2/17/2007 nathan grau, wwnd 2007 1 the heavy ion physics program with atlas at the lhc nathan grau...
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2/17/2007
Nathan Grau, WWND 2007
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The Heavy Ion Physics Program with ATLAS at the LHC
Nathan Grau
Columbia University, Nevis LabsOn behalf of the ATLAS Heavy Ion Working Group
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Outline
ATLAS Detector and Performance Up-to-date software, geometry of the as-built
detector Physics Program
Global observables, jet physics, quarkonia, and low-x physics
Something to take away: ATLAS ability for isolated photon identification
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The physics of HIC at the LHC Build on the strong base of work done at RHIC Strongly-coupled QGP (sQGP)
Azimuthal anisotropy is large at high-pT 0, K, , , J/, e, etc.
Single particle suppression is large at high-pT 0, K, , , J/, e, etc.
Two-particle azimuthal correlation suppression and shape modification Near-side and Away-side
Color Glass Condensate Slow rise of dN/d with energy in Au+Au Single particle suppression at forward rapidity in d+Au Searched for mono-jet production at forward rapidity in d+Au
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The ATLAS Detector: Coverage
Full azimuthal acceptance in all detectors Unprecedented pseudorapidity coverage for A+A
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Global Observables Particle and Energy density: dN/d, dET/d
Extend root-s dependence of dN/d: test CGC
Azimuthal Anisotropy: v2, etc. What happens to v2/ at higher root-s?
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Tracking with the Inner Detector Inner detector has full
azimuthal coverage within ||<2.5 and consists of Pixel detector Silicon tracking
detector Transition radiation
tracker (occupancy too large for central Pb+Pb?)
Results from p+p tracking algorithm optimized for HI environment.
Reconstructed tracks with ||<1
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Tracking to lower pT
Work extending pT reach important for p+p and A+A. dN/d in both cases v2 in A+A
Ongoing with high energy and heavy ion participation.
Efficiency: red/blackFake rate: red/green
Preliminary
Minimum bias p+p
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dN/d via Tracklets a la PHOBOS
1. Truth tracks2. “B-Layer” Hits3. Layer 1 Hits4. Matched Tracklets
Measurement of track density
flat with truth density
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Jet Physics with ATLAS See W. Holzmann’s talk for all of the details
STAR, PRL 93 (2004) 252301
interm. pT interm. pT correlationscorrelations
high pT correlationshigh pT correlations
RRAAAA
-h correlations-h correlations
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ATLAS CalorimetryHadronic Barrel
Hadronic EndCap
EM EndCap
EM Barrel
Forward
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Longitudinal Segmentation: 3-d JetsSampling of a 100 GeV jet (no background)
1
2 3
4
5 6
Note the region is 0.8x0.8:a typical jet size
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Photon Isolation and Identification
Barrel EMCal front layer finely segmented in for vectoring H events and 0 rejection.
Example of jet embedded in central b=2 fm HIJING event.
Jet
Background
Single slice 0.1 rad
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Photon Isolation and Identification
Barrel EMCal front layer finely segmented in for vectoring H events and 0 rejection.
Example of jet embedded in central b=2 fm HIJING event.
Jet
Background
All too wide for single photons
Single slice 0.1 rad
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Photon Isolation and Identification
EM
Layer
1 E
T
(GeV
)
Single slice 0.1 rad
-jet event embedded
Barrel EMCal front layer finely segmented in for vectoring H events and 0 rejection.
Example of jet embedded in central b=2 fm HIJING event.
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/0 Separation Variables
Left: fractional energy deposited outside the cluster core in the strip layer
Right: Energy of a 2nd maximum peak in the strip layer
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/0 Separation
Rejection of 0 with appropriate cuts on previous variables
Efficiency in p+p is ~90%, flat with ET and
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Jet Position Resolutions
From standard R=0.4 seeded cone algorithm
Results are important for studies of hard radiation in jets (sub-jets).
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Jet Energy Resolution
Energy resolution as a function of ET and Important for studies of jet RAA, fragmentation
functions, etc.
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Azimuthal Anisotropy from Calorimeters Flow afterburner on HIJING events based on
Poskanzer and Voloshin [PRC 58 (1998) 1671] Simulated “physical” flow based on RHIC data
v2(pT,,centrality) Azimuthal ET distribution in different barrel EM
calorimeter layers (||<1.5)Presampler Strip layer (front) Middle Layer Back Layer
0.003 x 0.1 0.025 x 0.025 0.05 x 0.025 x
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Reaction Plane Resolution
In measuring the physical v2 you must correct by the resolution: v2 = v2
meas/res Resolution measurement from the Barrel (||<1.5), Endcap
(3.2<||<1.5), and Forward (4.9 < || < 3.2) calorimeters Extremely good resolution
Comparison to true RP Comparison of subevents
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Heavy Flavor Physics
Lattice Calculations indicates bounds states melt at different temperatures
But suppression of J/ similar between SPS and RHIC…
SPSRHIC
A. Bickley Hard Probes 2006
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Muon Spectrometer
Coverage up to ||<2.7 Low background because the spectrometer is
behind the calorimeters
Muon Chamber # hits/chamber
Barrel Inner (=0.2) 0.3
Middle (=0.2) 0.5
Outer (=0.2) 0.5
End Cap (=2.0) 0.9
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Heavy Flavor Bound State Measurements
Both charm and bottom states should be accessible to through the +- decay channel
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Resolution and Acceptance for Good mass
resolution Large acceptance Loss of efficiency
near ~0 due to material.
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Possiblity of c
c measurements important because of feeddown to J/. Couple the J/ measurements with the photon isolation
capabilities of the calorimeter should make the c measurement possible.
Measurements of many states necessary to pin down temperature.
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Zero Degree Calorimeter Contribution from the Heavy Ion effort Single highly segmented EMCal module and hadronic
calorimeter modules Expected response (for 1-7 TeV neutrons)
E/E ~ 15-20%, x,y ~ 1-2 mm
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Low-x Measurements from ZDC Measurement of
forward mesons in the decay channel.
The 0 in the ZDC at very low x – possibly into the saturation region.
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Summary of Physics Covered in this talk:
Bulk observables dN/d, v2
Inclusive jets and γ+jets Spectra, hard radiation
Quarkonia (Υ and J/ψ) Possibility of c
Low-x physics For the future:
Ultraperipheral collisions Heavy quarks (esp. b physics) Z+jet, jet-jet correlations
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ATLAS Heavy Ion Working Group A. Ajitanand10, A. Angerami3, G. Atoian11, M. Baker1, P. Chung10, B. Cole3, R. Debbe1,
A. Denisov5, J. Dolejsi2, N. Grau3, J. Hill7, W. Holzmann3, V. Issakov11, J. Jia10, H. Kasper11, R. Lacey10, A. Lebedev7, M. Leltchouk3, A. Moraes1, R. Nouicer1, A.
Olszewski6, A. Poblaguev11, V. Pozdnyakov8, M. Rosati7, L. Rosselet4, M. Spousta2, P. Steinberg1, H. Takai1, S. Timoshenko9, B. Toczek6, A. Trzupek6, F. Videbaek1, S.
White1, B. Wosiek6, K. Wozniak6, M. Zeller11
1 Brookhaven National Laboratory, USA2 Charles University, Prague
3 Columbia Unversity, Nevis Laboratories, USA4 University of Geneva, Switzerland
5 IHEP, Russia6 IFJ PAN, Krakow, Poland
7 Iowa State University, USA8 JINR, Dubna, Russia
9 MePHI, Moscow, Russia10 Chemistry Department, Stony Brook University, USA
11 Yale University, USA