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The GLD Concept

This study investigates the GLD detector concept for the International Linear Collider (ILC) and its impact on detector design, focusing on issues such as background radiation, detector hit occupancy, TPC resolution, and design of forward detectors. The baseline design aims to be compatible with high luminosity requirements and has parameters optimized for high energy physics analyses.

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The GLD Concept

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  1. The GLD Concept

  2. MDI Issues • Impact on Detector Design • L*  Background (back-scattered e+- ,g, n) into VTX, TPC • Crossing angle  Minimum veto angle for 2-photon process (important for SYSY search), back-scattered e+- into VTX • Pair background  VTX radius • Synchrotron radiation  Beam pipe / VTX radius, background hits in trackers • Muons  Detector hit occupancy • Neutrons from the extraction line  Radiation damage on Si • DID  TPC resolution • Anti-solenoid  Design of very forward detectors • Beam timing  Readout scheme of VTX, etc. • etc. • GLD detector concept study includes all these issues. • The baseline design should be compatible with the most severe case: High Lumi option

  3. Requirement from Physics • Impact parameter:sb = 5  10/(pb sin3/2q ) mm (c/b-tagging) • Momentum:spt/pt2 = 5x10-5 /GeV (e.g. H recoil mass reconstruction from Zm pairs) • Jet energy:sE/E = 30%/E1/2 (W/Z invariant mass reconstruction from jets) • Hermeticity:q=5 mrad (for missing energy signatures, e.g. SUSY) • Sufficient timing resolution to separating events from different bunch-crossings • Must also be able to cope with high track densities due to high boost and/or final states with 6+ jets, therefore require: • High granularity • Good pattern recognition • Good two track resolution • General consensus:Calorimetrydrives ILC detector design

  4. Calorimetry at the ILC • Much ILC physics depends on reconstructing invariant masses from jets in hadronic final states • Kinematic fits won’t necessarily help – Missing particles (e.g. n) + Beamstrahlung, ISR • Aim for jet energy resolution ~ GZ for “typical” jets • Jet energy resolution is the key to calorimetry • The best jet energy resolution is obtained by reconstructing momenta of individual particles avoiding double counting • Charged particles (60%) by tracker • Photons (30%) by ECAL • Neutral hadrons (10%) by ECAL+HCAL  Particle Flow Analysis • The dominant contribution to jet energy resolution comes from “confusion”, not from single-particle resolution of CAL • Separation of particles by fine segmentation / large distance from the IP is important for CAL

  5. Calorimetry: Optimization for PFA • To avoid the “confusion” and get good jet energy resolution, separation of particles is important for CAL: How? • Fine segmentation of CAL • High B field • Large distance from the IP  Large Detector Often quoted “Figure of Merit”: s : CAL granularity RM: Effective Moliere length

  6. Dense Jet: B-field neutral +ve - ve Dense Jet: B=0 neutral +ve - ve Calorimetry: B or R? • B-field just spreads out energy deposits from charged particles in jet –not separating neutral particles or collinear particles • Detector size is more important – spreads out energy deposits from all particles • R is more important than B GLD Concept: Investigate detector parameter space with large detector size (R) and slightly lower magnetic field (B) and granularity

  7. GLD Baseline Design • Large gaseous central tracker: TPC • Large radius, medium/high granularity ECAL: W-Scint. • Large radius, thick(~6l), medium/high granularity HCAL: Pb-Scint. • Forward ECAL down to 5mrad • Precision Si micro-vertex detector • Si inner/forwad/endcap trackers • Muon detector interleaved with iron structure • Moderate B-field: 3T VTX, IT not shown

  8. Vertex detector • Role: Heavy flavor tagging • Important for many physics analyses: e.g. Higgs branching ratio measurement • Efficient flavor tagging requires excellent impact parameter resolution: Goal: s= 5  10/(pb sin3/2q ) mm • Sensor technologies • Must cope with high background rate • Readout 20 times/ train, or • Fine pixel (20 times more pixels) option : readout once/ train

  9. Vertex detector • Main design consideration • Inner radius: • Beam pipe radius: Dense core of pair background should not hit the beam pipe • B-dependence not so large: ~B-1/2 • Large machine-option dependence • Back scattered e+- from BCAL (Low-Z mask in front of BCAL should cover down to R<RVTX ) • Layer thickness: • As thin as possible to minimize multiple scattering  I.P. resolution / tracking efficiency for low p particles • GLD baseline design • Fine pixel CCD • Inner/outer radius: 20(?) – 50 mm • Angle coverage: |cosq|<0.9/0.95

  10. Si trackers • Role: Cover large gap between TPC and VTX  Si Inner Tracker (IT) TPC and endcap ECAL  Si Endcap Tracker (ET) to get better • Track finding efficiency • Momentum resolution • Track-cluster maching in ECAL (PFA) • Design optimization • Number of layers and their position • Wafer thickness • Strip or pixel? for the very forward region

  11. Main tracker: TPC • Performance goal: spt/pt2 = 5x10-5 /GeV combined with IT and VTX • Advantages of TPC • Large number of 3D sampling • Good pattern recognition • Identification of non-pointing tracks (V0 or kink particles) : e.g. GMSB SUSY • Good 2-hit resolution • Minimal material • Particle ID using dE/dx e+ e-  ZH  m m X

  12. TPC • Baseline design • Inner radius: 40 cm • Outer radius: 200 cm • Half length: 230 cm • Readout: ~200 radial rings • Open questions • Readout: GEM or Micromegas? • Material budget of inner/outer wall and end plate • Background hit rate and its effect on spatial resolution due to positive ion buildup (occupancy is OK even with 105 hits in 50ms)

  13. spt/pt2 (GeV -1) Monte Carlo By A.Yamaguchi(Tsukuba) Tracking performance • GLD conceptual design achieves the goal of spt/pt2 = 5x10-5 /GeV

  14. Calorimeter • Performance requirement • Goal for jet energy resolution is sE/E = 30%/E1/2 • Then, what is the requirement for CAL? • The answer is not simple. We need a lot of simulation study of PFA

  15. ~100um ~85um ECAL • Current baseline design • 33 layers of [3mm W + 2mm Scinti. + 1mm gap (readout elec.)] • ~28 X0, ~1 l, RM~18mm • Wavelength shifter fiber + MPC (Multi-pixel Photon Counter, =SiPM) readout • 4cmx4cm tile and 1cm-wide strips • Granularity has to be optimized by PFA simulation study • Calibration method for small segments is worrisome • Very fine segmentation with Si for first few X0 is also discussed MPC 400pixels MPC 100pixels (10x10pixels)

  16. HCAL • Current baseline design • 50 layers of [20mm Pb + 5mm Scinti. + 1mm gap (readout elec.)]: (“Hardware compensation” configuration) • ~6 l • Wavelength shifter fiber + MPC (Multi-pixel Photon Counter, =SiPM) readout • 20cmx20cm tile and 1cm-wide strips • Granularity has to be optimized by PFA simulation study • Digital HCAL is also considered as an option • Open questions • Global shape: Octagon, dodecagon, or hexadecagon? • How to extract cables? Hamamatsu MPC (H100) spectrum Up to ~40 photon peak! is observed

  17. FCAL/BCAL • BCAL • Locates just in front of final Q • Coverage: down to ~5mrad • W/Si or W/Diamond (No detailed design yet) • FCAL • Z~2.3m • Also work as a mask protecting TPC from back-scattered photon from BCAL • W/Si (No detailed design yet)

  18. Muon detector / Magnet • Muon detector • Possible technology: Scintillator strip array read out with wavelength shifter fiber + MPC • Number of layers, detector segmentation, etc. have to be studied • Magnet • 8 mf 3T superconducting solenoid • Stored energy: 1.6 GJ • Excellent field uniformity for TPC:

  19. Cost Issues • Major cost consumers: Solenoid, HCAL, ECAL • Solenoid • Cost~0.523xE(MJ)0.662 [PDG]~70M$ • HCAL • Volume~230m3, Area (all layers)~87Mcm2 • Cost~87M x cost/cm2 • ECAL • Volume~22m3, Area (all layers)~37Mcm2 • Cost~37M x cost/cm2 • Requirement for granularity from physics determines the CAL design and the cost: Simulation study is urgent

  20. Summary • GLD design study is being carried out both from accelerator point of view and from physics point of view • ILC detectors should be optimized for PFA performance, and large detectors are suitable for that • In GLD concept study, we investigate detector parameter space with large detector size and slightly lower B and CAL granularity • Baseline design of GLD has been shown, but current GLD baseline design is not really optimized. More simulation study, sub-detector R&D effort, and new ideas are necessary The purpose of this workshop

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