WASHINGTON (AP) — Senators have fired a barrage of criticism at a Facebook executive over the social-networking giant’s handling of internal research on how its Instagram photo-sharing platform can harm teens. The lawmakers accused Facebook of concealing the negative findings about Instagram and demanded a commitment from the company to make changes. During testimony before a Senate Commerce subcommittee, Facebook’s head of global safety Antigone Davis defended Instagram’s effort to protect young people using its platform. The panel is examining Facebook’s use of information from its own researchers that could indicate potential harm for some of its young users, especially girls, while it publicly downplayed the negative impacts.