Quark–hadron duality constraints on γZ box corrections to parity-violating elastic scattering

N.L Hall,P.G Blunden,W Melnitchouk,A.W Thomas,R.D Young

doi:10.1016/j.physletb.2015.11.081

Abstract

We examine the interference γZ box corrections to parity-violating elastic electron–proton scattering in the light of the recent observation of quark–hadron duality in parity-violating deep-inelastic scattering from the deuteron, and the approximate isospin independence of duality in the electromagnetic nucleon structure functions down to Q2≈1 GeV2. Assuming that a similar behavior also holds for the γZ proton structure functions, we find that duality constrains the γZ box correction to the proton's weak charge to be ℜe□γZV=(5.4±0.4)×10−3 at the kinematics of the Qweak experiment. Within the same model we also provide estimates of the γZ corrections for future parity-violating experiments, such as MOLLER at Jefferson Lab and MESA at Mainz.

Highlights

Parity-violating precision measurements have for many years provided crucial low-energy tests of the Standard Model
We examine the interference γ Z box corrections to parity-violating elastic electron–proton scattering in the light of the recent observation of quark–hadron duality in parity-violating deep-inelastic scattering from the deuteron, and the approximate isospin independence of duality in the electromagnetic nucleon structure functions down to Q 2 ≈ 1 GeV2
Since the electromagnetic structure functions are reasonably well approximated by the leading twist (LT) results even below the traditional resonance-deep-inelastic scattering (DIS) boundary of W 2 = 4 GeV2, we examine the effect of lowering the W 2 cut into the peripheral resonance region down to W 2 = 3 GeV2

Summary

Introduction

Parity-violating precision measurements have for many years provided crucial low-energy tests of the Standard Model. Recent analysis of moments of the free neutron electromagnetic structure function [28] has demonstrated that duality in the lowest three neutron moments is violated at a similar level ( 10%) as in the proton for Q 2 1 GeV2 [20,21,26]. This suggests that the isospin dependence of duality and its violation is relatively weak.

Duality in electromagnetic structure functions

Findings

Conclusion