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Christine Nattrass (UTK), University of Virginia, 30 March 2011 1.

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Presentation on theme: "Christine Nattrass (UTK), University of Virginia, 30 March 2011 1."— Presentation transcript:

1 Christine Nattrass (UTK), University of Virginia, 30 March 2011 1

2 2 Phase diagram of nuclear matter Here be dragons

3 Christine Nattrass (UTK), University of Virginia, 30 March 2011 3 How to make a Quark Gluon Plasma

4 Christine Nattrass (UTK), University of Virginia, 30 March 2011 4 The phase transition in the laboratory

5 Christine Nattrass (UTK), University of Virginia, 30 March 2011 5 ALICE CMS ATLAS LHCf LHCb 2.2 km 8.6 km

6 Christine Nattrass (UTK), University of Virginia, 30 March 2011 6 p+p collisions

7 Christine Nattrass (UTK), University of Virginia, 30 March 2011 7 Pb+Pb collisions

8 Christine Nattrass (UTK), University of Virginia, 30 March 2011 8 8 Size: 16 x 26 meters Weight: 10,000 tons Detectors: 18

9 Christine Nattrass (UTK), University of Virginia, 30 March 2011 9 dN ch /d  versus √s KLN CGC dN ch /d  versus  √s NonSingleDiffractive all Inelastic Inelastic N ch ≥ 1 in |  |<1 ALICE CMS Relative increase in dN ch /d  Results: increase with energy significantly stronger in data than MC’s - ALICE & CMS agree to within 1  (< 3%) Eur. Phys. J. C (2010) 68: 345–354 Eur. Phys. J. C (2010) 68: 89–108 Eur. Phys. J. C (2010) 65: 111- 125

10 Christine Nattrass (UTK), University of Virginia, 30 March 2011 10 Vertex detector p T (min)<100MeV/c TOF 150k channels!  ≈ 90 ps TPC dE/dx  ≈5-6% No vertex cut ! Particle identification

11 Christine Nattrass (UTK), University of Virginia, 30 March 2011 11 Identified particle spectra Identified Particle p T  K p ITS dE/dx TPC dE/dx TOF Kaon p T distributions stable & decays K →  K 0 S →  3 detectors Good agreement 5 methods for measuring kaons Submitted to EPJC

12 Christine Nattrass (UTK), University of Virginia, 30 March 2011 12 ` p/p ratio 900 GeV |y|<0.5 7 TeV |y|<0.5 0.9 TeV:`p/p = 0.957±0.006(stat) ±0.014(syst) 7 TeV: `p/p = 0.990±0.006(stat) ±0.014(syst) Phys Rev Lett Vol.105, No.7, (2010)

13 Christine Nattrass (UTK), University of Virginia, 30 March 2011 13 Strange particles at 900 GeV K 0 S →   →p  19  →KK  →  ● PYTHIA and PHOJET consistently below data arXiv:1012.3257v2

14 Christine Nattrass (UTK), University of Virginia, 30 March 2011 14 Monte Carlo scoreboard 900 GeV 2.36 TeV 7 TeV Conclusion: ● None of the tested MC’s (adjusted at lower energy) does really well ● Tuning one or two results is doable, getting everything right will require more effort (and may, with some luck, actually teach us something on soft QCD rather than only turning knobs). MC << Data MC ≈ Data MC >> Data MC <<<< Data 20

15 Christine Nattrass (UTK), University of Virginia, 30 March 2011 15 Charged particle multiplicity in central Pb+Pb Phys. Lett. B 696 (2011) 30-39

16 Christine Nattrass (UTK), University of Virginia, 30 March 2011 16 How do the models compare? Phys. Lett. B 696 (2011) 30-39

17 Christine Nattrass (UTK), University of Virginia, 30 March 2011 17 A simple picture of a heavy ion collision

18 Christine Nattrass (UTK), University of Virginia, 30 March 2011 18 Jets as a probe of the quark gluon plasma

19 Christine Nattrass (UTK), University of Virginia, 30 March 2011 19 One jet “absorbed” by the medium

20 Christine Nattrass (UTK), University of Virginia, 30 March 2011 20 Jet quenching nucleus nucleus nucleus nucleus Phys. Rev. Lett. 105, 252303 (2010) ATLAS Phys. Rev. Lett. 105, 252303

21 Christine Nattrass (UTK), University of Virginia, 30 March 2011 21 Single particles ● Measure spectra of hadrons and compare to those in p+p collisions or peripheral A+A collisions ● If high-p T hadrons are suppressed, this is evidence of jet quenching ● Assumption: sufficiently high-p T hadrons mostly come from jets ● Unmodified spectra:

22 Christine Nattrass (UTK), University of Virginia, 30 March 2011 22 Renk – 8 GeV hadron Experimental results No suppression Observed Here be dragons Phys. Lett. B 696 (2011) 30- 39

23 Christine Nattrass (UTK), University of Virginia, 30 March 2011 23 Experimental results Phys. Lett. B 696 (2011) 30- 39

24 Christine Nattrass (UTK), University of Virginia, 30 March 2011 24 Hydrodynamical flow ● When nuclei collide, the overlap region is roughly elliptical ● If we have a fluid when we collide nuclei, there will be pressure gradients, pushing particles out ● We have measured this – and the liquid is made of quarks and gluons Au+Au  s NN = 200 GeV b=7 fm arXiv:nucl-th/0305084 Particles pushed out Equipotential lines

25 Christine Nattrass (UTK), University of Virginia, 30 March 2011 25 Elliptic flow at 2.76 TeV Phys. Rev. Lett. 105, 252302 (2010)

26 Christine Nattrass (UTK), University of Virginia, 30 March 2011 26 Elliptic flow at 2.76 TeV Phys. Rev. Lett. 105, 252302 (2010)

27 Christine Nattrass (UTK), University of Virginia, 30 March 2011 27 Conclusions ● ALICE is capable of precision measurements in p+p and Pb+Pb ● QGP at the LHC already appears to be hotter and denser than at RHIC ● We will have many, many more probes available at the LHC More information on ALICE ● ALICE web site ALICE web site ● US LHC Blog posts US LHC Blog posts

28 Christine Nattrass (UTK), University of Virginia, 30 March 2011 28 Backup slides

29 Christine Nattrass (UTK), University of Virginia, 30 March 2011 29 How do we know it's a QGP? ● Temperature – it is hot enough to match where we think it should be ● Jet quenching – high momentum quarks and gluons get stopped in the medium ● Hydrodynamical flow – it moves like a fluid of quarks and gluons ● Chemistry – what we produce is roughly at equilibrium

30 Christine Nattrass (UTK), University of Virginia, 30 March 2011 30 Momentum distributions at 900 GeV p T distribution 12

31 Christine Nattrass (UTK), University of Virginia, 30 March 2011 31 versus multiplicity ● Substantial discrepancies between Monte Carlo and the data 14

32 Christine Nattrass (UTK), University of Virginia, 30 March 2011 32 Multiplicity distributions 900 GeV ALICE CMS 2.36 TeV7 TeV ● Data from 900 GeV, 2.36 TeV, and 7 TeV ● Substantial discrepancies between Monte Carlo and the data ● Agreement between ALICE & CMS 10

33 Christine Nattrass (UTK), University of Virginia, 30 March 2011 33  K 0 S  ratio at 900 GeV |  | < 1 ● Very good agreement between STAR (200 GeV) and ALICE (900 GeV) ● Very different from CDF (630/1800) and UA1 (630) for p T > 1.5 GeV ● - UA1(630) and CDF(630) don’t agree either … – Different triggers, acceptance, feed-down correction? 21

34 34 Christine Nattrass (UTK), SCUWP, January 16, 2011 Chemistry - equilibrium ● Ratios of particles expected from a model ● Even strange quarks are at equilibrium! Nuclear Physics A Volume 757, 102-183

35 Christine Nattrass (UTK), University of Virginia, 30 March 2011 35 Ridge composition ● Baryon/meson ratios in Ridge similar to bulk for both strange and non-strange particles Suarez, QM08 M. Lamont (STAR), J.Phys.G32:S105-S114,2006 J. Bielcikova (STAR), v:0707.3100 [nucl-ex] C. Nattrass (STAR), arXiv:0804.4683/nucl-ex

36 Christine Nattrass (UTK), University of Virginia, 30 March 2011 36 More to come...    →  7 TeV  →   →  < 2% of statistics at 7 TeV    →  7 TeV 22

37 Christine Nattrass (UTK), University of Virginia, 30 March 2011 37 Bose-Einstein correlations QM enhancement of identical Bosons at small momentum difference: E nhancement of e.g. like-sign pions at low momentum difference q inv =|p 1 -p 2 | ➡ M easure the space-time evolution of the dense matter formed in heavy-ion collisions. ➡ I nterpretation for “small systems” (p+p, e + +e - ) is less obvious... Pb+Au p+p radius ~/width 23

38 Christine Nattrass (UTK), University of Virginia, 30 March 2011 38 Bose-Einstein correlations QM enhancement of identical Bosons at small momentum difference: E nhancement of e.g. like-sign pions at low momentum difference q inv=|p 1 -p 2 | ➡ M easure the space-time evolution of the dense matter formed in heavy-ion collisions. ➡ I nterpretation for “small systems” (p+p, e + +e - ) is less obvious... Pb+Au p+p radius ~/width Source radius vs N ch PRD: Vol. 82 (2010) 052001ource radius 23

39 Christine Nattrass (UTK), University of Virginia, 30 March 2011 39 D 0 and D + dN/dp t - Most of the cross section at low p T - Shape at low p T very uncertain - 10 9 MB events => measure below 1 GeV (PID important at low p T !) 24

40 Christine Nattrass (UTK), University of Virginia, 30 March 2011 40 J/  production  at 7 TeV Measurement of J/ψ over wide pseudorapidity range Rapidity spectra Transverse-momentum spectra J/  → e + e - |y| < 1 J/  →    , y = 2.5–4.0 25

41 Christine Nattrass (UTK), University of Virginia, 30 March 2011 41 J/  production  at 7 TeV (ICHEP 2010) very good agreement with LHCb pt spectra and cross section cross-section measurement in central–forward regions match 26

42 Christine Nattrass (UTK), University of Virginia, 30 March 2011 42 Electromagnetic calorimeter ● EMCal: -0.7 <η< 0.7, 80°<φ< 120° in 2010 → 80°<φ< 180° in January 2011 – Ahead of schedule! ● DCAL: -0.7 <η< 0.7, 260°<φ< 320° in 2013 ● Access to di-jets, γ-jet, improve p T reach of e ± 27

43 Christine Nattrass (UTK), University of Virginia, 30 March 2011 43 Physics papers submitted/published: 2010 Strange particle production at central rapidity in proton-proton collisions at √s = 0.9 TeV with ALICE at LHC (Submitted?) Transverse momentum spectra of charged particles in proton–proton collisions at √s=900 GeV with ALICE at the LHC (Physics Letters B 693 (2010) 53–68) Two-pion Bose-Einstein correlations in pp collisions at √s=900 GeV (Phys. Rev. D 82, 052001 (2010)) Midrapidity Antiproton-to-Proton Ratio in pp Collisons at √s=0.9 and 7 TeV Measured by the ALICE Experiment (Phys Rev Lett Vol.105, No.7, (2010)) Charged-particle multiplicity measurement in proton–proton collisions at √s=7 TeV with ALICE at LHC (Eur. Phys. J. C (2010) 68: 345–354) Charged-particle multiplicity measurement in proton–proton collisions at √s=0.9 and 2.36 TeV with ALICE at LHC (Eur. Phys. J. C (2010) 68: 89–108) First proton–proton collisions at the LHC as observed with the ALICE detector: measurement of the charged-particle pseudorapidity density at √s=900 GeV (Eur. Phys. J. C (2010) 65: 111-125)

44 Christine Nattrass (UTK), University of Virginia, 30 March 2011 44 Evolution of the Universe Reheating Matter ?The universe gets cooler ! ? Need temperatures around 1.5·10 12 K ~10 5 times hotter than the core of the sun 10 6 yrs 3 min 6 sec 2·10 -6 sec 2 10 -10 sec 10 -35 sec 10 9 yrs ? 10 -44 sec

45 Christine Nattrass (UTK), University of Virginia, 30 March 2011 45 Exploring QCD at high temperatures F. Karsch, et al. Nucl. Phys. B605 (2001) 579 Confined - fewer degrees of freedom Deconfined - more degrees of freedom ε/T 4 ~ # degrees of freedom T C ~ 175 ±8 MeV →ε C ~ 0.3 -1 GeV/fm 3 2 Quark-gluon plasma

46 Christine Nattrass (UTK), University of Virginia, 30 March 2011 46 d+Au d+Au Phys.Rev.C80:064912,2009 Near-side Away-side Near-side Away-side Away-side

47 Christine Nattrass (UTK), University of Virginia, 30 March 2011 47 In two dimensions in Au+Au nucl-ex/0701074 Phys.Rev.C80:064912,2009

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