I updated the momentum settings in the run database. Both arms had been set at 1.1615 GeV/c and had not been updated since 6/27/2010. I set them both to the correct setting of 1.131 GeV/c, and set the "date updated" to 7/04/2010. Now all runs after this date will have the correct momentum (after being replayed again of course).
Attached are plots of the momentum of each arm summed together (left_p + right_p). There was a cut made on the D.t1 coincident peak, so only coincident events are plotted. Figure 1 was made before the database was updated, and Figure 2 was made after. The beam energy was 2.261 GeV/c. One can see that the summed momentums are larger than the beam energy before the update (not physical for coincident events). The peak of the 2nd plot is right around the correct beam energy.