We study persistent currents for interacting one-dimensional bosons on a tight ring trap, subjected to a rotating barrier potential, which induces an artificial U (1) gauge field. We show that, at intermediate interactions, the persistent current response is maximal, due to a subtle interplay of effects due to the barrier, the interaction and quantum fluctuations. These results are relevant for ongoing experiments with ultracold atomic gases on mesoscopic rings. 03.75.Lm, 71.10.Pm, 73.23.Ra A quantum fluid confined on a ring and subjected to a U (1) gauge potential displays a periodicity in the particle current as a function of the flux of the corresponding classical gauge field. This persistent current phenomenon is a manifestation of the Aharonov-Bohm effect, and reflects the macroscopic coherence of the manybody wave function along the ring. Such currents were observed more than 50 years ago in bulk superconductors [1] and, more recently, in normal metallic rings, overcoming the challenges of the decoherence induced by inelastic scattering [2]. The most recent developments in the manipulation of ultracold atoms on ring traps [3, 4] have disclosed a novel platform for the study of persistent currents, which can be induced by the application of a rotating localized barrier or, alternatively, by inducing suitable artificial gauge fields [5]. Tunable localized barriers in toroidal Bose-Einstein condensates have been realized, using well-focused, repulsively tuned laser beams [4]. Also, recently the engineering of an atomic superconducting quantum interference device was demonstrated [6]. The unprecedented variety of interaction and barrier strength regimes paves the way to applications such as high-precision measurements, atom interferometry and quantum information, e.g., by the construction of macroscopic superposition of current states and flux qubits [7][8][9].The scenario becomes particularly intriguing if the transverse section of the ring is sufficiently thin to effectively confine the system in one dimension (1D): the rich interplay between interactions, quantum fluctuations, and statistics acquires a role of primary relevance. In absence of any obstacle along the ring, the persistent currents display an ideal sawtooth behavior as a function of the flux, i.e., perfect superfluidity for any interaction strength at zero temperature [10, 11]. Diamagnetic or paramagnetic response depending on the population parity is expected [12] for fermions but not for bosons. If a localized barrier is added, persistent currents are smeared-their shape taking a sinusoidal form in the case of large-barrier or small-tunneling limit-as obtained for thin superconducting rings from a Luttinger-liquid approach [13]. Beyond these limiting regimes the physics of bosonic persistent current remains unexplored.The aim of the present work is to provide a complete characterization of persistent currents for 1D bosons, in all interaction and barrier strength regimes. By combining analytical as well as numerical techniques suited fo...