Results from the Experiment at RHIC Abigail Bickley University of Maryland For the Collaboration...
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Transcript of Results from the Experiment at RHIC Abigail Bickley University of Maryland For the Collaboration...
Results from the
Experiment at RHIC
Abigail BickleyUniversity of Maryland
For the Collaboration
Topics in Heavy Ion CollisionsJune 25-28, 2003, Montreal
Collaboration (May 2003)
Birger Back, Mark Baker, Maarten Ballintijn, Donald Barton, Bruce Becker, Russell Betts,
Abigail Bickley, Richard Bindel, Andrzej Budzanowski, Wit Busza (Spokesperson), Alan Carroll,
Patrick Decowski, Edmundo Garcia, Tomasz Gburek, Nigel George, Kristjan Gulbrandsen,
Stephen Gushue, Clive Halliwell, Joshua Hamblen, Adam Harrington, Conor Henderson,
David Hofman, Richard Hollis, Roman Holynski, Burt Holzman, Aneta Iordanova, Erik Johnson,
Jay Kane, Nazim Khan, Piotr Kulinich, Chia Ming Kuo, Jang Woo Lee, Willis Lin, Steven Manly,
Alice Mignerey, Gerrit van Nieuwenhuizen, Aaron Noell, Rachid Nouicer, Andrzej Olszewski,
Robert Pak, Inkyu Park, Heinz Pernegger, Corey Reed, Louis Remsberg, Christof Roland,
Gunther Roland, Joe Sagerer, Pradeep Sarin, Pawel Sawicki, Iouri Sedykh, Wojtek Skulski,
Chadd Smith, Peter Steinberg, George Stephans, Andrei Sukhanov, Ray Teng,
Marguerite Belt Tonjes, Adam Trzupek, Carla Vale, Robin Verdier, Gábor Veres, Bernard
Wadsworth, Frank Wolfs, Barbara Wosiek, Krzysztof Wozniak, Alan Wuosmaa, Bolek Wyslouch,
Jinlong Zhang
ARGONNE NATIONAL LABORATORY BROOKHAVEN NATIONAL LABORATORYINSTITUTE OF NUCLEAR PHYSICS, KRAKOW MASSACHUSETTS INSTITUTE OF TECHNOLOGYNATIONAL CENTRAL UNIVERSITY, TAIWAN UNIVERSITY OF ILLINOIS AT CHICAGO
UNIVERSITY OF MARYLAND UNIVERSITY OF ROCHESTER
Broad Capabilities of the Phobos Spectrometer
• Low pT: PID
– Stopping in Si (pT<0.2 GeV/c)
– dE/dx versus p (pT<1GeV/c)• Particle Ratios (Au+Au)
• High pT: Non-PID– Charged particle spectra
• Au+Au compared to d+Au
Particle Ratios: Energy Dependence
p/p
K–/K+
pT = 0.07 – 1.0 GeV/c
PHOBOS 130 GeV PRL 87, 102301, 2001
PHOBOS 200 GeV PRC 67, 021901(R), 2003
At RHIC see a rapidly decreasing net baryon density near midrapidity.
A+A central collisions
K-/K+
€
p p
Energy evolution of BUsing measured <K–>/<K+>,<p>/<p> and statistical model
of F. Becattini et al., (PRC64,024901,2001) with Tch 160 – 170 MeV
Estimated baryochemical potential at sNN = 200 GeV: B = 26 2 MeV
Fit:P.Braun-MunzingerNP. A697, 902, 2002.
Centrality and pT dependence
Ratios are independent of pT and Npart
PHOBOS preliminary
Au+Au 200 GeV
10% most central
p/p
K–/K+
/+
PHOBOS preliminary
p/p
K–/K+
/+
Systematic Errors not shown
Phobos Preliminary
PT Distribution of Charged Particles
Particle ratios dominated by particles with pT<1GeV/c; “Soft” part of spectrumWhat about high pT particle production? Look at the “Hard” part of the spectrum.
65 ± 4
93 ± 5
138 ± 6
200 ± 8
276 ± 9
344 ± 12<Npart>
45-50%
35-45%
25-35%
15-25%
6-15%
0-6%
Centrality
Transverse Momentum Distributionsfor Au+Au @ 200 GeV
0.2<y <1.4
nucl-ex/0302015: Submitted to Phys Lett B
Ratio of Au+Au and pp Spectra at 200 GeV
• Observe a significant change in the spectral shape between pp and Au+Au collisions already for mid-peripheral events.
• Central Au+Au collisions show a strong violation of (expected) collision scaling at high pT.
mid-peripheral
central
Npart = 65 ± 4
Npart = 344 ± 12
pp from UA1: Nucl.Phys.B335, (1990) 261.
Transverse Momentum Distributionsfor d+Au @ 200 GeV
0.2<<1.4
Centrality Determination:Energy in Silicon Ring Counters
Energy (arb. units )
Cou
nts
3.0<||<5.4
Transverse Momentum Distributions
0 – 20%
20 – 40%
40 – 70%70 – 100%
3.3 ± 1.0
6.7 ± 0.9
10.9 ± 0.915.5 ± 1.0
<Npart>
70-100%
40-70%
20-40%
0-20%Centrality
nucl-ex/0306025: Submitted to PRL
pp from UA1:Nucl.Phys.B335,
(1990) 261
Phobos d+Au Results
€
dAuR =σ
pp inel
< collN >
dAud2NTdp dη
d2σ (UA1)pp
Tdp dηPHOBOS d+Au: nucl-ex/0306025
central Au+Au
Spectrometer Results
• Low Pt– Au+Au particle ratios: show that a net baryon free
region is being approached at RHIC
• High Pt– Au+Au spectra: central spectrum shows strong
suppression relative to collision scaling– d+Au spectra: suppression observed in Au+Au
spectra is not due to initial state effects