If user experience is the brand, then what is marketing? Marketing is deciding how to get what products to which customers via which channels at what price, and how to tell the customers about it. Of course, each of these impacts user experience.
The normal domain of user experience professionals (usability, human factors, interaction design, graphic design, industrial design, etc.) is on the product and one potential channel, the web site. Retail stores and advertising are left to other groups of professionals, who generally do not call themselves user experience professionals.
In one model of working together, Marketing tells User Experience (and other groups) what product features to make for which user groups. The UX team then performs its own research to fill in the holes and determines detailed product requirements. UX then works closely with the development team to design and implement the product.
In a second model of working together, Marketing and UX have a more equal role. UX knowledge of detailed user behavior influences Marketing's decision on target segments and product requirements, which influence UX research and development activities. UX then works with the development team to deliver the product.
The former model is more common, but the latter can help drive revenues - particularly for companies that derive revenues after the purchase decision has been made, during normal use. If Brita water pitchers were really difficult to use, users would switch over to another brand. If Gilette razors are not smooth, users will switch. And if a wireless carrier has difficult to use products and a poor user experience in general, users will switch as soon as local number portability and their contract allows.
For the wireless industry at least, Marketing and Sales were responsible for the user experience up to the point of purchase; User Experience and Customer Care were responsible for the user experience after the point of purchase. If the company understands this, profits rise.