# Presentation: 273328

## The Physics of high baryondensities

- Probing the QCD phase diagram
- The critical end point
- Properties of mesons in matter
- Baryon density vs. temperature
- Probing cold dense matter
- Conclusions

- B. Friman, GSI

## The QCD phase diagram

- T

- B

- Hadronic
- matter

- Quark-Gluon Plasma

- Nuclei

- Chiral symmetry
- broken

- Chiral symmetry
- restored

- Baryon
- dominated

- Meson
- dominated

- Neutron stars

- Early universe

- Neutron stars:
- -low T
- -high B
- -strangeness
- -quark matter
-  (CSC ?)

## The QCD phase diagram

- B

- Quark-Gluon Plasma

- Nuclei

- Chiral symmetry
- broken

- Chiral symmetry
- restored

- Hadronic
- matter

## The critical end point

- Fodor & Katz:
- Tc  160 MeV, Bc  720 MeV

- Adiabatic extrapolation to
- freeze-out curve: E ~ 10 AGeV

**Notes:**
Critical point most spectacular finite density effect

## Signatures of the critical end point?

- So far no convincing experimental evidence
- for the nuclear matter gas-liquid critical point

- Critical point: fluctuations of
- the order parameter are soft

- Ejiri et al.

- Look for rise and fall
- of fluctuations! (E-by-E)
- (Stephanov, Rajagopal, Shuryak)

- E-by-E fluctuations of:
- transverse momentum (SRS)
- pion multiplicity (SRS)
- proton number (Hatta, Stephanov)
-  . . . . .

- Take care of finite time and
- finite size effects (Berdnikov, Rajagopal)

- Exciting prospects, but still many unknowns!

- Quark number susceptibility

## Effects of baryon density

- Mass splittings because
- charge conjugation symmetry
- broken at nB  0

- K+

- K-

- ~100
-  MeV

- 0

- Easier to produce K- in dense matter

## Kaon production near threshold

- Ni+Ni (1.93 GeV)

- Enhancement of K-

- KaoS & FOPI @ GSI

- Repulsive potential

- Suppression of K+

- Attractive potential

- Calculation:
- Cassing & Bratkovskaya

**Notes:**
Chiral partners of D-mesons, chiral dynamics in matter, heavy-light system

## Effects of baryon density (2)

- Effects of baryon density (2)

- Explore D-meson
- properties in dense
- matter at energies
- around charm threshold
- E  10-20 AGeV

- D-Meson mass splitting
- at nB  0

## Chiral partners of D-mesons?

- D-mesons:
- heavy-light system
- hydrogen atom of QCD

- Light-quark-cloud
- probes chiral symmetry

- D(1869)

- D*(2010)

- ~1/mQ

- 0-

- 1-

- Heavy-quark-symmetry

- + chiral symmetry:
- chiral doubling of D-mesons
- (Nowak-Rho-Zahed and Bardeen-Hill, 92-93)

## Restoration of Chiral Symmetry

- at non-zero baryon density and temperature

- Role of chiral symmetry
- for hadron masses?

- Explore dependence
- of hadron properties
- on quark condensate

- Chiral partners become
- degenerate

## D mesons in matter

- If chiral doubling scenario for D mesons correct

- then m(0+)-m(0-)  0 etc.
- as qq  0 (chiral limit)

- Harada, Rho, Sasaki (2003)

- D-meson production in nuclear collisions offer a unique
- opportunity to explore chiral dynamics in dense matter

- m(0+)-m(0-)

- 0

## Beyond mean-field approximation

- Spectral functions change due to interactions

- Low-density expansion:

- Resonances in scattering amplitude:
- peaks in spectral function

## Baryon density vs. temperature 

- Baryon dominated matter:
- meson spectral functions
- determined by baryon resonances

- Meson dominated matter:
- meson spectral functions
- determined by
- meson resonances

- Resonances
- smeared by
- collision broadening

- These effects must be unfolded before one can draw
- conclusions on chiral symmetry and masses

- Need high resolution, high statistics data at
- a wide range of energies  (T vs. B)

- Meson mixing at B  0

**Notes:**
These effects must be unfolded before one can draw any conclusions on chiral symmetry and masses

## Strangeness and baryon density

- Braun-Munzinger,Cleymans,
- Oeschler and Redlich

- No peak for B = 0!

## Probing cold dense matter in nuclei

## Photo induced ω production

- Photo induced ω production

- Simulation by
- Meschendorp et al.

- Measured at ELSA by
- TAPS collaboration

- Data analysis in progress

- Assume at  = 0:
- m  660 MeV,   60 MeV

## Summary  

- Critical endpoint: fluctuations
- Light-heavy mesons: mass splitting
- Chiral partners become degenerate
- New D mesons
- Data at different energies/different B/T
- 	useful for unraveling meson/baryon
- 	resonances, meson mixing etc.
- pA, A, A etc. provide complementary
- 	information

## Most of them can be explored at the

-         GSI Future Facility

- Protons                     E ****** **90 GeV
- Heavy ions (N=Z)      E **** 45 AGeV
- Pb                             E ****** **35 AGeV
- Stored antiprotons**  **E** ******** **15 GeV

- Some of these issues are being
- addressed at CERN SPS.

- Comprehensive heavy-ion program with strangeness,
- charm, lepton pairs and photons

**Notes:**
Photons?