1. Heinz Pernegger for First performance results from Phobos at RHIC Heinz Pernegger for the PHOBOS collaboration Vertex 2000

2. Heinz Pernegger for PHOBOS Collaboration ARGONNE NATIONAL LABORATORY Birger Back, Nigel George, Alan Wuosmaa BROOKHAVEN NATIONAL LABORATORY Mark Baker, Donald Barton, Mathew Ceglia, Alan Carroll, Stephen Gushue, George Heintzelman, Hobie Kraner,Robert Pak,Louis Remsberg, Joseph Scaduto, Peter Steinberg, Andrei Sukhanov INSTITUTE OF NUCLEAR PHYSICS, KRAKOW Wojciech Bogucki, Andrzej Budzanowski, Tomir Coghen, Bojdan Dabrowski, Marian Despet, Kazimierz Galuszka, Jan Godlewski, Jerzy Halik, Roman Holynski, W. Kita, Jerzy Kotula, Marian Lemler, Jozef Ligocki, Jerzy Michalowski, Andrzej Olszewski , Pawel Sawicki, Andrzej Straczek, Marek Stodulski, Mieczylsaw Strek, Z. Stopa, Adam Trzupek, Barbara Wosiek, Krzysztof Wozniak, Pawel Zychowski JAGELLONIAN UNIVERSITY, KRAKOW Andrzej Bialas, Wieslaw Czyz, Kacper Zalewski MASSACHUSETTS INSTITUTE OF TECHNOLOGY Wit Busza*, Patrick Decowski, Piotr Fita, J. Fitch, C. Gomes, Kristjan Gulbrandsen, P. Haridas, Conor Henderson, Jay Kane, Judith Katzy, Piotr Kulinich, Clyde Law, Johannes Muelmenstaedt, Marjory Neal, P. Patel, Heinz Pernegger, Miro Plesko, Corey Reed, Christof Roland, Gunther Roland, Dale Ross, Leslie Rosenberg, John Ryan, Pradeep Sarin, Stephen Steadman, George Stephans, Katarzyna Surowiecka, Gerrit van Nieuwenhuizen, Carla Vale, Robin Verdier, Bernard Wadsworth, Bolek Wyslouch NATIONAL CENTRAL UNIVERSITY, TAIWAN Yuan-Hann Chang, Augustine Chen, Willis Lin, JawLuen Tang UNIVERSITY OF ROCHESTER A. Hayes, Erik Johnson, Steven Manly, Robert Pak, Inkyu Park, Wojtech Skulski, Teng, Frank Wolfs UNIVERSITY OF ILLINOIS AT CHICAGO Russell Betts, Christopher Conner, Clive Halliwell, Rudi Ganz, Dave Hofman, Richard Hollis, Burt Holzman,, Wojtek Kucewicz, Don McLeod, Rachid Nouicer, Michael Reuter UNIVERSITY OF MARYLAND Richard Baum, Richard Bindel, Jing Shea, Edmundo Garcia-Solis, Alice Mignerey

3. Heinz Pernegger for Relativistic Heavy Ion Collider RHIC environment: Highest energy density ever produced in lab Au-Au collisions with total  s= 25TeV About 4000 charged particle per central collision 12 June: 1 st Collisions @  s = 56 AGeV 24 June: 1 st Collisions @  s = 130 AGeV 5 Sept: end of first Au-Au physics run

4. Heinz Pernegger for PHOBOS Detector

5. Heinz Pernegger for What does Phobos measure ? Phobos searches for signs of Quark-Gluon Plasma at RHIC Measures multiplicity of charged particles over full solid angle Reconstruct tracks in mid-rapidity range with low Pt threshold and identifies them Measures particle ratio/spectra, particle correlation Phobos “lives” on analog signals of our silicon detectors Multiplicity measurement use dE/dx as multiplicity estimator Spectrometer uses dE/dx method for particle identification Analog information used to reject background Analog signals partially used in pattern recognition

6. Heinz Pernegger for The Multiplicity detector 1 layer of large silicon pad detectors “everywhere” Count single hits or sum of analog signals in a detector area as measure of particle multiplicity Has to deal with high occupancy (>80%) Vertex octagon

7. Heinz Pernegger for The silicon spectrometer 16 layer of smaller silicon pad detectors near mid rapdity Tracks and Identifies particles (dE/dx) in 2T magnetic field All silicon readout with Viking VAHDR1 chips Very high dynamic range (>100MIPs), peaking time 1.1  s 1x1mm to 0.7x19mm

8. Heinz Pernegger for Our silicon detectors Double Metal, Single sided, AC coupled, polysilicon biased detectors produced by ERSO, Taiwan p+ Implant n+ Polysilicon Drain Resistor bias bus signal lines vias 300um 5kOhm nSi 0.2um ONO 1.2um ONO AC coupled Pad (p-implant + metal 1 pad) polisilicon bias resistor metal 2 readout line contact hole metal 1- metal 2

9. Heinz Pernegger for Before installation The full silicon detector in numbers: 500 wafers, 1600 Viking VAHDR1 readout chips 9 different wafer layouts produced by Miracle/Erso, Taiwan Assembled to 240 modules with 140 000 channels Commissioning setup (15% of full) March-July Study environment and measure first collisions Full installation for physics run on July 13 200/200 modules functional 1082/1084 chips functional = 99.8% In channels: 98.8% channels fully functional Peak Signal/Noise = 13:1 to 20:1 depending on sensor layout Original requirements : S/N>10 and full functional channels >95%

10. Heinz Pernegger for RHIC beams in Phobos Physics Run 2000 Luminosity estimated using coincidence of signals in the Zero Degree Calorimeters.  =10.7barn used to convert counts to luminosity. PR00 Start 6 Bunches Start 55 Bunches Integrated Luminosity  B -1 Date RHIC Integrated Luminosity 65+65 GeV

11. Heinz Pernegger for Run 5332 Event 35225 08/31/00 06:59:24 PHOBOS Online Event Display Spectrometer Arm N Spectrometer Arm P Octagon Multiplicity detector Trigger Scintillators N Trigger Scintillators P Not to scaleNot all sub-detectors shown Au-Au Beam Momentum = 65.12 GeV/c

12. Heinz Pernegger for Performance of the Multiplicity Detector phi Z (beam) One high multiplicity event in the octagon occupancy up to 80% Color encodes pulse height Opening to Vtx Opening to Spec

13. Heinz Pernegger for Dealing with high occupancy Problems associated with high occupancy: Few channels left to determine common- mode-noise correction Event-by-event baseline shift dependent on input signal Base line before and after correction

14. Heinz Pernegger for Signal dependence on occupancy Problems associated with high occupancy: Gain dependence on occupancy can distort the multiplicity measurement Multiplicity measured = dE(meas)/ Gain loss at highest occupancy: 20% NO baseline corr. 6% WITH baseline corr.

15. Heinz Pernegger for Multiplicity sensor uniformity +/- 1% +/- 3% No substantial signal variation due to different layout (double metal line routing/ varying pad size) 3.6 x 8.4 cm 8.3 cm x 6.5 cm Smp= 93 keV Smp= 85keV

16. Heinz Pernegger for Performance of tracking detectors Hits in VTX Hits in SPEC Tracks in SPEC 130 AGeV 56 AGeV 130 AGeV

17. Heinz Pernegger for Signal uniformity in Spec/Vertex Signal distrbutions for different layouts: All signal distribution after calibration (20% effect!) Small pads (type 1 & 2, 1mm 2 ) Larger pads (type 3,4,5 10 mm 2 ) “strips” (vertex : 0.4x20 mm 2) Very uniform in shape and peak T1 Smp= 90 T2 Smp=85 T3 Smp= 85 T4 Smp=85 T5 Smp=85 Inner Vtx Smp=87 Outer Vtx Smp=85

18. Heinz Pernegger for Uniformity within sensors Pad row (along readout lines accros sensor) Relative signal variation +/- 2% 1 x 1 mm 2 0.4 x 6 mm 2 0.7 x 7.5 mm 2 0.7 x 15 mm 2 0.7 x 19 mm 2 0.3 x 23 mm 2 0.3 x 46 mm 2 Typical variation <+/-1% within sensor over large range of pad size and readout line length

19. Heinz Pernegger for Signal/Noise vs sensor layout Signal peak [e-] Noise [e-] Large pads Longs readout lines (high capacitance) Chip dominated base offset (ENC = 900 e-+5e-/pF @ 1.1  s) =24000e- Closest to beam

20. Heinz Pernegger for Focus on Si signal simulation Critical test of detector understanding Both distributions contain the same number of central events Points are for VTX data No correction for detector thickness Histogram is for simulated VTX signals GEANT Response from test- beam Electronics noise Shulek correction (CR setup)

21. Heinz Pernegger for Optimizing our signal simulation Measured dE/dx in silicon in a testbeam and verified simulation: Measure dE/dx and distribution shape, test PID Cover large momentum range (130MeV – 8GeV), measure  & K  Data Geant  

22. Heinz Pernegger for Measuring charged multiplicity VTX Tracklets Two hit combinations that point to the vertex d  =  2 –  1 Good tracklets have d  <.1 SPEC Tracklets Two hit combinations that point to the vertex dR =  (d  2 + d  2) Good tracklets have dR<.015

23. Heinz Pernegger for :PHOBOS Measurement of Charged Particle Multiplicitynear Mid-rapidity Results :PHOBOS Measurement of Charged Particle Multiplicitynear Mid-rapidity hep-ex/0007036 Accepted for publication in PRL Oct 02 2000 dN ch /d  ( |  |<1) at  s NN = 56 GeV: 408±12±30 dN ch /d  ( |  |<1) at  s NN =130 GeV: 555±12±35

24. Heinz Pernegger for Summary The good performance allowed a very fast physics analysis Submitted within 5 week after first recorded collision The first publication of all RHIC experiment Phobos successfully completed its first physics run: 3.5 million Au-Au collisions on tape (collected mainly in 2 weeks) Phobos silicon detector operated flawlessly 98 % off al channels fully functional Not a single module failure during installation and all running Operates at S/N >15 Phobos is well equipped for future analysis Very uniform and well calibrated signal response Can operate at high occupancies Detector showed to be reliable and stable

25. Heinz Pernegger for Next transparencies are backup + additions

26. Heinz Pernegger for Readout & Calibration system Readout with Viking VAHDR1 chips Very high dynamic range (>100MIPs), peaking time 1.1  s Phobos “lives” on analog signals Multiplicity measurement use dE/dx as multiplicity estimator Spectrometer uses dE/dx method for particle identification Analog information used to reject background Analog signals partially used in pattern recognition Dedicated calibration system Measures full gain curve for each channel (1-2/day) Verifies functionality and normalizes gain of different detector modules and sensors

27. Heinz Pernegger for Derivation of dN/d  Extract  from correlation of Primaries in –1 <  < 1 Measured number of tracklets dN/d  Number of Tracklets 5<z<10 SPEC VTX

28. Heinz Pernegger for Measuring dN/d  with tracklets Number of reconstructed tracklets is proportional to dN/d  |  <1 To reconstruct tracklets Reconstruct vertex Define tracklets based on the vertex and hits in the front planes of SPEC and VTX Redundancy essentially eliminates feed-down, secondaries, random noise hits To determine  Run the same algorithm through the MC Folds in detector response and acceptance

29. Heinz Pernegger for z x Measuring Vertex Pointing accuracy describes how extrapolated tracks deviate from calculated vertex. Compares well with HIJING simulation Spectrometer sits very close to vertex High resolution tracking in 6 planes gives excellent vertex resolution