HIGH ENERGY
NUCLEAR PHYSICS:
THEORY
E. Zabrodin (UiO)
for the
heavy-ion theory groups from
UiB (leader – L. Csernai) and
UiO (leader – L. Bravina)
Norwegian CERN committee meeting (Bergen, 16-17.04.2009)
HEAVY-ION THEORY AND PHENOMENOLOGY
Theory Group at UiO:
I.C. Arsene, L. Bravina, G. Eyyubova, R. Kolevatov, L. Malinina*,
M.S. Nilsson, K. Tywoniuk*, E. Zabrodin
cooperation with ALICE experimental group
other collaborators:
FIAS, Frankfurt M. Bleicher, G. Burau, H. Stocker
MSU, Moscow
I. Lokhtin, L. Malinina*, A. Snigirev
LPT, Orsay
A. Capella
ITEP, Moscow
A. Kaidalov, K. Boreskov
ITP, Tuebingen
J. Bleibel, C. Fuchs, A. Faessler
BITP, Kiev
Yu. Karpenko, Yu. Sinyukov
IGFAE, Santiago de Compostella E.G. Ferreiro, K. Tywoniuk*
21 – papers in international refereed journals
10 – published conference contributions
29 – oral and poster presentations (for 5 years)
MODELS AT OUR DISPOSAL: HYDJET++, QGSM, URQMD
Current projects:
Bulk particle production in soft and hard processes;
anisotropic flow; equation of state; particle freeze-out;
role of resonances; HBT correlations; jet quenching; shadowing; …
HYDJET++ = HYDJET + FASTMC
FASTMC
I. Lokhtin et al., Comput. Phys. Commun. 180 (2009) 779
N. Amelin et al., Phys. Rev. C 77 (2008) 014903
HYDJET
K. Tywoniuk et al., Phys. Lett. B 657 (2007) 170
THE GLAUBER MODEL
heavy-ion collisions
 in each rescattering there is a
certain probability for particle
production

COHERENT INTERACTION
the projectile becomes large compared to the
target
 interacts simultaneously with the whole system
 effectively less interaction - shadowing


dramatic change of space-time picture
CHANGE OF SPACE-TIME PICTURE
σ
(2)
tot
1

E
σ tot 
+
+ ...
the diagrams corresponding to ”classical”
rescatterings are suppressed at high energies!
 Gribov trick: Glauber is OK after all!
Almost...
 have to take into account diffractive
intermediate states!

SHADOWING: PREDICTIONS FOR LHC
K. Tywoniuk et al., J. Phys. G 35 (2008) 104156
A. Capella et al., Eur. Phys. J. C 58 (2008) 437
Soft physics: Elliptic flow
Flow with HYDJET++
model: study of jet
influence and resonance
decay on flow of different
particles.

dN
1

(1   2vn ( pt ) cos[n(   r )])
d 2
n 1
v2  cos 2(   r ) ,   tan (
1
py
px
)
Jet influence : inverse of
mass ordering at pT ≈ 2
GeV
Resonance decay
influence: increase of v2.
V2 IN HYDJET++ FOR DIFFERENT TYPES OF PARTICLES
The model
possesses
crossing of
baryon and
meson branches.
Hydrodynamics
gives mass
ordering of v2
L. Bravina,
G. Eyyubova et al.,
arXiv:0903.5175
Influence of resonance decays for different
types of particles on v2 value
L. Bravina, G. Eyyubova, et al., arXiv:0903.5175
30%
44%
20%
39%
Protons flow : direct and from Δ decays
Pions flow : direct and from Δ decays
Because of the kinematics of the decay, protons carry practically the same flow as mother Δ
particles while pion flow is shifted to low pT
Pions flow : direct and from ω decays
Pions flow : direct and from ρ decays
QUARK-GLUON STRING MODEL (QGSM) AND
ULTRA-RELATIVISTIC QUANTUM MOLECULAR DYNAMICS (URQMD)
Excitation of color neutral strings
EQUILIBRATION IN THE CENTRAL CELL
Kinetic equilibrium:
Isotropy of velocity distributions
Isotropy of pressure
Thermal equilibrium:
Energy spectra of particles are
described by Boltzmann distribution
Chemical equlibrium:
Particle yields are reproduced by SM with the same values of
”Big” cell (V = 5x5x5 fm^3)
0)
“Small” cell (V =>
L. Bravina et al., Phys. Rev. C 78 (2008) 014907
EOS: HOW DENSE CAN BE THE MEDIUM?
Dramatic differences at the non-equilibrium stage; after beginning of
kinetic equilibrium the energy densities and the baryon densities are the
same for ”small” and ”big” cell
EOS IN THE CELL: OBSERVATION OF KNEE
temperature vs. chemical potentials
L.Bravina et al.,
PRC 78 (2008) 014907
E. Zabrodin et al.,
arXiv:0902.4601
S. Ejiri et al., PRD 73
(2006) 054506
Although the “knee” is similar to that in 2-flavor lattice QCD, it is
related to inelastic (chemical) freeze-out in the system
FREEZE-OUT AT RHIC: URQMD
M.S. Nilsson, ”LHC and beyond” (Lund, Feb. 2009)
FREEZE-OUT AT RHIC: QGSM
M.S. Nilsson , ”LHC and beyond” (Lund, Feb. 2009)
FREEZE-OUT AT RHIC: URQMD
FREEZE-OUT AT RHIC: QGSM
MULTI MODULE MODELING (MMM)
L. Csernai , talk at SQM’08 (Beijing, Oct. 2008)
FLOW AND FREEZE-OUT IN MMM
FLOW AND FREEZE-OUT IN MMM
QGSM PREDICTIONS FOR PP AT LHC
A.B. Kaidalov, K.A.Ter-Martirosyan, PLB 117 (1982)
N.S.Amelin, L.V.Bravina, Sov.J.Nucl.Phys. 51 (1990) 133
N.S.Amelin, E.F.Staubo, L.P.Csernai, PRD 46 (1992) 4873
At ultra-relativistic energies: multi-Pomeron scattering, single and double
diffraction, and jets (hard Pomeron exchange)
Gribov’s Reggeon Calculus + string phenomenology
RAPIDITY AND PT SPECTRA: MODEL VS. DATA
NSD collisions
LHC predictions
Inelastic collisions
J. Bleibel, L. Bravina, E. Zabrodin et al., (in progress)
Description of both pseudorapidity
and transverse momentum
distributions seems to be good
PREDICTIONS FOR PP @ LHC
QGSM: extended longitudinal scaling in p+p collisions holds
VIOLATION OF KNO SCALING AT LHC
High-multiplicity tail
is pushed up, whereas
maximum of the
distribution is shifted
towards small values
of z
2
4
6
8
=> Enhancement of high multiplicities
At energies below 100
GeV different
contributions overlap
strongly, whereas at
higher energies –
more multi-string
processes
Summary and outlook
• LHC is a discovery machine for both hard and soft
physics in HI collisions
• Event generators are an indispensable tool for planing
the experiments and analysis of data
• => Further development of existing MC generators
• Utilizing it to study :
elliptic flow, particle freeze-out, HBT correlations of
unlike particles, particle-jet correlations, heavy quark
production in a large pt range, scaling properties
Back-up Slides
MOTIVATION: EXPERIMENTAL RESULTS
W. Busza, JPG 35 (2008) 044040
Extrapolation of NSD pp data to LHC using ㏑√s scaling of the
width and height of the distribution
MOTIVATION: EXPERIMENTAL RESULTS
W. Busza, JPG 35 (2008) 044040
e+e－
Example of extended longitudinal scaling in different reactions
HYPOTHESIS OF FEYNMAN SCALING
R. Feynman, PRL 23 (1969) 1415; also in ”Photon-hadron interactions”
In terms of rapidity
 ln[ x0 s / mT ]  y*  ln[ x0 s / mT ]
Basic assumption:
scaling of inclusive
spectra within the
whole kinematically
allowed region of xF
(or c.m. y)
In addition:
existence of central
area  x0  xF  x0 ,
where x0  (0.1  0.2)
is assumed.
CONSEQUENCES OF FEYNMAN SCALING
(1) Logarithmic rise of the central
rapidity region with energy
(y* )  2ln( x0 s / mT )
(2) Fragmentation regions are
fixed
(y* )  ln(1/ x0 )
(3) Main contribution to mean
multiplicity comes from the
central area
(4) In the central area particle
density does not depend on energy
and rapidity
 ( y* , pT ; s )   ( pT )
n
ln( x0 s / mT )
(5) Contribution from the
fragmentation regions is
energy independent
VIOLATION OF FEYNMAN SCALING
UA5 Collab., Phys. Rep. 154 (1987) 247
Charged particle pseudorapidity
density at h  0 as a function of √s
W. Busza, JPG 35 (2008) 044040
Violation of Feynman scaling,
but ext. long. scaling holds?!
PREDICTIONS FOR P+P @ LHC
LHC
QGSM: pseudorapidity distribution of particles
VIOLATION OF ELS IN A+A AT LHC?
J. Cleymans, J.Struempfer, L.Turko, PRC 78 (2008) 017901
s
Statistical thermal model: ELS will be violated in A+A @ LHC. What about p+p ?
WHY SCALING HOLDS IN THE MODEL?
Correlation function
C ( yi , y j )  exp{ ( yi  y j )}
Particles are uncorrelated if
yi  y j  y
1
Consider now inclusive process
1 2  i  X
Particle inclusive cross section
d 2s ( y1  yi , yi  y2 , piT2 )
fi 
dyi d 2 piT
x
(i )
F

pi
p max
 exp{( y1  yi )}
therefore
ni   ( xF(i ) , piT2 )
In the fragmentation region of particle 1
y1  yi  1 , yi  y2  y1  y2
Inclusive density
n i  fi / s inel   ( y1  yi , piT2 )
In string models both FS and ELS holds in the fragmentation regions
1
KOBA-NIELSEN-OLESEN (KNO) SCALING
Z.Koba, H.B.Nielsen, P.Olesen, NPB 40 (1972) 317
They claim that if Feynman
scaling holds, then the
multiplicity distribution is
independent of energy except
through the variable
z  n /  n
s n ( s)
1
 n 
Pn ( s ) 


s tot ( s )  n   n 
Experimental data: KNO scaling holds in hh collisions
up to √s = 53 GeV (ISR)
VIOLATION OF KNO SCALING
A.B.Kaidalov, K.A.Ter-Martirosyan, PLB 117 (1982) 247
UA5 Collaboration, Phys. Rep. 154 (1987) 247
N.S.Amelin, L.V.Bravina, Sov.J.Nucl.Phys. 51 (1990) 133
√s
Charged-particle
multiplicity distributions
in the KNO variables in
nondiffractive
antiproton-proton
collisions at
√s = 546 GeV and
53 GeV