The Alice Inner Tracking System Federico Antinori INFN

The Alice Inner Tracking System Federico Antinori (INFN – Padova, Italy) Federico Antinori - Vertex, Kona - Nov. 2002

Contents • Introduction – Alice and the Inner Tracking System (ITS) • ITS subdetectors (a bird’s eye view) – Si strips (SSD) – Si drifts (SDD) – Si pixels (SPD) • ITS performance • Concluding remarks Federico Antinori - Vertex, Kona - Nov. 2002

Contents • Introduction – Alice and the Inner Tracking System (ITS) • ITS subdetectors (a bird’s eye view) – Si strips (SSD) – Si drifts (SDD) – Si pixels (SPD) • ITS performance • Concluding remarks Federico Antinori - Vertex, Kona - Nov. 2002

Alice • Ultrarelativistic nucleus-nucleus collisions at LHC • Why: – study behaviour of hadronic matter under extreme conditions of heating / compression – investigate confinement / deconfinement, generation of constituent masses Federico Antinori - Vertex, Kona - Nov. 2002

B< 0. 4 T) Federico Antinori - Vertex, Kona - Nov. 2002

An inner tracker in Alice… • Vertexing (s, c, b) – strangeness: production sensitive to decrease of effective quark mass in deconfined phase – charm and beauty: “hard” probes of system formed in collision Challenge: track densities at r = 4 cm (1 st pixel layer): up to 100 / cm 2 • Improve TPC tracking – high p. T (extend TPC lever arm, improve spatial precision) – low p. T (standalone ITS) • 1/b 2 particle id (analogue r/o for drifts and strips) Federico Antinori - Vertex, Kona - Nov. 2002 (2º slice)

Alice ITS 2 strips longitudinal coverage: |h| < 1 (tracking), |h|<2 (multiplicity) 2 drifts 2 pixels Rout=43. 6 cm Federico Antinori - Vertex, Kona - Nov. 2002

Contents • Introduction – Alice and the Inner Tracking System (ITS) • ITS subdetectors (a bird’s eye view) – Si strips (SSD) – Si drifts (SDD) – Si pixels (SPD) • ITS performance • Concluding remarks Federico Antinori - Vertex, Kona - Nov. 2002

Alice SSD • 2 layers, r = 38. 5, 43. 6 cm • double sided, stereo angle – (+ 27. 5, -7. 5) mradian • • strips: 95 µm × 40 mm analogue r/o module size: 75 × 42 mm 2 sensitive length (in z): 86. 2 and 97. 6 cm • 1698 modules • 2. 6 M channels Federico Antinori - Vertex, Kona - Nov. 2002

SSD front-end: HAL 25 • CMOS 0. 25 µm radtol layout • 128 analog channels, input pitch 80 µm • Design ENC 200 e- + 8 e-/p. F (1. 5 µs shape) • Tuneable shaping 1. 4 2 µs • Readout at 10 MHz, 200 Ω / 20 p. F • Δ current output (± 55 µA/MIP, 14 MIP range, linear 5%) • 2. 5 V single power supply • JTAG digital, analogue and pulser control Federico Antinori - Vertex, Kona - Nov. 2002

SSD module • Al-kapton microcables • all connections are done by TAB -bonding SSD Module Output cables Carbon ladder Cooling tubes Chips Detector Federico Antinori - Vertex, Kona - Nov. 2002 Hybrid Input cables

First STAR ladder: december 01 First ladder: pictures IRe. S-Subatech Federico Antinori - Vertex, Kona Nov. 2002

Alice SDD • • • 2 layers, r = 14. 9, 23. 8 cm drift along rj 294 µm anode pitch analogue r/o module size: 75. 3 × 70 mm 2 sensitive length (in z): 44. 4 and 59. 4 cm • 260 modules • 133 k channels Federico Antinori - Vertex, Kona - Nov. 2002

Drift Silicon Drift Detector segmented Drift 2 x 256 anodes MOS charge injectors for drift velocity monitoring Wafer: 5”, NTD, 3 k. cm, 300 m Active area: 7. 02 7. 53 cm 2 guard region implanted HV voltage dividers 256 anodes (294 mm pitch) 24/4/2002 12 th RRB J. Schukraft

SDD front-end PASCAL-64 prototype • CMOS 0. 25 mm rad-tol • Full custom design: 10*9 mm 2 • 64 preamplifiers (t ~ 40 ns, RC-CR 2 • • • shaping) 64 analogue memory channels (256 cells) 32 10 -bit linear ADCs Differential outputs preamplifiers analogue memory 16+16 ADCs AMBRA-4 prototype • CMOS 0. 25 mm rad-tol • 4 x 16 kbytes SRAM buffers • 40 MHz working frequency • Fast trigger-abort recovery • JTAG interface • Differential inputs Federico Antinori - Vertex, Kona - Nov. 2002 derandomization & data transmission

Resolution (mm) SDD resolution · Anode axis (z) · Drift time axis (rj) Drift distance (mm) Federico Antinori - Vertex, Kona - Nov. 2002 Corrections applied: • doping inhomogeneity map • residual non-linearity of voltage divider • T-dependence of drift velocity • drift-dependent nonlinearity of centroid due to diffusion widening

SSD, SDD cooling & support • lightweight, carbon-fibre support ladders • liquid cooling – C 6 F 14 (H 20 also considered) Federico Antinori - Vertex, Kona - Nov. 2002

Alice SPD Picture of a solder bump bond (courtesy of VTT) • 2 layers, r = 3. 9, 7. 6 cm • sensitive length (in z): 28. 6 cm (for both layers) • hybrid (bump-bonded) silicon pixel assemblies • In / Pb. Sn bumps • pixel size: 50 × 425 µm 2 bump-bonded assembly • binary r/o bump-bonded assembly • module size: 12. 8 × 69. 6 mm 2 • 240 modules • 9. 8 M channels Federico Antinori - Vertex, Kona - Nov. 2002 Sensor (200 µm thickness) Chip (150 µm thickness) Sensor Chip

SPD front-end Federico Antinori - Vertex, Kona - Nov. 2002 15. 8 mm • Alice 1 LHCb pixel chip mixed signal (analogue/digital) • commercial 0. 25 µm CMOS • radiation tolerant design • 50 µm x 425 µm pixel cell • JTAG controls • 8192 pixel cells • ~100 µW / pixel 13. 5 mm

SPD half-stave Each Stave is built of two HALFSTAVES, read out on the two sides of the barrel, respectively. Bus Ladder: 5 chips+1 sensor MCM ALICE 1 LHCb chip Silicon sensor 193 mm long Grounding foil Cooling tube Carbon-fibre sector Federico Antinori - Vertex, Kona - Nov. 2002

SPD bus 2 mm 1 2 4 3 11 mm SMD component 5 6 7 7 6 5 7 layer Al-Kapton flex 2 1 PIXEL DETECTOR READOUT CHIP COOLING TUBE Federico Antinori - Vertex, Kona - Nov. 2002 Aluminum Polyimide Glue

SPD test beam July 2002, CERN-SPS H 4 beam singles online residuals s=16. 4µm (along 50 µm axis) ladder Federico Antinori - Vertex, Kona - Nov. 2002

SPD cooling & support • lightweight carbon fibre support sectors • integrated cooling – evaporative C 3 F 8 Federico Antinori - Vertex, Kona - Nov. 2002

Contents • Introduction – Alice and the Inner Tracking System (ITS) • ITS subdetectors (a bird’s eye view) – Si strips (SSD) – Si drifts (SDD) – Si pixels (SPD) • ITS performance • Concluding remarks Federico Antinori - Vertex, Kona - Nov. 2002

Impact Parameter Resolution (rj) • better than 50 µm for p. T > 1. 3 Ge. V/c • ~10 µm at high p. T Federico Antinori - Vertex, Kona - Nov. 2002

Impact Parameter Resolution (z) Federico Antinori - Vertex, Kona - Nov. 2002

Momentum Resolution • Large effect of ITS on momentum resolution at high p. T – high spatial precision – increase of lever arm Federico Antinori - Vertex, Kona - Nov. 2002

Benchmark: D 0 K-p+ • Initial S/B ~ 5 · 10 -6 – Pb-Pb collisions at LHC with d. N/dy = 6000 – invariant mass and particle-id cuts only • Final S/B ~ 0. 1 – after vertexing and pointing cuts • Significance S/√(S+B) ≈ 35 – for 107 events (~15 days data taking) Federico Antinori - Vertex, Kona - Nov. 2002 107 events, all cuts applied total bkgd-subtracted

Benchmark: B e± + X electron tags vs impact parameter • i. p. from ITS • electron id: – TRD (transition radiation) – TPC (d. E/dx) Federico Antinori - Vertex, Kona - Nov. 2002

beauty / total e tags vs. impact parameter cut p. T> 3 Ge. V p. T> 2 Ge. V p. T> 1 Ge. V d 0 threshold (µm) Federico Antinori - Vertex, Kona - Nov. 2002

Contents • Introduction – Alice and the Inner Tracking System (ITS) • ITS subdetectors (a bird’s eye view) – Si strips (SSD) – Si drifts (SDD) – Si pixels (SPD) • ITS performance • Concluding remarks Federico Antinori - Vertex, Kona - Nov. 2002

Concluding remarks • ITS will allow Alice to access heavy flavour sector in nucleus-nucleus collisions – essential information from hot, dense initial stages of collision • ITS design ~ frozen – very tight integration constraints: getting here has taken years of hard work and dedication of tens of physicists and engineers • Very challenging times ahead – tight construction plan in order to be ready for 1 st beam (installation in Alice in 2006) Federico Antinori - Vertex, Kona - Nov. 2002