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 a
ssociated 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 $NgammatoDelta$ 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.
We evaluate the electromagnetic $Xi_c gamma rightarrowXi_c^prime$ transition on 2+1 flavor lattices corresponding to a pion mass of $sim 156$ MeV. We extract the magnetic Sachs and Pauli form factors which give the $Xi_c$-$Xi_c^prime$ transition magn
etic moment and the decay rates of $Xi_c^prime$ baryons. We did not find a signal for the magnetic form factor of the neutral transition $Xi_c^0 gamma rightarrowXi_c^{prime 0}$, which is suppressed by the U-spin flavor symmetry. As a byproduct, we extract the magnetic form factors and the magnetic moments of $Xi_c$ and $Xi_c^prime$ baryons, which give an insight to the dynamics of $u/d$, $s$ and $c$ quarks having masses at different scales.
We study the electromagnetic $Omega_c gamma rightarrowOmega_c^ast$ transition in 2+1 flavor lattice QCD, which gives access to the dominant decay mode of $Omega_c^ast$ baryon. The magnetic dipole and the electric quadrupole transition form factors ar
e computed. The magnetic dipole form factor is found to be mainly determined by the strange quark and the electric quadrupole form factor to be negligibly small, in consistency with the quark model. We also evaluate the helicity amplitudes and the decay rate.
