Radiative transitions of doubly charmed baryons in lattice QCD

We evaluate the spin-3/2 -> spin-1/2 electromagnetic transitions of the doubly charmed baryons on 2 + 1 flavor, 32(3) x 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 a minimal effect on the helicity and transition amplitudes. We predict the decay widths and lifetimes of Xi(cc)*(+,++) and Omega(cc)*(+) 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 -> Delta transition are discussed and compared to nonlattice determinations while keeping possible systematic artifacts in mind. A comparison to acy Omega(c)gamma -> Omega(c)* 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.