SALEM – A Lynn man may serve up to two and a half years in state prison after admitting he slapped his girlfriend and beat her daughter with a baton, causing a fractured nose and injury to her eye, during a domestic dispute at their Hanover Street home in June.Gary Cowart, 54, of 38 Hanover St., #10, pleaded guilty Monday afternoon in Salem Superior Court to charges of assault and battery with a dangerous weapon, causing serious bodily injury, and assault and battery.Judge David A. Lowry sentenced him to serve 2-21/2 years in state prison.Cowart slapped his 49-year-old girlfriend in the face and then took a baton bat to her daughter during a domestic dispute at their apartment at 34 Hanover St. in Lynn on June 11.Assistant District Attorney Karen Hopwood had argued for a four-year prison term with probation based on the facts of the case and Cowart’s past criminal record.Defense lawyer Christopher Norris asked for leniency, suggesting 30 months in the House of Corrections, and said his client has changed his life.The girlfriend’s daughter was present during the hearing.Cowart apologized to her, saying tearfully he was sorry.The judge credited Cowart for 206 days he has spent in jail awaiting trial.