Magnetic field dependence of nucleon parameters from QCD sum rules

TL;DR

This study uses QCD sum rules to analyze how nucleon parameters such as mass, coupling, and condensates change under strong magnetic fields, revealing flavor-dependent evolution of these parameters.

Contribution

It provides the first detailed calculation of nucleon and quark parameters' magnetic field dependence using finite energy QCD sum rules, including flavor asymmetries.

Findings

Parameters evolve differently for protons and neutrons.

Quantitative dependence of nucleon mass and condensates on magnetic field.

Applicable up to magnetic field strength of 1.4 GeV^2.

Abstract

Finite energy QCD sum rules involving nucleon current correlators are used to determine several QCD and hadronic parameters in the presence of an external, uniform, large magnetic field. The continuum hadronic threshold $s_0$, nucleon mass $m_N$, current-nucleon coupling $\lambda_N$, transverse velocity $v_\perp$, the spin polarization condensate $\langle\bar q\sigma_{12} q\rangle$, and the magnetic susceptibility of the quark condensate $\chi_q$, are obtained for the case of protons and neutrons. Due to the magnetic field, and charge asymmetry of light quarks up and down, all the obtained quantities evolve differently with the magnetic field, for each nucleon or quark flavor. With this approach it is possible to obtain the evolution of the above parameters up to a magnetic field strength $eB < 1.4$ GeV$^2$.