November 9, 2011icc.ub.edu/congress/ESP-RUS2011/Talks_Presentations/... · 2011-11-24 · We want to study not the properties of quarks and gluons, but the properties of a New State

November 9, 2011

Heavy Ion Collision Simulations

Main Collaborators: V.K. Magas (Barcelona, Spain)

L.P. Csernai (Bergen, Norway)

D.D. Strottman (LANL, USA/ Valencia, Spain/ Frankfurt, Germany)

H. Stöcker (Frankfurt, Germany)

Recent publications:

Nucl. Phys. A834 (2010) 261

Phys. Rev. C81 (2010) 064910

Phys. Lett. B692 (2010) 277

Phys. Rev. C84 (2011) 024914

Inaccessible region

Nuclear Matter Phase diagram

Heavy ion collisions: Compression + heating

We want to study not the properties of quarks and

gluons, but the properties of a New State of Matter

- QGP

We want to describe QGP evolution via collective quantities: -Energy density -Baryon density -Flow velocity -Pressure -Temperature And QGP, as a state of matter, we want to characterize by - Equation of State

QGP phase,

QGP EoS

Proper tools: Hydrodynamics,

Thermodynamics,

Statistical Physics

Global Flow

For the fixed y

in the transverse plane

Collective effects start to be seen, but these are due to initial conditions

Relativistic heavy ion collisions beam energies (Lab): 100 MeV/nucl – 10 GeV/nucl

Pre-QGP era

Directed Transverse flow

Squeeze out

Pre-QGP beam energies (fixed target): 0.1 – 10 GeV/nucl

Global Flow

Collective effects start to be seen

Most prominent – is the collective sidewards flow (directed flow) in the reaction plane.

Relativistic heavy ion collisions beam energies (Lab): 100 MeV/nucl – 10 GeV/nucl

Non-central collision =>

Bounce-off

Directed transverse flow

The same collision =>

Squeeze

out

y

Ultra-relativistic heavy ion collisions beam energies (Lab): > 10 GeV/nucl

- Strong and clear collective flow

-The flow now can not be generated in the initial NN collisions (like bounce-off) there is a pressure in the system and it is generated quite early

Directed Transverse flow

Elliptic flow

Antiflow Antiflow

Global Flow

Elliptic flow vs. Squeeze out

• At LBL, GSI, AGS

flow is orthogonal to

the reaction plane:

squeeze out – due to

initial conditions

• At SPS, RHIC central

flow is in the reaction

plane:

• elliptic flow - some

matter is accelerated by

pressure

As energy grows the directed flow

starts to deviate from the straight line behavior:

not just a simple Bounce-off –

there is some acceleration by pressure

CERN SPS

RHIC Strong antiflow is observed

PHOBOS Collaboration Phys.Rev.Lett.97:012301,2006

[Csernai, Röhrich, PL B458 (1999) 454]

The “firestreak” picture [Myers (1978), Gosset, Kapusta, Westfall (1978)]

Tilted initial state

Can be the source of antiflow

Initial state from effective string rope model

Au+Au at 100+100 GeV/nucl, b=0.25*2R

Magas, Csernai, Strottman, PRC 64 (2001) 014901, NPA 712 (2002) 167

Au+Au ECM=65 GeV/nucl. b=0.5 bmax Aσ=0.08 => σ~10 GeV/fm

e [ GeV / fm3 ] T [ MeV]

t=0.0 fm/c, Tmax= 420 MeV, emax= 20.0 GeV/fm3, Lx,y= 1.45 fm, Lz=0.145 fm

. .

EoS: p= e/3 - 4B/3

B = 397 MeV/fm3 8.7 x 4.4 fm




. .

14.5 x 4.9 fm




. .

20.3 x 5.8 fm

Proceedings of the Quark Matter 2006,

J. Phys. G34 (2007) S1077-S1082

Effective string rope model initial state & 3+1D Los Alamos (PIC) relativistic hydro code

Such a tilted initial state generates the first flow component

in the “antiflow” direction at RHIC

Constant time

FO hypersurface

Pb+Pb reaction at LHC

1.38 + 1.38 A*TeV collision energy

Peaks in opposite directions!!!

What has happened?

Csernai, Magas, Stöcker, Strottman,

Phys. Rev. C84 (2011) 024914

b=0.7bmax

Qualitatively agrees with the simulations

performed in a microscopic transport model:

Bleibel et. al., Phys. Lett. B659 (2008) 520

Rotation of the initial state

due to the

initial flow velocity distribution

Directed flow measurement in ALICE at LHC

I. Selyuzhenkov [ALICE], arXiv:1106.5425 [nucl-ex], talk given at “Quark Matter 2011”

Directed flow

is very small,

and in “antiflow”

direction

Quark Matter 2011 Initial state fluctuations are extremely important

for odd flow components… - talks by B. Schenke, F. Grassi, H. Holopainen, S. Jeon, P. Mota, H. Petersen

First results from real event-by-event hydrodynamics

For example - Gardim et. al., Phys. Rev. C.83, (2011) 064901

Directed flow has two physical sources:

-the global collective flow correlated with the reaction plane of the event - the random fluctuation flow, where the corresponding symmetry axes (e.g., for v1 and v3) have no correlation with the reaction plane; instead they are observed with respect to a participant plane event by event [Borghini, Dinh, and Ollitrault, Phys. Rev. C 64 (2001) 054901]

Random fluctuations create a strong v1 flow in “antiflow” direction [Gardim et. al., Phys. Rev. C.83, (2011) 064901]

The observed small antiflow might be a result of compensation of these two sources


Phys. Rev. C84 (2011) 024914

Sensitivity of the collective flow to the initial state fluctuations

b=0.7bmax

32.7 nucl

32.7 nucl

yCM=0

|y0|=8

The only fluctuations,

which we can easely

take into accoint in our model,

are the initial state

C.M. rapidity fluctuations


Phys. Rev. C84 (2011) 024914


b=0.7bmax

33 nucl

32 nucl

yCM≠0

|y0|=8

yCM is fluctuating around “0”

with Gaussian distribution

22 /

22

1)(

yy

CMCMe

yyP


b=0.7bmax

33 nucl

32 nucl

|y0|=8

yCM is fluctuating around “0”

with Gaussian distribution

22 /

22

1)(

yy

CMCMe

yyP

+ Experimental cuts ! -0.8 < y <0.8

yCM≠0


Phys. Rev. C84 (2011) 024914

b=0.7bmax

Sensitivity of first flow component to the initial state fluctuations

Results are strongly affected

by exp. rapidity cuts and

by initial state fluctuations

Drastic effect:

no peaks !


Phys. Rev. C84 (2011) 024914

Sensitivity of the elliptic flow to the initial state fluctuations

Reasonable agreement

with data

(NO FITTING)

b=0.7bmax

ALICE Collaboration,

PRL 105, 252302 (2010)

Pb+Pb reaction at LHC

1.38 + 1.38 A*TeV collision energy

Conclusions

New effect is predicted:

change of the direction of the global v1(y) flow

from RHIC to LHC

First flow component is extremely sensitive to the

random fluctuations, in particular to the

initial state CM rapidity fluctuations

Our simulations of the elliptic flow are

in a fair agreement with ALICE data (NO FITTING)

Our collaboration performs simulations of the

ultra-relativistic heavy ion collisions at RHIC and LHC

New method is proposed:

How to separate in the data the global flow from

the flow fluctuations in the 1st harmonic

Gracias!

Documents

November 9, 2011icc.ub.edu/congress/ESP-RUS2011/Talks_Presentations/... · 2011-11-24 · We want to study not the properties of quarks and gluons, but the properties of a New State