BEVERLY — A Lowell man who was carrying nearly half a pound of heroin, and an EBT card that belonged to a Beverly drug user, was sentenced to eight years in prison yesterday after pleading guilty to a drug trafficking charge. Campeo Armando Diaz-Carola, 45, was originally facing a 15-year minimum mandatory term, but under a recent change in the drug laws and a charge reduction by prosecutors, received the eight-year term in a plea agreement accepted by Salem Superior Court Judge David Lowy.