Quantum Monte Carlo calculations of electromagnetic transitions in light nuclei

Recently, we presented ab initio quantum Monte Carlo calculations of magnetic moments and M1 transitions in $A \le 10$ nuclei, which include two-body meson-exchange currents' contributions of one- and two-pion range, derived from chiral effective field. These corrections are found to always improve the theoretical predictions, leading to a very good agreement with the experimental data. Here, we report on a study, carried out within the same framework, of M1 transitions in low-lying states of $^8$Be. We also present a number of E2 transition calculations, evaluated in impulse approximation, with emphasis on transitions involving the $^8$Be resonant excited states at $\sim 3$ MeV and $\sim 11$ MeV.