1 Silicon Vertex Detector at PHENIX Atsushi Taketani RIKEN / RBRC 1.Physics Goal 2.Detector Concept 3.Structure 4.Pixel detector 5.Strip detector 6.Summary

2 Physics with Silicon Vertex Tracker QCD at high temperature Detail investigation of the hot and dense strongly interacting matter –Energy loss of heavy quarks in the dense –Elliptic flow of heavy quarks –Open beauty production. –Accurate charm reference for quarkonium. –Determine QQ background of Thermal dilepton continuum –Improve Upsilon  e + e - measurement Spin structure of nucleon Gluon spin structure of the nucleon –Gluon polarization  G/G with charm, beauty. – x dependence of  G /G with  -jet correlations. QCD in cold nuclei Nuclear structure in nuclei –Nuclear dependence of PDFs. – Saturation physics: – Gluon shadowing over broad x-range Key word = Heavy Quark production

3  charm and bottom identification by displaced vertex  Jet identification with larger acceptance PhysicsGoals: Gluon polarization  G(x) Physics Goals: Gluon polarization  G(x) Gluon Polarization Gluon polarization can be measured by doule-spin asymmetry A_LL of direct photon and heavy quark production in polarized pp collisions Jet + direct   constraint on x g Polarized p+p collisions

4 Expected Performance LayerradiusSensorOccupancy Layer 12.5 cmPixel 0.53 % Layer 25.0 cmPixel 0.16% Layer cmStrip 4.5 % (x-strip) 4.7 % (u-strip) Layer cmStrip 2.5 % (x-strip) 2.7 % (u-strip) Expected occupancy at Au-Au 200GeV most central event Distance to the Closest Approach [cm] D 0 decay Collision Vertex

5 Gamma+jets Q_  – jet_  dp T = 15 ⊕ 5.9p T %

6 What is Silicon Detector electrode P type N type Diode Sensor Depletion Layer Charged particle electron eeeee hhhhh

7 Feature of Silicon Detector High dE/dx ( ~ 2MeV /(g/cm^2) ) –Solid state detector comparing to gas chamber -> thin detector Low e-h pair creation energy –3.6 eV instead of 13.6 eV for gas chamber Available Technology by industry –Compact, fine pitch and precise –Huge number of read out channel –Cost performance per readout channel

8 Details of sensor Cross section Relatively small readout channel #ch ~ (Surface area)^1/2 1+1 dimensional readout ghost hits on high occupancy Strip Huge readout channel #ch ~ Surface area True 2 dimensional read out no ghost at all Pixel

9 Identifying long-lived particle Polarized Proton Charmed or Bottomed messon Charmed meson ~ 100  m Bottomed meson ~ 300  m Silicon detector

10 Requirements for Vertex Tracker High precision tracking for displaced vertex measurement. 40  m displaced vertex resolution, c  ~ 100  m(D), ~400  m(B) Large coverage tracking capability with momentum resolution (|  |<1.2, and full azimuthally with  /P ~ 6%P) High charged particle density ‘dN/d  ’ ~  =0 High Radiation Dose ~3.3E12 High -> High rate readout Low Material Budget <- avoid multiple scattering and photon conversion for electron measurement by outer detectors. Physics side Environment side

11 endcap VTX 1.2 <  < 2.7 barrel VTX |  < 1.2 NCC 0.9 <  < 3.0 Provides displaced vertex & jet measurement over 2  HBD NCC VTX Displaced vertex: VTX: silicon tracker FVTX: forward Si Jet measurement: NCC: nose cone calorimeter Other detectors: HBD: hadron blind detector Muon trigger PID in west arm MuonTrig

12 The PHENIX VTX group 92 people from 20 institutions as of 2006 May

13 Structure  Barrel region |  |<1.2, almost 2  in  Pixel sensor at inner 2 layers Strip sensors at outer 2 layers  Forward region 1.2<|  |<2.7, 2p in  4 layers of mini strip (50 x 2000 to  m) Trigger capable Pixel Strip R=2.5 and 5cm R=10 and 14cm

VTXLayerR1R2R3R4 Geometrical dimensions R (cm)  z (cm) Area (cm 2 ) Channel countSensor size R  z (cm 2 ) 1.28  1.36 (256 × 32 pixels) 3.43 × 6.36 (384 × 2 strips) Channel size 50  425  m 2 80  m  3 cm (effective 80  1000  m 2 ) Sensors/ladder 4  4 56 Ladders Sensors Readout chips Readout channels1,310,7202,621,440138,240239,616 Radiation length (X/X0) Sensor0.22%0.67 % Readout0.16%0.64 % Bus0.28% Ladder & cooling0.78% Total1.44%2.1 % Pixel detectorStrip detector VTX parameters BEAM Strip Pixel LayerradiusDetectorOccupancy in Central Au+Au collision 12.5cmPixel0.53 % 25.0cmPixel0.16% 310.0cmStrip4.5 % (x-strip)4.7 % (u-strip) cmStrip2.5 % (x-strip)2.7 % (u-strip)

15 PIXEL (Sensor and Readout) Pixel size(  x z ） 50 µm x 425 µm Sensor Thickness 200um  r  = 1.28cm,  z = 1.36 cm (Active area) 256 x 32 = 8192 channel / sensor 4 sensor/ chip 4 chip / stave Readout by ALICE_LHCB1 chip Amp + Discriminator / channel Bump bonded( 2 dim. Soldering) to each pixel Running 10MHz clock ( RHIC 106nsec ) Digital buffer for each channel > 4usec depth Trigger capability > FAST OR logic for each crossing 4 event buffer after L1 trigger

16 Pixel detector module Sensor module consists of 4 ALICE Pixel readout chips Bump-bonded to silicon sensor Sensor Half stave is mounted on the support structure Support structure + cooling Pixel BUS to bring data out and send control signal in to the readout chip is mounted on the half stave Each detector module is built of two half staves, read out on the barrel ends Half stave Pixel BUS Data One readout unit, half stave, made from two sensor modules Full stave 22cm 1.4cm ALICE LHCB1 chip SensorSensor Module

17 Pixel Readout Overview Half stave 11cm 45cm

18 Bus structure Power 50  m Al GND 50  m Al 5 layers structure GND, Power and 3 signal lines Signal 2; (Vertical line) line connected with pixel chip with wire bonding Signal 3; (Horizontal line) send signal to Pilot Module connected with vertical line with through hole Signal-3 3  m Cu Signal-2 3  m Cu Signal-1 3  m Cu Signal 1; (for Surface Mount Device) Signal-1, Signal-2, and signal-3 are connected with through hole Line spacing; 70  m pitch Material Budget; Total ~ 0.26 % < 240 µm 200 µm (13 µm) 150 µm Wire bonding Final configurationsensor Readout chip

19 Pixel LadderSPIRO FEM Readout pictures Extender

20 2. Set-up of the telescope Three half staves Three SPIROs One FEM Two trigger scintillator Analysis software –DAQ –Data converter –Tracking code –Event display Set-up of three layers

21 Layer 1 Layer 2 Layer 3 chip 1 chip 2 chip 3 chip 4 chip 5 chip 6 chip 7 chip 8 chip 9 chip 10 chip 11 chip 12 Event# 200 column row

22 Silicon Sensor Stripixel Concept a-pixels are connected to form X-strips, and b-pixels are connected to form stereo-angled (4.6 o ) U-strips X strips (connect a-pixels) a-pixels interconnect u strips (connect b-pixels) b-pixels interconnect Readout pulse height by ADC

23 Sensor elements: Pixels: 80 µm  1 mm, projective readout via double metal XU/V “strips” of ~3 cm length. Developed at BNL Instrumentation Gr. Two strip-pixel arrays on a single-sided wafer of 500 µm thickness, with channels on 3 x 3 cm 2 area. new design: “lateral” SVX4 readout. Made by Hamamatsu Initial design: “longitudinal” readout. Made by SINTEF Single sided 1+1 dimensional readout ( X and U direction) 3cmx3cm sensor x2 / chip 768 X strip and 768 U strips/chip Position resolution is 25  m by test beam

24 Prototype Detector Using HPK Sensor The 1 st prototype detector – 625 μm thickness – Tested at BNL – ROC+RCM+FEM prototype w/ SVX4 chips developed by ORNL – Gluing/wire-bonding at RIKEN Optical fiber + focuser XYZ micro-stage Bias line Data + Control cables Power cables

25 S/N ~ 20:1 for 625 μm thickness Charge-sharing test w/ IR laser pulse injection – Large spot size in the present setup – Focusing length (8 mm) was too short to shine only one pixel in 625 μm thick sensor. – The maximum focusing length available in the same company is 70 mm. Not enough. Planned: possible solution is to use a radioactive source, cosmic rays and beam. IR Laser Tests Results X-Strip U-Strip Laser spot U-Strip X3RU3R

26 R&D : Prototypes Sensors 1 st prototype sensor – Spiral p + electrode : 8 μm line, 5 μm gap, 3 turns – Thickness : 400/250 μm – R/O chip: VA2 (analog multiplexer) – Tests w/ source & beam S/N: 17:1 for 400 μm thickness 2-D sensitivity need improvements. 2 nd prototype sensor – Spiral p + electrode : 5 μm line, 3 μm gap, 5 turns – Thickness : 400/500 μm – R/O chip: SVX4(CDF SVX4 hybrid) – Tests w/ nano-sec pulsed laser S/N: 14:1 for 500 μm thickness Laser signals were seen 2 nd prototype sensor 1 st prototype sensor

27 Radiation damage of stripixel sensor PHENIX in RHIC2 for 10 years Saturation of circuit 15nA/strip 20 ℃ 10 ℃ 0 ℃ -10 ℃ Rikkyo PHENIX IR 3.3E+12 [N eq /cm 2 ] for 1 year from 2009 ~3E+11 [N eq /cm 2 ] Operation temperature will be 0 deg C

28 Summary PHENIX VTX will investigate many physics on both spin and heavy ion program of RHIC. Detector R&D and production is on going. VTX will be installed in You are welcome to visit our

29 endcap VTX 1.2 <  < 2.7 barrel VTX |  < 1.2 NCC 0.9 <  < 3.0 Provides displaced vertex & jet measurement over 2  HBD NCC VTX Displaced vertex: VTX: silicon tracker FVTX: forward Si Jet measurement: NCC: nose cone calorimeter Other detectors: HBD: hadron blind detector Muon trigger PID in west arm MuonTrig