Requirements and Specifications for Si Pixels Sensors in a CLIC Vertex Tracker A First Assessment M Battaglia CLIC WG-4 Meeting, CERN, April 22, 2010

Physics Motivation eTag = ebN (with N=2,4) e+e-gH0A0gbbbb at 3 TeV Multiple b and t quarks expected as main distinctive signature of many of the CLIC flagship physics processes (SM, SUSY, …) Signal cross sections often only O(1 fb) and S/B ~10-2 - 10-5 eTag = ebN (with N=2,4)  Need efficient b tag with low misid;

Track Extrapolation Resolution Space Granularity Track Extrapolation Resolution e+e-gH0A0gbbbb at 3 TeV Imp. Par. Significance of Secondary Tracks

Track Extrapolation Resolution sIP Space Granularity Track Extrapolation Resolution sIP VTX standalone Imp. Par. Resolution Given CLIC constraints this can be achieved with a multi-layered VTX with single point resolution ~ 3 mm, i.e. a ~ 10 mm binary pixel or a 15-20 mm analog pixel with charge interpolation

Single Point Resolution Space Granularity Single Point Resolution spoint vs. ADC bits for CMOS pixels active thick ~15 mm, pitch 40 mm spoint vs. pixel pitch for CMOS pixels active thickness ~15 mm, S/N ~ 20 spoint vs. S/N for SOI pixels active thick ~30 mm, pitch 10 mm Many ways to get to spoint ~3 mm, mostly technology/readout dependent, two track separation also important.

Machine-induced Backgrounds Hit Density from incoherent pairs on VTX vs time from start of train GuineaPig +MOKKA G4 Simulation A Sailer Radius Pairs gg g hadrons 31 mm 0.0382 hits mm-2 ns-1 0.0021 hits mm-2 ns-1 43 mm 0.0075 hits mm-2 ns-1 0.0014 hits mm-2 ns-1 61 mm 0.0018 hits mm-2 ns-1 0.0008 hits mm-2 ns-1 Need safety factor of 5-10 A Sailer + MB

Cluster Characterisation Detector Occupancy: Cluster Characterisation Real Low-energy e- Clusters on CMOS Pixels Simulated Track Path Length in 50 mm of Si Clusters in CMOS 15 mm Pixels due to low energy electrons from 1.5 GeV e- beam on Al scraper at LBNL ALS High pt Tracks Pairs MB et al., IEEE TNS 55 (2008) De Masi,TIPP09 Expect 0.04 hits/mm2/ns, but depending on technology and layout each hit spreads over few to > 10 pixels

Detector Occupancy MOKKA G4 Simulation + Marlin Reconstruction Overlay pair hits to 3 TeV e+e- events and study standalone VTX pattern recognition efficiency/purity vs time stamping. 20 mm pixel, single hit efficiency 99.5% Efficiency for reco tracks with pt>0.5 GeV MOKKA G4 Simulation + Marlin Reconstruction (Very Preliminary) Quality Cuts: Trk Fit Prob > 0.1% Nhits > 3 No outlier hits At least one hit on innermost layer

Detector Occupancy 40 mm pixel pitch 20 mm pixel pitch Requirements in terms of space granularity from occupancy and single point resolution are comparable

Material Budget: Si and Support 0.282% X0 STAR Low mass carrier: 50mm CFC+3.2mm RVC+50mm CFC (=0.11%X0); Impact Parameter Component Thickness (% X0) 50 mm Chip 0.054 Adhesive 0.014 Kapton Cable 0.090 Carrier 0.110 Total 0.282 Sensor Thickness mm a mm b 25 3.5 8.9 50 3.7 9.6 125 3.8 11.7 300 4.0 17.5

Power Dissipation and Cooling Material Budget: Power Dissipation and Cooling Material minimisation dictates passive cooling, Preliminary tests with thin monolithic CMOS sensors on CFC ladder support structure in collaboration with STAR HFT indicate that 1-3 m/s airflow removes 70-100 mW/cm2 without inducing large vibrations. Assuming power dissipation to be concentrated at the end of column, 20 mm pixels and 1 cm column height, this corresponds to a limit of ~0.15 mW/column This power budget appears to be realistic for a variety of monolithic pixel sensor technology, but is/will this be feasible when including time-stamping capabilities ? Is power pulsing at 50 Hz an option ? IR Camera Image Air Cooling Test Thin Chips Heating cable (80mW/cm2) T(0C)

(Cluster multiplicity Data Rates Preliminary estimate from hit rates (Cluster multiplicity = 2.5 high p trks | = 5 pairs) physics 150 hits/layer 2500 pixels gg g hadrons 100 hits/layer/ns 1500 pixels/ns pairs 1900 hits/layer/ns 25000 pixels/ns CLIC ~190 Mpixels /s ~1-2 GB/s ILC@ILD 40 Mpixels /s 250 MB/s

Expect significant effort in detector benchmarking with physics, layout optimisation, machine-induced background studies and reconstruction/analysis tools in the next 6 months (WG-3), which will better define granularity requirements; Some studies will include digitisation (need guidance on assumptions); Realistic material budget (sensor thickness, support structure, services, cables and connectors….) will be essential to these studies (again need guidance); Significant cross-feed of information and test configurations ahead of data production for simulation physics studies.