Change%20of%20Co-ordinate%20system

1
Change of Co-ordinate system

• Niels proposal, 28-Nov-2006
• Will not solve all problems, each test beam
  running period will be different from others
• Will reduce confusion between simulation/data
  systems by use of same co-ordinate system
• Changes to many separate parts of Mokka/reco code
• Risk of delays to analysis/calibration
• Few email/telephone discussions, mostly with
  authors of Mokka drivers (Gabriel, Oliver W.,
  Fabrizio, Roman, Erika, ?Guilherme)
• Check technical feasibility of changes
• Timescale/willingness for (possible)
  implementation
• Commitment to make changes by mid-Jan. 2007,
  allow for testing/debugging before the DESY
  meeting 12-14 Feb.

2
Current Proposal

• 1. z axis defined by nominal beam direction. In
  the experimental area, this is physically
  indicated on the floor (I believe).
• 2. y axis vertically upwards.
• 3. x axis completes right-handed coordinate
  system.
• 4. Origin define z0 as intersection of the
  upstream face of first scintillator counter in
  the beamline with nominal beam direction. This
  is SC1 in Fabrizio's diagrams,
• DESY May'06 http//www.pp.rhul.ac.uk/7Ecalice/fab
  /TestBeams/DesytbArea.ps,
• CERN Aug'06 http//www.pp.rhul.ac.uk/7Ecalice/fab
  /TestBeams/CerntbArea.ps
• CERN Oct'06 http//www.pp.rhul.ac.uk/7Ecalice/fab
  /TestBeams/CerntbAreaOct.ps
• Note that detector "Sc1" is not the same physical
  device in each configuration.
• 5. Assume that SC1 is centred on the z-axis in
  both x and y-directions (unless we have actual
  measurements to the contrary.
• 6. Relative locations of all detectors in z are
  from these diagrams. (For DESY 2006 run, origin
  proposed is 4449mm upstream of its current
  position, according to the above diagram.)
• For runs after 2006, we should
• a) Ask local survey groups to assist with
  measurements (relative to fiducial markers in the
  hall and specified on each piece of our
  equipment).
• b) Define origin relative to a fixed point in
  the hall rather than a (re-)movable device. Not
  possible in 2005/6 as no such accurate
  measurements were made.

3
Discussion - All

• Understand that changes could be made
• Probably on reasonable timescale
• Should changes be made
• Discussion of pros/cons
• Decision?