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Simulations

• Purpose of the simulation codes

• Structure of the E866 simulation codes

• Issues of simulations for E906

Jen-Chieh Peng

University of Illinois

Fermilab E906 Software Meeting Los Alamos, January 8, 2009

Outline

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• To optimize the design and data-taking of the experiment– Simulate signals and backgrounds to optimize the design of

the spectrometer and detectors.– Simulate the acceptance for various physics processes for

optimal setting of the spectrometer configuration.– Determine the triggers to optimize the signal/background ratios

for various physics.

• To optimize the data analysis – Good agreement between the analysis of M-C data and real

data is necessary for optimizing the various cuts and analysis algorithm.

– Efficiency and spectrometer acceptance are often required for extracting the final physics results.

Purpose of the simulation codes

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• Read in the survey files for the spectrometer and detectors, and the efficiency and field map files identical to those for the analysis code.

• Select a physics process to be simulated– Drell-Yan, J/Psi, open-charm, B-meson, di-hadron, like-

sign dimuons, single muons, etc. • “Swim” the particles through the spectrometer and the

detectors, taking into account the multiple scattering and energy loss effects.

• For each event surviving all aperture cuts, convert hits on various detectors into a format identical to that of real data.– Additional hits on the detectors can be added using real

data to simulate realistic background hits • A Monte-Carlo data file is generated with identical structure

as the real data. This M-C can then be analyzed by the reconstruction code.

Features of the E605/772/789/866 simulation code

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• MONTEC– The main program to control the flow of the simulation code– (MAIN, INIT, BEGRUN, SPILL, EVENT, ENDRUN, FINI, etc.)

• SURVEY– Read in the survey files for target, spectrometer, and various detectors– (READBM, READTG, READHD, READPL, READEFF, etc.)

• KINGEN– Event generator for various physics– (KINGEN, KINCONVRT, LORENZ, PTRES, XFRES, BDECAY, etc.)

• SWIMMER– Swim the tracks through the spectrometer and detector planes– (BEAMANG, TARGPT, TARGSCAT, SWIM, ELOSS, CHAMBERS, COUNTERS,

etc.)• MAGSWIM

– Swim tracks through the magnets (bending, energy loss and multiple scattering through thick absorbers, etc.)

– (MAGSWIM, BSM12, BSM3, NFLPFLD, DEC24, DEPB15, etc.)• PACK

– Converts hits on hodos and chambers to look like real data– (PACK, HODHIT, PWCWIR, PAKCRS, PAKTDC, PAKTRG, etc.)

Main components of the E605/772/789/866 simulation code

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• KINGEN– We have been using simple parametrizations

for the XF and PT distributions, or tables based on separate QCD calculations.

• SWIMMER– We do not use GEANT to swim the tracks.

Everything is written by users.

• MAGSWIM– Energy loss distributions in the absorbers are

calculated using the code by Voss, and the results are tabulated as tables.

More on the E605/772/789/866 simulation code

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• Entirely new survey files and field maps need to be generated.

• Energy loss of lower energy muons is needed. • Suitable parametrizations for events at 120

GeV proton energy need to be provided.• Relatively little flexibility for the spectrometer

configurations.• Some overlap between the simulation and

analysis codes (survey, for example). Parallel effort is required for the simulation and the analysis codes.

Some remarks on the E906 simulation