Batter-Runner Misses First Base on Ground Ball

 
With no runners on base, the batter (B1) grounds to the shortstop. The throw from the shortstop to 1st base is a off-line and pulls the first baseman off the base before he catches the throw. 
 
As the first baseman moves back to touch the base, B1 crosses the base (but steps over the base without touching it). The first baseman does return to touch the bag -- but he touches the base just after B1 has passed over the base.
 
What is the base umpire's initial call on this play?
 
Can the defense appeal the missed base? If so, how?
 
Call
If the batter-runner beats the play to first base but the batter-runner misses touching first base, the umpire should signal "safe". The defense can appeal the missed base by then touching the batter-runner or the base (with the ball) before the batter-runner returns to first base.  
 
In the play below, although the first baseman returned to touch 1st base after B1 passed over the base, the umpire should not rule on an appeal until the defense makes an intentional appeal of the missed base and tags either the runner or the base before the runner returns to retouch 1st base (see NF Casebook 8.2.6f).