Baryon Octet to Decuplet Electromagnetic Transitions

TL;DR

This paper uses lattice QCD simulations to study electromagnetic transition moments between baryon octet and decuplet states, finding results consistent with experiments and quark models, and revealing new insights into quark contributions and multipole ratios.

Contribution

It provides the first lattice QCD calculations of baryon octet to decuplet electromagnetic transition moments, including detailed analysis of multipole ratios and quark contributions.

Findings

Magnetic transition moment for N to Delta matches experimental data.

Lattice results for hyperon M1 transition moments agree with quark models.

Significant nonzero E2/M1 ratios observed in Xi- and Sigma- transitions.

Abstract

The electromagnetic transition moments of the $SU(3)$-flavor baryon octet to decuplet are examined within a lattice simulation of quenched QCD. The magnetic transition moment for the $N \; \gamma \to \Delta$ channel is found to be in agreement with recent experimental analyses. The lattice results indicate $\mu_{p \Delta} / \mu_p = 0.88(15)$. In terms of the Particle Data Group convention, $f_{M1} = 0.231(41)$ GeV${}^{-1/2}$ for $p \; \gamma \to \Delta^+$ transitions. Lattice predictions for the hyperon $M1$ transition moments agree with those of a simple quark model. However the manner in which the quarks contribute to the transition moments in the lattice simulation is different from that anticipated by quark model calculations. The scalar quadrupole form factor exhibits a behavior consistent with previous multipole analyses. The $E2/M1$ multipole transition moment ratios are also determined. The lattice results suggest $R_{EM} \equiv -{\cal G}_{E2}/{\cal G}_{M1} = +3\pm 8$ \% for $p \; \gamma \to \Delta^+$ transitions. Of particular interest are significant nonvanishing signals for the $E2/M1$ ratio in $\Xi^-$ and $\Sigma^-$ electromagnetic transitions.