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Phobos at RHIC Edmundo Garcia University of Illinois at Chicago for the PHOBOS Collaboration IV Latin American Symposium on Nuclear Physics Mexico City Septiembre 2001
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-2- Edmundo Garcia, UIC PHOBOS Collaboration ARGONNE NATIONAL LABORATORY BROOKHAVEN NATIONAL LABORATORY INSTITUTE OF NUCLEAR PHYSICS, KRAKOW MASSACHUSETTS INSTITUTE OF TECHNOLOGY NATIONAL CENTRAL UNIVERSITY, TAIWAN UNIVERSITY OF ROCHESTER UNIVERSITY OF ILLINOIS AT CHICAGO UNIVERSITY OF MARYLAND Birger Back, Nigel George, Alan Wuosmaa Mark Baker, Donald Barton, Alan Carroll, Joel Corbo, Stephen Gushue, Dale Hicks, Burt Holzman,Robert Pak, Marc Rafelski, Louis Remsberg, Peter Steinberg, Andrei Sukhanov Andrzej Budzanowski, Roman Holynski, Jerzy Michalowski, Andrzej Olszewski, Pawel Sawicki, Marek Stodulski, Adam Trzupek, Barbara Wosiek, Krzysztof Wozniak Wit Busza (Spokesperson), Patrick Decowski, Kristjan Gulbrandsen, Conor Henderson, Jay Kane, Judith Katzy, Piotr Kulinich, Johannes Muelmenstaedt, Heinz Pernegger, Michel Rbeiz, Corey Reed, Christof Roland, Gunther Roland, Leslie Rosenberg, Pradeep Sarin, Stephen Steadman, George Stephans, Gerrit van Nieuwenhuizen, Carla Vale, Robin Verdier, Bernard Wadsworth, Bolek Wyslouch Chia Ming Kuo, Willis Lin, Jaw-Luen Tang Joshua Hamblen, Erik Johnson, Nazim Khan, Steven Manly,Inkyu Park, Wojtek Skulski, Ray Teng, Frank Wolfs Russell Betts, Edmundo Garcia, Clive Halliwell, David Hofman, Richard Hollis, Aneta Iordanova, Wojtek Kucewicz, Don McLeod, Rachid Nouicer, Michael Reuter, Joe Sagerer Richard Bindel, Alice Mignerey
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-3- Edmundo Garcia, UIC Outline Introduction The detector Trigger System Multiplicity Detector Spectrometer Physics Measurements Multiplicity Particle Ratios Flow Final Notes
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-4- Edmundo Garcia, UIC atoms particles nucleus qgp energy/density Big quark-gluon p + n low mass nuclei neutral atom star dispersion of TODAY Bang plasma formation formation formation formation heavy elements time 10 -6 s 10 -4 s 3 min 400,000 yr 10 9 yr >10 9 yr 15x10 9 yr Copyright 1998 Contemporary Physics Education Project (CPEP) time Physics
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-5- Edmundo Garcia, UIC AGS: s = 4.8 GeV SPS: s = 17 GeV RHIC: pp, pA, AA s : 30 - 200 GeV Relativistic Heavy Ion Collider LHC s = 5.2 TeV
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-6- Edmundo Garcia, UIC PHENIXSTAR PHOBOS BRAHMS Two nuclei approach relativistically contracted Hard collisions take place during first stages of reaction Interactions of produced particles act at soft and hard scales Final particles freeze out towards the detectors RHIC collisions
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-7- Edmundo Garcia, UIC Experiment
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-8- Edmundo Garcia, UIC One of the “small” RHIC experiments, size (6 x 6 x 3 m), and people (50 scientist) Designed to be able to examine and analyze a very large amount of minimum bias interactions (high trigger rate capability) Measurements Multiplicity and angular distribution of charged particles < 5.3 over 4 coverage event by event Particle spectra 0.5 < < 1.5 and 2 x 11 o in (azimuthal) Covers about 1% of particles Capable to reconstruct low momentum particles ( 55 MeV/c ) pseudorapidity ln (tan )) rapidity y = 1/2 * ln [( E + p) L / (E - p L )] Phobos
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-9- Edmundo Garcia, UIC t (ns) Events ZDC N ZP Au x z PP PN CN CP paddle counters Valid Collision cerenkov counters zdc good vertex Phobos Trigger
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-10- Edmundo Garcia, UIC Centrality. number of spectator neutrons in ZDC number of spectator neutrons in ZDC = f ( E paddles ) Centrality E paddles Centrality measurement charged spectators
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-11- Edmundo Garcia, UIC peripheral central 6% Centrality selection
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-12- Edmundo Garcia, UIC Phobos silicon
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-13- Edmundo Garcia, UIC Position Sensitive Silicon Detectors Strip Drift Pad/Pixel
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-14- Edmundo Garcia, UIC Multiplicity and Vertex Detector Run 5374, Event 79495 vertex octagon rings Multiplicity and vertex detectors
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-15- Edmundo Garcia, UIC Spectrometer -- K-K- pbar pid
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-16- Edmundo Garcia, UIC Use energy deposited in each Si pad Hit Counting, Analog and Tracklet methods agree to better than ±4% Multiplicity measurement Count hits above threshold, assume Poisson statistics Analog information Counting Tracking detectors Count three-point tracklets: two layers of Si and event vertex match Single Layer Silicon
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-17- Edmundo Garcia, UIC Energy Systematics: 3-200 GeV pp
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-18- Edmundo Garcia, UIC 200 GeV 6% central Pseudo-Rapidity Dependence
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-19- Edmundo Garcia, UIC Centrality Dependence at =0 Kharzeev/Nardi
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-20- Edmundo Garcia, UIC Anti-particle / particle ratios z x 10 cm y Tracking in the spectrometer Alternate 2T magnetic fields Energy loss and momentum Determine ratio of - / +, K - /K +, p/p Compare to lower energy (AGS/SPS) results 70 cm
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-21- Edmundo Garcia, UIC = 1.00 ±0.01 (stat) ± 0.02 (syst) K - /K + = 0.91 ± 0.07 (stat) ± 0.06 (syst) p/p = 0.60 ± 0.04 (stat) ± 0.06 (syst) K - /K + vs Energy p/p vs Energy Particle Ratios at 130 GeV from PHOBOS
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-22- Edmundo Garcia, UIC Elliptic Flow dN/d( R ) = N 0 (1 + 2V 1 cos ( R ) + 2V 2 cos (2( R )) +... ) Elliptic flow reaction plane RR
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-23- Edmundo Garcia, UIC Peripheral b Central b Normalized Paddle Signal (STAR : Normalized N ch ) PHOBOS Systematic error ~ 0.007 V2V2 Centrality dependence of V 2 | |<1.0 s NN =130GeV preliminary ~4 Elliptic Flow @ 130 GeV SPS 17 GeV
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-24- Edmundo Garcia, UIC Multiplicity Increase in the slope of dn/d as a function of the energy when compared to ppbar dn/d increase with energy from 130 to 200 GeV is modest and concentrated at mid-rapidity Other measurements: Elliptic flow: Strong and -dependent K - /K + ratio does not follow linear extrapolation from lower energy Antiproton/proton ratio increasing towards unity (approaching a baryon-free regime) Centrality dependence of dN/d . No conclusive/clear signal of QGP (so far), it seems that any finding will take a systematic scan of all QGP probes at RHIC energies Summary
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-25- Edmundo Garcia, UIC Acceptance 0+3-3 +5.5 -5.5 multiplicity detector spectrometer
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-26- Edmundo Garcia, UIC dN/d Background subtraction on tracklets < ±5% Uncertainty on due to model differences < 5% Total contribution due to feed-down correction < 4% (typically 1%) Total fraction lost due to stopping particles < 5% Both are corrected via MC normalization Total uncertainty on dN/ d is ±8% N part Loss of trigger efficiency at low-multiplicity <10% Uncertainty on N part <1% Uncertainty in modeling paddle fluctuations Uncertainty on N part <6% ( dN/d / N part ) 130 / ( dN/d / N part ) 56 Many uncertainties cancel in the ratio Systematic Uncertainties
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-27- Edmundo Garcia, UIC Particle Ratios (Chemistry) stat sys
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-28- Edmundo Garcia, UIC Double Metal, Single sided, AC coupled, polysilicon biased detectors produced by ERSO, Taiwan AC coupled Pad (p-implant + metal 1 pad) polisilicon bias resistor metal 2 readout line contact hole metal 1- metal 2 Phobos silicon p+ Implant n+ Polysilicon Drain Resistor bias bus signal lines vias 300um 5kOhm nSi 0.2um ONO 1.2um ONO
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