• The files are stored - for the moment - on AFS.
• Tracks can be visualized using a simple plotter called gnuplot (version 3.6 or 3.7).
  
  • HP-UX: it is available on ion01, ion02, ion03.
  • PC Linux: only the old 3.5 version is installed, but you can have it using my compiled 3.7 version which is at ~fsikler/public/gnuplot/bin/gnuplot (make an alias to this).
  • Otherwise you can get the latest gnuplot 3.7 version from here.
  
  
  

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• Full event scan:
  100 p+p (pp) and 100 p+Pb (CD>=7) (ppbc) events are prepared for study.
  The event selection is identical to what was used in p+p analysis before, the validity of the cuts is checked (look at ® cuts here).
  No track selection is applied, thus all the global rtracks are used, this can help us understand the meaning of the various iflags.
  
  The viewer call is given below.
  The 'event' field composition, just an example:
  
  • 'ppbc/15'
    means reacion p+Pb, 15th event.
    
  
  
  

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• Bin-by-bin track scan:
  The aim is to look at tracks with both positive and negative charges, in selected 5×5 bins in (p,p_T).
  Now p+Pb (CD>=7) (ppbc) events are prepared for study.
  The event selection is identical to what was used in p+p analysis before, the validity of the cuts is checked (look at ® cuts here).
  Track selection: global rtracks with iflag=0,1,2,3,4,5 are used. Tracks with iflag>0 are in principle not compatible with the vertex: in their case the rtrack momentum was used to determine p and p_T at vertex_fit->z.
  
  The viewer call is given below.
  The 'event' field composition, just two examples:
  
  • 'ppbc/pos_p=3-6_pt=0.7-0.9'
    means positive, p between 3 and 6 GeV/c and p_T between 0.7 and 0.9 GeV/c.
    
  • 'ppbc/neg_p=10-15_pt=0.0-0.2'
    means negative, p between 10 and 15 GeV/c and p_T between 0.0 and 0.2 GeV/c.
  Hopefully we will have 100 tracks in each bin that can be accessed via the 'track' field by giving numbers between 0 and 99.
  
  

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• How to use it?
  Read the following thoroughly!
  • Login to AFS
  • Type cd ~fsikler/public/ips/tracking/view
  • Type gnuplot (look at machine dependencies here)

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  • The viewer call (after the prompt):
    gnuplot> call "plot" 'event' 'low z' 'high z' 'low x/y' 'high x/y' 'track' 'view'
    where
    • 'event': see above
    • 'track': track number 0-
      if there are no more tracks in the event the message
      "No tracks with sequential number ..." appears
      The 'track'='-1' setting gives all points and global tracks, an overview (available only for 'full event scan').
    • 'view' : 0 for topview (z-x), 1 for sideview (z-y)
      Look at both views!
    • 'low and high x/y/z': determines the vertical and horizontal range for the plot, given in cm. Change this values to zoom in/out.
    Example:
    gnuplot> call "plot" 'pp/17' '-600' '800' '-400' '400' 1 0
    will display track 1 from the p+p event number 17, in topview mode.
    Single and double quotes are important!
    

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  • Graphics
    

    Blue:	points belonging to the chosen track
    Red:	surrounding points of another tracks
    Lightblue:	unused points
    Open square:	fitted first point
    Green:	result of the tracking without vertex constraint, line
    Purple:	result of the tracking with vertex constraint, line

    Labels - the above mentioned track numbers - are also plotted, centered on track pieces. They allow cross-checks with other tracks. The borders of the TPCs are indicated using straight lines (MTPCs are not rotated).
    Make the graphics window big enough in order to see the points.

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  • Printout
    After each call a line in the following format is printed and appears as a title in the graphics window:
    p=('px','py','pz') b=('bx','by') fit='fitted points' a/p=('vt1','vt2','mt') iflag='iflag'
    where
    • 'px','py','pz': track momentum components in GeV/c
    • 'bx','by': impact parameters at vertex->z in cm
    • 'a/p': actual over potential point ratios in the three TPCs in percent
      0% means: no actual points, although there are potential points
      -1% means: track cannot have points, i.e. there are no potential points
      
    • 'iflag': track iflag
    Example:
    gnuplot> call "plot" 'pp/17' '-600' '800' '-400' '400' 1 0
    p=(-0.179 0.164 5.013) b=(-0.08 0.09) fit=80 a/p=(66%|96%|71%) iflag=0

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  • You can quit gnuplot by typing q or quit or exit