1. Background Simulations at Fermilab
Accelerator Physics Center
Background Simulations at Fermilab
Sergei Striganov
Nikolai Mokhov and Igor Tropin
Fermilab
MAP 2013 Collaboration Meeting
Fermilab
June 19-22, 2012

2. Background Simulation at Fermilab - S. Striganov
Outline
Introduction
Background spectrum and fluxes at central part of detector
Basic characteristics of backgrounds coming into detector
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

3. Background Simulation at Fermilab - S. Striganov
MARS15 Modeling
Detailed magnet geometry, materials, magnetic fields maps, tunnel, soil outside and a simplified experimental hall plugged with a concrete wall.
Detector model with Bz = 4 T and tungsten nozzle, starting at ±20.45 cm from IP with R = 2.8 cm at this z. ROOT geometry.
62.5-GeV bunches of 2×1012 m- and m+ approaching IP are forced to decay at |S| < Smax, where Smax up to 23 m at 5.13×106 / m rate.
Cutoff energies in this study MeV (n, gamma), 1 MeV (charged hadrons) and 0.5 MeV (e+-) . Cutoffs could be reduced substantively in production runs.
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

4. Background Simulation at Fermilab - S. Striganov
HF MDI Versions
No nozzles, no other MDI shielding
v0 - minimal 7.6 deg, 5σ nozzles
v1 - minimal 7.6 deg, 5σ tungsten nozzles, tungsten collimator in IR and concrete collars in IR
v2 - thicker 15 deg, 4σ tungsten nozzles in BCH2 cladding, tungsten collimator in IR, concrete colars in IR, new magnets geometry, magnetic field maps
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

5. Machine-Detector Interface - v2
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

6. Gamma Flux (1/cm2/bunch)
without nozzle v2
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

7. Electron/Positron Flux (1/cm2/bunch)
without nozzle v2
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

8. Neutron Flux (1/cm2/bunch)
without nozzle v2
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

9. Background Simulation at Fermilab - S. Striganov
Gamma Flux in Plane Perpendicular to Muon Beam Direction at IP (1/cm2/bunch)
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

10. Background Simulation at Fermilab - S. Striganov
e+- Flux in Plane Perpendicular to Muon Beam Direction at IP (1/cm2/bunch)
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

11. Background Simulation at Fermilab - S. Striganov
Neutron Flux in Plane Perpendicular to Muon Beam Direction at IP (1/cm2/bunch)
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

12. Background Simulation at Fermilab - S. Striganov
Energy Spectra in Plane Perpendicular to Muon Beam Direction at IP (1/cm2/GeV/bunch) r<50cm
gamma
electron/positron
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

13. Background Simulation at Fermilab - S. Striganov
Energy Spectra in Plane Perpendicular to Muon Beam Direction at IP (1/cm2/GeV/bunch) r<50cm
neutron
charged hadron
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

14. Background File Simulation
Simulation of background particles coming into detector takes a lot of CPU. To look at detector background in detail file with particles on some interface surface is prepared. Different detector geometries and different codes (Geant4, Fluka) can be used in further studies starting from this file. Muon decay points are simulated randomly from -10 to 23 m from IP using MARS code. Electron/positron shower in accelerator structure is simulated. Calculation is stopped at interface surface. Following results were obtained with cutoff energies (±23 m from IP): gamma, neutron keV, charged hadron - 1 MeV, e± keV, muon – 1 MeV.
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

15. Where is Background Produced? Number of Particles Entering Detector
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

16. Number of particles per bunch crossing entering detector
10deg
(750 GeV) v0
(62.5 GeV) v2
Photon
1.8 x 108
8.1x109
3.2x109
Electron
1.0 x 106
3.0x108
1.2x108
Neutron
4.1 x 107
3.2x108
1.7x108
Charged hadron
4.8 x 104
3.0x106
1.0x105
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

17. Where is Background Produced? Energy Flow Entering Detector
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

18. Energy (TeV) per bunch crossing entering detector
Particle
10deg
(750 GeV) v0
(62.5 GeV) v2
Photon
1.6 x 102
4.6x104
1.2x104
Electron
5.8
4.2x104
9.0x103
Neutron
1.7 x 102
6.9x102
3.0x102
Charged hadron 12
1.2x102 26
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

19. Momentum Spectra of Particles Entering Detector
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

20. Average momentum (MeV/c) of particle entering detector
10deg
(750 GeV) v0
(62.5 GeV) v2
Photon
0.9
3.8
2.8
Electron 6 29 16
Neutron 45 40 38
Charged hadron
513
662
444
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

21. Time Distribution wrt Bunch crossing at Detector Entrance
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

22. Where is Background Enters Detector?
70% gamma, 80% e+-, 60% of hadrons coming into detector through quad (Z>350cm and R > 350 cm) – more than 15 ns from IP.
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

23. Where is Energy Enters Detector?
40% gamma, 40% e+-, 60% of hadrons coming into detector through quad (Z>350cm and R > 350 cm) – more than 15 ns from IP.
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

24. Background Simulation at Fermilab - S. Striganov
Time distribution wrt Bunch crossing at Detector Entrance (|Z| > 350 cm)
90% gamma, e+-, charged hadrons coming into detector through quad (Z>350cm and R > 350 cm) can be rejected by 15 ns time gate
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

25. Background Simulation at Fermilab - S. Striganov
Summary
Background loads in tracker and vertex detector can be substantially reduced by 15 degree & 4σ tungsten nozzle with borated poly cladding
About 70% of background particles enter into detector at large distance from IP (> 350 cm) before shielding nozzle through first quad. Influence of this background can be reduced by timing cut depending on detector position. If this way is not effective enough additional shielding and reduction of detector sensitive volume at large angle should be considered
Beam-line description should be improved by adding more elements to correct estimate muon background
Simulation of hits in tracker/vertex detector are needed to understand is achieved background in acceptable level
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

26. Background Simulation at Fermilab - S. Striganov
Backup
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

27. Where is Background Produced? Number of Particles Entering Detector
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

28. Where is Background Produced? Energy Flow Entering Detector
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

29. Energy Spectra Entering Detector
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov

30. Time Distribution wrt Bunch crossing at Detector Entrance
MAP13, Fermilab, June 19-22, 2013
Background Simulation at Fermilab - S. Striganov