# Presentation: 842610

## Wolf Gerrit Holzmann

***Probes of High-Energy Nuclear Collisions, June 9 – 16,  2006***

**Wolf Gerrit Holzmann**
**for the                     Collaboration**

- High (and intermediate) pT Physics in PHENIX

## The Big Picture

**Today’s Cold Universe**

**The Big Picture**

**Can we learn about the history of the universe from Heavy Ion Collisions?**

## Strongly Interacting Matter at RHIC

**Strongly Interacting Matter at RHIC**

**Evidence for **
**strongly **
**interacting **
**high energy **
**density matter **
**is compelling!**

## How can we probe the properties of

**strongly interacting partonic matter **
**at RHIC?**

**Jets are remarkable probe **
**for medium:**
**   ****Auto-generated early**
**   ****Calculable (pQCD)**
**   ****Calibrated**
**   ****Accessible statistically**
**      ****at RHIC via correlations**

**Strongly Interacting Matter at RHIC**

## The Game Plan

- p+p

- d+A

- A+A

**The Game Plan**

**Operational Strategy**

## p+p and d+Au jet correlations:

***p+p and d+Au jet correlations:***

**Clear (di)jet peaks observed in correlation function**
**Jet properties in p+p and d+Au very similar**

**Jet Correlations well Calibrated**

## Jets via:

***Jets via:***
***Two Particle Correlations***

***Jets via:***
***Nuclear Modification Factor***

**Jet Modification in Au+Au**

**Strong jet modification observed in Au+Au**

**What are the next steps?**

- _[Phys. Rev. ](http://link.aps.org/abstract/PRL/v96/e202301)__[Lett](http://link.aps.org/abstract/PRL/v96/e202301)__[. 96, 202301 (2006)](http://link.aps.org/abstract/PRL/v96/e202301)_

## Status report of PHENIX efforts follows

** ****interactions of jets with medium**
** ****particle species dependence of jet modification**
** ****system size dependence of jet modification**
** ****energy calibration: (direct ********-jet correlations**

_***Status report of PHENIX efforts follows***_

**Need to address issues:**

**It is time to become quantitative!**

***Prerequisite: Better experimental insights into ***
***                       ******mechanistic details of jet modification ***

**The Next Steps, ....**

## The Need for Decomposition

**The Need for Decomposition**

***Asymmetries and Anisotropies present ***
***in Au+Au Correlation Functions***

**Need to Reliably Decompose Flow and Jet Signals!**

## Decomposition of Flow and Jet Signals

**    ****a****0**** is obtained  without putting any **
**   ****constraint on the Jet shape by requiring**

**Two source model :  Flow (H) & Jet (J)**

***N.N. Ajitanand et al.***
***Phys. Rev. C 72, 011902 (2005)***

**High pt**** particle constrained**
**perpendicular to RP  **

- Constraint byte

**Decomposition of Flow and Jet Signals**

**Subtraction**

**Extinction**

**Reliable Decomposition of Flow and Jet **
**Signals via two separate Methods**

## Test of Ansatz

**Test of Ansatz**

**Simulation**

**Strong Away-Side Modification in Au+Au Revealed via Both Methods**

***Phys. Rev. C 72, 011902 (2005)***

## Possible Modification of Jet Topology

**Can we use jets to probe the equation of state at RHIC?**

## Three Particle Correlation Method

*Same Side*

*Away Side*

*p2n, p3n*

**Three Particle Correlation Method**

## 3-particle Correlation Function

***3-particle Correlation Function***

**Uncorrected, NO v****2**** subtraction**

******= 0**

- Cent=0-5%

**Three Particle Correlations**

**Further study needed to distinguish between cone or deflected jets**

**PHENIX *****Preliminary***

**PHENIX Acceptance**

***See N.N. Ajitanand’s talk***

**Indication of abnormal jets  without harmonic removal**

## Large p/ ratio

***Large p/************ ratio***

***Protons appear to scale ***
***with N******coll***
***Mesons are suppressed***

***Are jet associated baryons modified by the medium?***

**Particle Species Dependent Jet Modification?**

- _[Phys. Rev. C 72, 014903 (2005) ](http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PRVCAN000072000001014903000001&idtype=cvips&gifs=Yes)_

_**Phys.Rev.Lett. 91, 172301 (2003)**_

## Meson vs. Baryon associated partner (for fixed Hadron trigger)

**Jet Associated Identified Partner Particles**

***Yes, jet associated baryons are modified by the medium***

## Meson vs. Baryon associated partner (for fixed Hadron trigger)

*Meson** vs. **Baryon** associated partner (for fixed Hadron** **trigger)*

***Different p******T****** trends of associated meson and baryon yields***

**Jet Associated Identified Conditional Yields**

## Meson vs. Baryon associated partner (for fixed Hadron trigger)

*Meson** vs. **Baryon** associated partner (for fixed Hadron** **trigger)*

**Jet Associated Baryon to Meson Ratio**

***Does the medium modify the chemistry within the jet?***

## Meson vs. Baryon trigger (for fixed Meson partner)

*Meson** vs. **Baryon** trigger (for fixed **Meson **partner)*

**Fully Identified Jet Functions**

***Trigger particle species dependent jet modification ***
***at intermediate p******T****** ?***

## What about Higher pT Range, ...

***Trigger:       2.5<pT<4 GeV/c***
***Associated: 1.7<pT<2.5 GeV/c***

***At higher p******T ******the story seems different ?***

***see A. Sickles’ talk***

## Mechanistic Details of Jet Modification

***What are the relative influences of:***
***Energy-density***
***Path-length (L, L******2******, L******a******)***

**nucl-ex/0409015**

***Need to look at problem in several ***
***different ways to pin down mechanistic***
***details!***

**Mechanistic Details of Jet Modification**

## Complementary Approach: Varying System Size

**dN****ch****/d******** very similar for Au+Au and Cu+Cu at the same N****part**** !**
**At RHIC almost all transverse energy **
**goes into particle production**
**Complementary opportunity for jet-tomography:**
**-> fix energy density**
**-> vary path length  **

**nucl-ex/0409015**

**Complementary Approach: Varying System Size**

## 

***Energy density major actor!***

********

***Jets via:***
***Nuclear Modification Factor***

***Jets via:***
***Two Particle Correlations***

**Jet Modification in Au+Au and Cu+Cu**

## Jet Modification in Cu+Cu at higher pT

- 30-40% Au+Au
- Npart = 114

- 0-10% Cu+Cu
- Npart = 98

**At higher pT still striking similarities between jet functions for Au+Au and Cu+Cu at the same Npart!**

**J. Jia, PANIC2005**

## Similarity between Cu+Cu and Au+Au for equivalent Npart also seen for production of several other identified particles

***Similarity between Cu+Cu and Au+Au for equivalent N******part ******also seen for production of several other identified particles***

***It will be interesting to see the identified jet correlations in Cu+Cu...***

**Particle Production in Au+Au and Cu+Cu**

**C.M. Vale, WWND2006**

## (inclusive! )-jet correlations

**(**_**inclusive!**_** ********)-jet correlations**

**Need to decompose correlations to **
**disentangle (direct********)-jet correlations, ...**

**En Route for ********-jet Correlations, ...**

***For new results ***
***on single particle (!)***
***direct *********
***see T. Isobe’s talk***

## Summary

##  13 Countries;  62 Institutions;  550+ Participants*

*** ******13 Countries;  62 Institutions;  550+ *****Participants*********

***as of March 2005**

## Backup

## Slide 30

## Strong centrality dependent modification 

**nucl-ex/0507004**

***Strong centrality dependent modification ***
***of away-side jet in Au+Au***

***Away-side peak consistent***
***with mach-cone scenario***
**nucl-th/0406018 Stoecker**
**hep-ph/0411315 Casalderrey-Solana, et al **
***Not the only explanation:***

***What is (are) the mechanism(s)***
***for modification ?***

**Cherenkov gluon radiation: nucl-th/0507063 **
**Koch, Majumder, X.-N. Wang**

**Jets and Flow couple: hep-ph/0411341 **
**Armesto,Salgado,Wiedemann**

## Slide 32

## Baryon yield dependence 

***DELPHI***

***Baryon yield dependence ***
***consistent with jet physics***
***in e-e collisions***

## PID analysis is an extension 

- Analysis performed with the PHENIX detector

- PID analysis is an extension
- of  **PRL. 91, 182301, 2003**  (TOF)
-   _Differences_
-   PID analysis with EMCAL (PbSc)
-     (6 sectors) + TOF detector
-   High statistics
-   detailed centrality and pT results

- New PID results for

**PHENIX EMC (PbSc)**

- EMC  timing resolution: ~400 ps

- TOF  timing resolution: ~120 ps

## Two Source Model

***Two Source Model***

## Broadening of away-side jet observed in central/semicentral Cu+Cu collisions

**PHENIX Preliminary**

***Broadening of away-side jet observed in central/semicentral Cu+Cu collisions***

## Slide 37