An investigation prompted by a Connecticut fire chief’s refusal to hang a photograph of the department’s first black chief on a wall of honor faulted him for racial insensitivity and concluded minority firefighters have reason to perceive racial bias in the department. The city of New Britain commissioned the investigation in May after receiving a complaint from an African-American firefighter who was disciplined for removing the portraits of five other white former chiefs from a hallway at the department headquarters. The law firm that did the investigation said in its report last week that interviews with minority employees found some felt they were held to a higher standard for disciplinary infractions than white firefighters.