What do we see ? Kai Schweda 1/53 LHC lecture, Heidelberg, 1 Feb, - - PowerPoint PPT Presentation

1/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

What do we see ?

2/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Hadron spectra from RHIC

p+p and Au+Au collisions at 200 GeV

White papers - STAR: Nucl. Phys. A757, p102.

Full kinematic reconstruction of (multi-) strange hadrons in large acceptance of STAR

3/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Outline

• Introduction
• Collectivity at RHIC
• transverse radial flow
• tranverse elliptic flow
• extracting η/s
• Heavy − quark dynamics
• Outlook

4/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

HI - Collision History

Plot: R. Stock, arXiv:0807.1610 [nucl-ex].

• Tc(ritical): quarks and gluon ⇒ hadrons, Tc(ritical) = 160 MeV
• Tch(emical): hadron abundancies freeze out
• Tfo: particle spectra freeze out

5/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Chemical Freeze-out Model

Hadron resonance ideal gas Compare particle ratios to experimental data

Qi : 1 for u and d, -1 for u and d si : 1 for s, -1 for s

gi

: spin-isospin freedom mi : particle mass All resonances and unstable particles are decayed

• Refs. J.Rafelski PLB(1991)333
• P. Braun-Munzinger et al., nucl-th/0304013

Tch : Chemical freeze-out temperature µq : light-quark chemical potential µs : strange-quark chemical potential V : volume term, drops out for ratios! γs : strangeness under-saturation factor

Density of particle i

µB = 3µq µS = µq-µs

6/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Example

At RHIC, Au+Au @ 200 GeV: Tch = 160 MeV, µB = 20 MeV Anti-proton to proton ratio: Volume drops out Pbar/p = exp[(-20 MeV - 20 MeV)/160 MeV] = 0.77 ψ’/J/ψ = (mψ’/mJ/ψ)2 * K2(mψ’/160 MeV)/ K2(mJ/ψ/160 MeV) = 3% Experimentally: measure particle yields and ratio to extract Tch and µB

LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Hadron Yield − Ratios

1) At RHIC: Tch = 160 ± 10 MeV µB = 25 ± 5 MeV 2) γS = 1. ➠ The hadronic system is thermalized at RHIC. 3) Short-lived resonances show deviations. ➠ There is life after chemical freeze-out.

RHIC white papers - 2005, Nucl. Phys. A757, STAR: p102; PHENIX: p184; Statistical Model calculations: P. Braun-Munzinger et al. nucl-th/0304013.

8/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

• A. Andronic et al., NPA 772 (2006) 167.

With increasing energy:

• Tch increases and saturates

at Tch = 160 MeV

• Coincides with Hagedorn

temperature

• Coincides with early lattice results

 limiting temperature for hadrons, Tch

ch ≈ 160 MeV !

• µB decreases, µB = 1MeV at LHC

 Nearly net-baryon free !

Chemical Freeze-Out vs Energy

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

QCD Phase Diagram

10/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Baryon Ratios

Compilation: N. Xu

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

11/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

‘Elementary’ p+p Collisions

 Low multiplicities  use canonical ensemble: Strangeness locally conserved!  particle yields are well reproduced  Strangeness not equilibrated ! (γs = 0.5)

Statistical Model Fit: F. Becattini and U. Heinz, Z. Phys. C 76, 269 (1997).

12/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

HI - Collision History

Plot: R. Stock, arXiv:0807.1610 [nucl-ex].

• Tc(ritical): quarks and gluon ⇒ hadrons, Tc(ritical) = 160 MeV
• Tch(emical): hadron abundancies freeze out, Tch(emical) = 160 MeV
• Tfo: particle spectra freeze out

LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Collective Flow

14/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Pressure, Flow, Pressure, Flow, Pressure, Flow, Pressure, Flow, … …

pdV dU d + =

• Thermodynamic identity

σ – entropy p – pressure

U – energy V – volume τ = kBT, thermal energy per dof

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

15/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Momentum Distributions* Momentum Distributions* Momentum Distributions* Momentum Distributions*

2

] [(GeV/ 2 c)-1 dy dp N d

T

π

] [GeV/ c pT

π

K (dE/dx)

p Λ

K (kink)

*Au+Au @130 GeV, STAR

Tth=107±8 [MeV] <βt>=0.55±0.08 [c] n=0.65±0.09 χ2/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

• Tth = 90 ± 10 MeV
• <βt> = 0.55 ± 0.08 c

 Disentangle collective motion from thermal random walk

π

K (dE/dx)

p Λ

K (kink)

16/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

(anti-)Protons From RHIC (anti-)Protons From RHIC (anti-)Protons From RHIC (anti-)Protons From RHIC

Au+Au@130GeV Au+Au@130GeV Au+Au@130GeV Au+Au@130GeV

More central collisions

2 2

mass p m

T T

+ =

Centrality dependence:

• spectra at low momentum de-populated, become flatter at larger momentum

➠ stronger collective flow in more central tronger collective flow in more central coll

• ll.!

.!

STAR: Phys. Rev. C70, 041901(R).

17/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Thermal Model + Radial Flow Thermal Model + Radial Flow Thermal Model + Radial Flow Thermal Model + Radial Flow Fit Fit Fit Fit

Source is assumed to be: – in local thermal equilibration: Tfo – boosted in transverse radial direction: ρ = f(βs)

random boosted E.Schnedermann, J.Sollfrank, and U.Heinz, Phys. Rev. C48, 2462(1993)

E d

3N

dp

3

e

(uµ pµ )/T fo p

• d µ

dN mTdmT

• rdrmTK1

mT cosh Tfo

• R
• I0

pT sinh Tfo

• = tanh

1T

T = S r R

• = 0.5, 1, 2

18/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

D-meson collective flow

Large collective flow velocity ⇒ Spectrum moves to larger momentum

19/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

HI - Collision History

Plot: R. Stock, arXiv:0807.1610 [nucl-ex].

• Tc(ritical): quarks and gluon ⇒ hadrons, Tc(ritical) = 160 MeV
• Tch(emical): hadron abundancies freeze out, Tch(emical) = 160 MeV
• Tfo: particle spectra freeze out, Tfo ≈ 100 MeV :π, K, p

20/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

1) Multi-strange hadrons 1) Multi-strange hadrons φ φ and and Ω Ω freeze-out earlier freeze-out earlier than than ( (π π, , K K, , p p) )   Collectivity prior to Collectivity prior to hadronization hadronization 2) Sudden single freeze-out*: 2) Sudden single freeze-out*: Resonance decays lower Resonance decays lower T Tfo

fo

for ( for (π π, , K K, , p p) )   Collectivity prior to Collectivity prior to hadronization hadronization

 

Partonic

Partonic Collectivity Collectivity ? ?

Kinetic Freeze-out at RHIC

STAR Data: Nucl. Phys. A757, (2005 102), *A. Baran, W. Broniowski and W. Florkowski, Acta. Phys. Polon. B 35 (2004) 779.

STAR Preliminary

Anisotropy Parameter v2

y x py px

coordinate-space-anisotropy ⇔ momentum-space-anisotropy

= y 2 x 2 y 2 + x 2 v2 = cos2 , = tan1( py px )

Initial/final conditions, EoS, degrees of freedom

22/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

v2 in the Low-pT Region

• P. Huovinen, private communications, 2004
• v2 approx. linear in pT, mass ordering from light π to heavier Λ

➠characteristic of hydrodynamic flow ! ➠ sensitive to equation of state

23/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Non-ideal Hydro-dynamics

• s < 6/4

M.Luzum and R. Romatschke, PRC 78 034915 (2008); P. Romatschke, arXiv:0902.3663.

• finite shear viscosity η reduces elliptic flow
• many caveats, e.g.:
• initial eccentricity ε (Glauber, CGC, …)
• equation of state
• hadronic contribution to η/s

String theory predicts: η/s > 1/4π

24/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Elliptic Flow vs Collision Energy

• Centrality dependence:
• initial eccentricity ε
• overlap area S
• Collision energy dep.:
• multiplicity density dNch/dy
• in central collisions

at RHIC, hydro-limit seems reached !

NA49, Phys. Rev. C68, 034903 (2003); STAR, Phys. Rev. C66, 034904 (2002); Hydro-calcs.: P. Kolb, J. Sollfrank, and U. Heinz, Phys. Rev.C62, 054909 (2000).

Glauber initial conditions

25/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

v2 of φ and multi-strange Ω

• Strange-quark flow - partonic collectivity at RHIC !

QM05 conference: M. Oldenburg; nucl-ex/0510026.

26/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Collectivity, Deconfinement at RHIC

• v2, 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, 182301(03) STAR: PRL92, 052302(04)

• S. Voloshin, NPA715, 379(03)

Models: Greco et al, PRC68, 034904(03)

• X. Dong, et al., Phys. Lett. B597, 328(04).

….

27/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Collectivity − Energy Dependence

• Collectivity parameters <βT>

and <v2> increase with collision energy

• strong collective

expansion at RHIC ! <βT>RHIC ≈ 0.6

• expect strong partonic

expansion at LHC, <βT>LHC ≈ 0.8, Tfo ≈ Tch

K.S., ISMD07, arXiv:0801.1436 [nucl-ex].

28/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Partonic Collectivity at RHIC

1) Copiously produced hadrons freeze-out π,K,p: Tfo = 100 MeV, βT = 0.6 (c) > βT(SPS) 2) Multi-strange hadrons freeze-out: Tfo = 160-170 MeV (~ Tch), βT = 0.4 (c) 3) Multi-strange v2: φ and multi-strange hadrons Ξ and Ω do flow! 4) Model - dependent η/s: (0?),1 - 10 x 1/4π

Deconfinement & Deconfinement & Partonic Partonic (u,d,s)

) Collectivity

• llectivity !

LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Heavy Quarks

LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Heavy − flavor: a unique probe

• X. Zhu, M. Bleicher, S.L. Huang, K.S., H. Stöcker,
• N. Xu, and P. Zhuang, PLB 647 (2007) 366.

mc,b >> ΛQCD : new scale mc,b ≈ const., mu,d,s ≠ const.

• initial conditions:

σ , σ test pQCD, µR, µF probe gluon distribution

• early partonic stage:

diffusion (γ), drag (α), flow probe thermalization

• hadronization:

chiral symmetry restoration confinement statistical coalescence J/ψ enhancement / suppression

Q2 time

cc bb

31/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

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, pT=0, x1=x2
• 2 x mcharm ≈ 3 GeV

RHIC (√s=0.2TeV): x = 0.015 LHC (√s=14TeV): x = 2x10-4

32/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Heavy − Quark Production

(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, s10052-008-0809-x (2008).

Heavy-quark production at LHC, compared to RHIC expect factors Charm ≈ 10 Beauty ≈ 100

33/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Heavy − quark Correlations

• 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 among partons ! PYTHIA: p + p @ 14 TeV

• 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: 0908.0427.

34/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

How to measure Heavy- Quark Production

• e.g., D0, cτ = 123 µm
• displaced decay vertex is signature of heavy-quark decay
• need precise pointing to collision vertex

35/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Heavy − Flavor production at RHIC

• large discrepancy between

STAR and PHENIX: factor > 2 (!)

• need Si-vertex upgrades

(> 2011)

• large theoretical

uncertainties (factor > 10)

• Measure charm production

at RHIC, LHC, FAIR and provide input to theory:

• gluon distribution,
• scales µR, µF

Plot: J. Dunlop (STAR), QM2009, Open Heavy-flavor in heavy-ion collisions, Calcs: R. Vogt,Eur. Phys. J. C, s10052-008-0809-x (2008),

• M. Cacciari, 417th Heraeus Seminar, Bad Honnef (2008).

36/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Where does all the charm go?

D0 D± Ds Λc J/ψ

• Total charm cross section: open charm hadrons,

e.g. D0, D*, Λc, … 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.

37/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda Plot: A. Shabetai

D0  π+ + K- Reconstruction

D0, cτ = 123 µm π+ K-

38/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

 Measure secondary decay vertex ⇒ Direct reconstruction of D0 ⇒ address heavy-quark production with 1st year of data taking  Many other channels, e.g. D+, D*  Also: single-electrons from heavy-flavor decays

Open − Charm Performance

ALICE: PPR.vol.II, J. Phys. G 32 (2006) 1295.

Simulation: 109 p+p, 108 p+Pb, 107 Pb+Pb collisions

39/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

D*− meson Identification

D*± analysis: Yifei Wang, Ph.D. thesis, University of Heidelberg, in preparation.

 D*+ → D0 + π+  Identify D*+ through ΔM[D*+ - D0]  Subtract resonance decay to D0  Two different methods to address total charm production

40/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Viele neue interessante Signale in ALICE bei LHC: z.B.

Hadro ronen m mit s it schwere ren Quark rks (charm rm u und b beauty ty)

D0, D+, D*, Ds, J/ψ, ψ’, Λc, Λb, ϒ, ...

LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Quarkonia

42/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Charmonium

• Bound state of charm- and anti-charm quark
• Hidden-charm meson
• mJ/ψ = 3.1 GeV, rJ/ψ = 0.45 fm, mJ/ψ' = 3.6 GeV, JP = 1- states
• Minimum formation time τ = rJ/ψ / c = 0.45 fm
• Charm-quark production at time scale tc~ 1/2mc ≈ 0.08 fm
• Separation between initial production and hadronization (factorization)

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

Debye Screening

44/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Quarkonia as a Thermometer

• Check for melting of bottomonium (b-bbar)

at Tdeconfined ≈ 2 Tc

• Check for melting of charmonium (c-cbar)

at Tdeconfined ≈ 1.2 Tc

• Absolute numbers model-dependent Tfo:

45/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

J/ψ Production

⇒ suppression, compared to scaled p+p ⇒ regeneration, enhancement

Low energy (SPS): few ccbar quarks in the system  suppression of J/ψ High energy (LHC): many ccbar pairs in the system  enhancement of J/ψ  Signal of de-confinement + Signal of de-confinement + thermalization thermalization of light quarks ! f light quarks !

(SPS)

• P. Braun-Munzinger and J. Stachel, Nature 448 (2007) 302.

46/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Statistical Hadronization of Charm

• large charm production at LHC
• strong generation of J/ψ
• striking centrality dependence
• Signature for QGP

formation !

• Initial conditions at LHC ?
• Need to measure total

charm production in PbPb !

• Assumes kinetic

equilbration of charm !

∼σcc

• A. Andronic, P. Braun-Munzinger, K. Redlich, J. Stachel, Phys. Lett. B 652 (2007) 259.

47/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Charmonium production

• In central Pb+Pb collisions at

top SPS energy:

• J/ψ’ to J/ψ ratio approaches

thermal limit

• Indicates kinetic equilibration
• f charm

48/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

 Examples of the ALICE physics potential

• Open charm: D0 → K- + π+ (already shown)
• Quarkonia: J/ψ, ϒ
• Global event properties

 Will be addressed in first year of pp collisions

49/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

First Physics with ALICE

• Results from simulations
• 1 day of data taking
• Address:
• multiplicity
• mean transverse momentum
• hadro-chemistry

50/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

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: 2·108 central PbPb collisions

J/ψ χc1 χc2

Simulation: pp coll.

51/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

Heavy Flavor in Muon Channel

• muon channel: J/ψ, Υ → µ+µ- (2.5 <η<

4) 60000 J/ψ and 2000 Υ

• initial sample sufficient to study

production rates of J/ψ and Υ states in muon channel

J/ψ Υ

 b → µ

52/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

LHC: Schedule

Nov 2009: first pp collisions at 900 GeV Dec 2009: pp collisions at 2.36 TeV Mar 2010: Long run of pp collisions at 7 TeV end of 2010: 3 - 4 weeks Pb+Pb collisions at 2.8 - 3.9 TeV

53/53 LHC lecture, Heidelberg, 1 Feb, 2010 Kai Schweda

ALICE − Ready for Physics !