# Presentation: 774926

## Slide 1

## Approximations to QCD tested in Au+Au and d+Au

**Approximations to ****QCD**** tested in ****Au+Au**** and ****d+Au**

- F. Karsch *et al.*

-  Deconfinement phase transition
-  Chiral symmetry restoration
-  Thermal equilibration of the partonic medium

**AGS, ****SPS****, ****RHIC****, ****LHC**

- t

**RHIC**

- _A note on “first principles scales”_

-  QCD has no scale in itself, e.g.
-  What QCD computes is evolution

## High-pT Hadron Production from LO pQCD 

**High-p****T**** Hadron Production from ****LO**** pQCD**

-    Parton distribution functions

-     Fragmentation functions

****

- zc

- IS nuclear broadening

- IS energy loss

- FS energy loss

## The Reaction Operator Approach to Multiple Elastic and Inelastic Scatterings

**The ****Reaction Operator Approach ****to Multiple**** Elastic ****and ****Inelastic ****Scatterings**

- Reaction Operator = all possible
- on-shell cuts through a new Double Born interaction with the propagating system

- +

- +

**For the ****elastic**** scattering **
**case  illustrated here :**

**M.Gyulassy, P.Levai, I.V., Nucl.Phys. B594, (2001); Phys.Rev.Lett. 85, (2000).**

**For the ****inelastic**** scattering case:**

## The Center of Mass Energy Systematics 

**The Center of Mass Energy ****Systematics **
**of ****Mono-jet Tomography**** **

**I.V. and M.Gyulassy, Phys.Rev.Lett. 89 (2002)**

**?**

## Differential Comparison and Discussion 

**Differential**** Comparison and Discussion **

**I.V. and M.Gyulassy, Phys.Rev. Lett., 89 (2002)**** **

**PHENIX**

**STAR**

- charged

** ****There is ****no need (room)****  for ****“down-and-up”**** **
**   ****models.**

**a) The ****hydro feedback**** at low p****T, ****See e.g.  **
**                                 **
** ****b) The ****baryons. ****See e.g.**

_**Known issues**_

** ****Z.Lin,C.M.Ko,S.Pal, nucl-th/0205056**

** ****The shape of ****R****AA****, R****CP**  **is a function of the **
**  ****interplay**** of the ****known nuclear effects**.

-  **One needs to compute the energy loss for the **
**  ****non-asymptotic**** RHIC**)

## Stability of the Centrality Dependence of RAA in GLV E-loss 

- Stability of the Centrality Dependence of RAA in GLV E-loss

**Full numerical**
**calculation**

**X.N.Wang, nucl-th/0305010**

**M.Gyulassy, I.V. and X.N.Wang, Phys.Rev.Lett. 89 (2002)**

**a) ****Gyulassy-Wang****: transverse gluon **
**     ****dynamics is neglected **
**b) ****Baier *****et al.***** (BDMPS)****: thick medium, **
**     ****large number of  scatterings, LPM only **
**c) ****Zakharov; Wiedemann****: thick medium, **
**     ****path integral formalism    **
**d) ****Gyulassy *****et al.***** (GLV)****: thin media with few**
**     ****scatterings. Low order correlations **
**     ****(few scattering centers) dominate.   **

## Impact Parameter Dependence of the Cronin Effect at RHIC

- Impact Parameter Dependence of the Cronin Effect at RHIC

**I.V., nucl-th/0302002, Phys.Lett.B 562 (2003)**

**The Cronin ****peak**** is located at **

**Antishadowing plays an important role for **

**- an ****approximately constant**

**contribution (experiments can constrain it)**

**The ****maximum Cronin enhancement**** for the **
**total invariant cross section is ****20%**** **

**The Cronin effect ****decreases**** in ****going from **
**central  to peripheral  reactions  **

_**In contrast:**_

** ****since**

**D.Kharzeev et al., PLB 561 (2003)**

**If**** it is initial wave-function**

**I.V. and M.Gyulassy, Phys.Rev.Lett. 89 (2002)**

## Experimental Resolution: Part 1

- Experimental Resolution: Part 1

## Multiple Elastic Scatterings  from Different Points of View

- Multiple Elastic Scatterings  from Different Points of View

**pQCD partonic level ****Glauber-Gribov**

## Medium-induced Jet Acoplanarity

- Medium-induced Jet Acoplanarity

**<|j********y****|>**** = **the mean transverse momentum of the
- hadron with respect to the jet axis in the plane
- perpendicular to the beam axis.

**<|k********y****|>**** = **the mean effective transverse momentum
- of the two colliding partons in the plane perp. to
- the beam axis (+FS contribution in d+Au).

**Credit:**** P.Constantin, J.Rak, **
**J.Lajoie, C.Ogilvie **
**M.Tannenbaum**
**G.Altarelli, R.K.Ellis, G.Martinelli, **
**Phys.Lett. 151B (1985)**

**Projection**

## Experimental Resolution: Part 2

- Experimental Resolution: Part 2

**I.V., J.W.Qiu, to be published**

**True**** monojets?**

_**Regge-Muller cut diagrams**_

**T.Hirano and Y.Nara, nucl-th/0301042**

## Measures of Energy Loss

- Measures of Energy Loss

- Preliminary

- From GLV energy loss

**STAR correlations Phys.Rev.Lett.**

**Correspondence can be **
**established between the **
**different ****measures**** of ****E-loss**

## Conclusions

**Conclusions**