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  1. ITS Upgrade Proposal CERN, LHCC Upgrade Session, 20 March 2012 L. Musa for the ALICE Collaboration Outline • Overview on ALICE Upgrade Strategy • ITS Upgrade Proposal • Physics motivations and design goals • Detector performance studies • Benchmark channels • Technical implementation and R&D roadmap • Conclusions

  2. Beyond the ALICE approved physics programme • Progress on the characterization of QGP properties is made by studying • multi-differential observables: • Flavour, Centrality, Transverse momentum, Reaction plane, … • This requires high statistics (high luminosity) • Physics plans focused on physics observables where ALICE is unique at (PID, low material thickness, precise vertexing down to low pt, …), such as • precision measurements of spectra, correlations and flow of heavy flavour hadrons and quarkonia at low transverse momenta • precision measurements of low-mass lepton pairs emitted from the QGP • energy loss and flavour tagging of partons in the QGP via g-jet and jet-jet with hadron PID • search for the existence of exotic objects such as the H dibaryon or L-neutron bound states and systematic study of production of anti-matter •  This requires high statistics and precision measurements • Standard trigger strategy not applicable in most cases

  3. ALICE Upgrade Strategy • “ALICE at High Rate”  submitted to LHCC • A document has been prepared defining the physics goals and the experimental approach for a run of at least 10 nb-1 with PbPb • run ALICE at high rates, 50kHz Pb-Pb (i.e. L = 6x1027 cm-1s-1), with minimum bias (pipeline) readout ( max readout with present ALICE set-up ~500Hz) • Improve vertexing and tracking at low pt The Pb-Pb run would be complemented by p-Pb and pp running • It entails building • New beam pipe • New silicon tracker (scope and rate upgrade) • High-rate upgrade for the readout of TPC, TRD, TOF, CALs, Muons, DAQ/HLT • This will allow a data driven readout architecture with continuous readout and event selection done by software algorithms in the online systems (DAQ/HLT) • Targets LS2

  4. ALICE at High Rate - Readout Architecture • 50 kHz Pb–Pb collisions inspected with the least possible bias with online event selection based on topological and PID criteria •  max readout with present ALICE set-up ~500Hz • HI run 2011: online cluster finding data compression factor of ~5 for TPC • Two HLT scenarios for the upgrade: • Partial event reconstruction: Factor of 5 (in use) → Rate to tape: 5 kHz • Full event reconstruction: Overall data reduction by a factor of 25 → Rate to tape: 25 kHz • min. bias event size ~20 MB  ~4-1 MB after data reduction • throughput to mass storage: 20 GB/s. • Event rate reduction from 50kHz to 5kHz (25kHz) can only be reached with online event reconstruction and selection

  5. Readout and Online Systems Architecture Readout scheme Fast Trigger Processor (FTP) Event Processors (EPN) L1 L2 L3 inter. L0 t0+10ms t0+ ~1s t0+ >10s t0 t0+ ~1ms FTP  Fast Trigger Processor FLP  First Level Processor EPN Event processor Node

  6. ALICE Upgrade Strategy • Contextually, submitted to LHCC the CDR for the ITS upgrade which is an essential part of the General Strategy • Furthermore, three major proposals are under consideration to extend the scope of ALICE: VHMPID, MFT, and FOCAL (a decision will be taken by September) • New high momentum PID capabilities • b-tagging for low pt J/psi and low-mass di-muons at forward rapidities • Low-x physics with identified g/p0 • Meanwhile, R&D program continues for the different proposed upgrades, and the negotiations with the Funding Agencies to define the resource boundaries have been launched

  7. ALICE New Inner Tracking System Conceptual Design Report

  8. Physics measurments – examples where ITS plays a key role • Study the thermalization of heavy quarks in the QGP • Measurement of baryon/meson for charm (Lc /D) and possibly for beauty (Lb /B) for pt > 2 GeV/c • Elliptic flow for B and HF baryons (Lc , Lb ?) for pt > 2 GeV/c • Possible in-medium thermal production of charm quarks (D down to pt = 0) • Study of the quark mass dependence of energy loss in the QGP • Nuclear modification factors RAA of the pt distributions of D and B mesons separately • Beauty via displaced D0 Kp • Beauty via displaced J/y  ee

  9. Heavy Flavour – Experimental measurement Topological Identification of open charm D0 K-+ Impact parameter resolution • Analysis based on decay topology and invariant mass technique • Essential selection cuts • impact parameter, distance of closest approach • distance of secondary vertex to primary vertex • pointing angle • High precision tracking (ITS+TPC) • p/K/p identification (TPC+TOF)  reducing • background at low pT

  10. Heavy Flavour – Experimental measurement Current detectors: • ALICE uniqueness: PID ( charm); low pt (low material budget); • Present limits: • charm difficult for pt0 (background is too large); • resolution not sufficient for charmed baryons (Lcct=1/2 D0=1/5 D+); • Lc impossible in Pb-Pb collisions , at the limit in pp (only high pt); • Lb impossible in Pb-Pb collisions (insufficient statistics and resolution) • B/D separation difficult, especially at low pt (e PID + vertexing); • indirect B measurement via electrons; • CMS limits: • much larger material thickness (even after upgrade) • minimum pt at about 5-6 GeV/c? • no PID  low pt charm and Lcvery difficult;

  11. Design goals • 1. Improve impact parameter resolution by a factor of ~3 • Get closer to IP • Reduce material budget • Reduce pixel size • 2. High standalone tracking efficiency and pt resolution • Increase granularity • Increase radial extension • 3. Fast readout • readout of Pb-Pb interactions at > 50 kHz and pp interactions at > 2MHz • 4. Fast insertion/removal for yearly maintenance • possibility to replace non functioning detector modules during yearly winter shutdown

  12. How to improve the impact parameter resolution • I) Get closer to the IP • radius of innermost pixel layer is constrained by central beam pipe • Present beam pipe: ROUT = 29.8 mm, DR = 0.8 mm •  • New reduced beam pipe: ROUT = 19.8 mm, DR = 0.8 mm • II) Reduce material budget (especially inner layers) • present ITS: X/X0 ~1.14% per layer •  • target value for new ITS: X/X0 ~0.3 – 0.5% per layer (STAR HFT 0.37% per layer) •  reduce mass of silicon, electrical bus (power and signals), cooling, mechanics • III) Reduce pixel size • currently 50mm x 425mm • monolithic pixels  O(20mm x 20mm), • hybrid pixels  O(30mm x 30mm), state-of-the-art O(50mm x 50mm)

  13. How to improve standalone tracking efficiency and pt resolution • Higher granularity • increase number of layers in the outer region (seeding) and inner region (high occ.) • present detector: 6 layers, optimized for track matching with TPC • new detector: 7 layers (assuming 95% efficiency) • increase granularity of central and outer layers • pixels 20mm x 20mm • Combination of pixels (20mm, 20mm) and strips (90mm, 20mm) • Increase radial extension • present detector: 39mm – 430mm • new detector: 22mm – 430mm(*) (CDR value) • (*) increasing outer radius to 500mm results in a 10% improvement in pt resolution

  14. Upgrade options • Two design options are being studied • 7 layers of pixel detectors • better standalone tracking efficiency and pt resolution • worse PID • 3 inner layers of pixel detectors and 4 outer layers of strip detectors • worse standalone tracking efficiency and momentum resolution • better PID 4 layers of strips Option B Option A 7 layers of pixels 3 layers of pixels • 685 krad/ 1013neq per year • Includes safety factor > 4 Pixels: O(20x20µm2 – 50 x 50µm2) Pixels: O( 20x20µm2 – 50 x 50µm2) Strips: 95 µm x 2 cm, double sided

  15. Improvement of impact parameter resolution MAPS Case Simulations for two upgrade layouts • Option A: “All New” – Pixels (7 pixel layers) • Resolutions: srf = 4 mm, sz = 4 mm for all layers • Material budget: X/X0 = 0.3% for all layers • Option B: “All New” Pixel/Strips (3 layers of pixels + 4 layers of strips) • Resolutions: srf = 4 mm, sz = 4 mm for pixels srf = 20 mm, sz = 830 mm for strips • Material budget: X/X0 = 0.3% for pixels X/X0 = 0.83% for strips radial positions (cm): 2.2, 2.8, 3.6, 20, 22, 41, 43 Same for both layouts

  16. ITS standalone tracking efficiency MAPS Case Central events at sqrt(sNN) = 5.5 TeV Simulations for two upgrade layouts • Option A (all pixel layers) • Resolutions: srf = 4 mm, sz = 4 mm for all layers • Material budget: X/X0 = 0.3% for all layers • Option B (3 layers of pixels + 4 layers of strips) • Resolutions: srf = 4 mm, sz = 4 mm for pixels srf = 20 mm, sz = 830 mm for strips • Material budget: X/X0 = 0.3% for pixels X/X0 = 0.83% for strips radial positions (cm): 2.2, 2.8, 3.6, 20, 22, 41, 43 Same for both layouts

  17. Performance studies for heavy flavor detection • Benchmark channels presented in the CDR • Charm meson production via D0 → K−π+ • Charm baryon production via Λc → pK−π+ • Beauty production via B → D0 (→ K−π+) • Beauty production via B → J∕ψ (→ e+e−) • Beauty production via B → e+ • Simulation method • Fast simulation scheme based on MC productions including detailed geometry and response of current ALICE detector. • Impact of new ITS by recomputing reconstructed track parameters by means of a simple scaling of the residuals of the impact parameters in rf and z, as well as of the transverse momentum, with respect to their true values (Fast Estimation Tool)

  18. Some examples of physics performance (D0) Further optimization In progress Benchmark channel at very low pt: D0Kp S/B improved x 5 - Assuming ~ 109 central events: Significance better than 100 in all pt bins

  19. Some examples of physics performance (Lc) Further optimization In progress LcpKp as benchmark channel in Pb-Pb Assuming ~ 1.7 x 1010 central events (10 nb-1) in centrality class 0-20% pt(GeV/c)significance (3s) 2-4 7 4-6 40 6-8 53 The background level in the Lc mass region will be determined precisely using the invariant mass side-bands Lc production measurable down to 2GeV/c: RCP and Lc /Dfor pt> 2GeV/c in central collisions v2 for pt > 4GeV/c in semi-central collisions (e.g. 30-50%) v2 for pt > 2GeV/c in peripheral (e.g. 60-80%)

  20. Detector technologies • Several technologies are being considered for pixel detectors • Hybrid pixel detectors • Edgeless sensors (100mm) + front-end chip (50mm) in 130 nm CMOS • Monolithic pixel detectors • MIMOSA like in 180 nm CMOS • INMAPS in 180 nm CMOS • LePix in 130nm CMOS 4 layers of strips Option B Option A 7 layers of pixels 3 layers of pixels • 685 krad/ 1013neq per year • Includes safety factor > 4 Pixels: O(20x20µm2 – 50 x 50µm2) Pixels: O( 20x20µm2 – 50 x 50µm2) Strips: 95 µm x 2 cm, double sided

  21. Pixel Technologies • Hybrid pixels • 2 components: CMOS chip and high-resistivity (4-8 kWcm) sensor connected via bump bonds • Optimize readout chip and sensor separately with in-pixel signal processing • Charge collection by drift • Monolithic pixels • All-in-one, detector-connection-readout • sensing layer (resistivity ~1kWcm epitaxial layer) included in the CMOS chip • Charge collection mostly by diffusion (MAPS) • intrinsically more prone to signal loss due to charge trapping by radiation induced defects • … but some development based on charge • collection by drift • Made significant progress, soon to be installed in STAR (Heavy Flavor Tracker) Figure - Rossi, L., Fischer, P., Rohe, T. & Wermes, N. (2006). Berlin: Springer. Figure Stanitzki, M. (2010). Nucl. Instr. and Meth. A doi:10.1016/j.nima.2010.11.166

  22. Monolithic Pixels - MIMOSA • State-of-the-art (MIMOSA family – IPHC Strasbourg) uses rolling-shutter readout • Continuous charge collection (mostly by diffusion) inside the pixel • Charge collection time ~200ns • Pixel matrix read periodically row by row: column parallel readout with end of column discriminators (integration time  readout period ) • Integration time (~180ms for ULTIMATE chip) • Pixel size ~ 20 µm • Low power consumption: only one row is powered at time • Total material budget X/X0 ~ 0.3 % per layer (STAR HFT detector) • R&D for ITS upgrade: MISTRAL MImosaSensor for the TRacker of ALICE • further development of the low-power rolling shutter architecture of ULTIMATE • reduce readout time (20-40 ms) • improve radiation resistance by a factor ~3 • AMS 0.35mm  TowerJazz 0.18mm • Target power consumption: < 250 mW / cm2 ULTIMATE sensor for STAR HFT

  23. Monolithic Pixels – MISTRAL • 2 designs for MPW run completed: • MIMOSA32 designed by IPHC submitted in Nov. 2011 – delivered (Jan 2012) • MonaliceT1 test chip designed by CERN/CCNU/IPHC to be submitted in Feb 2012 • Goal for 2012: • Evaluation of the technology (detection efficiency, S/N, quadrupole-well, ..) • Test of radiation hardness Tower-Jazz CMOS 0.18mm - submissions

  24. Monolithic Pixels – Evaluation of TowerJazz technology MIMOSA 32 (IPHC) • Digital and analog blocks • Analog blocks (2T and 3T structures with various diodes) • Source tests and testbeam • 100 circuits delivered January 2012 5.7 mm • MONALICET1 (CERN/CCNU) • Single transistors • Breakdown structures • Memories • Digital structures • Shift register 3.7 mm 2.2 mm 4.1 mm Breakdown diodes CMOS test structures w/o deep p-well

  25. Monolithic Pixels - INMAPS • In-pixel signal processing using an extension (deep p-well) of a triple-well 0.18mm CMOS process developed by RAL in collaboration with TowerJazz (owner of the technology) • CMOS Imaging Sensor with additional deep p-well implant • CMOS electronics in the pixel compatible with • charge collected 100% by in-pixel diode • charge collection (mostly) by diffusion • New development dedicated to ITS upgrade started in 2012 • (Daresbury, Birmingham, RAL, … - ARACHNID Collaboration) • R&D objectives • Verify radiation resistance • Reduce power consumption exploiting • detector duty cycle (5% for 50 kHz int. rate) • Develop fast sparse readout TPAC prototype 50 µm pixel - over 150 CMOS transistors RAL Irradiation test structrues (Single transistors w/o deep p-well)

  26. Monolithic Pixels – Le Pix LePIX:monolithic detectors in advanced CMOS • Scope: • Develop monolithic pixel detectors integrating readout and • detecting elements by porting standard 90 nm CMOS to wafers • with resistivity of about 1 kWcm • Reverse bias of up to 100 V to collect signal charge by drift • Key parameters: • Pixel ~10x10 mm2 • Very large signal to noise ratio • Signal processing at end of column • ORTHOPIX readout architecture: multiple projections in a pixel matrix beyond X and Y. The method compresses the hit information by a factor of about 100 to a fixed data size and moves it to the periphery immediately (within one clock cycle) •  Low power consumption and reduced digital circuitry Track in telescope of 4 planes (beam test at PSI – Nov 2011)

  27. LePIX: Fe-55 spectrum and charge collection • Illuminating the back side with a laser confirms that signal charge is collected only from the pixel center, not from the pixel corners. This leads to a 70 % efficiency for MIPs. Simulations and focused ion beam repair are in progress to fully understand and fix this issue • The collected charge increases with reverse bias • Fe-55 spectrum at room temperature • Clearly two peaks: • (5.90 & 6.45 keV) • Sigma ~ 140 eV or 40 e RMS (for a 10 microsecond integration time) • Illustrates S/N potential of the device

  28. Hybrid Pixels and Ongoing R&D • Current flip-chip bonding technology permits pitch ~ 50 µm • 30 µm seems achievable but R&D is needed • Total material budget target X/ X0 < 0.5% (100 µm sensor, 50 µm chip) • High S/N ratio, ~ 8000 e-h pairs/MIP  S/N > 50 • Edgeless sensors to reduce insensitive overlap regions (~ 20µm) • Possible to operate at room temperature in high radiation environment up to 1013neq • Cost driven by fine-pitch bump-bonding of sensor to readout chip • Could be considered for the three inner layers • R&D: • Assembly of ultra-thin components • Finer pitch bump bonding • Edgeless detectors • FEE chip floor-plan optimization • Power/Speed optimization • possible (shaping time O(µs)) to reduce power budget Sensor 100mm, readout chip 50mm, glass carrier 300mm

  29. Hybrid Pixels – example of R&D on thin assemblies sensor 100mm FEE chip 50mm glass carrier FEE CHIP 50mm glue glass carrier

  30. Strip Sensor Design • The sensor of the present detector • Layout:  300 µm thick, double-sided, 768 strip/side, 35 mrad stereo angle • Sensor area: 0.0028 m2 -- Cell size: 95um x 40000um • The new strip sensor layout has been designed (Trieste) • decrease the strip length from ~40mm to 20mm • cell size ~ -50% • Cstrip ~ -50% • 2 x # of channels • same cluster size • 2 rows of strips per sensor side draft • New front-end chip with integrated ADC

  31. Preliminary Studies on the mechanical structure CONSTRAINTS TO THE MECHANICAL DESIGN External Detector integration and accessibility New Beam Pipe side C Internal X0 radiation length Sensor Type Sensor Power Dissipation Sensor Distribution The new ITS design should ensure a rapid accessibility to the inner detectors ❶ No TPC moving ❷ Services only at one side, side A ❸ Detector in two half side A

  32. Preliminary Studies on Mechanical Structure Several concepts are being studied STAR PXL detector centered in the Middle Support Cylinder single end support allows rapid insertion and removal ALICE New ITS Ultra-Light Concept ALICE New ITS Clam-shell Concept Cooling and support mechanics strongly coupled

  33. Mechanical Structure – foam shell concept • Developed on a solid cooling concept extensively tested in similar application (Atlas, Panda) • Modularity stave level • Stiff ends • Carbon fiber + Carbon foam • Various option for pipe material Carbon fiber Sensor + electrical bus Carbon foam Prototype

  34. Cooling – liquid with polymide micro-channels • Multilayer polyimide composite • A layer of Pyralux LF110  at the bottom • Photoimageable PC 1020  layer in the middle • Pyralux LF7001  layer glued on the top. • The multilayer PC 1020, which is 200 μm thick, is glued on the LF110. The rectangular pattern which defines the channels is created with a photolithography process, and the foil of LF7001 is hot pressed on the top of the substrate to cover the channels.

  35. Cooling – Evaporative with silicon micro-channels • Cooling technique developed by CERN/PH-DT with Microsystems Laboratory (EPFL) and CSEM (Neuchatel) • Considered by NA62 for Giga-Tracker detector • Detector and cooling structure are both silicon reduce mechanical stress due to thermal stress • Micro-channels (100x200mm2) etched on a silicon substrate (130mm thick) closed by a cover-layer fusion bonded on top

  36. Mechanical Structure – U-light shell concept • Structure based on CFRP with possibility to integrate different cooling concepts (silicon micro-channels, polymide channels) • Light structure with openings along the sensitive region • Modularity from stave level can be reduced to half barrel with gain in stiffness and reduction in material Sensor Electrcial bus cooling Prototype under construction

  37. Mechanical Structure – U-light shell concept …to Half Barrel from Single StavetoHalfLayer • The external (L3) end-stiffening surface shall be a complete honeycomb shell (half cylinder) • This external shell, linked through the endcap to the different layers, provides the overall structure stiffness

  38. Mechanical Structure – U-light shell concept Endcap cooling ONLY Based on sensor final choice, i.e. minimum power dissipation, the possibility to have a cooling system only in the ITS Layer endcap is being considered. Heat will be tranferred by high thermal conductive material along the stave

  39. Mechanical Structure – Clam shell Clam shell Concept • Move all support to the outside shell(s) • Clam-shell structure (i.e. two halves) • Low-z materials • carbon fiber composite (Xo=25cm) • Airex (Xo=1326cm) • Tedlar film (Xo=26.2cm) • air cooling scheme

  40. Three beams made of carbon fiber are fixed to the inner surface of the TPC to support/guide the insertion of the outer barrel The outer barrel (split in two halves) is mounted outside the TPC before being moved to final position The inner barrel (also in two halves) is installed at the end Installation mechanics Inner barrel insertion Cut view after installation

  41. Upgrade Studies - organization Four working groups to study the upgrade and coordinate R&D activties I) Physics Motivations and Detector Functional requirements (convenors: A. Dainese, G. Usai) II) Detector Specifications and Performance Simulations (convenors: G. Bruno, M. Sitta) III) Detector design and implementation (convenors: P. Riedler, A. Rivetti, G. Contin) IV) Cooling, Cabling, Services, mechanics and integration (convenors: A. Tauro, R. Santoro) CDR preparation editorial board: L. Musa, V. Manzari, G. Usai, A. Dainese, G. Bruno, P. Riedler, G. Contin, A. Rivetti, R. Santoro, A. Tauro, R. Lemmon, S. Rossegger contributing authors:  C. Di Giglio, M. Kweon, M. Mager, A. Mastroserio, S. Moretto, A. Rossi, C. Terrevoli, S. Bufalino, S. Piano, F. Prino, S. Senyukov, R. Shahoyan, L. Bosisio, M. Campbell, C. Cavicchioli, T. Kugatashan, W. Snoeys, M. Winter, G. Aglieri Rinella, R. Turchetta, C. Pastore, I. Sgura, E. Da Riva, C. Bortolin, A. Mapelli, S. Coli

  42. Institutes that participate in the upgrade studies Institutes in the present ITS Project • About 10 new Institutes joined the ITS project to participate in the upgrade studies and the preparation of the CDR CERN, INFN, St-Petersburg, Kharkow- long standing expertise in • ASIC design • construction of detector ladder and support mechanics • manufacturing of composite materials • integration and characterization of hybrid pixel and microstrip IPHC, RAL - among world leaders • Monolithic pixels detectos

  43. Project timeline • Project timeline (to be adapted according to LHC schedule) • 2012 – 2014 R&D • 2012 finalization of detector specifications • evaluation of detector technologies (radiation and beam tests) • first prototypes of sensors, ASICS, and ladders (demonstrators) • 2013 selection of technologies and full validation • engineered prototypes (sensors, ASICs, ladders, data links) • engineered design for support mechanics and services •  Technical Design Report • 2014 final design and validation • start procurement of components • 2015-16 production, construction and test of detector modules • 2017 assembly and pre-commissioning in clean room • 2018 installation in ALICE

  44. Conclusions • In line with the ALICE general upgrade strategy, we propose to build a new ITS based on 7 silicon layers characterized by • Continuous readout • Factor ~3 improvement in impact parameter resolution • Very high standalone tracking efficiency down to low pt(> 95% for pt> 200MeV/c) • Fast access (winter shutdown) for maintenance interventions • After a couple of years of studies, we are confident that this ambitious proposal can be turned into a real detector to be ready for physics in 2019 • Strong support from Funding Agencies for R&D phase • We wish it can be reviewed and approved by the LHCC such that the we can secure the necessary resources


  46. ITS PID performance 4 layers of Hybrid + 3 layers of strips 7 layers of MAPS 4 layers silicon strips Pion to kaon separation (black circles) and proton to kaon separation (red triangles) in unit of sigma in the case of 4 layers of 300 μm (left panel), 7 layers of 15 μm (central panel) and 4 layers of 100 μm + 3 layers of 300 μm (right panel) silicon detectors. The horizontal lines correspond to a 3 sigma separation.

  47. Some examples of physics performance (BD0) Further optimization In progress This will provide a direct measurement of RAA for charm (prompt D) and b (non-prompt D) Measuring D mesons from pt=2 GeV/c gives access to B meson from pt=0 GeV/c (due to the decay kinematics)

  48. Requirements on integration time and time resolution At high interaction rate (e.g. p-p at 2 MHz, Pb-Pb at 50 kHz) significant pile-up in the detector occurs depending on the integration time (or time resolution). This causes two separate problems for the reconstruction and analysis of collected data: the reconstruction efficiency drops due to the ambiguity of track-cluster association at inner layers distinguishing triggered event from surrounding pile-up interactions Same as the plot on the left but with three fast layers: e.g. 1, 2 and 6 Reconstruction efficiency for triggered Pb-Pb central collision with increasing number of pile-up collisions

  49. Requirements on integration time and time resolution, cont’d • Tracks can be correctly assigned to the vertex of triggered interaction if • the vertices of pile-up events are at a distance larger than 1mm from the triggered vertex • comparing its “time stamp” to trigger • Further constraints are imposed by the extraction of signal from different off-vertex decays. • for short lived particles, e.g. Λc or D0, same ∼1 mm isolation should be enough • B-mesons will require ∼1 cm isolation of the triggered vertex Problem can be solved if each track has at least one point with precise time stamp associated to trigger. For 2 MHz p-p interaction rate one (100% efficient) layer with ~1μs time resolution allows to eliminate the effect of pile-up.

  50. Improvement of impact parameter resolution HYBRID PIXELS (state-of-the-art) and comparison with MAPS radial positions (cm): 2.2, 2.8, 3.6, 20, 22, 41, 43 Same for both layouts Simulations for two upgrade layouts • Layout 2: Pixel/Strips (3 layers of pixels + 4 layers of strips) • Resolutions: srf = 12 mm, sz = 12 mm for pixels srf = 20 mm, sz = 830 mm for strips • Material budget: X/X0 = 0.5% for pixels X/X0 = 0.83% for strips