Notes About MARS background simulations for BTeV A Summary of how far we’ve come and how far we have to go. By DJ Wagner 9/12/98 Vanderbilt University and Rensselaer Polytechnic Institute

The Organization of MARS Magnetic Fields Detector Geometry STRUCT (halo events) Event Generator MARS Lattice Geometry (+- ~50m) Fluences, Nrg Loss

STRUCT 4 HAVE STRUCT code and a basic understanding of how it works 4 HAVE current Tevatron lattice 4 NEED new locations of lattice magnets around C0 before realistic halo background can be estimated STATUS: On hold

Event Generators 4 HAVE event files for simulations done by others for BTeV in STDHEP format 4 HAVE STDHEP installed 4 NEED to convert STDHEP format to MARS input STATUS: Wrestling with STDHEP

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

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.

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

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

Detector Geometry 4 HAVE input file and subroutine for current detector geometry in standard option 4 NEED idea of how much detail to put into detector STATUS: Good start, two geometries done

Silicon Vertex Detectors

Lattice Geometry 4 HAVE current lattice in STRUCT code 4 HAVE coded approximate locations of lattice magnets in non-standard option 4 NEED information on how lattice will change for BTeV STATUS: On Hold

MARS Output - Histograms Histograms are available for 4 or 6 quantities: 4 Vertex (stars/cm 3) 4 Fluence (particles/cm 2 ) 4 Energy deposition (GeV/g), 4 Energy spectrum (1/cm 2 /Del) 4 Surface energy spectra (1/cm 2 /Del) 4 Surface time spectra

MARS Output - Histograms II Histograms are sorted by particle type: 4 Neutrons 4 Charged hadrons 4 Total hadrons 4 Photons 4 Charged e + e - 4 Total EM 4 Muons (charged)

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.

Results So Far 4 Simulations run for fixed target of thin wire, E=900 GeV protons 4 Histograms created using PAW 4 Magnetic fields modeled

Where I’ll Leave It 4 Geometry as accurate and adaptable as possible 4 Event conversion figured out 4 Preliminary background calculations done