Neutron magnetic polarisability with Landau mode operators

Abstract

The application of a uniform background magnetic field makes standard quark operators utilising gauge-covariant Gaussian smearing inefficient at isolating the ground state nucleon at nontrivial field strengths. In the absence of QCD interactions, Landau modes govern the quark energy levels. There is evidence that residual Landau mode effects remain when the strong interaction is turned on. Here we introduce novel quark operators constructed from the two-dimensional $U(1)$ Laplacian eigenmodes that describe the Landau levels of a charged particle on a periodic finite lattice. These eigenmode-projected quark operators provide enhanced precision for calculating nucleon energy shifts in a magnetic field. Using asymmetric source and sink operators, we are able to encapsulate the predominant effects of both the QCD and QED interactions in the interpolating fields for the neutron. The neutron magnetic polarizability is calculated using these techniques on the $32^3\times 64$ dynamical QCD lattices provided by the PACS-CS Collaboration. In conjunction with a chiral effective-field theory analysis, we obtain a neutron magnetic polarizability of ${\beta }^n=2.05(25)(19)\times 10^{-4}$ fm${}^3$, where the numbers in parentheses describe statistical and systematic uncertainties.

arXiv commentv2:Improved discussion on crucial points, systematics; new version to match published version

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Cited by in corpus (11)

• Nuclear matrix elements from lattice QCD for electroweak and beyond-Standard-Model processes
• Pion magnetic polarisability using the background field method
• Magnetic polarisability of the nucleon using a Laplacian mode projection
• Pion in a uniform background magnetic field with clover fermions
• Nucleon polarizabilities in covariant baryon chiral perturbation theory with explicit $\Delta$ degrees of freedom
• Chiral extrapolation of the charged-pion magnetic polarizability with Padé approximant
• Chiral extrapolation of the magnetic polarizability of the neutral pion
• Chiral Analysis of the Nucleon Mass and Sigma Commutator
• Magnetic Polarisability of Octet Baryons via Lattice QCD
• Recent results of nucleon structure & matrix element calculations
• Energy of a point-like neutron in an external electromagnetic field