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Tungsten HCAL simulation studies

Tungsten HCAL simulation studies. Peter Speckmayer CLIC 09 12 – 16 October 2009. considerations for HCAL depth and material. shower leakage worsens energy resolution to reduce leakage: deeper calorimeter  denser calorimeter (more interaction lengths)

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Tungsten HCAL simulation studies

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  1. Tungsten HCAL simulation studies Peter Speckmayer CLIC 09 12 – 16 October 2009 CLIC09, Peter Speckmayer

  2. considerations for HCAL depth and material shower leakage worsens energy resolution to reduce leakage: deeper calorimeter denser calorimeter (more interaction lengths) depth limited by feasible coil size: larger coil with smaller B-field larger B-field with smaller coil depth limited by tracker size: larger tracker better p-resolution Barrel Endcap here would be a tail-catcher COIL HCAL ECAL Tracker Vertex IP beam CLIC09, Peter Speckmayer

  3. HCAL absorber material • which material for the absorber? • steel, tungsten, ... ? • Tungsten • expensive! • more contained showers (compared to Fe) with the same HCAL geometrical depth  less leakage • smaller shower diameter  better separation of showers (probably good for particle flow) • final goal  good energy resolution with whole detector CLIC09, Peter Speckmayer

  4. Energy reconstruction with neuronal network • (information from fine granularity of calorimeter not used  traditional approach) • variables describe shower shape and size and energy • train NN with pion energy numbers denote HCAL length in units of interaction lengths 5 mm scintillator, 2.5 mm G10 steel ~40 λ tungsten shorter HCAL  more leakage  worse resolution CLIC09, Peter Speckmayer

  5. tungsten Tail-catcher • coil thickness: 2 λ • zero λ tail-catcher implies no active material after the coil • having some tail-catcher (1 λ) improves resolution • effect of bigger tail-catcher is small CLIC09, Peter Speckmayer

  6. Tungsten HCAL • Tungsten used in ECALs • typically ~1λ deep • No experience with tungsten HCALs • ~4 – 9 λ deep • simulation of tungsten not validated • no MC/data comparisons • no validation for high granularity • If tungsten is used  have to be sure, that energy resolution of whole detector is better (PFA) CLIC09, Peter Speckmayer

  7. physics-list differences (Geant4)simulations of pion showers in block of tungsten tungsten, QGSP_BERT tungsten, QGSP_BERT_HP Evisible/EMC Evisible/EMC with HP (high precision neutron tracking) enabled  much less energy deposit by ionization transition regions of models which one can we trust more? in QGSP_BERT  more n produced, more n captured  ~8MeV of photons each  accounts for difference CLIC09, Peter Speckmayer

  8. physics-list differences (Geant4)simulations of pion showers in block of lead/tungsten lead, QGSP_BERT tungsten, QGSP_BERT_HP Evisible/EMC Evisible/EMC lead simulations for hadrons are better validated similar widths of lead and tungsten, when HP is used  “feeling” says: this is more trustworthy CLIC09, Peter Speckmayer

  9. Effect of physics list on predicted resolution 5 mm scintillator, 2.5 mm G10 less energy deposited by ionization, but ... Improved resolution! ~10-15% improvement (at 40 GeV) considerable effect but: perfect readout assumed why: n are captured farther away from shower core  “halo” produced which reduces reconstruction performance. removing halo (with HP n tracking) CLIC09, Peter Speckmayer

  10. Further reason for validation • Time structure of signal broadened by n-content • time stamping • used to separate signal/background on a time basis • (slow) n-content smears out energy deposits in calorimeters • know time-structure of n-content to set requirements for time stamping • dependent on active material (e.g. scintillator, gas) • measurements necessary CLIC09, Peter Speckmayer

  11. Particle flow results so far Comparison of around 8 ½ interaction lengths of HCAL with Fe and W W delivers comparable resolution to Fe no optimization of the PFA for W done Angela Lucaci-Timoce CLIC09, Peter Speckmayer

  12. Tungsten HCAL PrototypeWhat can we learn? • Physics performance • Verify simulations (resolution, shower shapes, ...) • Include realistic noise levels (read-out, neutrons, ...) • Tungsten plate production process • Test production of large thin plates • Feasibility of needed flatness • Machining of tungsten plates • Bolting, cutouts CLIC09, Peter Speckmayer

  13. Longitudinal shower size 95% contained energy → ~40 layers (~4.8 λ) 95% C. Grefe 12 mm tungsten + 5 mm Scint + 2.5 G10 CLIC09, Peter Speckmayer

  14. Lateral shower size 95% contained energy → ~40 cm radius 95% C. Grefe 12 mm tungsten + 5 mm Scint + 2.5 G10 CLIC09, Peter Speckmayer

  15. Longitudinal shower sizes: tungsten + micromegas 11 mm tungsten + micromegas 95% J. Blaha CLIC09, Peter Speckmayer

  16. Lateral shower sizes: tungsten + micromegas J. Blaha CLIC09, Peter Speckmayer

  17. more about prototype • see following talk by W.Klempt CLIC09, Peter Speckmayer

  18. Conclusions & Outlook • From tungsten simulations: • 8-9 λ ’s ECAL+HCAL seems sufficient up to 300 GeV (pions) • ~10-15 mm W absorber optimal • tail catcher useful • choice of GEANT4 physics list important (different results for W simulations) • Particle Flow algorithm  W and Fe first results are comparable  will be extended • From future prototype results: • feed back prototype to G4-team CLIC09, Peter Speckmayer

  19. backup CLIC09, Peter Speckmayer

  20. Tail-catcher tungsten steel • coil thickness: 2 λ • zero λ tail-catcher implies no active material after the coil • having some tail-catcher (1 λ) improves resolution • effect of bigger tail-catcher is small CLIC09, Peter Speckmayer

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