class HMdcHit: public HMdcCellGroup6

_HADES_CLASS_DESCRIPTION

 HMdcHit

	This class represents one hit in one of the MDC
 planes. A hit is defined as a piece of a straight line
 reconstructed by a MDC chamber. It is, therefore, the highest
 level of information an individual chamber can provide.

	The coordinate system used in the MDC is the local
 MDC coordinate system. That is, in the z-midplane. For a
 particle moving outwards in the spectrometer, the z-midplane is
 defined at the entrance into the fourth cathode plane. x and y are
 expressed in mm

	xDir,yDir are the components of the three dimensional
 tangent unit vector to the track in the z-midplane, values equal
 to -1 indicate that the direction has not been calculated

      cov is the 5x5 covariance matrix of the fit.

 	The base class HMdcCellGroup  provides a mechanism to know
      which cells contributed to a particular hit. This info is retrieved
      with the following functions of this base class:

 * Int_t getNCells(Int_t layer)
	Returns the number of cells in layer "layer" which contributed
	to the hit.

 * Int_t getCell(Int_t layer,Int_t idx)
      For idx=0 returns the cell number of the first fired cell
      For idx=1 returns the cell number of the second fired cell
	.... (maximum idx=3)

 * Int_t HMdcHit::getSignId(Int_t layer,Int_t idx)
	Returns signal id (time/distance) in cell designed by
	idx (same criterium as before).

 * Int_t setSignId(Int_t layer,Int_t cell, Int_t t1,t2=0,t3=0,t4=0)
	Sets the signal ids and base cell number for layer "layer"
	Input:
	  layer --> Number of layer to set
	  cell  --> Number of the first cell fired in this layer
	  t1 - t4 --> SignalId for cells: "cell"+0, "cell"+1 ... "cell"+4
	              Possible values are:
	                0 --> This cell has not fired
	                1 --> First signal (time/distance) was used
	                2 --> Second signal (time/distance) was used

 * Short_t getTrackFinder()
      Returns the type of track finder (Dubna, Santiago, ...)
      For Dubna track finder it retutns 1.

    The meanings of data member "index" depend from type of track finder
 (Dubna, Santiago, ...)

 Dubna track finder:
   "index" is index of HMdcClusInf object
   in category catMdcClusInf (see mdctrackD/hmdcclusinf.cc)
   Function  getClusInfIndex() return this index.

   Number and oder of HMdcClusInf objects in catMdcClusInf
   are the very same as number and order of HMdcHit objects in
   catMdcHit. You can use it in T->Draw(...) function:
   T-Draw("HMdcHit.fData.y : HMdcClusInf.fData.clusSize", ...)