With this commit, db_run.dat is not needed in hcana
  If THcRunParms is used, hcana will get the beam momentum from the
  parameter "gpbeam" instead of db_run.dat.  To use, use the
  THaRun::SetRunParamClass method to set the run parameter class
  to "THcRunParameters".

  THaRun* run = new THaRun(RunFileName);
  run->SetRunParamClass("THcRunParameters");