Magnetic moments and polarizabilities of hadrons from dynamical QCD configurations.

摘要

We present the first calculations of magnetic polarizabilities of hadrons within the framework of dynamical lattice QCD. From the same data set, we also extract magnetic moments. The dynamical gauge configurations were generated by the CP-PACS collaboration on lattices of sizes 123x24, 163x32 and 243x48 with a constant spatial volume of (2.5 fm)3. We follow two approaches of introducing the magnetic field onto the lattice and have found much disagreement between the two. The linearization of the U(1) gauge field, which has been employed in numerous works previous, produces strong signals for nearly every particle. These calculations are also the first to employ the alternative method in the magnetic case, namely, using the full U(1) exponential phase. These data are noisy and fail to produce a plateau in several cases. The magnetic moment data for the full exponential case are clean and produce strong plateaus with small errors. With the smallest quark mass being around 500 MeV, a chiral extrapolation was not attempted. However, our linear results show little mpi-dependence, and thus where available we compare with experiment and theoretical calculations from the lattice, effective field theories, and other models.