class THaHRS: public THaSpectrometer

 THaHRS

 The standard Hall A High Resolution Spectrometers (HRS).
 Contains three standard detectors,
    VDC
    Scintillator S1
    Scintillator S2

 The usual name of this object is either "R" or "L", for Left
 and Right HRS, respectively.

 Defines the functions FindVertices() and TrackCalc(), which are common
 to both the LeftHRS and the RightHRS.

 Special configurations of the HRS (e.g. more detectors, different
 detectors) can be supported in on e of three ways:

   1. Use the AddDetector() method to include a new detector
      in this apparatus.  The detector will be decoded properly,
      and its variables will be available for cuts and histograms.
      Its processing methods will also be called by the generic Reconstruct()
      algorithm implemented in THaSpectrometer::Reconstruct() and should
      be correctly handled if the detector class follows the standard
      interface design.

   2. Write a derived class that creates the detector in the
      constructor.  Write a new Reconstruct() method or extend the existing
      one if necessary.

   3. Write a new class inheriting from THaSpectrometer, using this
      class as an example.  This is appropriate if your HRS
      configuration has fewer or different detectors than the
      standard HRS. (It might not be sensible to provide a RemoveDetector()
      method since Reconstruct() relies on the presence of the
      standard detectors to some extent.)

  For timing calculations, S1 is treated as the scintillator at the
  'reference distance', corresponding to the pathlength correction
  matrix.