Bose-glass and entanglement - disentanglement transitions in YBa2Cu3O7

The Bose-glass transition field B-BG in YBa2Cu3O7 single crystals with columnar defects is tracked by the onset of the third harmonic generation. The progressive upward shift of the B-BG(T)-line with the irradiation dose is followed by a saturation for the matching fields B-phi=20 kG - 100 kG. The uppermost position of the Bose-glass transition is interpreted as a boundary between entangled and disentangled vortex Liquids in virgin YBa2CU3O7.