DEDX93VC

 

      Subroutine DEDX93VC (ITrk,TCVC,IOpt,dEdx,PresCor,NTrunc,NSat,IErr)  

This routine calculates a dE/dx value for the 1993 data -- VC version. It will return the necessary dE/dx information for a particular track in the CTD.

Depending on the various inputs the user can:

       Look at VC# tracks (TCVC# = 'VC')

       Obtain the dE/dx value already existing in the data (IOpt = 0)
    or Recalculate a value for dE/dx                       (IOpt = 1)
    or Just obtain a pressure correction for the data      (IOpt = 2)

    The outputs obtained are:

        dEdx - The truncated mean dE/dx value in FADC# counts
     PresCor - A pressure correction that the user should multiply
               dEdx by to get a rough pressure corrected dE/dx value
      NTrunc - Number of hits used in the truncated mean dE/dx
               calculation. The user should make cuts using this
               variable when analysing dE/dx data
        NSat - Number of hits used in the truncated mean dE/dx
               calculation that were saturated. The user should make
               cuts using this variable when analysing dE/dx data.
               Could be of use if trying to distinguish between very
               slow K and P.  

If There is an error dEdx will return as RNull. One of the possible errors for TC# is that there were insufficient hits on the track for a dE/dx value to be calculated.

IMPORTANT - The Pressure Correction

A rough pressure correction is output from the routine. This correction has many limitations and so has not been automatically applied to the data. Instead it is up to the user to decide whether to apply it by multiplying dEdx by PresCor. The correction works as follows. The pressure for the data is found using a routine supplied by Dave Bailey. 1013 is subtracted from this pressure, then it is multiplied by -0.013 (a change of pulse size of -1.3% per mBar) and inverted to obtain the pressure correction. When corrected the dE/dx value should correspond to what it would have been at 1013 mBar (Standard Atmospheric). The value of -0.013 was obtained by studying a range of runs. A general trend was clear, however an obvious correlation wasn't and the -0.013 is from a linear fit to data that had large fluctuations. You have been warned.

    INPUT:

      Tables:
            ZREVT ........ Event table
           VCTRHL ........ VCRECON track table
          TCRECON ........ TCRECON track table

      Arguments:
             ITrk ........ CTD track no. (TGTRAK_ID !)
             TCVC# ........ Track package to be used
                           'TC' => Use TCRECON tracks - NOT available
                           'VC' => Use VCRECON tracks - always used
             IOpt ........ Package Options
                           IOpt = 0 : Use existing dE/dx value
                           IOpt = 1 : Recalculate dE/dx value
                           IOpt = 2 : Find just the pressure
                                      correction

    OUTPUT:

      Tables:
             None ........ At present

      Arguments:
             dEdx ........ Truncated mean dE/dx value for track
          PresCor ........ Factor that dEdx should be multiplied by
                           to option a rough dEdx value corrected for
                           pressure in 1993
           NTrunc ........ No of hits used to calculated the
                           truncated mean dE/dx value
             NSat ........ No of hits used to calculated the
                           truncated mean dE/dx value that were
                           saturated

      Error codes:
         IErr = 0 ........ All OK
                1 ........ Error in obtaining pressure
                2 ........ Error in VC# Initialization
                3 ........ Error in VC# dE/dx calculation
                4 ........ No TC/TG track tables
                5 ........ Error in TC# event Initialization
                6 ........ Error in remaking TCHIT from TCBHRL
                7 ........ Error in making TCTRAK from TGTRAK
                8 ........ Error in TG Hit navigation
                9 ........ Error in TC# track refit
               10 ........ Error in TC# dE/dx calculation
               11 ........ Couldn't understand user input TCVC


      Author:              Julian Shulman

      Updates:
      Date      ^     Version    ^       Comments
^----------------^------------------------------------
    15/02/94    ^       1.0      ^     First release   (DEDX93)
     19/12/94    ^       1.1      ^     VC only version (DEDX93VC)
^----------------^------------------------------------