was performed. Research of RJH was supported by a NIST Precision Measurement Grant. Research at Perimeter Institute is supported by the Government of Canada through the Department of Innovation, Science and Economic Development and by the Province of Ontario through the Ministry of Research and Innovation. Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. The work of PK was supported by the US Department of Energy Office of Science, Office of Nuclear Physics under Award No. DE-FG02-97ER41020. The work of WJM was supported by the US Department of Energy under grant DE-SC0012704. The work of AS was supported in part by the National Science Foundation under Grant PHY-1620039.
The work of PK was supported by the US Department of Energy Office of Science, Office of Nuclear Physics under Award No. DE-FG02-97ER41020. The work of WJM was supported by the US Department of Energy under grant DE-SC0012704. The work of AS was supported in part by the National Science Foundation under Grant PHY-1620039.
© 2018 IOP Publishing Ltd.
- muon capture
- neutrino oscillation
- neutrino scattering
- nucleon form factors
- radiative corrections
- weak axial current
ASJC Scopus subject areas
- Physics and Astronomy (all)