# Presentation: 354114

## Milestones at the PHENIX experiment at RHIC

- Máté Csanád, Eötvös University Budapest
- for the PHENIX collaboration

- Milestone #1: High pt suppression
- Milestone #2: The erfect fluid of quarks
- Heavy flavour
- Chiral dynamics
- Further results

## BNL Facility

**protons: Linac ******** Booster ******** AGS ******** RHIC**
**ions: Tandems ******** Booster ******** AGS ******** RHIC**

## The Plan circa 2000

**Use RHIC’s unprecedented capabilities**
- Large √s →
- Access to reliable pQCD probes
- Clear separation of valence baryon number and glue
- To provide definitive experimental evidence for/against Quark Gluon Plasma (QGP)
- Polarized p+p collisions → proton spin structure!
**Two small detectors, two large detectors**
- Complementary & overlapping capabilities
- Small detectors: BRAHMS and PHOBOS
- 3-5 year lifetime
- Large detectors: STAR and PHENIX
- Major capital investments
- Longer lifetimes
- Potential for upgrades in response to discoveries

## Since then ...

**Accelerator complex**
- 22 GeV (Au, Cu, p)
- 56 GeV (Au)
- 62 GeV (Au, Cu, p
- 130 GeV (Au)
- 200 GeV (Au, Cu, d, p)
- 410 GeV (p)
- 500 GeV (p)
**Science**
- 100 publications in Phys. Rev. Letters
- Major discoveries
**Future: RHIC-II and eRHIC**
- Key science questions identified
- Accelerator and experimental upgrade program underway

## Event geometry

**In these complicated events, we have a posteriori control over the event geometry:**
- Degree of overlap, number of participants (Npart)
- Orientation with respect to overlap (Reaction Plane)

**Central Au+Au**
**N****part****~300**

**Peripheral Au+Au**
**N****part****~****5****0**

**d+Au**

**p+p**

## PHENIX capabilities

**Central arm****, ****|y|<0.35****, ****Δφ=***π*
- Tracking: DC, PC and TEC
- Calorimetry: PbGl and PbSc (EMCal)
- Particle ID: RICH and TOF
**Muon arms****, 1.2<****|y|<****2.4, ****Δφ****=2***π*
- Tracking: 3 muon tracker
- Identification 5 detection planes
- Front absorber to stop hadrons
**Global detector****s**
- BBC, MVD
- Centrality, vertex, reaction plane
**Physics**
- Charged hadrons ( *π*±, K±, etc.)
- Photons, direct or decay (→ η , *π*0)
- Light mesons φ, ω and η
- Single leptons → heavy flavor
- Di-leptons → heavy flavor, J/Ψ

## Detector upgrades

**Detector upgrades**

**2006**
- Aerogel
- Hadron-Blind Detector
- Reaction Plane Detector
- Time Of Flight West
- Muon Piston Calorimeter
**2007 – 2009**
- Silicon Vertex Tracker
**2008 – 2011**
- Forward Vertex Tracker
- Nose Cone Calorimeter

## The PHENIX Collaboration

## A PHENIX event

## Run-7 Au+Au: major success!

**+ Upgrades: RXNP, TOF-W, MPC, HBD**

## Milestone #1: jet suppression

**Nuclear modification factor: **
**	****Measured in Au+Au, reference: p+p**
**High p****t**** particles suppressed!**
**Counter-probe: d+Au → Medium effect (not color gl. cond.)**
**2 PRL covers**

**Au+Au**

**d+Au**

## Systematic suppression of π0

**Appr. c****onstan****t ****for p****T**** > 4 GeV/c for all centralities**
- PQM (Loizides) hep-ph/0608133:	6 ≤ q^ ≤ 24 GeV2/fm
- GLV (Vitev) hep-ph/0603010:	1000 ≤ dNg/dy ≤ 2000
- WHDG (Horowitz) nucl-th/0512076:	600 ≤ dNg/dy ≤ 1600

**Phys.Rev.C76:034904,2007 **

## Photons shine, Pions don’t

**No direct photon suppression until 14 GeV**
- Decreasing trend at >14 GeV
- Isospin, shadowing and energy loss, see F. Arleo, hep-ph/0601075
**S****uppression**** of *****π*****0**** stays nearly constant**** ****up to 20 GeV/c**
**Direct photons are not inhibited by hot/dense medium**

## J/Ψ suppression in Au+Au

**J/****Ψ**** ****suppression**** in Au+Au**

**Even J/ ****Ψ**** suppressed!**
- beyond extrapolations from cold nuclear matter effects
**R****AA**** ~ 0.3 for central collisions**
**Larger suppression at |y|>1.2**

**Phys. Rev. Lett. 98, 232001 (2007)**

## Milestone #2: The perfect fluid

**Milestone #2: The perfect fluid**

**Momentum distribution axially symmetric?**
**Azimuthal angle w.r.t. reaction place**
**Elliptic flow v****2****: azimuthal asymmetry**
- Measures collective behavior
- Zero v2 for a rare gas
- Hydrodynamic behavior: v2 > 0

**nucl-th/0512078**

**Δ****φ**

**Reaction plane**

## Top Story 2005

**According to the American Institut of Physics the top physics story in 2005 was the discovery of the perfect liquid**

## Perfect fluid of quarks

**Relevant variable: not p****t****, but transverse kinetic energ KE****t**
**Elliptic flow scales with number of constituent quarks!**
**Degrees of freedom: quarks?**

**PHENIX Collaboration, Phys.Rev.Letters 98:162301, 2007**

## Even d, D and Φ flow

**Even d, D and ****Φ**** flow**

- Strange and even charm quarks participate in the flow
- v2 for the φ follows that of other mesons
- v2 for the d follows thatof other barions
- v2 for the D follows that of other mesons

**nucl-ex/0703024**

## Heavy flavour

**Heavy flavour**

**Electrons from heavy flavour measured**
**Even heavy flavour is suppressed**
**Even heavy flavour flows**
**S****trong coupling of charm****+bottom**** to the medium**
**S****mall charm****+bottom**** relaxation time in medium and small viscosity**

## Signal of chiral dynamics

**S****ignificant excess at ****   ****m****ee****<**** ****1GeV/c **** in ****Au+A****u**
**Not in p+p**
**Not in peripheral Au+Au**
**Present in central Au+Au**
**Enhancement of ****η****’, ****η****, ****ω****?**

- arXiv:0706.3034 [nucl-ex]

## Restoration of chiral symmetry?

**Prediction: mass of ********’ decreases in hot and dense matter due to  U****A****(1) symmetry restoration**
**Idea: measure ********(m****t****) at low momenta!**

- Hot and dense matter:
- Modified ’ mass
- 
- Enhanced ’ production
- Decay:
- ’++ +- (0+++−)+++−
- with long lifetime
- Average  pt: 138 MeV
- 
- More non interacting ’s at 138 MeV
- (mt) measures fraction of interacting ’s
- 
- Hole in (mt)

**nucl-ex/0509042**

**PHENIX PRELIMINARY**

## Three particle correlations

**Two angles:**** ΔΦ**** and ****Δ****Θ**
**Simulations: jet deflection and Mach structures**
**Data****: compatible with**** Mach cone like structure**
**U****nderlying v****2**** contribution not subtracted**** yet**

## 3D two-pion source imaging

**A new technique successfully applied**
**Two-pion correlation functions ↔ source functions**
**Distribution of pair separation measured**
**Information on hadronization**
**In LCMS: expected elongation in out (x) direction**
**Excess: elongation on the x and z axis; why?**
**Model-dependent answer: Resonance decays and ****Δτ****=2fm/c**

**PHENIX PRELIMINARY**

## Critical phenomena

**Density correlations measured**
- Well described by Negative Binomial Distributions
- Interpolating between Bose-Einstein and Poisson
- Basic parameter k ↔ ξ ↔ susceptibility χω=0~|T-Tc|-1
**Parameter ****ξ**** monotonical in temperature**
**Not at the critical point!**
**Local max. at N****part****≈90**
**Critical phenomenon?**
- in Landau-Ginzberg
- framework

## Summary and conclusions

**High p****t**** hadrons suppressed**
**	****→ **_**strongly interacting matter**_
- Even J/Ψ and heavy flavour, photons not
**Flow effects observed, quark number scaling**
**	****→ **_**perfect fluid of quarks**_
- Scaling valid for *π*, K, D, φ, p, d
- Even charm and bottom flow
**Details being explored**
- Source geometry
- Critical phenomena

## Thank you for your attention

**Thank you for your attention**

## System size dependence of π0 RAA

**R****AA**** is the same in Cu+Cu and Au+Au at equal N****part**

## J/Ψ production in p+p collisions

**10 times more statistics ****than**** previous measurement**
- better constraints on rapidity and pt spectrum
- better reference for the nuclear modification factor

**Phys. Rev. Lett. 98, 232002 (2007)**

## J/Ψ RAA vs pT in Au+Au

**Phys. Rev. Lett. 98, 232001 (2007)**

**	****No significant change of the p****t**** distributions with respect to p+p, but error bars are large**

## J/Ψ RAA vs rapidity in Au+Au

- 0-20%

- 20-40%

- 40-60%

- 60-92%

**Phys. Rev. Lett. 98, 232001 (2007)**

**Peripheral****:**
- no modification of the rapidity distribution with respect to p+p collisions
**Central: **
- narrowing of the rapidity distribution

## Viscosity

**An AdS/CFT lower bound:**
- hep-th/9711200, gr-qc/0602037, hep-th/0405231
**Measurements**
- R. Lacey et al., nucl-ex/0609025
- H.-J. Drescher et al., arx:0704.3553
- S. Gavin, M. Abdel-Aziz, nucl-th/0606061
- A. Adare et al., nucl-ex/0611018

- W.A. Zajc

## Perfect ≠ ideal!
Perfect: negligible viscosity and heat conduction
Ideal: incompressible
Viscosity : measure of resistance to shear stress
Approx.:
Low viscosity  High cross-sect.  Strong coupling
Important measure: kinematic viscosity 
AdS/CFT duality:
hep-th/9711200, gr-qc/0602037, 
	hep-th/0405231
Measurements:
nucl-ex/0609025, arxiv:0704.3553,
	nucl-th/0606061, nucl-ex/0611018

- Perfect: negligible viscosity and heat conduction
- Ideal: incompressible
**Vi****scosity**** ********: measure of resistance to shear stress**
- Approx.:
**Low viscosity**** ******** ****High cross-sect. ******** ****Strong coupling**
**Important measure: kinematic viscosity **
**AdS/CFT duality:**
- hep-th/9711200, gr-qc/0602037,
- 	hep-th/0405231
**Measurements:**
- nucl-ex/0609025, arxiv:0704.3553,
- 	nucl-th/0606061, nucl-ex/0611018

**A perfect fluid?**

## Light mesons RAA

**ω**** ****in Au+Au@200 GeV****, cent: ****60-92% and 0-20% **

**High**** p****t**** suppression for ****φ**** ****and ω,**** s****imilar to *****π***** and η**
**R****dA**** also compatible with (equal to 1)**

******, p and *****π***** in Au+Au@200 GeV**** ****0-10% **

## Comparison: ρ mass modification

-  calculations for min bias QGP, thermal radiation included

- Broad range enhancement
- 150 < mee < 750 MeV3.4±0.2(stat.) ±1.3(syst.)±0.7(model)

## Mean pt2 vs Npart

**<p****t****2****>**
- 0<pt<5 GeV/c
**Constant vs ****N****part**
- For Au+Au, Cu+Cu, p+p

## 1st milestone: new phenomenon

**1****st**** milestone: new phenomenon**

**Suppression of high p****t**** particles: PHENIX result on the cover of Physical Review Letters**
**Is this a medium effect?**

## 2nd: new type of matter

**The new phenomenon is not obserable in d+Au collisions**
**Not the modification of the nucleus**
**Au+Au: it is a new type of matter!**

## Proton spin structure via heavy flavor

**L****ongitudinally polarized proton beams**
**J/Ψ**** measured**
**Sensitive to PDF**

**proton**

**proton**

**gluon**

**gluon**

**heavy fl****.**