Search for double-electron capture in ¹⁵² Gd with GAGG:Ce scintillator

Abstract Double-electron capture in 152 Gd was searched for over 1336 h with a 286-g GAGG:Ce crystal scintillator at the Gran Sasso underground laboratory of the INFN (Italy). New, improved by four orders of magnitude, limit on the near-resonant 0ν2EC capture in 152 Gd was set as lim T 1/2 = 8.1 x 10 16 yr at 90% C.L. Moreover, for the first time, a laboratory experiment has established a lower limit on the half-life of the allowed 2νKL process in the nuclide, with lim T 1/2 = 9.2 x 10 16 yr at 90% C.L.