The Physics of Compressed Nuclear Matter at GSI and FAIR

Mazurian Lakes Conference on Physics 2009Joachim Stroth, Goethe-University / GSI, Germany

Agenda

o Motivationo Recent remarkable results from SIS18o The persepective and challenge at FAIRo Summary

The phase diagram of nuclear matter

Chemical freeze-out points derived from Statistical Hadronization Model Universal conditions for

freeze-out (?) Limiting temperature Tmax? Why is it woking at low beam

energies?

QCD inspired models demonstrate the melting of the condesates.A. Andronic, P. Braun-Munzinger, K. Redlich, J. Stachel

J. Cleymans, K. Redlich

LQCD explores unknown regions from solid grounds at mB=0.

Tc = Tmax? 1st order phase transition Critical point ?

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Schäfer, Wambachpriv. communication

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Schäfer, Wambachpriv. communication

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LeupoldJ.Phys.G32:2199,2006

LHCRHIC

SPSFAIR

SIS

AGS

3fm/GeV6.0

QGP

Hadron gas

F. Karsch et al., Z. Fodor et al.

Ignorant interpretation (Cloudy Bag Model)

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T Tc , mB ~ 0

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qq-Excitation/melting of the vacuum/cloud. smooth cross over

T << Tc , finite mB

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T << Tc , finite mB

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Bag fusion mixed phase

Phase diagram from large Nc

limitMcLerran, Pisarski: QM09 conjecture for Nc = 3

Quarkyonic Matter: Confined gas of perturbative quarks!

Strange Particle Production at SIS18• HADES,• Ar+KCl at 1.76 GeV/u • FOPI (P. Gasik CPOD 2009),

• Al+Al at 2 GeV/u

Tchem = 70 3 MeV B = 746 15 MeVRC = 2.6 0.4 fm

preliminary

Statistical Model:THERMUS, S. Wheaton and J. Cleymans, hep-ph/0407174Transport:UrQMD, M. Bleicher, S. Vogel at al.

HADES collab.: arXiv:0907.3582 and arXiv:0902.3487

Properties of the Fireball below Ebeam < 30 GeV/u

• Long lifetime of the high-density phase

• Baryon dominated• Extented region of a

strongly interacting hadron gas

1meson

baryon

N

N

Red line from Hadron Gas Model,Sasaki QM09

Dileptons from 1 and 2 GeV/u 12C+12C runs

Phys.

Rev.

Lett

98

(2007

) 05

2302

Phys.

Lett

. B

66

3 (

200

8)

43

Good normalization established in p0 region

Measured pair excess in C+C scales with beam energy as p0 production

What is the contribution from the initial phase?

l+l-

g*

g*

l+l-

g*

l+l -

The solution to the DLS puzzle

C+C collisions compared to NN referenceHADES data agrees with DLS

Electron pairs from Ar+KCl at 1.76 GeV/u

First observation of w mesons in HI collisions at these energies

x 2PLUTO A

Compared to reference after subtraction of contributions from h

•preliminary

• F ~ 3

The Future at GSI and FAIRSIS18Several FOPI runs on strangeness production in 2008 – 2010Upgraded HADES (20 KHz reaction rate) Au+Au and Ag+Ag, pion induced reactions from 2010 on.SIS100:Joint running of HADES and preCBM,multistrange particle and lepton pair excitation function,charm production in proton induced reactionsSIS300:Full exploitation of rare probes a high mB;

fluctuations, flow

Particle multiplicities in detection channel• Au+Au at 25 GeV/u• HSD transport calculation and

statistical hadronization model.

Not fully dressed in HI collisions at AGS and lower SPS energies

The Quest for the Highest Densities

J. Ra

ndru

p an

d J.

Cley

man

s,

hep-

ph/0

6070

65

Freeze-out configurations for X+X collisions in the net-baryon density and energy density plane.

Low-mass vector mesons:what do they tell about chiral symmtery restoration?

Low-mass lepton pairs, …

… the link to the microscopic properties of dense baryonic matter.Special role of the r meson:

– short life time– „photon-like“– coupling to baryons!

xxxxp

dvTd

d

dMdydp

NdcollB

tt

),..(),(),(0

43

oVT ,, 00

isentropic expansion

Thermal dilepton rates

see e.g. R. Rapp, J. Wambach and H. Hees : arXiv:0901.3289,and S. Leupold, U. Mosel and V. Metag arXiv:0907.2388

*,N

h

h

l

l

R.Arnaldi,etal.[NA60collaboration],Phys.Rev.Lett.96,162302(2006)

New approaches in theory

• Hybrid codes for modeling the reaction dynamics

1. Non-equilibrium initial conditions via UrQMD2. Hydrodynamic evolution or transport calculation3. Freeze-out via hadronic cascade (UrQMD)

hydro running time

hydro start time

Pb+Pb, central

(Petersen et al., PRC 78:044901, 2008, arXiv: 0806.1695)

• Introduce virtual photon emissivity from in-medium spectral functions into hydro codes

R. Rapp, H. van Hees, V. Toneev, J. Wambach, B. Friman, Texas A&M, TU Darmstadt, GSI, Giessen, Frankfurt

Ring ImagingCherenkovDetector

Transition Radiation Detectors

Electron identification in CBM

Electron-pair reconstruction in CBM Challenge

- No electron identification before tracking - Background due to material budget of the STS- Sufficient p discrimination (600 p+/-/event, misidentification 10-4)

® Reduction of background by reconstructing pairs fromg-conversion and p0 Dalitz decay via their track topology.

e-

e+

g*p0

g

gp0

g

Track Segment

Track Fragment

Background rejection performance

• Central Au+Au collisions at 25 GeV/u• Free cocktail only (without medium contribution)• Statistic: 200000 events = beam spill on target

All e+e-

Combinatorial bg

Invariant mass spectrumafter all cuts appliedInvariant mass spectrum identified e+e-

Mll > 200 MeV/c2

safetyfactor

;)

NA60 In+In @ 158 AGeVCERES Pb+Au @ 40 AGeVCERES Pb+Au @ 158 AGeV (σ/σtot = 28%)CERES Pb+Au @ 158 AGeV (σ/σtot = 7%)CERES Pb+Au @ 158 AGeV PHENIX Au+Au @ √s = 200 AGeV

Comparison of expected performance to existing dilepton experiments

Charmonium suppression.

c c-

The Charm of CBM

Rare but measurement feasible!– Very sparse experimental

information– At threshold, production

mechanism in pA and AA unclear.

Open charm in CBMBR M / 1012 events1)

4 10-5 56000

1 10-4 174000

9 10-5 195000

4 10-5 103000

1012 events 40 weeks running at 105 interaction rate.Event selection: Real-time vertex finding in 20 Gbyte data/s.

KD0

KD 0

KD

KD

W. Cassing, E.L. Bratkovskaya, and A. Sibirtsev,Nucl.Phys.A691,753(2001)

Charm propagation

How are the produced charm quarks propagating in the dense phase, quark like or (pre-)hadron like ?

– Charmonium over open charm as indicator!– Charmed baryons important for a complete picture.– Are there indications of collectivity.

O. Linnyk, E. Bratkovskaya and W. Cassing, arXiv:0808.1504v1A. Andronic, P. Braun-Munzinger, et al., Phys. Lett. B 659 (2007) 149, arXiv:0708.1488

Summary

– „Long-lived“ states of dense nuclear matter are produced in collisions of heavy ion at energies of a few GeV/u.

– The phase in the high-density region might be much more exotic then a hadron/resonance gas.

– Unfortunately, there is no smoking gun, but:• Fast equillibration• „Sub-threshold“ production• Strong broadening of in-medium states

– Close collaboration with, and novel approaches in theory are necessary to make the case.