# Presentation: 593105

## Heavy Ion Collisions at Collider EnergiesInsights from PHENIX

- ICPAQGC

**Results from run 2000  **
**~ 3.5 10****6**** minimum bias Au-Au events at ********s****NN**** = 130 GeV **

**Global observables: ****	****E****T  ****and  N****ch**
**Hadrons: ****	****	****yields and spectra**
**	****	****	****suppression of high p****T**** hadrons**
**Electron:****	****	****inclusive spectra**

**Tue. Session 6****	****David Silvermyr: ****	****Charged Particle Multiplicity in Au-Au Collisions at RHIC**
**Tue. Session 7 ****	****Julia Velkovska: ****	****Identified Charged Hadron Production at RHIC**
**Fr.  Session 19****	****John Sullivan: ****	****Global Observables and Identified Hadrons in PHENIX**

**Other PHENIX talks:**

## Pioneering High ENergy Ion EXperiment

**    ****	****11 ****	****  Countries          51 ****	****  Institutions  400+ Collaborators**

- India

- Axel Drees

## PHENIX Physics Capabilities

**2 central arms: **
**	****electrons, photons, hadrons**
**charmonium  J/********, ********’ *********e**********e*******
**vector meson  ******** *********e**********e********* **
**high p****T****           **************************
**direct photons**
**open charm **
**hadron physics**
**2 muon arms:**
** ****	****muons**
**“****onium” J/********, ********’, ******** **************************
**vector meson ******** **************************
**open charm**
**combined central and muon arms:**
-  		**charm production  ****	*****DD **********e*******

**global detectors **
**	****forward energy and multiplicity**
**event characterization**

**designed to measure rare probes:**** ****	****+ high rate capability & granularity**
**	****	****	****	****+ good mass resolution and particle ID**
**	****	****	****	****-  limited acceptance****	**

**Au-Au   &   p-p spin**

- Axel Drees

## PHENIX Installation During Au-Au Run 2001

**collaborator**

**EMCAL**

**MuID**

**MuTrk**

**RICH**

**PCs**

**TEC/TRD**

**DC**

**TOF**

**BBC**

**MVD**

**ZDC**

- Axel Drees

## West Arm
tracking:
DC,PC1, PC2, PC3
electron ID:
RICH, 
EMCal
photons:
EMCal

**West Arm**
**tracking:**
**DC,PC1, PC2, PC3**
**electron ID:**
**RICH, **
**EMCal**
**photons:**
**EMCal**

**East Arm**
**tracking:**
**DC, PC1, TEC, PC3**
**electron & hadron ID:**
**RICH,TEC, TOF, EMC**
**photons:**
**EMCal**

**PHENIX Setup During Year 2001 Run**

**full heavy ion program and first spin physics**
**	****including electron & muon pairs**

**South Arm**
**tracking:**
**MuTr**
**muon ID:**
**MuID**

**Other Detectors**
**Vertex **
**        ****& centrality:**
**ZDC, BBC,**
**MVD**

**end of Au-Au run Nov. 26**
**  ****~200 10****6 ****Au-Au sampled**
**5 weeks of p-p run**
**           ****December/January**

- Axel Drees

## PHENIX Year 2000 Configuration

**Physics Results Presented in this Talk**

**Global Observables**
**event characterization**
**ZDC, BBC**
**transverse energy**
**PbSc**
**charged particle multiplicity**
**PC1 & PC2**

**Neutral Pions**
**two photon mass**
** ****EMCal **
**(east & west)**

**Charged Particles**
**tracking & momentum**
**DC, PC1, PC3 **

**Charged Hadrons**
**tracking & momentum**
**DC, PC1, PC3 **
**hadron ID**
**TOF**

**Inclusive Electrons**
**electron ID:**
**RICH, EMCal**
**tracking & momentum**
**DC and PC1**

- Axel Drees

## Event Characterization

**peripheral**

**central**

**correlation of zero degree energy (ZDC)**
**	****     ****with multiplicity of produced particles (BBC)**
**cover 92********4% of nuclear cross section in trigger**
**select event classes with certain fraction **
**	****	****of cross section **
**Glauber model simulation of collision geometry ****	****                    ****	****and ZDC&BBC responds **

**5%**

**5-10%**

- Axel Drees

## Transverse Energy and Energy Density

**Transverse Energy and Energy Density**

**significantly above expected critical density**
**	****	****lattice:    ********c**** ~ 0.6 - 1.2 GeV/fm****3**
**> 1.5 increase compared to CERN (********0 ****~ 1 fm)**

*Phys. Rev. Lett. 87, 52301 (2001)*

- Bjorken estimate for initial energy density

**E****T**** measured**

**formation time: 0.2 - 1 fm**

****** ****~ 3.2 GeV/fm****3**

**Initial condition: energy density**

- Axel Drees

##  Transverse Energy and Particle Production

** ****Transverse Energy and Particle Production**

**E****T**** increases faster than number of participants **
**E****T****/N****Part**** larger than at CERN **
****** ****E****T******** /********N****ch********  ~ 0.8  independent of centrality **

*Phys. Rev. Lett. 87, 52301 (2001)*

**(PHENIX excludes baryon mass,**
**        ****WA98 includes baryon mass)**

-  ET /Nch

**charged particle production increases**
**	****	****with centrality and ********s**

- Axel Drees

## Charged particle density increases by:   ~ 1.3 from peripheral to central collisions 
					    ~ 1.15 with s from 130 to 200 GeV 

**	****hard component more pronounced in central collisions and at higher ********s**
**Ansatz II: gluon saturation**  (all particle production from parton scattering)
- 	**consistent with data:  initial energy density   ******** ~ 18 GeV/fm****3**

**Charged particle density increases by:   ~ 1.3 from peripheral to central collisions **
**	****	****	****	****	****    ****~ 1.15 with ********s from 130 to 200 GeV **

**Multi-Particle Production**

- Eskola, Kajantie, and Tuominen:  hep-ph/0009246
- Kharzeev, Nandi:  nucl-th/0012025

- with quenching

- no jet quenching

- saturation

- e.g.   HIJING

*Phys. Rev. Lett. 86, 3500 (2001)*

**preliminary**
**go see D.Silvermry tomorrow**

- Axel Drees

## PHENIX Hadron Identification

**Charged hadrons via TOF**
**effective resolution  ******** ~ 100 ps **

******0**

**m******

**2.00 < pt < 2.5 GeV**

**Neutral mesons via EMCal**
**two independent measurements:**
**- Pb scintillator**
**- Pb glass **

- Axel Drees

## Hadron Yields as Function of Centrality

**Hadron Yields as Function of Centrality**

**moderate 20% increase of pions**
**larger increase by factor ~1.7 **
**	****for kaons, protons and anti-protons**

**significant fraction of dN/d******** increase **
**	****due to K, p and ********p increase **

**large number of **
**	****produced p and********p **
**    ********p/p ~ 0.7**

-  1.2

-  1.7

- Axel Drees

## Baryon Density at Mid Rapidity

- substantial net baryon density at y = 0
- indication for increases with centrality
- 		 more stopping in central collisions
- 30% of net baryon density observed at CERN

- (NB: <25% p from  decays included)

- large number of produced baryons and anti-baryons
- sum of baryons + anti baryons increase slightly from SPS to RHIC

**~100**

**~90**

**total baryon density**

**PHENIX**
**Au-Au**

**SPS**
**Pb-Pb**

**central collisions**

- Axel Drees

## MT Spectra: Large Radial Flow

- Hydro+Cascade
- 	D. Teaney et al.

**soft physics up to **
**	****p****T**** ~ 3 GeV?**

- slope of  transverse mass spectra
- 	increases with particle mass
- pions and anti-protons well described by  Hydro+Thermal model

****** ****~ 0.6c  T~130 MeV**

- Axel Drees

## Transverse Momentum Spectra of Hadrons

**excellent agreement between charged and neutral pions !**
**pion and proton spectra from 0.5 to 3.5 GeV**
**(anti)proton yield increases above  pion yield**

**combine ************  with ********0**** for maximum p****T ****coverage**

- Axel Drees

## Nucleon to Pion Ratios and Soft to Hard Transition

**p/******** rising with p****T**** up to 3 GeV **

**empirical determination **
**of soft/hard transition at ISR**

**ISR  ****	****     p-p****	**** soft/hard transition below 2 GeV **
**RHIC   Au-Au****	**** soft/hard transition above 3 GeV?**

**particle ratios have **
**different p****T**** dependence **
**for soft and hard component**

- Axel Drees

## Other PHENIX Preliminary Results on Hadron Production

**Other ****PHENIX**** ****Preliminary**** Results on Hadron Production**

**Gamma Distribution Calculation**

**<P****t****> (GeV/c)**

**Centrality:**
**0-5%**

**charge and pt fluctuations**

**HBT**

**elliptic flow**

**particle ratios and spectra**

**see J.Velkovska’s talk on Tuesday and**
**          ****J.Sullivan’s talk on Friday for details **

- Axel Drees

## interpolate pp data to 130 GeV
scale by number of binary collisions to Au-Au

pion reference scaled by 1/1.6  (/h ratio from ISR)

**interpolate pp data to 130 GeV**
**scale by number of binary collisions to Au-Au**
**pion reference scaled by 1/1.6  (********/h ratio from ISR)**

**Hard Scattering in Heavy Ion Collisions  **

**large momentum transfer ******** jets**

**power law spectrum**

******pp**** = d****2****N/dp****t****2**** = A (p****0****+p****t****)****-n**

**N-N reference spectrum for Au-Au**

- Axel Drees

## PHENIX first high pt data from RHIC 

charged particle spectra
at  ~ 0
 pT range to ~ 5 GeV
neutral pion spectra
two independent data sets
at  ~ 0 
out to 4 GeV
central (0-10%) and 
	peripheral (60-80%)
 Au+Au collisions

comparison to N-N reference
peripheral collisions
described at high pT
central collision
suppressed at high pT

**PHENIX first high p****t**** data from RHIC **
**charged particle spectra**
**at ******** ~ 0**
** ****p****T**** range to ~ 5 GeV**
**neutral pion spectra**
**two independent data sets**
**at ******** ~ 0 **
**out to 4 GeV**
**central (0-10%) and **
**	****peripheral (60-80%)**
** ****Au+Au collisions**
**comparison to N-N reference**
**peripheral collisions**
**described at high p****T**
**central collision**
**suppressed at high p****T**

**Suppression of High p****T**** Hadrons at RHIC**

** ****PHENIX**

*Phys. Rev. Lett. (2001) in print*

- Axel Drees

## nuclear shadowing at small x	  at RHIC  x ~ 2pT/s  < 0.02  
					  high pT mostly in anti-shadowing region	

initial state multiple scattering of partons:   “Cronin effect”

						modeled as pt broadening

**	****	****	****	****	********  ****high p****T**** mostly in anti-shadowing region****	**
**initial state multiple scattering of partons:   “Cronin effect”**
**	****	****	****	****	****	****modeled as p****t**** broadening**

**“****Ordinary” Nuclear Effects Modifying p****t**** Spectra**

**traditional analysis:**

- “anomalous” nuclear enhancement
-      	  > 1  above ~ 2 GeV/c

**Nuclear Modification Factor:**

**saturates at ~ 2 **
** ****above 2.5 GeV        **

**increase above 1**
**at 1.5 GeV **

- compiled by X.N.Wang

- Axel Drees

## Nuclear Modification Factor Au-Au to p-p

**Nuclear Modification Factor Au-Au to p-p**

**ratio exhibits characteristic features:**
**charged:**
**	****	****increases up to ~ 2 GeV**
**	****	****saturates at R****AA**** ~ 0.6**
**neutral pions:**
**	****	****~ constant at R****AA**** ~ 0.4**
**difference between ********0**** and h**
**large proton contribution at RHIC **
**estimate of systematic error **
**data: **
**	****charged****	****16 - 30 %**
**	********0**** ****	****21 - 35 %**
**<N ****binary****> ****	****    11 % **
**NN ref.****	****20 - 35 %**
**	****total****	****30 - 50 %**
**	****	****	****(p****T ****dependent)**

**within systematic errors:**
**R****AA**** < 1**

**PHENIX**

*Phys. Rev. Lett. (2001) in print*

- Axel Drees

## centrality dependence of charged particle production
full systematic available for 92% of interaction cross section
gradual change from central to peripheral
calculate RAA for 5 centrality bins 
                                (normalize to Nbinary and divide by N-N reference)

**centrality dependence of charged particle production**
**full systematic available for 92% of interaction cross section**
**gradual change from central to peripheral**
**calculate R****AA**** for 5 centrality bins **
**                                ****(normalize to N****binary**** and divide by N-N reference)**

- F. Messer, PHENIX, QM2001, updated

**Centrality Dependence of the Charged Hadron Suppression**

**PHENIX preliminary**

**PHENIX preliminary**

- Axel Drees

## Centrality Dependence of the Nuclear Modification Factor

**Centrality Dependence of the Nuclear Modification Factor**

**peripheral sample: “Cronin effect”? **
**continuos increase**
**increases above unity **
**	****but, at high p****t**

- peripheral

- central

**central sample: “high p****t**** suppression”**
**continuous modification of spectra**

******  ****p****t**** < 1.5 GeV                                       **
**increase of slope with centrality**
**increasing Kaon                                 contribution?**

****** ****p****t**** > 2.0 GeV**
**decrease of slope with centrality**
**expect opposite effect from ********p&p!!**

****** ****overall decrease of **
**yield relative to N****binary*************pp**
**systematic error large**

**PHENIX preliminary**

- Axel Drees

## Increasing Suppression of Charged Hadrons with Increasing pT 

**Increasing Suppression of Charged Hadrons with Increasing p****T**** **

**yield integrated above p****T**** cut**

**average p****T**** above p****T**** cut**

**yield/N****binary****  **
**decreases for 1.8 GeV cut**
**decreases faster for higher p****T**
**yield/N****part**** **
**increases for 1.8 GeV cut**
**similar to Nch**
**scales with Npart for 3.5 GeV cut **

**  ********p****T******** - p****T****min**
**decreases by ~50 MeV for 1.8 GeV cut**
**not due to proton contribution**
**slope mesonic spectra decrease faster **

**gradual onset of suppression **
**with centrality and p****T**

**PHENIX preliminary**

**PHENIX preliminary**

- Axel Drees

## Inclusive Electron Production

**contributions to electron spectra**
**photon conversions**
**Dalitz decays**
**vector meson decays**
**open charm decays**
**tune Pythia to all existing data**
**extrapolate ********cc**** ~ 350 ********b at 130 GeV**
**scale to central Au-Au with N****binary**

**excess above these contributions**

**large charm contribution above 1.0 GeV**
**consistent with data**

- Axel Drees

## Large Amounts of Results from PHENIX 

**global observables**
**Initial energy density > 4.6 GeV/fm****3**
**dN****ch****/d******** and dE****T****/d********  ******** hard+soft component or gluon saturation**
**hadron p****T**** spectra: soft physics**
**dN****baryon****/dy ~ 100 (baryon + anti-baryon)**
**hydro+thermal interpretation of p****T**** spectra ********  large radial flow**
**hadron p****T**** spectra: hard physics**
**p/********  increases up to 3.5 GeV to values above 1 ********  no sign of soft/hard transition **
**high p****T**** charged hadron and ********0  ****yield suppressed in central collisions **
**	****	****	****	****	********  ****different from Cronin effect and shadowing**
**continuous centrality dependence: peripheral ******** similar to Cronin effect **
**suppression sets in gradually for more central collisions**
**increasing centrality: decreasing relative yield with increasing p****T**
**increasing centrality: decreasing average p****T**** above 1.8 GeV**
**electron spectra**
**consistent with large charm cross section**

**3.5 10****6**** event in 2000 ********  ~200 10****6**** events in 2001 + pp data**

- Axel Drees

## Mean Transverse Momentum vs Centrality

**Mean p****T**** growing with N****part ****and mass - consistent with flow**
**(Anti) proton  ******** p****T**** ******** significant increase from pp collisions **
**The same relative increase from peripheral to central for all particles**

**20+/- 5 %  increase**

**20+/- 5 %  increase**

- Axel Drees