Cops are after a man who allegedly assaulted a 54-year-old woman on the L train. 

Police say the suspect got into an argument with the woman at the Lorimer Street station last month and then followed her into a car. 

He's accused of slamming the victim's head against a metal pole and throwing her to the ground. 

Investigators released a surveillance photo of the man, and urge anyone with information to call Crime Stoppers at 1-800-577-TIPS.