Heinz Pernegger for

First performance results from Phobos at RHIC

First performance results from Phobos at RHIC

Heinz Pernegger for the PHOBOS collaborationVertex 2000

Heinz Pernegger for

PHOBOS CollaborationPHOBOS CollaborationARGONNE NATIONAL LABORATORY

Birger Back, Nigel George, Alan Wuosmaa

BROOKHAVEN NATIONAL LABORATORYMark 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, KRAKOWWojciech 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, KRAKOWAndrzej Bialas, Wieslaw Czyz, Kacper Zalewski

MASSACHUSETTS INSTITUTE OF TECHNOLOGYWit 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, TAIWANYuan-Hann Chang, Augustine Chen, Willis Lin, JawLuen Tang

UNIVERSITY OF ROCHESTERA. Hayes, Erik Johnson, Steven Manly, Robert Pak, Inkyu Park, Wojtech Skulski, Teng, Frank Wolfs

UNIVERSITY OF ILLINOIS AT CHICAGORussell Betts, Christopher Conner, Clive Halliwell, Rudi Ganz, Dave Hofman, Richard Hollis, Burt Holzman,, Wojtek Kucewicz, Don

McLeod, Rachid Nouicer, Michael Reuter

UNIVERSITY OF MARYLANDRichard Baum, Richard Bindel, Jing Shea, Edmundo Garcia-Solis, Alice Mignerey

Heinz Pernegger for

Relativistic Heavy Ion ColliderRelativistic Heavy Ion Collider

RHIC environment:Highest energy density ever produced in labAu-Au collisions with total s= 25TeVAbout 4000 charged particle per central collision

12 June: 1st Collisions @ s = 56 AGeV24 June: 1st Collisions @ s = 130 AGeV5 Sept: end of first Au-Au physics run

Heinz Pernegger for

PHOBOS DetectorPHOBOS Detector

Heinz Pernegger for

What does Phobos measure ?What does Phobos measure ?

Phobos searches for signs of Quark-Gluon Plasma at RHICMeasures multiplicity of charged particles over full solid angleReconstruct tracks in mid-rapidity range with low Pt threshold and identifies themMeasures particle ratio/spectra, particle correlation

Phobos “lives” on analog signals of our silicon detectorsMultiplicity measurement use dE/dx as multiplicity estimatorSpectrometer uses dE/dx method for particle identificationAnalog information used to reject backgroundAnalog signals partially used in pattern recognition

Heinz Pernegger for

The Multiplicity detectorThe 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 multiplicityHas to deal with high occupancy (>80%)

Vertex

octagon

Heinz Pernegger for

The silicon spectrometerThe silicon spectrometer

16 layer of smaller silicon pad detectors near mid rapdityTracks and Identifies particles (dE/dx) in 2T magnetic fieldAll silicon readout with Viking VAHDR1 chips

Very high dynamic range (>100MIPs), peaking time 1.1s

1x1mm to 0.7x19mm

Heinz Pernegger for

Our silicon detectorsOur silicon detectorsDouble Metal, Single sided, AC coupled, polysilicon biased detectorsproduced by ERSO, Taiwan

p+ Implant

n+

Polysilicon Drain Resistor

bias bussignal lines

vias

300um 5kOhm nSi

0.2um ONO1.2um ONO

AC coupled Pad (p-implant + metal 1 pad)

polisilicon bias resistor

metal 2 readout line

contact hole metal 1- metal 2

Heinz Pernegger for

Before installationBefore installationThe full silicon detector in numbers:

500 wafers, 1600 Viking VAHDR1 readout chips9 different wafer layouts produced by Miracle/Erso, TaiwanAssembled to 240 modules with 140 000 channels

Commissioning setup (15% of full) March-JulyStudy 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%

Heinz Pernegger for

RHIC beams in PhobosRHIC 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 Start6 Bunches

Start 55 Bunches

Integrated Luminosity

B-1

Date

RHIC Integrated Luminosity 65+65 GeV RHIC Integrated Luminosity 65+65 GeV

Heinz Pernegger for Run 5332 Event 35225 08/31/00 06:59:24Run 5332 Event 35225 08/31/00 06:59:24PHOBOS Online Event DisplayPHOBOS Online Event Display

Spectrometer Arm N

Spectrometer Arm P

Octagon Multiplicity detector

Trigger Scintillators N

Trigger Scintillators P

Not to scale Not all sub-detectors shown

Au-A

u B

eam

Mom

entu

m =

65

.12

GeV

/c

Heinz Pernegger for

Performance of the Multiplicity Detector 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 Vtx

Opening to Spec

Opening to Spec

Heinz Pernegger for

Dealing with high occupancyDealing with high occupancy

Problems associated with high occupancy:

Few channels left to determine common-mode-noise correctionEvent-by-event baseline shift dependent on input signal

Base line before and after

correction

Heinz Pernegger for

Signal dependence on occupancy

Signal dependence on occupancy

Problems associated with high occupancy:

Gain dependence on occupancy can distort the multiplicity measurementMultiplicity measured =

dE(meas)/<dE(part)>Gain loss at highest occupancy: 20% NO baseline corr.6% WITH baseline corr.

Heinz Pernegger for

Multiplicity sensor uniformityMultiplicity 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

Heinz Pernegger for

Performance of tracking detectors

Performance of tracking detectors

Hits in VTX

Hits in SPECTracks in SPEC

130 AGeV

56 AGeV

130 AGeV

Heinz Pernegger for

Signal uniformity in Spec/Vertex

Signal uniformity in Spec/Vertex

Signal distrbutions for different layouts:

All signal distribution after calibration (20% effect!)Small pads (type 1 & 2 , 1mm2)Larger pads (type 3,4,5 10 mm2)“strips” (vertex : 0.4x20 mm2)

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

Heinz Pernegger for

Uniformity within sensorsUniformity within sensors

Pad row (along readout lines accros sensor)

Rela

tive s

ignal vari

ati

on

+/- 2%1 x 1 mm2 0.4 x 6 mm2 0.7 x 7.5 mm2

0.7 x 15 mm2 0.7 x 19 mm2 0.3 x 23 mm2

0.3 x 46 mm2

Typical variation <+/-1% within sensor over large range of pad size and readout line length

Heinz Pernegger for

Signal/Noise vs sensor layoutSignal/Noise vs sensor layoutSig

nal peak

[e-]

Nois

e [

e-]

Large pads

Longs readout

lines (high capacitance)

Chip dominated base offset

(ENC = 900 e-+5e-/pF @ 1.1s)

=24000e-

Closest to beam

Heinz Pernegger for

Focus on Si signal simulationFocus on Si signal simulationCritical test of detector understandingBoth distributions contain the same number of central eventsPoints 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)

Heinz Pernegger for Optimizing our signal simulation

Optimizing our signal simulation

Measured dE/dx in silicon in a testbeam and verified simulation:

Measure dE/dx and distribution shape, test PIDCover large momentum range (130MeV – 8GeV), measure & K

Data

Geant

Heinz Pernegger for

Measuring charged multiplicityMeasuring charged multiplicity

VTX TrackletsTwo hit combinations that point to the vertexd = 2 – 1

Good tracklets have d<.1

SPEC TrackletsTwo hit combinations that point to the vertexdR = (d2 + d2) Good tracklets have dR<.015

Heinz Pernegger for

Results :PHOBOS Measurement of Charged :PHOBOS Measurement of Charged Particle Multiplicitynear Mid-rapidity Particle Multiplicitynear Mid-rapidity

hep-ex/0007036hep-ex/0007036 Accepted for publication in PRL Oct 02 2000Accepted for publication in PRL Oct 02 2000

dNch/d (||<1) at sNN= 56 GeV: 408±12±30 dNch/d (||<1) at sNN=130 GeV: 555±12±35

Heinz Pernegger for

SummarySummaryThe good performance allowed a very fast physics analysis

Submitted within 5 week after first recorded collisionThe 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 flawlessly98 % off al channels fully functionalNot a single module failure during installation and all runningOperates at S/N >15

Phobos is well equipped for future analysisVery uniform and well calibrated signal responseCan operate at high occupanciesDetector showed to be reliable and stable

Heinz Pernegger for

Next transparencies are backup + additions

Heinz Pernegger for

Readout & Calibration systemReadout & Calibration system

Readout with Viking VAHDR1 chipsVery high dynamic range (>100MIPs), peaking time 1.1s

Phobos “lives” on analog signalsMultiplicity measurement use dE/dx as multiplicity estimatorSpectrometer uses dE/dx method for particle identificationAnalog information used to reject backgroundAnalog signals partially used in pattern recognition

• Dedicated calibration systemMeasures full gain curve for each channel (1-2/day)Verifies functionality and normalizes gain of different detector modules and sensors

Heinz Pernegger for

Derivation of dN/dDerivation of dN/d

Extract from correlation of

Primaries in –1 < < 1Measured number of tracklets

dN/d

Nu

mb

er

of

Tra

ckle

ts

5<z<10

SPEC

VTX

Heinz Pernegger for

Measuring dN/d with tracklets

Measuring dN/d with tracklets

Number of reconstructed tracklets is proportional to dN/d | <1

To reconstruct trackletsReconstruct vertexDefine tracklets based on the vertex and hits in the front planes of SPEC and VTXRedundancy essentially eliminates feed-down, secondaries, random noise hits

To determine Run the same algorithm through the MCFolds in detector response and acceptance

1

d

dNZ

d

dN primarytracklets

Heinz Pernegger for

z

x

Measuring VertexMeasuring Vertex

Pointing accuracy describes how extrapolated tracks deviate from calculated vertex.Compares well with HIJING simulation

Spectrometer sits very close to vertexHigh resolution tracking in 6 planes gives excellent vertex resolution