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Strawman Detector

Strawman Detector. F.Forti, Università and INFN, Pisa UK SuperB Meeting Daresbury, April 26, 2006. Experimental issues. Babar and Belle designs have proven to be very effective for B-Factory physics Follow the same ideas for SuperB detector Try to reuse same components as much as possible

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Strawman Detector

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  1. Strawman Detector F.Forti, Università and INFN, Pisa UK SuperB Meeting Daresbury, April 26, 2006

  2. Experimental issues • Babar and Belle designs have proven to be very effective for B-Factory physics • Follow the same ideas for SuperB detector • Try to reuse same components as much as possible • Main issues • Machine backgrounds • Beam energy asymmetry • Strong interaction with machine design • Impact on • Detector segmentation • Radius of beam pipe and first sensitive layer • Radiation hardness F.Forti - SuperB Strawman Detector

  3. EMC 6580 CsI(Tl) crystals 1.5 T solenoid DIRC (PID) 144 quartz bars 11000 PMs Drift Chamber 40 stereo layers Instrumented Flux Return iron / RPCs&LSTs (m / neutral hadrons) Silicon Vertex Tracker 5 layers, double sided strips The BABAR Detector e+ (3.1 GeV) e- (9 GeV) • SVT: 97% efficiency, 15 mm z hit resolution (inner layers, perp. tracks) • SVT+DCH:(pT)/pT= 0.13 %  pT+0.45 %, s(z0) = 65 mm @ 1 GeV/c • DIRC: K- separation 4.2  @ 3.0 GeV/c  3.0  @ 4.0 GeV/c • EMC:E/E = 2.3 %E-1/4 1.9 % F.Forti - SuperB Strawman Detector

  4. F.Forti - SuperB Strawman Detector

  5. Machine backgrounds • In “traditional” Super BFactory designs • Luminosity obtained with large beam currents (among other things) • 4.1/9.4 A for SuperKEKB @ 4x1035 • 6.8/15.5 A for SuperPEP-II @ 7x1035 • Background a significant problem • In December Linear SuperB design • Small fraction of store beam extracted from damping ring at each collision. • Very low current at the IP make backgrounds negligible • Low collision frequency implies event pileup • In March SuperB design • Beam currents are moderate: 1.5A @ 1036 • Background important, but should not be a huge problem (smaller than in current BFactories) • Collision at every turn: no pileup, and continuous time-structure as in current BFactories. F.Forti - SuperB Strawman Detector

  6. Types and level of backgrounds • Extrapolations from current machines • Full simulation is needed to completely understand backgrounds • Beam gas • Synchroton radiation •  Both proportional to current • Should not be a problem at SuperB • They become a problem at higher currents • Luminosity sources (eg radiative Bhabhas) • Need careful IR design. • Angle crossing helps (see PEP-II/KEKPB comparison) F.Forti - SuperB Strawman Detector

  7. BABAR Interaction Region Detector

  8. Radiative Bhabhas

  9. More sources of background • Beam-beam interactions • Potentially important, but probably under control in the low disruption regime. • Touschek background • Intra beam scattering. Goes like 1/E2. Improves with smaller asymmetry. Increases with beam density. Need further study • Thermal outgassing • Due to HOM losses. Not an issue with small currents • Injection background • Needs further study with the 1 collision/turn scheme. • Bursts • Due to dust. No real cure. Need robustness of detector F.Forti - SuperB Strawman Detector

  10. Background bottom line • Probably reasonable to assume machine background is not larger than what with have today at Babar and Belle. • Need to design a robust detector with enough segmentation and radiation hardness to withstand surprises (x5 safety margin) • Seems within reach of current technology • There are critical points, though: • Inner detector radius likely to be reduced  more background • Bhabha scattering at small angle can become an issue because of smaller boost  more occupancy, more radiation damage • IR design is critical • Radiative Bhabhas • Syncrotron radiation shielding • Shielding from beam-beam blow up F.Forti - SuperB Strawman Detector

  11. Beam Energy Asymmetry • Machine design prefers lower boost • Damping rings more similar • Babar: 9 + 3.1 βγ=0.56 • Belle: 8 + 3.5 βγ=0.45 • SuperB?: 7 + 4 βγ=0.28 • Most obvious effect on detector •  Larger solid angle coverage •  Smaller decay vertices separation • We can afford to have a lower boost only if the vertexing resolution is good: • small radius beam pipe • very little material in b.p. and first layer • Studies indicate a b.p. of 1cm would be OK • Need a realistic beam pipe design to confirm the viability of the lower boost. • How much cooling is needed in the beampipe ? • Symmetric running is also being studied • Could reduce boost-induced energy smearing in tmg analysis F.Forti - SuperB Strawman Detector

  12. Beam Pipe Radius • Small beam pipe radius possible because of small beam size • Studied impact of boost on vertex separation (Bpp) • Beampipe hypothesis (no cooling) • 5um Au shield to protect from soft photons • 0.5cm  200um Be and 5um hit resolution (0.21% X0) • 0.5cm  300um Be and 10um hit resolution (0.24% X0) • 0.5cm  500um Be and 10um hit resolution (0.29% X0) • Rest of tracking is Babar Separationsignificance Proper timedifferenceresolution F.Forti - SuperB Strawman Detector

  13. Beam Pipe Thickness • With 1.5A beam currents the beam pipe will require cooling. • Beampipe design is being developed • Study effect of beampipe thickness • Assume boost=0.28 • Bpp decay • 10um hit resolution •  1cm beampipe should allow good performance even with bg=0.28 Proper timedifferenceresolution BaBar F.Forti - SuperB Strawman Detector

  14. Energy • Is it interesting to run at different energies ? • Υ(5s): not an issue for the machine • oscillation of Bs rapid for TD analysis • Required resolution very hard to obtain • Still it might be possible to measure g through time-integrated measurement branching fractions • BsDf • BsK+p+p0 Renga/Pierini F.Forti - SuperB Strawman Detector

  15. Energy II • Is it interesting to run at the tt threshold or at the y(3770) ? • Luminosity will be around 1035 • Still more than at tau-charm factories • Studies going to on on physics case • Absolute D branching fractions, rare decays • Form factors • Unitarity tests with charm • D mixing ? Use coherence of initial state • CP violation • Boosted operation • Is there something to be gained to run at low energywith boost ? • It might be possible to separate (a little bit) the D vertices <Dz>/s(Dz) vs bg F.Forti - SuperB Strawman Detector

  16. Silicon Vertex Tracker x5 scale with 10mm radius BP, 6mm pixel chip • Vertexing • Two monolithic active pixel layers glued on beam pipe • Since active region is only ~10um, silicon can be thinned down to ~50um. • Good resolution O(5um). • Good aspect ratio for small radius (compared to strips) • Improves pattern recognition robustness and safety against background • needs R&D: feasability of MAPS, overlaps, cables, cooling • Quite a bit of R&D going on on MAPS F.Forti - SuperB Strawman Detector

  17. MAPS R&D Vdd Vdd CAP1: simple 3-transistor cell Source follower buffering of collected charge TSMC 0.35mm Process Reset M1 M2 Collection Electrode M3 Row Bus Output Restores potential to collection electrode Gnd Column Select Column Ctrl Logic Pixel size: 22.5mmx 22.5mm 1.8mm 132col*48row ~6 Kpixels CAPs sample tested: all detectors (>15) function. TESTED IN BEAM. CAP chip (Belle collaborators) F.Forti - SuperB Strawman Detector

  18. MAPS R&D II Charge sharing =105 mV =12 mV threshold 55Fe X-rays Noise only (no source) PRE SHAPER DISC LATCH Landau peak 80 mV 90Sr electrons threshold saturation due to low energy particle. 1250 2200 3000(e-) 1640 • SLIM chip (Babar collabor.) ST 0.13um triple well technology Single pixels tested with source Full signal processing chain F.Forti - SuperB Strawman Detector

  19. Silicon Vertex Tracker 20 cm 30 cm 40 cm • Intermediate silicon tracking • More or less like the current Si strip detectors: • 5 layers of 300um Si, strip lengths 5-20cm, pitch 50-200um, shaping time 100-400ns • Reduction in thickness would be desirable, but not essential • Possibility of 200um Si in inner layers • Small angle region will require special attention due to the high Bhabha rate F.Forti - SuperB Strawman Detector

  20. Central Tracker Normal cell(17.3mm) Small cell(5.4mm) • Babar and Belle Drift Chambers • Both use He based gas mixture • Cell size 12-18mm • Maximum drift time ~500ns • Resolution in the best part of the cell ~100µm • Expect that either OK. • Solid state tracking • an all-silicon solution evaluated, but not performant at low momentum, expensive, and not really needed with moderate backgrounds • Need to optimize cell size against occupancy • Belle has developed a fast gas small cell DCH, but with a degraded resolutions (5.4mm, ~150µm) • Solutions exists, although a full design is needed F.Forti - SuperB Strawman Detector

  21. Particle Identification • Current solutions for K identification • Low p: • dE/dx (both Babar and Belle) • TOF (Belle only) • High p: dedicated Cherenkov detector • DIRC (Babar) – ring imaging cherenkov counter • ACC(Belle) – aerogel threshold cherenkov counter • Coverage: • only barrel(Babar) • barrel+endcap (Belle) • Evolution • Ring imaging is superior to threshold counters • Need to resolve background and mechanical issues • Forward and backward endcap coverage very desirable to increase effective luminosity • A different kind of problem • R&D is needed F.Forti - SuperB Strawman Detector

  22. Babar PID • Stand-off box, filled with water expands cone on PM • Source of backgrund • Barrel-only device • Mechanical interference in the backward direction F.Forti - SuperB Strawman Detector

  23. Belle PID • Aerogel Cherenkov Counters, Time of Flight • No high mom. PID for endcap • Material (ACC+TOF ~ 0.35X0) F.Forti - SuperB Strawman Detector

  24. Evolution: Babar-Style Fast DIRC • Replace SOB with compact readout • Tested in beam with • Hamamatsu Multi Anode Photo Multipliers • Burle Micro Channel Plate PMTs F.Forti - SuperB Strawman Detector

  25. DIRC with timing: TOP Simulation 2GeV/c, q=90 deg. K p d-ray, had. int. • Cherenkov ring imaging with precise time measurement • Quartz radiator (2cm-thick) • Basic study was already done. • Photon detector (MCP-PMT) • Good time resolution < ~40ps • Single photon sensitive under 1.5T • Test with GaAsP photo-catode + MCP-PMT very promising p-K separation power F.Forti - SuperB Strawman Detector

  26. Focusing Aerogel-RICH • New imaging technique by introducing multiple radiators n1<n2 n1>n2 n1 n2 n2 Focusing type Defocusing type n2 n4 n2 n4 n1 n3 n1 n3 n1<n2<n3<n4 n2<n1<n4<n3 Increase Cherenkov photons without loosing single angle resolution due to emission point uncertainty Take full advantage of controllable index of aerogel F.Forti - SuperB Strawman Detector

  27. Electromagnetic calorimeter • Both Babar and Belle use CsI(Tl) calorimeters are suitable for SuperB • signal decay time of ~.75µs (dominant) and ~3µs are OK • CsI(Tl) is too slow for endcap • need to deal with Bhabha rate spatial and temporal overlaps. • especially if possible to extend coverage to 100 mrad, beam line elements allowing. • Babar forward is 350 mrad, Belle forward 200 mrad, backward 400 mrad • Encap replacement is needed • In the case of Babar, a backward endcap needs to be added altogether • Solutions seem to be viable with some R&D F.Forti - SuperB Strawman Detector

  28. Candidate materials • Pure CsI • Fast (16ns) • Low light yield (2500 g/MeV) • LSO or LYSO • High light yield (27000 g/MeV) • Speed OK (47ns) • Expensive F.Forti - SuperB Strawman Detector

  29. Other Detector components • Muon and KL detector • Inside the return yoke of magnet • It doesn’t seem to be a problem • avalanche mode RPC, LST, scintillator are all viable • Trigger/DAQ • Not substantially different from current schemes. • Keep open trigger scheme • Need to try vetoing Bhabhas at level 1 • Data rate seems well manageable F.Forti - SuperB Strawman Detector

  30. Reusability of Babar and Belle • Large (expensive) portions of Babar or Belle would be reusable • Barrel calorimeter • Magnet • Barrel LSTs for Babar • But large subsystems need to be replaced or significantly upgraded • Tracking and vertexing • Particle ID • Endcap calorimeter • Trigger/DAQ • Babar or Belle seem good foundations for a SuperB detector • But need to look in detail at integration and mechanical structure issues F.Forti - SuperB Strawman Detector

  31. From Hitlin’s talk at March 06 LNF F.Forti - SuperB Strawman Detector

  32. From Hitlin’s talk at March 06 LNF F.Forti - SuperB Strawman Detector

  33. Outlook • A detector for SuperB seems to be feasible • An R&D plan needs to be formulated to address the remaining issues • Vertexing • Particle ID • Calorimetry • Babar and Belle provide excellent foundations for a detector at SuperB • More detailed studies will be possible once the machine parameters have settled. F.Forti - SuperB Strawman Detector

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