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Higgs Factory Backgrounds

This workshop presentation provides an introduction to the background spectrum and fluxes at the central part of the detector in Fermilab's Higgs Factory. It discusses the basic characteristics of the backgrounds coming into the detector and analyzes hits in the vertex detector. The presentation concludes with a comparison of different versions of the HF MDI and the locations where background particles enter the detector.

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Higgs Factory Backgrounds

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  1. Fermilab Accelerator Physics Center Higgs Factory Backgrounds Sergei Striganov Nikolai Mokhov and Igor Tropin Fermilab MAP 2014 Spring Workshop Fermilab 27-31 May, 2014

  2. Outline • Introduction • Background spectrum and fluxes at central part of detector • Basic characteristics of backgrounds coming into detector • Hits in vertex detector • Conclusion

  3. HF MDI Versions – MAP12 • 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, 5 sigma tungsten collimator in IR, concrete colars in IR, new magnets geometry, magnetic field maps • v3 – additional shielding installed around first quad. • Tungsten collimators reduced to 4 sigma. Beam pipe • radius near IP enlarged from 3 to 5 cm. Minor • changes in inner nozzle surface.

  4. Machine-Detector Interface - v2 vs v3 v2 v3

  5. Where is Background Enters Detector?V2 – MAP13 70% gamma, 80% e+-, 60% of hadrons coming into detector through quad (Z>350cm and R > 50 cm) – more than 15 ns from IP.

  6. Gamma Flux (1/cm2/bunch X) without nozzle v3

  7. Gamma Flux in Plane Perpendicular to Beam at IP (1/cm2/bunch X) without nozzle v3

  8. Electron/Positron Flux (1/cm2/bunch X) v3 without nozzle

  9. Electron/Positron Flux in Plane Perpendicular to Beam at IP (1/cm2/bunch X) v3 without nozzle

  10. Neutron Flux (1/cm2/bunch X) without nozzle v3

  11. Neutron Flux in Plane Perpendicular to Beam at IP (1/cm2/bunch X) without nozzle v3

  12. Where Background Hits Nozzle INNER surface-v3 2.2 105 decay e+- through Be beam pipe (25 GeV/c)

  13. Angle between electron/positron and beam as function of nozzle entrance point

  14. Momentum spectra of electron from muon decay and momentum spectra of electron entered into nozzle (|z|<120 cm)

  15. Where Background Hits Nozzle INNER surface -II v3 nozzle Reduced v3 nozzle

  16. Where Background Hits Nozzle INNER surface -III v3 nozzle: 2.2 105 decay e+- through Be beam pipe (25 GeV/c) reduced v3 nozzle: 106 decay e+- through Be beam pipe (25 GeV/c)

  17. How to choose minimal nozzle radius? electron distribution after first quad 350 cm from IP minimal nozzle radius

  18. Nozzle geometry – considered setups

  19. Where Background Hits Nozzle INNER surface -IV v4 nozzle- no decay electron through Be beam pipe v7 – no decay electron through Be beam pipe

  20. Electron flux near IP for different nozzle inner shapein accelerator plane v3 nozzle: electron/cm2/BX v7 nozzle: electron/cm2/BX

  21. Electron flux at IP in Plane Perpendicular to Beam v3 nozzle: electron/cm2/BX v7 nozzle: electron/cm2/BX

  22. Gamma flux near IP for different nozzle inner shapein accelerator plane v3 nozzle: gamma/cm2/BX v7 nozzle: gamma/cm2/BX

  23. Gamma flux at IP in Plane Perpendicular to Beam v3 nozzle: gamma/cm2/BX v7 nozzle: gamma/cm2/BX

  24. Neutron flux near IP for different nozzle inner shapein accelerator plane v3 nozzle: neutron/cm2/BX v7 nozzle: neutron/cm2/BX

  25. Neutron flux at IP in Plane Perpendicular to Beam v3 nozzle: neutron/cm2/BX v7 nozzle: neutron/cm2/BX

  26. Gamma Flux in Plane Perpendicular to Beam at IP (1/cm2/bunch X)

  27. e+- Flux in Plane Perpendicular to Beam at IP (1/cm2/bunch X)

  28. Neutron Flux in Plane Perpendicular to Beam at IP (1/cm2/bunch X)

  29. 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 -23 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): • neutron - 100 keV, muon– 1 MeV, • charged hadron - 1 MeV, • gamma, e± - 200 keV.

  30. Where is Background Produced?Number of Particles Entering Detector

  31. Number of particles entering detector per bunch X-ing

  32. Where is Background Produced?Energy Flow Entering Detector

  33. Energy (TeV) entering detector per bunch X-sing

  34. Momentum Spectra of Particles Entering Detector: v3 and v7 v7: 92% of e+- momentum < 0.5 MeV/c

  35. Average momentum (MeV/c) of particle entering detector

  36. Where is Background Enters Detector?v3 and v7

  37. Where is Energy Enters Detector?v3 and v7

  38. Where background enters to nozzle - v7? Most of electrons/positrons are produced from nozzle jaws

  39. Gamma flux: entrance to detector vs entrance to nozzle.Beam pipe – 5 cm radius, nozzle minimal radius – 2 cm vertical coordinate horizontal coordinate Maximum at positive (negative) entrance to nozzle and negative (positive) entrance to detector – backscattering from nozzle jaws!

  40. Nozzle geometry – 2 vertex setups

  41. Vertex Barrel

  42. Vertex Endcup

  43. Number of particles entering detector per bunch X-ing.ch. Hadron > 1 MeV; γ,e > 0.2 MeV; neutron> 0.1 MeV

  44. Energy (TeV) entering detector per bunch X-sing

  45. V7x2 setup – origin and spectra (low energy thresholds!!!)

  46. V7x2 setup – time

  47. Hit calculations • MARS improvements : all weights equal 1 and EGS5 simulation up to 1 keV. We can simulate hits now! • Hit definition: charged track left sensitive volume + charged • track is stopped in sensitive volume. To estimate occupancy we • need to perform simulation for chosen pixel size. Appropriate • electron transport threshold should be determined as function of • pixel size. • In MARS minimal energy of produced δ-electron Ed= electron • transport threshold. Number of produced δ-electron ~ 1/Ed . Low energy • δ-electron are produced with large angle to δ-electron direction. • Electron ranges in silicon:3 keV – 0.14 μm and 10 keV – 1.5 μm. • With 3 keV threshold most of δ-electrons are stopping in same pixel as • outgoing track - double counting! 10 keV threshold looks like more • realistic.

  48. ILC experience – Tatsuya Mori (Tohoku University) Important numbers: pixel size 5-10 μm and occupancy < 3%

  49. Occupancy in vertex detector (3 keV threshold)

  50. Occupancy in vertex detector (10 keV threshold)

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