arXiv subjects

N. L. Hall

Publications and source records attributed to N. L. Hall.

5 recordsLinked to original sources

arXiv2015

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

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 Q^2 \approx 1 GeV^2. 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 e\, \square_{γZ}^V = (5.4 \pm 0.4) \times 10^{-3} at the kinematics of the Q_{\text{weak}} 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.

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arXiv2014

Hadronic gamma-Z box corrections in M\oller scattering

The possibility of measuring the parity-violating asymmetry in M\oller scattering with sufficient accuracy to determine sin^2 theta_W to 0.1% offers a complementary path to the discovery of new physics to that followed at high energy colliders. We present a new calculation of the gamma-Z box contribution to parity-violating electron-proton scattering, which constitutes an important uncertainty in computing the background to this process. We show that while the gamma-Z correction grows rapidly with energy, it can be relatively well constrained by data from parity-violating inelastic scattering and parton distribution functions.

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arXiv2014

Momentum transfer dependence of the proton's electric and magnetic polarizabilities

The Q^2-dependence of the sum of the electric and magnetic polarizabilities of the proton is calculated over the range 0 \leq Q^2 \leq 6 GeV^2 using the generalized Baldin sum rule. Employing a parametrization of the F_1 structure function valid down to Q^2 = 0.06 GeV^2, the polarizabilities at the real photon point are found by extrapolating the results of finite Q^2 to Q^2 = 0 GeV^2. We determine the evolution over four-momentum transfer to be consistent with the Baldin sum rule using photoproduction data, obtaining α+ β= 13.7 \pm 0.7 \times 10^{-4}\, \text{fm}^3.

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arXiv2013

Constrained gamma-Z interference corrections to parity-violating electron scattering

We present a comprehensive analysis of gamma-Z interference corrections to the weak charge of the proton measured in parity-violating electron scattering, including a survey of existing models and a critical analysis of their uncertainties. Constraints from parton distributions in the deep-inelastic region, together with new data on parity-violating electron scattering in the resonance region, result in significantly smaller uncertainties on the corrections compared to previous estimates. At the kinematics of the Qweak experiment, we determine the gamma-Z box correction to be ReBox^V_{gamma-Z} = (5.57 +- 0.36) x 10^{-3}. The new constraints also allow precise predictions to be made for parity-violating deep-inelastic asymmetries on the deuteron.

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arXiv2012

Volume Dependence of the Axial Charge of the Nucleon

It is shown that the strong volume-dependence of the axial charge of the nucleon seen in lattice QCD calculations can be understood quantitatively in terms of the pion-induced interactions between neighbouring nucleons. The associated wave function renormalization leads to an increased suppression of the axial charge as the strength of the interaction increases, either because of a decrease in lattice size or in pion mass.

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