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Day 1 heavy-ion - What can we do?

Day 1 heavy-ion - What can we do?. Outline. I’m just going to cover soft physics that can be done with “first day” of Pb-Pb collisions However should remember high p T and heavy flavour will also be possible with only a few events at LHC. h coverage. PHOS. HMPID. h. -.12 <. < 0.12.

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Day 1 heavy-ion - What can we do?

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  1. Day 1 heavy-ion - What can we do?

  2. Outline I’m just going to cover soft physics that can be done with “first day” of Pb-Pb collisions However should remember high pT and heavy flavour will also be possible with only a few events at LHC

  3. h coverage PHOS HMPID h -.12 < < 0.12 h -.45 < < 0.45 -6 Df = 100 o Df = 57 o -4 h FMD -5.4 < < -1.6 h PMD -2.3 < < -3.5 -3 -2 -1 Rapidity ITS+TPC+TRD+TOF: h -0.9 < < 0.9 0 1 h ITS multiplicity -2 < < 2 h FMD 1.6 < < 3 2 3 h Muon arm 2.4 < < 4 4 Azimuth 90 180 270 360 o o o o • Designed for dNch/dh|h=0 up to 8000 (probably over-designed) • pT~100 MeV/c –~100 GeV/c (Acceptance for charged particles w/o muons) Pythia used to generate event

  4. Tracking efficiency for central region Tracking Efficiency / Fraction of Fake Tracks for dN/dy = 2000, 4000, 6000, 8000 Probably over designed Full chain, ITS + TPC + TRD FordN/dy = 2000 ÷4000 efficiency > 90% fake track prob. < 5%!!! pT (GeV)

  5. Momentum resolution Low mtm dominated by - ionization-loss fluctuations • High mtm determined by • - hit measurement precision • alignment & calibration Relies on ITS

  6. Particle Identification separation @ 2s separation @ 3s (dE/dx) Have reasonable PID with just TPC

  7. Strangeness reconstruction High purity / efficiency for strange particle reconstruction Plan to use LDA/Neural Net for reco. – better effic. Effic. similar to those at STAR

  8. Charged particle yield Will be one of the first (and important) results

  9. Naïve extrapolation 6 5 5.5 TeV 1000 6.4 = RHICx1.6 Most central events: dNch/dh ~1200 PHOBOS White Paper: Nucl. Phys. A 757, 28

  10. Other predictions 5 15.0 10.0 Nch/(0.5Npart) dNch/dh|h<1 103 5.0 5 1.0 2 10 102 103 103 104 102 √s (GeV) hep-ph0104010 Saturation model dNch/dh~ 2500 Naïve dNch/dh~ 1200 Gluon saturation model dNch/dh ~ 1/as(Q2s) Hijing dNch/dη ~ 3200

  11. dNch/dh as a function of Npart Charged multiplicity parametrized as a function of Npart 9 LHC where : λ= 0.288 GBW parameter δ = 0.79 ± 0.02 fit parameter N0 = 47/2overall normalization The model perfectly fits RHIC data, and can be easily extrapolated to LHC dNch/dh ~1500 for Npart = 350 Arnesto,Salgado,Wiedemann - hep/ph 0407018

  12. Rapidity shapepredictions Humanic Rescattering Model D Kharzeev – Soft physics workshop Catania Sept. 2006 Variety in shapes as well as magnitudes

  13. Multiplicity measurement at mid-rapidity Two fast techniques: Clusters: alignment not needed (results “on-line”), reliable at high mult. |η|<2 for Zv=0. (Largest occupancy < 2% at dN/dη = 8000) Tracklets: cluster association with straight line to main vtx More reliable at low multiplicity (background excluded); small inefficiency at high multiplicity. |η|<1.4 for Zv=0 True day 1 measurement

  14. dN/dh reconstruction At mid-rapidity using ITS True day 1 measurement At higher rapidities using FMD

  15. Energy density estimates dNch/dη = 2600 • Bjorken energy density estimate from charged particle density dNch/dη = 1200 3-10x increase ofeBjat the LHC

  16. Hyperon excitation functions dN/dy extrapolations at the LHC for L : 10~30 for X : 3~6 for W : 0.4~0.7

  17. Raw hyperon spectra Ξ Λ These are for 1 month running with higher yields than I expect Ω In 1 day still reco. several 1000 W Physics Performance Report Vol 2: J. Phys. G 32 (2006) 1295-2040

  18. Baryon transport to mid-rapidity Net baryon number dropping rapidly as function √s BRAHMS: nucl-ex/0312023 Baryon junction prediction: 5% baryon asymmetry at mid-rapidity D.Kharveez PLB378 (96) 238

  19. Thermal parameters On the freeze-out curve: TLHC ≈ TRHIC ≈ 170 MeV T ≤ TC ≈ 170 MeV μB from parametrised freeze-out curve: μB(√(sNN) = 5.5TeV) = 1 MeV Nucl. Phys. A 697 (2002) 902 Grand canonical ensemble for Pb+Pb predictions hep-ph/0511094 Ingrid Kraus – Soft physics workshop Sept. 2006

  20. Statistical model predictions Measurable differences in predictions from the models Expectations at the LHC energies Tch 125 - 170 MeV Calculations from Kraus et al., (Eq.) Rafelski et al., (Non Eq.) gs 1-5

  21. Statistical model centrality dependence Close to net-baryon free Tch flat with centrality ● p, K,p ● p, K,p ● p, K,p, L, X ● p, K,p, L, X Close to chem. equilibrium ! STAR preliminary Au+Au at √sNN=200GeV and 62 GeV TLQCD~160-170MeV TLQCD~160-170MeV Including L is important for gs Using Kaneta model How fast does LHC reach gs =1?

  22. Resonance reconstruction K* signal extraction with realistic PID: 15500 events K invariant mass after background subtraction All pt Resonance measurements possible with only few thousand events Invariant mass (GeV/c2) ~15000 events 107events Length of hadronic phase can be determined

  23. Radial flow predictions T. Humanic, Int.J.Mod.Phys.E15197(2006) Steeper pT-dependence due to more flow

  24. Elliptic flow – the “perfect fluid” RHIC observed flow for the first time consistent with ideal hydrodynamics!! Understood as strongly interacting QGP with small viscosity The almost perfect liquid? CGC initial conditions lead to larger ellipticity Generic feature of saturation models T.Hirano et al. hep-ph/0511046 H.Drescher et al. nucl-th/0605012

  25. Higher harmonics Ideal hydro : universal prediction v4=0.5 (v2)2 at large pT . v4/(v2)2 J-Y. Ollitraut Soft physics workshop Sept. 2006 pT No thermalisation at RHIC! Data ~1.2 suggest Kn~1: Kn: Knudsen number~ no. collisions/particle = mean free path/system size The hydro limit is Kn«1. If not satisfied, one expects smaller v2 than in hydro.

  26. Revisiting the “perfect liquid” Model inputs Exp. constraints • Initial density profiles: participant scaling • The color glass condensate gives much larger values of ε! • Global observables: multiplicity • Equation of state • Pt-spectra • Thermalization assumed: Kn«1 • Elliptic flow « saturates the hydro limit » • Elliptic flow no longer saturates the hydro limit! • Thermalization not seen!! Now have problem with this scenario?

  27. Elliptic flow predictions Higher multiplicity smaller Kn: closer to hydro. There is room for significant increase of v2 v4/(v2)2 somewhat smaller than at RHIC J-Y Ollitraut T. Hirano Contribution from hadron phase very small

  28. Femtoscopy - naïve extrapolation p HBT radii from different systems and at different energies scale with (dNch/dη)1/3 power 1/3 gives approx. linear scale Most central events: dNch/dh ~1200 dNch/dh1/3 ~10.5 Ro = Rs = Rl = 6 fm

  29. “Real” model predictions T. Humanic, Int.J.Mod.Phys.E15197(2006) LHC / RHIC = 2 (recall Rlong~~ ) dN/dt Rlong[LHC] ~ 2xRlong[RHIC] RS, RO larger, but not a simple factor Rlong (fm) Stronger pT dependence at LHC

  30. Azimuthal HBT “RHIC” “IPES” (LHC) O’Hara, et al, Science 298 2179 (2002) Heinz&Kolb, PLB542 216 (2002) Heinz&Kolb, PLB542 216 (2002) • probes timescale & dynamics hydro @ RHIC • misses scale (well-known) • impressive agreement on -dep prediction @ LHC Sign change in shape & oscillations

  31. Event-by-event femtoscopy? Single event pion-pion interferometry (with FSI)... by Zbyszek Chajęcki, (ro=8fm) Feasible if multiplicities at high end of prediction range

  32. Summary Many of these variable will be determined soon after turn on

  33. Determination of centrality Centrality selection

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