Notes About MARS background simulations for BTeV

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Notes About MARS background simulations for BTeV

• A Summary of how far weve come and how far we
  have to go.
• By DJ Wagner 9/12/98
• Vanderbilt University and
• Rensselaer Polytechnic Institute

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The Organization of MARS
Magnetic Fields
Detector Geometry
Lattice Geometry (- 50m)
MARS
Fluences, Nrg Loss
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STRUCT

• HAVE STRUCT code and a basic understanding of how
  it works
• HAVE current Tevatron lattice
• NEED new locations of lattice magnets around C0
  before realistic halo background can be estimated
• STATUS On hold

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Event Generators

• HAVE event files for simulations done by others
  for BTeV in STDHEP format
• HAVE STDHEP installed
• NEED to convert STDHEP format to MARS input
• STATUS Wrestling with STDHEP

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Magnetic Fields

• HAVE 3D map for dipole and 1D map for muon toroid
  magnetic fields, in MARS
• HAVE analytic fields from Mohkov for Q2-Q4 quads,
  lattice toroid
• NEED to know how Q1 compares w/ Q2-4
• NEED to know position of lattice magnets
• STATUS Good start, routines adaptable

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Detector Geometry - Option 1

• Standard Geometry
• Can divide detector into z-slices, r-slices, and
  phi. Material in a z-section is easily
  changeable in input file. For radial dependence,
  material indices must be put in by hand in
  program. Adding more z-sections means completely
  re-doing indexing.
• PROS Currently available, Fluences are
  normalized in output.
• CONS Difficult to change, Introduces many extra
  sections so more computing time.

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Detector Geometry - Option 2

• Non-Standard Geometry
• Can assign indexing to user-defined regions in
  program. Boundaries in x,y,z are specified by
  user and can be any contiguous shape. Supercedes
  standard geometry material indexes
• PROS Currently available, Allows odd shapes,
  Flexible
• CONS Fluences are not normalized

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Detector Geometry - Option 3

• Object-Oriented (Extended) Geometry
• Can place any of a set of shapes in the detector.
  Material assigned to shape in input file.
• PROS Very Flexible
• CONS Not currently available, uses C, not all
  shapes available

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Detector Geometry

• HAVE input file and subroutine for current
  detector geometry in standard option
• NEED idea of how much detail to put into detector
• STATUS Good start, two geometries done

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Silicon Vertex Detectors
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Lattice Geometry

• HAVE current lattice in STRUCT code
• HAVE coded approximate locations of lattice
  magnets in non-standard option
• NEED information on how lattice will change for
  BTeV
• STATUS On Hold

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MARS Output - Histograms

• Histograms are available for 4 or 6 quantities
• Vertex (stars/cm3)
• Fluence (particles/cm2)
• Energy deposition (GeV/g),
• Energy spectrum (1/cm2/Del)
• Surface energy spectra (1/cm2/Del)
• Surface time spectra

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MARS Output - Histograms II

• Histograms are sorted by particle type
• Neutrons
• Charged hadrons
• Total hadrons
• Photons
• Charged ee-
• Total EM
• Muons (charged)

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MARS Output - Text file

• All information used to make the histograms is
  found in the MARS output file too. In addition,
  many of the distributions are given with relative
  statistical errors, dose equivalents may be
  found, and un-normalized fluences for
  non-standard geometry sections are included.

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Results So Far

• Simulations run for fixed target of thin wire,
  E900 GeV protons
• Histograms created using PAW
• Magnetic fields modeled

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Where Ill Leave It

• Geometry as accurate and adaptable as possible
• Event conversion figured out
• Preliminary background calculations done