Radiative transitions of doubly charmed baryons in lattice QCD

TL;DR

This study uses lattice QCD to analyze electromagnetic transitions of doubly charmed baryons, revealing that magnetic dipole transitions dominate and providing decay predictions relevant for experimental searches.

Contribution

First lattice QCD calculation of spin-3/2 to spin-1/2 electromagnetic transitions in doubly charmed baryons, including form factors and decay widths.

Findings

Magnetic dipole (M1) transition is dominant.

Electric quadrupole (E2) form factors are negligible.

Predicted decay widths and lifetimes for specific doubly charmed baryons.

Abstract

We evaluate the spin-$3/2 \to$ spin-$1/2$ electromagnetic transitions of the doubly charmed baryons on 2+1 flavor, $32^3 \times 64$ PACS-CS lattices with a pion mass of $156(9)$ MeV/c$^2$. A relativistic heavy quark action is employed to minimize the associated systematic errors on charm-quark observables. We extract the magnetic dipole, $M1$, and the electric quadrupole, $E2$, transition form factors. In order to make a reliable estimate of the $M1$ form factor, we carry out an analysis by including the effect of excited-state contributions. We find that the $M1$ transition is dominant and light degrees of freedom ($u/d$- or $s$-quark) play the leading role. $E2$ form factors, on the other hand, are found to be negligibly small, which in turn, have minimal effect on the helicity and transition amplitudes. We predict the decay widths and lifetimes of $\Xi_{cc}^{\ast +,++}$ and $\Omega_{cc}^{\ast +}$ based on our results. Finite size effects on these ensembles are expected to be around 1\%. Differences in kinematical and dynamical factors with respect to the $N\gamma\to\Delta$ transition are discussed and compared to non-lattice determinations as well keeping possible systematic artifacts in mind. A comparison to $\Omega_c \gamma \rightarrow \Omega_c^\ast$ transition and a discussion on systematic errors related to the choice of heavy quark action are also given. Results we present here are particularly suggestive for experimental facilities such as LHCb, PANDA, Belle II and BESIII to search for further states.