The assoault happened at around 8.20pm on Friday 30 August, the victim, a 14 year old girl was hit in the head by a woman. The BTP have released and image of a woman in connection with the assault, the woman also left the train at Rhyl
Officers would like to speak to the woman pictured as they believe she may have information which could help with their investigation.
Anyone with information is asked to contact BTP by texting 61016 or by calling 0800 40 50 40, quoting reference 2400095981 of 30 August.
Alternatively, you can contact Crimestoppers anonymously on 0800 555 111.