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Hadron multiplicities, pT-spectra and net-baryon number in central Pb+Pb collisions at the LHC

Kari J. Eskola,Department of Physics, University of Jyväskylä

Helsinki Institute of Physics

based on:K. J. Eskola, H. Honkanen, H. Niemi, P. V. Ruuskanen and S. S. Räsänen, Phys. Rev. C 72 (2005) 044904 [arXiv:hep-ph/0506049]

Heavy Ion Collisions at the LHC: Last Call for Predictions, CERN, 28 June, 2007

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pQCD + saturation + hydrodynamics (EKRT) framework

1. Initial conditions from pQCD+saturation:

- pQCD minijets in A+A [Eskola, Kajantie, Lindfors, Nucl.Phys.B323(1989)37]

collinear factorization, pT ≥ p0

LO; K = 1.6 for RHIC, 2.3 for LHC [from ET in NLO, hep-ph/0002008]

nPDFs: EKS98

- saturation of produced gluons (interaction vertices)

psat = p0 = 1.1 GeV … 2.0 GeV central Au+Au at RHIC Pb+Pb at LHC τform= 1/psat = 0.17 fm ... 0.10 fm

average ε(τform) = ET (psat)/(RA2τform)

nB(τform) = NB(psat)/(RA2τform)

- for ε(τform,r) & nB (τform,r) assume binary profiles

[EKRT,hep-ph/9909456]

hep-ph/0506049

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2. Hydrodynamics

- Fast & full thermalization: τ0 = τform

- Longitudinal boost-invariance: vz= z/t

- Transverse expansion; initially vr(τ0) = 0

- EoS: QGP: ideal gas, Nf = 3, m=0, B1/4 = 239 MeV, TC = 165 MeVHRG: ideal gas, m < 2 GeV

- Cooper-Frye dec. with single Tdec= 150 MeV from RHIC data; use this for LHC

- Resonance decays included

- Ideal 1+2 d hydro: evolution isentropic initial NAA ~ final NAA

predicted [hep-ph/9909456] correctly

RHIC Nch(η=0) for central Au+Au at 56, 130, 200 GeV.

hep-ph/0506049

nucl-th/0008014hep-ph/0111223

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Early LHC prediction from pQCD+saturation+ hydrodynamics

dNch/dη = 2560 for 6 % most central Pb+Pb collisions

Eskola, Ruuskanen, Räsänen, Tuominen, hep-ph/0104010

hep-ph/0104010

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Works at RHIC with Tdec = 150 MeV.

hep-ph/0506049

RHIC: charged hadrons at η = 0

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- Reproduce pi & K pT-spectra and p multiplicities well with Tdec = 150 MeV.- Proton pT-spectra need more detailed decoupling, recombination, … - Comparison with pQCD + FF + E-losses Hydrodynamic region pT < 3 GeV

RHIC: pi, K, p at y=0

hep-ph/0506049

~

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LHC predictions at η = y = 0 [hep-ph/0506049]

- Hydrodynamic region pT < 4…5 GeV; larger than at RHIC~

η = 0 y = 0

K.J. Eskola et al

Tdec=150 MeV

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For further LHC predictions with input from pQCD + saturation + hydrodynamics, see

• Harri Niemi: Minimum bias v2(pT)

• Thorsten Renk: Charged hadron RAA(pT)

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Extra slide: Tdec dependence of integrated observables

Our LHC predictions here

[hep-ph/0506049]