1. 2/17/2007 Nathan Grau, WWND 2007 1 The Heavy Ion Physics Program with ATLAS at the LHC Nathan Grau Columbia University, Nevis Labs On behalf of the ATLAS Heavy Ion Working Group

2. 2/17/2007 Nathan Grau, WWND 2007 2 The ATLAS HI Working Group

3. 2/17/2007 Nathan Grau, WWND 2007 3 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

4. 2/17/2007 Nathan Grau, WWND 2007 4 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-p T   0, K, , , J/ , e, etc. Single particle suppression is large at high-p T   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

5. 2/17/2007 Nathan Grau, WWND 2007 5 The ATLAS Detector

6. 2/17/2007 Nathan Grau, WWND 2007 6 The ATLAS Detector:  Coverage Full azimuthal acceptance in all detectors Unprecedented pseudorapidity coverage for A+A

7. 2/17/2007 Nathan Grau, WWND 2007 7 Global Observables Particle and Energy density: dN/d , dE T /d   Extend root-s dependence of dN/d  : test CGC Azimuthal Anisotropy: v 2, etc.  What happens to v 2 /  at higher root-s?

8. 2/17/2007 Nathan Grau, WWND 2007 8 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

9. 2/17/2007 Nathan Grau, WWND 2007 9 Tracking to lower p T Work extending p T reach important for p+p and A+A.  dN/d  in both cases  v 2 in A+A Ongoing with high energy and heavy ion participation. Efficiency: red/black Fake rate: red/green Preliminary Minimum bias p+p

10. 2/17/2007 Nathan Grau, WWND 2007 10 dN/d  via Tracklets a la PHOBOS 1. Truth tracks 2. “B-Layer” Hits 3. Layer 1 Hits 4. Matched Tracklets Measurement of track density flat with truth density  

11. 2/17/2007 Nathan Grau, WWND 2007 11 Jet Physics with ATLAS See W. Holzmann’s talk for all of the details STAR, PRL 93 (2004) 252301 interm. pT correlations high pT correlations R AA  -h correlations

12. 2/17/2007 Nathan Grau, WWND 2007 12 ATLAS Calorimetry Hadronic Barrel Hadronic EndCap EM EndCap EM Barrel Forward

13. 2/17/2007 Nathan Grau, WWND 2007 13 Longitudinal Segmentation: 3-d Jets Sampling of a 100 GeV jet (no background) 1 23 4 56 Note the  region is 0.8x0.8: a typical jet size

14. 2/17/2007 Nathan Grau, WWND 2007 14 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

15. 2/17/2007 Nathan Grau, WWND 2007 15 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 Back ground All too wide for single photons Single  slice 0.1 rad

16. 2/17/2007 Nathan Grau, WWND 2007 16 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.

17. 2/17/2007 Nathan Grau, WWND 2007 17  /  0 Separation Variables Left: fractional energy deposited outside the cluster core in the strip layer Right: Energy of a 2 nd maximum peak in the strip layer

18. 2/17/2007 Nathan Grau, WWND 2007 18  /  0 Separation Rejection of  0 with appropriate cuts on previous variables Efficiency in p+p is ~90%, flat with E T and 

19. 2/17/2007 Nathan Grau, WWND 2007 19 Jet Position Resolutions From standard R=0.4 seeded cone algorithm Results are important for studies of hard radiation in jets (sub- jets).

20. 2/17/2007 Nathan Grau, WWND 2007 20 Jet Energy Resolution Energy resolution as a function of E T and  Important for studies of jet R AA, fragmentation functions, etc. 

21. 2/17/2007 Nathan Grau, WWND 2007 21 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 v 2 (p T, ,centrality) Azimuthal E T distribution in different barrel EM calorimeter layers (|  |<1.5) Presampler Strip layer (front)Middle LayerBack Layer 0.003 x 0.1 0.025 x 0.025 0.05 x 0.025  x 

22. 2/17/2007 Nathan Grau, WWND 2007 22 Reaction Plane Resolution In measuring the physical v 2 you must correct by the resolution: v 2 = v 2 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

23. 2/17/2007 Nathan Grau, WWND 2007 23 Heavy Flavor Physics Lattice Calculations indicates bounds states melt at different temperatures But suppression of J/  similar between SPS and RHIC… SPS RHICRHIC A. Bickley Hard Probes 2006

24. 2/17/2007 Nathan Grau, WWND 2007 24 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

25. 2/17/2007 Nathan Grau, WWND 2007 25 Heavy Flavor Bound State Measurements Both charm and bottom states should be accessible to through the  +  - decay channel

26. 2/17/2007 Nathan Grau, WWND 2007 26 Resolution and Acceptance for  Good mass resolution Large acceptance Loss of efficiency near  ~0 due to material.

27. 2/17/2007 Nathan Grau, WWND 2007 27 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.

28. 2/17/2007 Nathan Grau, WWND 2007 28 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

29. 2/17/2007 Nathan Grau, WWND 2007 29 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.

30. 2/17/2007 Nathan Grau, WWND 2007 30 Summary of Physics Covered in this talk:  Bulk observables dN/d , v 2  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

31. 2/17/2007 Nathan Grau, WWND 2007 31 ATLAS Heavy Ion Working Group A. Ajitanand 10, A. Angerami 3, G. Atoian 11, M. Baker 1, P. Chung 10, B. Cole 3, R. Debbe 1, A. Denisov 5, J. Dolejsi 2, N. Grau 3, J. Hill 7, W. Holzmann 3, V. Issakov 11, J. Jia 10, H. Kasper 11, R. Lacey 10, A. Lebedev 7, M. Leltchouk 3, A. Moraes 1, R. Nouicer 1, A. Olszewski 6, A. Poblaguev 11, V. Pozdnyakov 8, M. Rosati 7, L. Rosselet 4, M. Spousta 2, P. Steinberg 1, H. Takai 1, S. Timoshenko 9, B. Toczek 6, A. Trzupek 6, F. Videbaek 1, S. White 1, B. Wosiek 6, K. Wozniak 6, M. Zeller 11 1 Brookhaven National Laboratory, USA 2 Charles University, Prague 3 Columbia Unversity, Nevis Laboratories, USA 4 University of Geneva, Switzerland 5 IHEP, Russia 6 IFJ PAN, Krakow, Poland 7 Iowa State University, USA 8 JINR, Dubna, Russia 9 MePHI, Moscow, Russia 10 Chemistry Department, Stony Brook University, USA 11 Yale University, USA