A 20-year-old Amherst man has been sentenced to up to nine years in prison for beating a 62-year-old woman during a burglary. Yaazziel Rivera was sentenced Monday in Hampshire Superior Court after pleading guilty to a pair of robberies in Northampton a few days apart in August 2011, one of which included the assault. Authorities said Rivera entered a home he thought was vacant by removing an air conditioner from a first-floor window. He struck the woman five or six times over the head and threatened to kill her if she got up off the floor. Rivera stole $60 in cash and some jewelry.