# Presentation: 119272

## Theory Highlights* of Quark Matter 2004

**Ralf Rapp**
**Texas A&M University**
**Oakland, 17.01.04**

- * biased and incomplete, apologies for omissions

## 1.Introduction: Exploring the Phase Diagram

*** *****Bulk Properties: ****Equation of State**
** ****Phase Transitions: ****(Pseudo-) Order Parameters**** **
** ****Microscopic Properties: ****Spectral Functions**

## Outline

- Color-Super-Conductor ;  Chiral vs. Deconfinement
-  Lattice: Critical Point, Charmonium
**3.)  **_**QCD Bulk Properties at RHIC**__** **_
- Color-Glass Condensate
- Opacity, Thermalization
- Quark Coalescence vs. Hydro
- HBT  “Puzzle”
**4.) **_** Microscopic Probes of QCD Matter **_
- Resonance Spectroscopy
- E.M. Emission (Photons)
- Charm/onium
**5.)  **_**Conclusions**_

_**Outline**_

## 2.1 Colorsuperconductivity and Compact Stars  

- color+charge neutral **u,d,s,e**** ̅** matter  **M****s**** ** key parameter** **

- 2

- 4

- gCFL

- CFL

- 2SC

- g2SC

- Normal

**M****s****2****/(******

**M****s**-asym  1 **d-s** pair gapless

**[Rajagopal]**

**Notes:**
 Also for neutron stars electroweak emission spectra are of great importance,
Albeit not really penetrating (only neutrinos for sufficiently low T)

## 2.2 Confinement vs. Chiral Symmetry Breaking    

_**Order Parameters:**_
** **Chiral Symmetry** (*****m******q******→0*****):****   *****‹qq›*****  **(quark condensate)
** **Deconfinement** (*****m******q******→∞*****):****       *****‹L›*****   **(Polyakov loop)** **
-                                     at **C**: ***m************→0 ***
-                                     at **D**: ***m******G******→0***

**Mixing **of**  ********-Meson**** **
- and** ****0****++**** Glueball**** connects *****‹qq›***** **and** *****‹L›*****  **

**[Fukushima]**

**[Mocsy]:**** **loop effects entangle** *****‹L›*****  **and** *****‹qq›***** **

**QCD**

## 2.3 QCD Lattice for GSI: The Critical Point

_**Quark Number Susceptibility at **__****__**q**__**>0**_**   ****[Karsch,Redlich,Ejiri]**

******  ********B,c **≥ ***400 MeV*****     ****(****[Fodor+Katz]****:**** ****~*****700MeV***** ****)**

**[Friman]**

## 2.4 QCD Lattice for RHIC: Charmonia  [Karsch]

***R*********

-  suggests boundstates at ***T****≤****1.5T******c***
-  reduced open-charm threshold?

_**Spectral Functions**__ _

** ****J/********,**** ********c** up to ***2T******c***
-  **χ****c** dissolves close to ***T******c***

**[Asakawa,Datta]**

***J/*********

## 
3.1  Initial:  CGC
3.2  QGP :  Opacity
3.3  QGP :  Thermalization (nonpert?) 
3.4  Tc      :  Quark Coalescence vs. Hydro
3.5  Tfo       :  HBT  “Puzzle”

- 3.1  Initial:  CGC
- 3.2  QGP :  Opacity
- 3.3  QGP :  Thermalization (nonpert?)
- 3.4  Tc      :  Quark Coalescence vs. Hydro
- 3.5  Tfo       :  HBT  “Puzzle”

_**3.)  QCD Bulk Properties at RHIC**_

## 3.1 Pre-Equilibrium: Color Glass Condensate?

**Look forward in ****d-Au**** **

## 3.2  Opacity of QCD Matter: High-pt Frontier

-  **GLV** works quantitatively, incl.
-    - **d-Au **(+away-side broad.)
-    - re-app. in-plane away-side jet
-    - connection to DIS
-               **[Vitev,Majumder****,Salgado,**
**                   ****Accardi,Barnaföldi,Povh****]**
**    ********  ********ini******≈ **20 GeV/fm****3**
-  **[Greiner]**** ****:** absorpt. of colorless
-    “prehadrons” ;  problems:
-      - **v****2** of supp.+bulk,   - SPS ?!

_**3.2  Opacity of QCD Matter: High-**__**p**__**t**__** Frontier**_

- _Notes:_  - non-jet ***baryon*****/*****meson*** for  **p****T ****< 6 GeV**
-             - where does ***R******AA**** *rise again?     LHC?!** **

**Notes:**
 flat R_AA: Moore consistent with GLV reaction operator approach

## 3.3 Thermalization and Nonperturbative QGP

- early** **thermalization**       **Hydro** ****v****0,1,2,4**

- Corrections:
**[Hirano,Heinz,Gavin]**

- Resonant  **qq , qg , gg**** ****↔**** ****“meson”**  rescattering ?

## 3.4 Hydro vs. Coalescence: The 2-6GeV Regime

**v****2**: mass-dependent But: **p/********(4GeV)**≈**0.3**
-    **[PHENIX]**: **1****±0.15**

**[Hirano,Nara]**

_**Challenges:**_**  ****p/********=1**** ****+ jet correlation**** ,  ************elliptic flow **** **

**Notes:**
Most reliable if at least one rare particle is involved 
relation to thermal spectra:
soft-soft: coincides with thermal model for large pt, possible mechanism for bulk hadronization including corrections
          (Q-value of the formed hadron, etc.), equilibrium limit simeq  statistical (thermal) model, 
             can be shown explicitly using current models only at sufficiently high momentum   
soft-hard: most promising to account for jet-like correlations in 2-6GeV region (recombination of subleading jet-particles [Hwa])
               explixitely treats the transition from thermal to pQCD
hard-hard: powerlaw not competitive with fragmentation 
HYDRO runs out of steam at 3.5GeV: cannot describe p/pi=1 AND near-side correlation at the same time

## 3.5 HBT “Puzzle”

- Hydro/Transport models overpredict
***(R******out******)******2******=D(x******out ******,x******out******) ******- 2D(x******out ******,************t ******t)****** + D(************t ******t,************t ******t)***

**[Kapusta,Wong]****:** incl. quant. phases in rescatt. ↔ ***initial*** size?!

- Multiphase
- Transport
- Model
**[Lin+Ko]**

**positive *****R******out ******- t***
- correlation
- (not in Hydro,
- UrQMD ...)

_**Potential Remedies:**_

**[Teaney]****:** viscosity in hydro

**Notes:**
 problem/discrepancy resides in the hadronization?

## 4.)  Microscopic Probes of QCD Matter

**     **4.1  Hadronic  In-Medium Effects:
-            Resonances and Chem. Freezeout
- 4.2  E.M. Emission
- 4.3  Charm/onium

## 4.1 Resonance Spectroscopy at RHIC

****** ******** ********,  ******** ******** ********N,  ***************≈**********5fm/c,*****  *****T******fo****≈****110MeV,******                ***** **

**Notes:**
 need to understand pp, sudden freezeout: thermodynamic potential, low-T/-rho: phase shifts -> Broniowski/Florkowski,
Rate equation: no interferences, medium effects: spectral function, 
Apparent rho-mass shift rises with multiplicity, non resonant background?
Delta->Npi mass stable, but width increases!

## From Thermal to Chemical Freezeout

-       at** ***** T******c ******** 175MeV ***:**  ****Chiral Restoration!**
****** **chiral partners** ****must **degenerate** ****(*****m***** **and** ********):**** **
**      ********,  ********a****1  ****,  N********N*********  ****(**or:** ********L**** ****[Harada]**** ****)**
****Substantial medium modifications required
-       (supported by **CERES** dileptons,**  ************ e****+****e****-**)

_**Challenge:**_** **** Reconcile with chem. f.o. systematics !?**
-            (à la [**Braun-Munzinger+Stachel etal],...**** **)
- _Optimistic:_ measure (and calculate!)
**                 ****a****1**** ******** ********  ,  N*(1535) ******** N ******

**Notes:**
   need selfconsistent thermodynamic potential approach
  can be simultaneously applied at Tc and Tfo

## 4.2 Direct Photons and Dileptons

_**Sources:**_
-  _Initial hard scatt.:_  Drell-Yan  /  Compton (tag jets! **[Gale]**)
-  _Pre-equilibrium:_  Radiation off jets **[Gale]** ,
-           rescatt.+fragment. of secondaries (parton cascade **[Bass]**)
-  _Thermal:_

***Im ******Π*****em*****(M,q)***

***Im ******Π*****em*****(q******0******=q)***

-  chemical off-equilibrium:
-    QGP:  ******q,g**** **≤** 1**
-    HG:    **********,K,..**** ****> 0**

**[****Niemi,Moore****]**

## Direct Photons at SPS and RHIC

_**Direct Photons at SPS and RHIC**_

-  large “pre-equilibrium” yield
-    from parton cascade   (**no LPM**)
-  thermal yields ~ consistent
-  QGP undersaturation small effect

-  pQCD Cronin ~ **π****0**
-    ***T******0***≈***205MeV*** sufficient
-  new **WA98** points:
-   ****-Bremsstr. via soft **** ?

**[Turbide etal]**

**Notes:**
Compare thermal fireball with Bass patoncascade and Niemi QGP-off-eq hydro

## 4.3 Charm I: Open Charm (Central A-A) 

_**4.3 Charm I: Open Charm (Central A-A) **_

_**(i)  Yields **_
- • _RHIC:_ ***-*****30%** for ******=0********2**: **CGC** **[Tuchin]**, Color-Dipole **[Raufeisen]**
- • _LHC:_   **CGC**: ***N******part***** **;   nonlin. DGLAP: enhanced!  **[Kolhinen]**
_**(ii) **__**p**__**T**__**-Spectra**_
-    **dE/dx** : Null Effect?! **[Djordjevic]**

**v****2****(e****±****) **: Thermalization?!

**Notes:**
Production: raufeisen vs. tuchin vs. Kolhinen
Rescattering: compare new phenix data with coalescence etc.
Important impact on studying charmonium physics

## • RHIC central: Ncc≈10-20,  
• QCD lattice: J/’s to~2Tc     

- • QCD lattice: **J/******’s to**~*****2T******c***

_**4.3 Charm II: Charmonium**_

**Regeneration** in **QGP** / at ***T******c***
-    **J/******** + g         c + c + X**

**→**

**←**

**[PBM etal, **
**Thews etal]**

- -

**Notes:**
Loic figure, stress consistency with lattice QCD
Npsi quadratic in Nccbar, sensiive to in-medium effects
    predictions for NA60??

## 5. Conclusions

**Produced Matter at RHIC is**
**Dense              (opacity)**
**Thermalized   (hydro)**
**probably nonperturbative   (resonances,...)**

**Microscopic probes required to assess the phase transition**

**Need to find broad consensus on signatures **
**to go beyond circumstantial evidence from the SPS **