scholarly journals Bounds on the tau and muon neutrino vector and axial vector charge radius

2003 ◽  
Vol 67 (3) ◽  
Author(s):  
Martin Hirsch ◽  
Enrico Nardi ◽  
Diego Restrepo
Keyword(s):  
Charge Radius ◽  
Axial Vector ◽  
Muon Neutrino ◽  
Vector Charge

scholarly journals CONNECTING STRUCTURE FUNCTIONS ON THE LATTICE WITH PHENOMENOLOGY

2003 ◽  
Vol 18 (08) ◽  
pp. 1343-1350 ◽  
Author(s):  
W. DETMOLD ◽  
W. MELNITCHOUK ◽  
A. W. THOMAS
Keyword(s):  
Chiral Symmetry ◽  
Quark Mass ◽  
Axial Vector ◽  
Mass Dependence ◽  
Lattice Data ◽  
Parton Distributions ◽  
Chiral Extrapolation ◽  
Vector Charge ◽  
Quark Mass Dependence

We examine the extraction of moments of parton distributions from lattice data, focusing in particular on the chiral extrapolation as a function of the quark mass. Inclusion of the correct chiral behavior of the spin-averaged isovector distribution resolves a long-standing discrepancy between the lattice moments and experiment. We extract the x-dependence of the valence u - d distribution from the lowest few lattice moments, and discuss the implications for the quark mass dependence of meson masses lying on the a2 Regge trajectory. The role of chiral symmetry in spin-dependent distributions, and in particular the lattice axial vector charge, gA, is also highlighted.

scholarly journals The proton size puzzle: experiment vs theory.

2018 ◽  
Vol 191 ◽  
pp. 04001 ◽  
Author(s):  
A. E. Dorokhov ◽  
A. P. Martynenko ◽  
F. A. Martynenko ◽  
A. E. Radzhabov
Keyword(s):  
Charge Radius ◽  
Axial Vector ◽  
Muonic Hydrogen ◽  
Current Status ◽  
Interaction Operator ◽  
Two Photon ◽  
Proton Charge ◽  
Proton Charge Radius ◽  
Points Of View ◽  
Precise Experimental Data

Current status of the proton size puzzle from experimental and theoretical points of view is briefly discussed. The interest to these studies is primarily related to experiments conducted by the CREMA collaboration (Charge Radius Experi- ments with Muonic Atoms) with muonic hydrogen and deuterium by methods of laser spectroscopy. As a result a more accurate value of the proton charge radius was found to be rp = 0:84184(67) fm, which is different from the value recommended by CODATA for 7σ. In the second part we discuss recent calculations of the contribution of light pseudoscalar (PS) and axial-vector (AV) mesons to the interaction operator of a muon and a proton in muonic hydrogen atom, with the coupling of mesons to the muon being via two-photon intermediate state. Numerical estimates of the contributions to the hyperfine structure of the spectrum of the S and P levels are presented. It is shown that such contribution to the hyperfine splitting in muonic hydrogen is rather important for a comparison with precise experimental data.

scholarly journals FURTHER COMMENTS ON A VANISHING SINGLET AXIAL VECTOR CHARGE

1999 ◽  
Vol 14 (03) ◽  
pp. 205-209 ◽  
Author(s):  
T. P. CHENG ◽  
N. I. KOCHELEV ◽  
VICENTE VENTO
Keyword(s):  
Heavy Quark ◽  
Quark Model ◽  
Perturbative Qcd ◽  
Axial Vector ◽  
Chiral Quark Model ◽  
Axial Charge ◽  
Vacuum Structure ◽  
Recent Suggestion ◽  
Quark Coupling ◽  
Vector Charge

The recent suggestion of a vanishing flavor-singlet axial-charge of nucleon due to a nontrivial vacuum structure is further amplified. A perturbative QCD discussion, applicable for the heavy quark contributions, relates it to the physics of the decoupling theorem. It is also shown that [Formula: see text] leads to a negative η′-meson-quark coupling, which has been found to be compatible with the chiral quark model phenomenology.

Sign in / Sign up

Export Citation Format

Share Document