Don't think it's Cooper. That guy you're talking about vaguely rembles Serge Chaloff, but his head ain't big enough, and I don't know that Chaloff played bass clarinet. Here's another shot from the same gig - Club Troubador, NYC, ca. 1947, with Georgie Auld standing up (and that's Red Rodney in both pix!)
BTW, Club Troubadour was a club opened by Auld, so that's probably his house band, not Kenton's. Don't think that's Kenton @ the piano.
Well, guess what? There's a photo of Chaloff as a member of Auld's band that I've heard is going to be used in the new Uptown Allan Eager set's booklet, and he's got the same doubles set up as in this picture. So that's definitely Serge Chaloff, big head or not.