# Presentation: 470918

## Experimental SummaryQuark Matter 2006

- Thomas K HemmickStony Brook University

- With great thanks and appreciation to M. van Leeuwen, R. Averbeck, S. Esumi

## Goals for the Talk

- You have already heard summaries of the best data from each of the 4 RHIC experiments (40 minutes each)
- How can this be different/interesting?
- Talk only about SPS data and LHC dreamsThat would be criminal...RHIC dominated QM.
- Talk about the “cutting room floor” (left out).That would purposely skip things most interesting.
- Choice:  String together a discussion cutting across experiments of a few very hot topics.

## Outline

- Jet Tomography
- Deconfinement
- Recombination
- Tunable Chemistry
- Chiral symmetry
- Heavy Quarks
- v2 Fluctuations
- Summary of Summary of Summary...

## 0 in p+p, d+Au

- M. Russcher

- 2005 p+p

- Good agreement with NLO pQCD

- PHENIX, B. Sahlmüller

- RdA centrality dependence

- initial state effects

- nucl-ex/0610036

## RAA for 0: medium density I

**R****AA**** for ********0****: medium density I**

- C. Loizides
- hep-ph/0608133v2

- I. Vitev

- PHENIX, B. Sahlmüller

- W. Horowitz

- Use RAA to extract medium density:

- I. Vitev:           1000 < dNg/dy < 2000
- W. Horowitz:   600  < dNg/dy < 1600
- C. Loizides:     6      <            < 24 GeV2/fm

## L-dependence I: azimuthal asymmetry

- PQM: Dainese, Loizides, Paic, Eur Phys J C38, 461

- RAA, Sloss vs azimuthal angle

- L(2) scaling sets in pT > 6-8 GeV

- v2 only described by models above pT> 6 GeV

- nucl-ex/0611007

**In Plane**

**Out of Plane**

- Au+Au 200GeV

- Uniform Density?  Color Glass?

## Energy dependence of RAA

**********

- nucl-ex/0504001

**Energy dependence of R****AA**

- RAA at 4 GeV: smooth evolution with √sNN

- J. Velkovska

- Agrees with energy loss modelsSuppression gone at SPS

## Di-hadrons: away-side shape

- 2.5 < pT,trig < 4.0 GeV/c
- 1.0 < pT,assoc < 2.5 GeV/c

- Clear evolution peripheral → central: Widening, flattening and ‘dip at ’

- nucl-ex/0611019

**0-12%**

**40-60%**

**0-12%**

- PHENIX: C. Zhang, N. Grau, J. Jia, E. Vazquez

- STAR, M. Horner

- High statistics Run IV data

## Away-side shape: energy dependence

- PHENIX, C. Zhang

- 0-5%

- 10-20%

- CERES, S. Kniege

- Similar trends seen at lower √s=62.4 GeV
- at RHIC

- nucl-ex/0611019

- 2.5 < pT,trig < 4.0 GeV/c
- 1.0 < pT,assoc < 2.5 GeV/c

- And at SPS

- Is this still jet-fragmentation?

- Compare p+p?

## Away-side shape: pT,trig dependence

**0-12%**

- 4.0 < pTtrig < 6.0 GeV/c

- 6.0 < pTtrig < 10.0 GeV/c

- 3.0 < pTtrig < 4.0 GeV/c

**0-12%**

- 1.3 < pTassoc < 1.8 GeV/c

- STAR, M. Horner

- Hint of re-emergence of central max?

## Summary of shape evolution

- Cu+Cu follows trend vs Npart

- PHENIX, C. Zhang, A. Sickles

- F. Wang

- Shape change due to yield increase away from =

- System size dependence

**p****T,trig**

- pT,trig dependence

- WAIT!!  Suppression is gone for low energy small systembut away-side double hump remains?

## 3-particle correlations

- 13

- 12

- 0

- 

- 

- 

- 

- 13

- 12

- 0

- 

- 

- 

- 

**Event by event **
**deflection of jets**

**Cone like structure **
**in each event**

- 3-particle - probes away-side structure:
- Distinguish event-by-event deflection vs conical (Mercedes) emission pattern

- However: Large backgrounds, background shapes not simple

## 3-particle results

- Au+Au 0-12%

- (12-13)/2

- (12+13)/2-

- PHENIX Preliminary

- C. Pruneau, J. Ulery

- C. Zhang, N. Ajitanand

- 13

- Cumulant analysis:
- Model-independent
- Non-zero 3-particle structure

- Jet+background analysis:
- Model-dependent, more sensitive
- Off-diagonal peaks consistent with conical emission

- Different co-ordinates:
- No ‘deflected-jet peak’ consistent with conical emission

- 12

- Tantalising results!

- Discussion/comparison of methods between experiments needed

- 3 < pT,trig < 4 GeV/c
- 1 < pT,assoc < 2 GeV/c

## 3-particle correlations at SPS

- Like sign

- Unlike sign

- CERES, S. Kniege

- All charge
- background subtracted

- 0-5% central

- Strong charge-dependence seen in raw signal

- Baryon density effect?

- Off-diagonal peaks seen after background subtraction
- Indicative of conical emission

- Mach cones at SPS? How do you get a Mack cone at Raa=1?

- 2.5 < pT,trig < 4.0 GeV/c
- 1.0 < pT,assoc < 2.5 GeV/c

- Raw signal

- Raw signal

## Fragmentation and energy loss I: near-side

- What is it ? ‘something’ coupling to long flow ?  Can this quantify E-loss ?
- How to deal with it?Need to subtract for near-side studies?

- Components
**Near-side jet peak**
**Near-side ridge**
**Away-side (and v****2****)**

- 3 < pt,trigger < 4 GeV
- pt,assoc. > 2 GeV

**Au+Au 0-10%**
- preliminary

- Two distinct questions:

- The near-side jet does interact with the mediumWhy is this not in the form of a Mach Cone?

- M. Calderon, J. Putschke

- associated

- Di-hadron correlations

## Ridge phenomenology

- nucl-ex/0611016

**Jet**

- Ridge observed for all trigger particle types

- After subtraction: jet-yield independent of centrality

**Jet + Ridge**

- PHENIX, A. Sickles

- J. Bielcikova

**Jet + Ridge**

- PHENIX: drop in baryon-triggered yield for most central events

## Subtracting the ridge II

**Subtracting the ridge II**

- STAR, M. Horner

- C. Zhang

- C. Zhang

- Near side increase at low pT,assoc seen by STAR and PHENIX

- Subtraction of -independent ‘ridge-yield’ recovers centrality-independent jet yield

- Vacuum fragmentation of “slowed Jet”?
- Is the Ridge the truer energy loss (instead of mach cone)?

**1**

**1**

- zT = pT,assoc/pT,trig

## pT-dependence of ridge

- Ridge pT-spectra are like the medium

- STAR, J. Putschke

- Jet spectra

** ****Yield (p****t,assoc ****> p****t,assoc,cut****)**

- Ridge spectra

** ****Yield (p****t,assoc ****> p****t,assoc,cut****)**

**p****t,assoc,cut**

**p****t,assoc,cut**

## -jet measurements

- J. Jin, M. Nguyen

- S. Chattopadhyay, F. Benedosso

- First results in p+p

- Promising results: statistical errors can be reduced in coming runs

- Consistent with expectations from Pythia
- Consistent between experiments

## -jet in Au+Au

- J. Jin, M. Nguyen

-  distribution

- Yields

- First results in Au+Au: consistent with suppression

- Upcoming RHIC run will improve statistics for this measurement

- But large statistical uncertainties

- Monochromatic source: differential measurement of jet-quenching

- Goal: Measure -jet suppression in A+A

- X.-N. Wang, Z. Huang, PRC 55:3047, F. Arleo et al JEHP 0411, 009, T. Renk, PRC 71, 034906

## Thermal radiation at RHIC

- thermal radiation: another holy grail
- Quark Matter 2005
- first measurement of virtual photons                                 beyond hadronic decays

- data consistent with sum of
- NLO pQCD (uncertain @ low pT)
- Gordon, Vogelsang, PRD 48(1993)3136
- thermal radiation
- d’Enterria, Perresounko, EPJ C46(2006)451
- required for firm conclusions
- reference data from p+p and d+Au
- real photon measurement to consolidate virtual photon excess

## cold matter reference (d+Au)
double ratio: (all )/(decay )
photons & internal conversion
consistent with 1 within errors
sys. uncertainty for internal                                                                     conversion analysis
smaller than for calorimeter data
larger than achieved for                                                                          Au+Au (larger background)

- consolidation ofAu+Au analysis
- measurement of externalphoton conversions
- in agreement within errors with previous results
- (calorimeter and internal conversion

- cold matter reference (d+Au)
- double ratio: (all )/(decay )
- photons & internal conversion
- consistent with 1 within errors
- sys. uncertainty for internal                                                                     conversion analysis
- smaller than for calorimeter data
- larger than achieved for                                                                          Au+Au (larger background)

**Thermal radiation at RHIC**

**D.**** ****Perresounko**

## Quarkonia	

- 20 years ago: Matsui & Satz
- color screening in deconfined matter                                           → J/ suppression = “smoking gun”

- experimental & theoretical progresssince then                                                                                     → story is much more complicated
- cold nuclear matter / initial state effects
- “normal” absorption in cold matter
- (anti)shadowing
- saturation, color glass condensate
- suppression via comovers
- feed down from c, ’
- sequential screening (first: c, ’, J/ only well above Tc)
- regeneration via statistical hadronization or charm coalescence
- relevant for “large” charm yield, i.e. RHIC and LHC

## J/ at SPS: pA reference measurement 

**J/******** at SPS: pA reference measurement **

- absorption with respect to what?
- need production cross section and nuclear absorption cross section absJ/ from proton data
- before: no pA data at 158 GeV
- production cross section                                                                     measured at 450(400) GeV                                                                       and rescaled to 158 GeV
-  absJ/measured with pA                                                                     NA50 data at 450(400) GeV
- preliminary NA60 pA data                                                             at 158 GeV
- currently averaged over various                                                              nuclear targets → no absJ/ yet
- rescaling of production cross                                                              section to 158 GeV is correct!

**E. Scomparin**

## J/ at SPS: suppression in In+In 

**J/******** at SPS: suppression in In+In**** **

- NA60: In+In @ 158 GeV/nucleon

- anomalous J/ suppression with respect to pure nuclear absorption
- precision measurement of suppression pattern
- qualitatively consistent with Pb+Pb
- quantitative description of In+In: challenge for models tuned to describe Pb+Pb

- evolution of J/ momentum distribution with centrality
- pT broadening consistent with initial state gluon scattering
- no J/ polarization in kinematical range probed by NA60

**E. Scomparin**

## J/ suppression: SPS vs. RHIC 

**J/******** suppression: SPS vs. RHIC**** **

- RAA versus Npart

- stunning similarity of J/ suppression pattern for
- Pb+Pb from NA50 (0<y<1)
- Au+Au from PHENIX (|y|<0.35)
- an accident?
- cold nuclear matter effects: (slightly) larger at SPS than at RHIC
- more d+Au data needed at RHIC for more quantitative statement
- plus recombination at RHIC?
- ‘sequential dissociation’ at   SPS and RHIC?
- J/ survives well above Tc
- dissociation of ’ and c
- feed down not well constrained (~40 %)

**many talks/posters**

## J/ at RHIC: rapidity dependence 

- RAA: rapidity dependence

- p+p reference                     → rapidity and pT spectra challenge for production models (                  )
- final Au+Au data
- more suppression at forward rapidity!
- opposite to trend from comover or CNM absorption
- suppression not only driven by local particle density
- more regeneration at y~0?
- gluon saturation at forward y?

**T. Gunji**

**A. Bickley**

- models
- no clear picture yet, but importantconstraints
- two (or more) ingredients needed”
- suppression + regeneration
- sequential dissociation + saturation

**nucl-ex/0611020**

## y and pT distributions ↔ recombination
rapidity: narrowing towards central collisions
<pT2>: reduced relative to pT broadening from initial gluon scattering
PHENIX: indications for both effects

- rapidity: narrowing towards central collisions
- <pT2>: reduced relative to pT broadening from initial gluon scattering
- PHENIX: indications for both effects

**J/******** at RHIC: hints for recombination? **

**A. Glenn**

- Need to measure J/ flow at RHIC

## y and pT distributions ↔ recombination
rapidity: narrowing towards central collisions
<pT2>: reduced relative to pT broadening from initial gluon scattering
PHENIX: indications for both effects

- rapidity: narrowing towards central collisions
- <pT2>: reduced relative to pT broadening from initial gluon scattering
- PHENIX: indications for both effects

**J/******** at RHIC: hints for recombination? **

**A. Glenn**

- decisive: J/ flow at RHIC (answer from next RHIC Run?)

## Quark vs gluon from quark energy loss

- 90% of p from gluons
- 40% of  from gluons

- X.N. Wang and X.F. Guo,  NPA 696, 788 (2001)
- W. Liu, C.M. Ko, B.W. Zhang, nucl-th/0607047

- Medium modifications to FF?

- STAR, L. Ruan

- PRL 97, 152301 (2006)

- Curves: X-N. Wang et al PRC70(2004) 031901

- No sign of stronger gluon energy loss in p/ or p/p ratios

- Need new calculations, with better baryon FF (AKK)

**p****T**** (GeV/c)**

**p/******

- STAR, B. Mohanty

## baryon transport + radial flow + recombination + jet suppression

- p/

**Au+Au 200GeV**
**STAR preliminary**

## -h correlation

- J. Bielcikova

- R. C. Hwa et al., nucl-th/0602024

******-h correlation**

- Near-side yield similar for , ,  triggered correlations

- Initial expectation:  dominantly from TTT recombination, no associated yield

- Revisited (at QM06): possible large contribution from reheated medium

- Experimental tests pending

## v2 scaling with mT-m + number of quark

- v2 scaling with mT-m + number of quark
- (same as hydro at low pT + number of quark)

**When the mass effect removed by m****T****-m, only the quark number ratio shows up! **
**Is mass ordering of v****2**** at low p****T**** generated during or after hadronization?**
**Feed-down for pion is visible in p****T****, but not in m****T****-m, because **
**p****T****(daughter) < p****T****(parent) , but m****T****-m(daughter) ~ m****T****-m(parent) ...**
**Decay kinematical effect is masked by the p****T**** to m****T****-m transformation.**

## v2 scaling with mT-m + number of quark

- v2 scaling with mT-m + number of quark

**v****2**

**p****T**** (GeV/c)**

**RQMD Au+Au 200GeV**

**Feng Liu**

**Number of quark scaling is not only the explanation**.

**Early freeze-out effect of multi-strangeness hadrons seen in spectra analysis with radial flow does not show up here in v****2**** analysis, this is an indication that v****2**** is already built up in early stage. **

## Light vector mesons and dilepton continuum

- chiral condensate changes as                              function of baryon density                             and temperature T
- study in-medium modifications of hadrons

## Light vector mesons in elementary reactions

- TAPS @ ELSA:  mesons photoproduction off nuclei
- low momentum  mesons decay in medium: →0

- difference in  line shape for proton and nuclear target consistent with  mass shift
- m = m0 (1 – 0);  = 0.13

**V. Metag**

-  in cold medium
- JLAB-CLAS: G7
-  → e+e- X
-  no mass shift
-  some broadening
- KEK-E325
- pA → e+e- X
- mass shift (9%), no broadening
- no consistent picture yet!

**C. Djalali**

**M. Naruki**

- Important:  Momentum of reaction products

## Low-mass dimuons at SPS: NA60

**Low-mass dimuons at SPS: NA60**

- precision data: In+In @ 158 GeV
- excess beyond cocktail  studies in 12 centrality bins
- excess rises with centrality and is more pronounced at low pT
- models predicting strong broadening & no mass shift are in fair agreement with data
- coupling to baryons important at low mass                          (also indicated by CERES: D. Adamova et al., submitted to PRL)

**J. Seixas**

## Open heavy-flavor at RHIC

- reference for J/ suppression
- medium probe in its own right
- experimental approaches at RHIC
- direct reconstruction of charm                                       decays (e.g. D0→K+-): STAR
- difficult in HI environment
- remaining residual background                                                              after subtraction of                                                                       combinatorial BG

- indirect measurement via semi-leptonic decays: PHENIX & STAR
- requires good control of lepton background from other sources

## PHENIX e± agree with FONLL pQCD calculation
STAR e±, ±, D mesons disagree with FONLL

- STAR e±, ±, D mesons disagree with FONLL

**Charm cross section at RHIC: PHENIX vs. STAR**

**F. Kajihara**

**C. Zhong**

- rescaled

## charm quark suppression and flow

**Charm quark interaction in bulk matter, this makes suppression and collectivity of charm quarks as well as light quarks.**** **

## Does charm flow?

**Does charm flow?**

- strong elliptic flow of electrons from D meson decays → v2D > 0
- v2c of charm quarks?
- recombination Ansatz:                            (Lin & Molnar, PRC 68 (2003) 044901)
- universal v2(pT) for all quarks
- simultaneous fit to , K, e v2(pT)

**a = 1**
**b = 0.96**
******2****/ndf: 21.85/27**

- within recombination model: charm flows as light quarks!

**S. Sakai**

## Constraining medium properties

**Constraining medium properties**

- large suppression and                          large v2 of electrons                        → charm thermalization
- transport models require
- small heavy quark                              relaxation time
- small diffusion coefficient                          DHQ x (2T) ~ 4-6
- this value constrains the                    ratio viscosity/entropy
-  /s ~ (1.5 – 3) / 4
- within a factor 2-3 of                      conjectured lower                             quantum bound
- consistent with light hadron                 v2 analysis (A. Taranenko et al.)
- electron RAA ~ 0 RAA at high pT
- is bottom suppressed as well?

**F. Kajihara, S. Sakai**

## Bottom production at RHIC?

**Bottom production at RHIC?**

- electron-hadron azimuthal correlation
- decay kinematics: heavy flavor e-h correlation is the sum of D and B decay contributions

- relative bottom contribution consistent with FONLL
- caveats
- subtraction of (large) background
- model dependent (PYTHIA)
- would imply excess of bottom production relative to FONLL

**X. Lin**

## event by event v2 fluctuation vs part fluctuation

- PHOBOS part prediction

- MC with nofluctuations

- event by event v2 fluctuation vs part fluctuation

**This relative v2 fluctuation can be explained by initial ********part**** fluctuation...**

- If no additional fluctuations is this perfect fluid?

## SummaryN

- RHIC has moved past the discovery phase and is fully engaged in characterization.
- More success than we dared hope.
- Measurements may be providing:
- Speed of sound.
- index of refraction
-  /s
- Serenity: