WORCESTER, Mass. — A Worcester police officer accused of beating a prisoner in a holding cell last December has pleaded not guilty to assault and battery with a dangerous weapon.The Telegram & Gazette reports 50-year-old Michael Motyka was arrested in April after an internal investigation found that he handcuffed 48-year-old Gerald Jones before punching and kicking him.Prosecutors say the investigation began after a complaint from Jones, who said Motyka made disparaging racial remarks while beating him.