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Optimising a Detector from the Tracking Point-of-View

Optimising a Detector from the Tracking Point-of-View. P.Colas, CEA Saclay. Optimisation : trade-off between constraints to help the detector to fulfill its role best. THE ROLE OF THE TRACKING. Reconstruct vertices Enough accuracy to separate b from c Determine vertex charge

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Optimising a Detector from the Tracking Point-of-View

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  1. Optimising a Detector from the Tracking Point-of-View P.Colas, CEA Saclay Optimisation : trade-off between constraints to help the detector to fulfill its role best P. Colas - Optimising tracking

  2. THE ROLE OF THE TRACKING • Reconstruct vertices • Enough accuracy to separate b from c • Determine vertex charge • Reconstruct most of V°s • Measure charged tracks • High efficiency down to low angles and momenta, even for close tracks, for particle flow • High accuracy to tell the charge at highest momenta • If possible, identify particle (e,m,p,K,free quark,…) P. Colas - Optimising tracking

  3. Linear Collider Specificity • Physics requirements • Flavour tagging by vertex finding • Higgs recoil mass (ZH->m+m- anything) • Multijet final states : two-track separation • Missing energy measurement : hermeticity • Processes peaked at low angle : good coverage • Environment • Backgrounds: muons, photons, neutrons : go 3D, go high segmentation P. Colas - Optimising tracking

  4. PHYSICS P. Colas - Optimising tracking

  5. Magnetic field (See talk by F. Kircher) • Roles: • Curve tracks for p measurmnt dpT/pT=8s/0.3Bl2 • Curve tracks to separate charged from neutrals (particle flow) • Background confinement • Parameters • Radius (transportation, cost), length • Field intensity • Homogeneity Mask B field P. Colas - Optimising tracking

  6. Backgrounds VxDet • Effect of the beam crossing angle (K.Büber, SLAC MDI meeting, 5 jan 2005) • Head-on ? 2mrad? 20 mrad? Small/large hole? • Input from the detector to the machine design! VxDet TPC P. Colas - Optimising tracking

  7. Backgrounds : neutrons • Impacts the aging of the silicon • Causes occupation in the TPC, especially if the gas contains Hydrogen P. Colas - Optimising tracking

  8. TECHNOLOGY • See talks by S. Aplin and T. Greenshaw • Digital TPC? • Could be used at an intermediate radius between the vertex detector and a standard TPC STANDARD TPC DIGITAL TPC Vx Det P. Colas - Optimising tracking

  9. GEOMETRY • What must be the radius of the TPC? Trading size (R2) against sagitta accuracy / B has a limit : V0s must be contained. • Up to which R do we need Silicon? Where from do we start gas? • Limit on the number of silicon layers fixed by the multiple scattering. About 5 for 300 micron wafers, more if layers are thinner. P. Colas - Optimising tracking

  10. LOW ANGLE COVERAGE • L has to be finite. A special device is needed to cover low angles (K. Moenig) A extended silicon envelope would allow TPC syst. to be corrected (A. Savoy-Navarro). But would not a few % of the surface be enough? Would the first layer of the calorimeter play this role? P. Colas - Optimising tracking q (deg.)

  11. An example : pad size in the TPC, momentum resol° • Depends on details of the design: gas, technology, electronics • What is acceptable? Twice the cost for half the resolution? • BON COURAGE TESLA TDR Goal Pad dimensions (mm x mm) D. Karlen P. Colas - Optimising tracking

  12. COST ISSUES • trade-off running time / resolution (s/N), N ~ time ~ money) • trade-off reliability / price of components • trade-off multi-technology / scale effect P. Colas - Optimising tracking

  13. BENCHMARKS (see M. Battaglia’s talk) P. Colas - Optimising tracking

  14. CONCLUSIONS A lot has been done already to optimize the tracking, but: x Technology evolution might lead us to revise some choices x Need to be realistic in supports / cables / services Benchmarks with realistic simulation and various options are strongly needed. P. Colas - Optimising tracking

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