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Analytic/Numerical Beam Simulation Model_B

Analytic/Numerical Beam Simulation Model_B. Beam simulation that incorporates the main characteristics of the beam using numerical and analytic methods Main motivation is to have a beam tool that is easily understood and can be used to compare to and validate the GEANT3 and GEANT4 simulations

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Analytic/Numerical Beam Simulation Model_B

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  1. Analytic/Numerical Beam SimulationModel_B • Beam simulation that incorporates the main characteristics of the beam using numerical and analytic methods • Main motivation is to have a beam tool that is easily understood and can be used to compare to and validate the GEANT3 and GEANT4 simulations • Hard to model processes are not included in Model_B but one can turn them off in GEANT to have a good comparison • No neutrino sources from secondary proton and pion interactions • Elastic scattering of pions in material (could be added) • Multiple scattering in material (could be added)

  2. Analytic/Numerical Beam SimulationModel_B • Procedure: • Pion production using Sanford-Wang parameterizations or MARS tables from GEANT4 for cross section weight • Model production point in target but no secondary production • Raytrace pions through horn using Cernlib Rugge-Kutta routine with same field and Al conductor as GEANT • Keep track of material traversed (Be target, Al horn,...) and calculate weight for absorption in material • After horn, trace pion until it hits pile, collimator, pipe wall, or dump • Calculate decay path and decay probability • Using average decay point, calculate acceptance for decay neutrino to hit MiniBooNE detector Overall weight for producing neutrinos in MiniBooNEweight = xsec*prot_int*not_aborb*decay_prob*acceptance

  3. Pion Raytracing in the Horn

  4. Decay path determined before pion hits material (pile, collimator, decay pipe wall, or dump) Material seen by pion trajectories Absorption and Decay Path Length

  5. Acceptance • Find minimum and maximum qcm subtended by the MiniBooNE detector • Acceptance calculated using the Df overlap with the detector • Also calculate the energy distribution in the lab associated with the qcm - Df region qcm qcmmax qcmmin f Pion Trajectory qp Distance = 541m - zdk Decay Pipe Detector Method and code checked against standard Monte Carlo throwing calculation

  6. Pion Production Distributions All Pions Pions thatmake n'sin MiniBooNE

  7. Some events agreed well between the two programs but others showed a big difference starting as the track exited from the inner conductor Problem was associated with a bug in GEANT4 where the bending in the magnetic field flipped sign for the first step after exiting the inner conductor It appeared to be associated with delta-ray production Problem fixed!! (Michel's hard work) Remove delta-ray production (cludge) Problem does not exist in newest version of GEANT4 Raytrace Comparison Model_B to GEANT4 Black Points: GEANT4Purple Line: Model_BRed Line: Model_B with Bug Match Pions: 1 GeV at 75mr

  8. Model_B to Geant4 Comparison of Pion Kinematics Solid: Model_BDotted: Geant4 Sanford_WangZGS (Michel C1)

  9. Comparison Model_B vs Old GEANT4 Pion Energy/Angle Making Neutrinos in MiniBooNE Neutrino Rate: Model_B = 5.9e-10 nus/cm^2/pot GEANT4 = 4.8e-10 nus/cm^2/pot Solid: Model_BDotted: Geant4

  10. Comparison Model_B vs New GEANT4Pion Energy/Angle Making Neutrinos in MiniBooNE Neutrino Rate: Model_B = 5.9e-10 nus/cm^2/pot GEANT4 = 5.6e-10 nus/cm^2/pot Solid: Model_BDotted: Geant4

  11. Neutrino Energy DistributionModel_B vs GEANT4 Solid: Model_BDotted: Geant4 Old Geant4 New Geant4

  12. Conclusions • Good agreement between Model_B and GEANT4 except at the smallest decay pipe angles. • Model_B sees factor of 23% more neutrinos than Geant4 with a mean energy that is higher by 7% (En = 0.87 vs 0.81 GeV) • The excess is coming from pions in the decay pipe with qp < 20 mr probably with energies around 2 to 2.5 GeV. • Elastically scattered particles broaden the qppipe distribution. • People are suspicious about "Redecay" program ?? • Does GEANT absorb too many particles in the target/horn material?  Very close to validating the full GEANT beam simulation from pion production to neutrino production with a program that is quite different very

  13. Elastic Scattering Angle Distribution Theta-distribution for 2 GeV pion elastic interactions in 200cm of Be Theta (rad.)

  14. Pion Angles for 2 < Ep< 2.5 GeV Solid: Model_BDotted: Geant4 Pions After Horn Pions After Collimator

  15. Ep and En vs Decay Pipe Angle (after coll.)(Compare Geant4 and Model_B) Geant4 Geant4 Scale Flip Model_B Model_B

  16. Pion Production Distributions(All pions or making neutrinos)

  17. Model_B: Ep and En vs Decay Pipe Angle (after coll.) epi vs thout

  18. Model_B Parameters vs Pion Decay Pipe Angle

  19. Pions That Make Neutrinos in MiniBooNE(Model_B)

  20. Model_B Parameters vs Decay Pipe Angle(Weights = 1.0)

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