Explanation: To document user goals, common tasks, and pain points for a new service experience, the tool that a UX Designer should use is user personas. User personas are fictional representations of the target users, based on real data and research. User personas help the designer to understand the needs, motivations, behaviors, and expectations of the users, as well as their challenges and frustrations. User personas can also help the designer to prioritize features, create scenarios, and design solutions that are relevant and meaningful for the users.