What does he have?

[milobloom]

1-2 No-limit, B&M game. Mostly young players, fairly loose. I am new to game. This player appears tighter than most at table. UTG calls and player to my right calls, I'm 3-off button. I raise to $15 with K [img]/images/graemlins/club.gif[/img]K [img]/images/graemlins/heart.gif[/img]. UTG calls, all others fold. Flop is T [img]/images/graemlins/club.gif[/img]A [img]/images/graemlins/club.gif[/img]3 [img]/images/graemlins/club.gif[/img]. UTG checks, I bet $20 into pot of $37. He calls. Turn is 4 [img]/images/graemlins/diamond.gif[/img]. He checks, I bet $40, he calls. River is 7 [img]/images/graemlins/heart.gif[/img], he bets $55. Now what?