# Presentation: 556539

## Heavy-Ion Results from PHENIX

**Martin L. Purschke, Brookhaven National Laboratory**
**for the PHENIX Collaboration**

**RHIC from space**

**Just in case you have forgotten where we are**

- C.Woody, IEEE MIC, 10/20/04

## What you’ll hear

**Heavy-Ion: Run 6 is a pp spin run, no heavy-ion component (a first), so there will be little about Run 6 in here, but:**
**There will be a pp/spin talk this afternoon by Abhay**
**Busy year for PHENIX: more than 800 new preliminary and final figures**
**Obviously just a teaser here, I’ll point out posters you should look at as we go along**

**Selected Topics:**
**Direct Photons**
**Nuclear Modification factors**
**J/******** suppression (brief, we had a workshop here)**
**Flow results **

- C.Woody, IEEE MIC, 10/20/04

## The PHENIX Detector

- J/e+e-

- J/************

- C.Woody, IEEE MIC, 10/20/04

## PHENIX Datasets

**p+p**

**d+Au**

**Au+Au**

**Cu+Cu**

**200 GeV**

**130 GeV**

**62.4 GeV**

**22.4 GeV**

**Run 1 - 3**

**Run 4 - 5**

**Run 6 (?)**

- C.Woody, IEEE MIC, 10/20/04

## 2005 was a good year...

**Advances in data logging and the implementation of “multi-event buffering” increased or Event rate dramatically in Runs 4 and 5**

**CuCu    200GeV        1.08 Billion Events       157TB on tape**
**CuCu   62.4GeV         630 Million Events        42TB on tape**
**CuCu      22GeV           48 Million Events          3TB on tape**
**p-p        200GeV         6.8 Billion Events      286TB on tape**
**                                                                    ****------------------------------**
**                                                                        ****488 TB**** on tape for Run 5**

**And we could continue this in Run 6.**

- C.Woody, IEEE MIC, 10/20/04

## Reaching out to High pT (0 spectra) 

**New Run4 Data**

_**Cu+Cu 200 GeV**_
- 2.2 B sampled

_**Au+Au 200 GeV**_
-  Luminosity 241b-1 (sampled)
- 1.5B events

**New Run5 Data**

- C.Woody, IEEE MIC, 10/20/04

## Direct Photon Detectors

**Central spectrometer arms ****|**********| < 0.35**
-  0 via 0 
- EMCal
- Lead scintillator calorimeter (PbSc)
- Lead glass calorimeter (PbGl)
- Charged particles
- DC, PC
- e**±** ID
- RICH

- C.Woody, IEEE MIC, 10/20/04

## Direct Photons

**Get “clean” inclusive-photon sample**
**Reconstruct  *****p*****T**** spectrum of ************ and ******** mesons through invariant mass, use *****m*****T**** scaling for ********’, ********, ...**
**Given those distributions, calculate number of decay photons that we would see (through simulations), derive what we call “background”**
**Subtract those photons from the measured inclusive photon spectrum**
- that means subtracting 2 large numbers, errors
**Usually shown as a “double ratio”**

****** ****/ ************(measured)**

****** ****/ ************(background)**

**(has some advantages since *****some***** syst. errors cancel out)**

**Direct Photon yields started out as one of the giveaway signals of a QGP**
**Photons probe the initial state of the reaction, no strong interactions, etc**
**Problem: there are so many *****other***** photons...**

- C.Woody, IEEE MIC, 10/20/04

## Direct Photons Au+Au 200GeV

- Expectation for *N*coll scaling of direct photons

- holds for all centrality classes

**Photons don’t strongly interact with medium**
**Allow test of *****N***coll** scaling for hard processes**
**Important for interpretation of observed high-*****p***T** hadron suppression**

**PRL 94, 232301**

- C.Woody, IEEE MIC, 10/20/04

## Limitations at Low pT

**Photons start to make a discernable signal in the scintillator only at about 1GeV**
**Until recently, no direct photon data at low p****T **

**PRL 94, 232301**

- C.Woody, IEEE MIC, 10/20/04

## New Approach (outline)

**New Approach (outline)**

**Start from Dalitz decay**
**Calculate invariant mass distribution of Dalitz pairs**
**Mass spectrum of DP’s:**

******0**

****

****

******0**

****

**e****+**

**e****-**

********

**Lowest bin gives you a reference for the yield**
**You know what to expect from **0 **and** ******Dalitz**
**ratio of next bin/reference lets you disentangle the direct ******** conversion contribution**
**Excess -> direct photons**

- C.Woody, IEEE MIC, 10/20/04

## Current State of the Art

**This is the Run 4 low p****T**** result from the “conventional” method**

**This was just a rough outline, lots of details in the poster Session**

- C.Woody, IEEE MIC, 10/20/04

## Nuclear Modification Factors

**yield in A+A/number of equivalent p+p collisions**

**yield in p+p**

**R****AA**** =**

**Quantifying a medium effect:**

**R****AA****  is ~1 if there is no medium effect, i.e. heavy-ion collisions are nothing more than an overlay of many p-p collisions**
**different from 1 if there are medium effects**

- C.Woody, IEEE MIC, 10/20/04

## RAA for Au+Au 200GeV

**New Run4**** ****D****ata**

**Au+Au – 200 GeV**

- C.Woody, IEEE MIC, 10/20/04

## RAA for 0, , and direct 

**New Run4 ********0 ****D****ata**

**Direct photons are not suppressed**
******0****, ********are suppressed even at high p****T**
**Suppression is flat at higher p****T**

- C.Woody, IEEE MIC, 10/20/04

## Reaction System Dependence

**Au+Au        Cu+Cu**

**********

***Au+Au 30-40 %, ******N******Part ******= 114.2****** ***

***Cu+Cu 0-10 %, ******N******Part ******= 98.2****** ***

**Centrality selections have been matched to roughly give the same number of participants for Au+Au and Cu-Cu**

**Similar suppression at similar values of N****part**
**One would naively assume that medium effects scale with N****part,****, independent of the reaction system**
**Systematic studies now possible and under way**

- C.Woody, IEEE MIC, 10/20/04

## J/ Suppression (upshot)

**Energy and gluon density larger than at the SPS by a factor of ~3**
**Yet the suppression is not dramatically different than what was observed by NA50**
**Models successful at SPS energies tend to “*****overestimate the suppression”, *****especially those without recombination**
**Models with recombination are in reasonable agreement with the data (but can’t explain all trends simultaneously)**
**New model “Sequential Charmonium Dissociation” -- covered at this meeting and the recent Satz-Fest**

- C.Woody, IEEE MIC, 10/20/04

## Elliptic Flow or v2

**Elliptic Flow or v****2**

- _Reaction plane_

- X

- Z

- Y

- Px

- Py

- Pz

**In not 100% central collisions, the nuclear overlap region is an ellipsoid**
**The pressure gradient is higher is the direction of the short axis**
**gives rise to a momentum anisotropy**
**v****2**** is defined as the 2****nd**** coefficient of the angular dependence of the momentum distribution**

- C.Woody, IEEE MIC, 10/20/04

## v2 vs pT for Charged Hadrons

- PHENIX : PRL 91, 182301 (2003)

**Large elliptic flow at RHIC**
**Was found to be consistent with hydrodynamics with rapid thermalization, ******** ~ 1 fm/c**

- C.Woody, IEEE MIC, 10/20/04

## Baryon/Meson v2 

**Meson v****2**

**Baryon v****2**

***KE******T****** ~ m******T****** – m******0****** at y ~ 0***

- K0S,  (STAR) : PRL 92, 052302 (2004)
-  (STAR) : PRL 95, 122301 (2005)
- , K, p (PHENIX) : preliminary

**Scaling holds up to KE****T**** = 1 GeV**
**Meson/Baryon v****2**

- C.Woody, IEEE MIC, 10/20/04

## Mesonv2 

** ******** ****meson behaves like a meson (i.e, number of quarks), not according to its mass**
**“****handle” for elliptic flow seems to be the parton, not the hadron**
**strong indication of partonic degrees of freedom**

- C.Woody, IEEE MIC, 10/20/04

## Hint of Charm Meson Flow

- V. Greco, C. M. Ko, R. Rapp: PL B 595, 202 (2004)

*e v**2** vs p**T*

- C.Woody, IEEE MIC, 10/20/04

## Summary

**That’s all I can cover in 20 mins**
**new results from direct photons, nucl. Modification factors (some awaiting better p-p reference data from Run 6)**
**J/******** suppression similar to SPS despite much higher density, favors recombination/regeneration models**
**Nice KE****T**** scaling for v2/n, seems to indicate partonic degrees of freedom**
** ******** ****meson behaves like a meson, not according to its mass**
**hint that charm and perhaps even bottom quarks flow**
**ok, this is just a teaser as I said**
**Go out an look at the posters. New results galore. Enjoy.**

- C.Woody, IEEE MIC, 10/20/04

## PHENIX Posters

**Torsten Dahms, Therminator: measurement of thermal photons via conversion  pairs in PHENIX at RHIC**
**Kentaro Miki, Measurement of pi0 and Direct photon v_2 in \sqrt{s_NN} =200GeV Au+Au collisions at RHIC-PHENIX**
**Masahiro Konno, Identified Charged Hadron Production at RHIC-PHENIX**
**Astrid Morreale, Accessing the Gluon's Polarization via Charged Pions in PHENIX**
**Alberica Toia, Measurement of low mass dielectron continuum in sqrt  s_NN=200GeV Au-Au  collisions in the PHENIX Experiment at RHIC**
**Anne Sickles, Particle Species Dependence of Jet Fragmentation in Au+Au  Collisions at PHENIX**
**Christine A. Aidala, Measurement of the Transverse Single-Spin Asymmetry for Mid- rapidity Production of Neutral Pions in Polarized p+p Collisions at  200 GeV Center-of-Mass Energy **

- C.Woody, IEEE MIC, 10/20/04