What do we see? LHC lecture, Heidelberg, 1 Feb, Kai Schweda

Transcription

1 What do we see? 1/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

2 Hadron spectra from RHIC p+p and Au+Au collisions at 200 GeV Full kinematic reconstruction of (multi-) strange hadrons in large acceptance of STAR White papers - STAR: Nucl. Phys. A757, p102. 2/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

3 Outline Introduction Collectivity at RHIC - transverse radial flow - tranverse elliptic flow - extracting η/s Heavy quark dynamics Outlook 3/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

4 HI - Collision History T c(ritical) : quarks and gluon hadrons, T c(ritical) = 160 MeV T ch(emical) : hadron abundancies freeze out T fo : particle spectra freeze out Plot: R. Stock, arxiv: [nucl-ex]. 4/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

5 Chemical Freeze-out Model Hadron resonance ideal gas Density of particle i Refs. J.Rafelski PLB(1991)333 P. Braun-Munzinger et al., nucl-th/ µ B = 3µ q µ S = µ q -µ s Q i s i g i m i : 1 for u and d, -1 for u and d : 1 for s, -1 for s : spin-isospin freedom : particle mass T ch : Chemical freeze-out temperature µ q : light-quark chemical potential µ s : strange-quark chemical potential V : volume term, drops out for ratios! : strangeness under-saturation factor All resonances and unstable particles are decayed γ s Compare particle ratios to experimental data 5/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

6 Example At RHIC, 200 GeV: T ch = 160 MeV, µ B = 20 MeV Anti-proton to proton ratio: Volume drops out Pbar/p = exp[(-20 MeV - 20 MeV)/160 MeV] = 0.77 ψ /J/ψ = (m ψ /m J/ψ ) 2 * K 2 (m ψ /160 MeV)/ K 2 (m J/ψ /160 MeV) = 3% Experimentally: measure particle yields and ratio to extract T ch and µ B 6/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

7 Hadron Yield Ratios 1) At RHIC: T ch = 160 ± 10 MeV µ B = 25 ± 5 MeV 2) γ S = 1. The hadronic system is thermalized at RHIC. 3) Short-lived resonances show deviations. There is life after chemical freeze-out. RHIC white papers , Nucl. Phys. A757, STAR: p102; PHENIX: p184; Statistical Model calculations: P. Braun-Munzinger et al. nucl-th/ LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

8 Chemical Freeze-Out vs Energy With increasing energy: T ch increases and saturates at T ch = 160 MeV Coincides with Hagedorn temperature Coincides with early lattice results limiting temperature for hadrons, T ch 160 MeV! µ B decreases, µ B = 1MeV at LHC Nearly net-baryon free! A. Andronic et al., NPA 772 (2006) /53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

9 QCD Phase Diagram 9/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

10 Baryon Ratios With increasing energy: Baryon ratios approach unity At LHC, pbar / p 0.95 with increasing collision energy, production of matter and anti-matter gets closer Compilation: N. Xu 10/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

11 Elementary p+p Collisions Low multiplicities use canonical ensemble: Strangeness locally conserved! particle yields are well reproduced Strangeness not equilibrated! (γ s = 0.5) Statistical Model Fit: F. Becattini and U. Heinz, Z. Phys. C 76, 269 (1997). 11/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

12 HI - Collision History T c(ritical) : quarks and gluon hadrons, T c(ritical) = 160 MeV T ch(emical) : hadron abundancies freeze out, T ch(emical) = 160 MeV T fo : particle spectra freeze out Plot: R. Stock, arxiv: [nucl-ex]. 12/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

13 Collective Flow LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

14 Pressure, Flow, Thermodynamic identity σ entropy p pressure U energy V volume τ = k B T, thermal energy per dof " d! = du + pdv In A+A collisions, interactions among constituents and density distribution lead to: pressure gradient collective flow number of degrees of freedom (dof) Equation of State (EOS) cumulative partonic + hadronic 14/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

15 Momentum Distributions* ] c) -1 [(GeV/ dy d N dp T π π π K (de/dx) p K (de/dx) p K (kink) K (kink) T th =107±8 [MeV] <β t >=0.55±0.08 [c] n=0.65±0.09 χ 2 /dof=106/90 solid lines: fit range Typical mass ordering in inverse slope from light π to heavier Λ Two-parameter fit describes yields of π, K, p, Λ T th = 90 ± 10 MeV <β t > = 0.55 ± 0.08 c Disentangle 2 2 Λ Λ collective motion from thermal random walk p T [GeV/c] GeV, STAR 15/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

16 (anti-)protons From RHIC More central collisions Centrality dependence: 2 T = pt + mass - spectra at low momentum de-populated, become flatter at larger momentum stronger collective flow in more central coll.! STAR: Phys. Rev. C70, (R). 16/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda m 2

17 Thermal Model + Radial Flow Source is assumed to be: Fit in local thermal equilibration: T fo boosted in transverse radial direction: ρ = f(β s ) E.Schnedermann, J.Sollfrank, and U.Heinz, Phys. Rev. C48, 2462(1993) E d 3 N dp! $ µ 3 e"(u p µ )/T fo pd# µ % # dn R ' m! rdrm T K T cosh &* ' p $ 1 m T dm 0 ) T ( T, I T sinh& * 0 ) fo + ( T, fo + ' r * & = tanh "1 - T - T = - S ), ( R+.. = 0.5, 1, 2 boosted random 17/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

18 D-meson collective flow Large collective flow velocity Spectrum moves to larger momentum 18/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

19 HI - Collision History T c(ritical) : quarks and gluon hadrons, T c(ritical) = 160 MeV T ch(emical) : hadron abundancies freeze out, T ch(emical) = 160 MeV T fo : particle spectra freeze out, T fo 100 MeV :π, K, p Plot: R. Stock, arxiv: [nucl-ex]. 19/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

20 Kinetic Freeze-out at RHIC 1) Multi-strange hadrons φ and Ω freeze-out earlier than (π, K, p) Collectivity prior to hadronization STAR Preliminary 2) Sudden single freeze-out*: Resonance decays lower T fo for (π,( K, p) Collectivity prior to hadronization Partonic Collectivity? STAR Data: Nucl. Phys. A757, ( ), *A. Baran, W. Broniowski and W. Florkowski, Acta. Phys. Polon. B 35 (2004) /53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

21 Anisotropy Parameter v 2 coordinate-space-anisotropy momentum-space-anisotropy y p y x p x! = "y 2 # x 2 $ "y 2 + x 2 $ v 2 = cos2%, % = tan #1 ( p y p x ) Initial/final conditions, EoS, degrees of freedom

22 v 2 in the Low-p T Region P. Huovinen, private communications, v 2 approx. linear in p T, mass ordering from light π to heavier Λ characteristic of hydrodynamic flow! sensitive to equation of state 22/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

23 Non-ideal Hydro-dynamics! s < 6 /4" finite shear viscosity η reduces elliptic flow many caveats, e.g.: - initial eccentricity ε (Glauber, CGC, ) - equation of state - hadronic contribution to η/s M.Luzum and R. Romatschke, PRC (2008); P. Romatschke, arxiv: String theory predicts: η/s > 1/4π 23/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

24 Elliptic Flow vs Collision Energy Glauber initial conditions Centrality dependence: - initial eccentricity ε - overlap area S Collision energy dep.: - multiplicity density dn ch /dy in central collisions at RHIC, hydro-limit seems reached! NA49, Phys. Rev. C68, (2003); STAR, Phys. Rev. C66, (2002); Hydro-calcs.: P. Kolb, J. Sollfrank, and U. Heinz, Phys. Rev.C62, (2000). 24/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

25 v 2 of φ and multi-strange Ω Strange-quark flow - partonic collectivity at RHIC! QM05 conference: M. Oldenburg; nucl-ex/ /53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

26 Collectivity, Deconfinement at RHIC - v 2, spectra of light hadrons and multi-strange hadrons - scaling with the number of constituent quarks At RHIC, it seems we have: Partonic Collectivity Deconfinement Thermalization? PHENIX: PRL91, (03) STAR: PRL92, (04) S. Voloshin, NPA715, 379(03) Models: Greco et al, PRC68, (03) X. Dong, et al., Phys. Lett. B597, 328(04).. 26/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

27 Collectivity Energy Dependence Collectivity parameters <β T > and <v 2 > increase with collision energy strong collective expansion at RHIC! <β T > RHIC 0.6 expect strong partonic expansion at LHC, <β T > LHC 0.8, T fo T ch K.S., ISMD07, arxiv: [nucl-ex]. 27/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

28 Partonic Collectivity at RHIC 1) Copiously produced hadrons freeze-out π,k,p: T fo = 100 MeV, β T = 0.6 (c) > β T (SPS) 2) Multi-strange hadrons freeze-out: T fo = MeV (~ T ch ), β T = 0.4 (c) 3) Multi-strange v 2 : φ and multi-strange hadrons Ξ and Ω do flow! 4) Model - dependent η/s: (0?),1-10 x 1/4π Deconfinement & Partonic (u,d,s) Collectivity! 28/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

29 Heavy Quarks LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

30 Heavy flavor: a unique probe m c,b >> Λ QCD : new scale m c,b const., m u,d,s const. Q 2 initial conditions: σ cc, σbb test pqcd, µ R, µ F probe gluon distribution X. Zhu, M. Bleicher, S.L. Huang, K.S., H. Stöcker, N. Xu, and P. Zhuang, PLB 647 (2007) 366. time early partonic stage: diffusion (γ), drag (α), flow probe thermalization hadronization: chiral symmetry restoration confinement statistical coalescence J/ψ enhancement / suppression LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

31 Limitations in PDFs Most charm created from gluons, e.g. g+g c + cbar increasing uncertainties in gluon distribution at smaller Bjorken x: Assume y=0, p T =0, x 1 =x 2 2 x m charm 3 GeV RHIC ( s=0.2tev): x = LHC ( s=14tev): x = 2x /53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

32 Heavy Quark Production Heavy-quark production at LHC, compared to RHIC expect factors Charm 10 Beauty 100 (i) Heavy-quarks abundantly produced at LHC energies! (ii) Large theoretical uncertainties energy scan (LHC,FAIR) will help! Plots: R. Vogt,Eur. Phys. J. C, s x (2008). 32/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

33 Heavy quark Correlations PYTHIA: p + 14 TeV c-cbar mesons are correlated Pair creation: back to back Gluon splitting: forward Flavor excitation: flat Exhibits strong correlations! Baseline at zero: clear measure of vanishing correlations! probe thermalization X. Zhu, M. Bleicher, S.L. Huang, K.S., H. Stöcker, N. Xu, and P. Zhuang, PLB 647 (2007) 366. G. Tsildeakis, H. Appelshäuser, K.S., J. Stachel, arxiv: among partons! 33/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

34 How to measure Heavy- Quark Production e.g., D 0, cτ = 123 µm displaced decay vertex is signature of heavy-quark decay need precise pointing to collision vertex 34/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

35 Heavy Flavor production at RHIC large discrepancy between STAR and PHENIX: factor > 2 (!) need Si-vertex upgrades (> 2011) large theoretical uncertainties (factor > 10) Plot: J. Dunlop (STAR), QM2009, Open Heavy-flavor in heavy-ion collisions, Calcs: R. Vogt,Eur. Phys. J. C, s x (2008), M. Cacciari, 417th Heraeus Seminar, Bad Honnef (2008). Measure charm production at RHIC, LHC, FAIR and provide input to theory: - gluon distribution, - scales µ R, µ F 35/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

36 Where does all the charm go? J/ψ D s Λ c D ± D 0 Total charm cross section: open charm hadrons, e.g. D 0, D *, Λ c, or c,b e(µ) + X Hidden-charm mesons, e.g. J/ψ carry ~ 1 % of total charm Statistics plot: H. Yang and Y. Wang, U Heidelberg. 36/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

37 D 0 π + + K - Reconstruction π + D 0, cτ = 123 µm K - Plot: A. Shabetai 37/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

38 Open Charm Performance Measure secondary decay vertex Direct reconstruction of D 0 address heavy-quark production with 1 st year of data taking Many other channels, e.g. D +, D* Also: single-electrons from heavy-flavor decays ALICE: PPR.vol.II, J. Phys. G 32 (2006) Simulation: 10 9 p+p, 10 8 p+pb, 10 7 Pb+Pb collisions 38/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

39 D* meson Identification D* + D 0 + π D* + Δ D* + - D 0 ] Subtract resonance decay to D 0 Two different methods to address total charm production D* ± analysis: Yifei Wang, Ph.D. thesis, University of Heidelberg, in preparation. 39/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

40 Viele neue interessante Signale in ALICE bei LHC: z.b. Hadronen mit schweren Quarks (charm und beauty) D 0, D +, D *, D s, J/ψ, ψ, Λ c, Λ b, ϒ,... 40/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

41 Quarkonia LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

42 Charmonium Bound state of charm- and anti-charm quark Hidden-charm meson m J/ψ = 3.1 GeV, r J/ψ = 0.45 fm, m J/ψ' = 3.6 GeV, J P = 1 - states Minimum formation time τ = r J/ψ / c = 0.45 fm Charm-quark production at time scale t c ~ 1/2m c 0.08 fm Separation between initial production and hadronization (factorization) 42/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

43 Debye Screening 43/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

44 Quarkonia as a Thermometer Check for melting of bottomonium (b-bbar) at T deconfined 2 T c Check for melting of charmonium (c-cbar) at T deconfined 1.2 T c Absolute numbers model-dependent T fo : 44/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

45 J/ψ Production P. Braun-Munzinger and J. Stachel, Nature 448 (2007) 302. (SPS) suppression, compared to scaled p+p regeneration, enhancement Low energy (SPS): High energy (LHC): few ccbar quarks in the system suppression of J/ψ many ccbar pairs in the system enhancement of J/ψ Signal of de-confinement + thermalization of light quarks! 45/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

46 Statistical Hadronization of Charm large charm production at LHC strong generation of J/ψ σ cc striking centrality dependence Signature for QGP formation! Initial conditions at LHC? Need to measure total charm production in PbPb! Assumes kinetic equilbration of charm! A. Andronic, P. Braun-Munzinger, K. Redlich, J. Stachel, Phys. Lett. B 652 (2007) /53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

47 Charmonium production In central Pb+Pb collisions at top SPS energy: J/ψ to J/ψ ratio approaches thermal limit Indicates kinetic equilibration of charm 47/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

48 Examples of the ALICE physics potential - Open charm: D 0 K - + π + (already shown) - Quarkonia: J/ψ, ϒ - Global event properties Will be addressed in first year of pp collisions 48/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

49 First Physics with ALICE Results from simulations 1 day of data taking Address: - multiplicity - mean transverse momentum - hadro-chemistry 49/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

50 Charmonia via Di-Electron Measurement electron ID with TPC and TRD expect 2500 ϒ mesons per Pb+Pb year with good mass resolution and S/B Simulation: pp coll. χ c1 χ c2 J/ψ Simulation: central PbPb collisions 50/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

51 Heavy Flavor in Muon Channel muon channel: J/ψ, Υ µ+µ- (2.5 <η< 4) J/ψ and 2000 Υ initial sample sufficient to study production rates of J/ψ and Υ states in muon channel J/ψ b µ Υ 51/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

52 LHC: Schedule Nov 2009: Dec 2009: first pp collisions at 900 GeV pp collisions at 2.36 TeV Mar 2010: end of 2010: Long run of pp collisions at 7 TeV 3-4 weeks Pb+Pb collisions at TeV 52/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

53 ALICE Ready for Physics! 53/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda