# Presentation: 946009

## In-Medium Properties of Hadrons

- Fuqiang Wang

- Berkeley School of Collective Dynamics in Honor of Gerry Brown

- Experimental Search for Mach Shock Conical Flow

**Notes:**
tool  goal.

## Outline

- Physics motivations
- How Mach cone comes into the picture
- How to observe it: 3-particle jet-like correlation results
- Summary

## Motivation: Probing Heavy-Ion Medium by Jets

- Hard-scattering between partons in pp.
- Fragmentation of partons produce back-to-back jets of hadrons.
- Jets are clustered in angle and rich in high-pt particles.

- Jets produced in AA traverse and interact with the medium, lose energy and thus carry information of the medium.

**Notes:**
partons mean quarks and gluons

## Motivation: Probing Heavy-Ion Medium by Jets

**away-side particles **
**suppressed at high p****T**

**leading  particle **
**suppressed**

**away-side particles**
**enhanced at low p****T**

**Notes:**
partons mean quarks and gluons

## Motivation: Probing Heavy-Ion Medium by Jets

- double-hump is harder:
- shock wave push?

- center part does not drop.
- hump increases with centrality.
- shock wave excitation?

**away-side particles**
**enhanced at low p****T**

- pTtrig=3-4 GeV/c, pTassoc=1-2.5 GeV/c

**Notes:**
partons mean quarks and gluons

## Mach cone shock waves?

- Perfect fluid of hot and dense matter at RHIC: cS, supersonic jets, jet-quenching.
- RHIC appears to have all the conditions to generate Mach-cone shock waves.

- Scheid, Muller, Greiner, Phys. Rev. Lett. 32, 741 (1974);
- Hofmann, Stoecker, Heinz, Scheid, Greiner, PRL 36, 88 (1976).

- Many recent studies:
- Stoecker, nucl-th/0406018; Casalderrey-Solana, Shuryak, Teaney, hep-ph/0411315; Ruppert, Muller, hep-ph/0503158; Chaudhuri, Heinz, nucl-th/0503028; Renk, Ruppert, PRC73 (06) 011901, Y.G. Ma, *et al.*, nucl-th/0601012. ...

## Why is it important?

- Mach cone angle M 
- speed of sound cS = sin(M)
- equation of state

- Casalderrey-Solana, Shuryak, Teaney, hep-ph/0411315

## Shock wave searches in AA collisions

## other scenarios

- Double-peak structure can also be generated by large angle gluon radiation:

- Armesto, Salgado, Wiedemann, PRL93, 242301 (2004)

- A.D. Polosa and C.A. Salgado, PRC75, 041901R (2007).

- or deflected jets:

- Vitev, Phys. Lett. B630 (2005) 78

## discrimination by 3-particle correlation

- Need 3-particle correlation to discriminate different physics mechanisms.

## 3-particle correlation backgrounds

**Δ********1**

**Δ**********

**-**

**+**

- trigger
- flow

- trigger
- flow

- bkgd x bkgd

- jet x bkgd

- 1/Ntrig d2N/d1d2

- Jason Ulery (STAR), HP’06, nucl-ex/0609047; J.G. Ulery, FW, nucl-ex/0609016.
- Jason Ulery (STAR), QM’06 poster, arXiv:0704.0224 [nucl-ex] .

- raw = (jet+bkgd) x (jet+bkgd)
- jet x jet = raw –
- 		(bkgd x bkgd) –
- 		 (jet x bkgd)

## 3-particle correlation signal

- J.G. Ulery (STAR), HP’06, nucl-ex/0609047;
- C. Pruneau (STAR), QM’06, nucl-ex/0703010;
- Jason Ulery (STAR), QM’06, 0704.0224.

- pTtrig=3-4 GeV/c, pTassoc=1-2 GeV/c

- 1/Ntrig d2N/d1d2

- Elongation along away diagonal: kT broadening, deflected jets.
- Evidence of conical emission in central Au+Au collisions.

## ZDC central 12% Au+Au

- Conical emission signal in central Au+Au.
- Other contributions (such as deflected jets) present.

- Major sources of systematic errors: flow, background normalization.

## Cone angle

- Cone angle consistent with no pT dependenc 
- Conical emission consistent with Mach-cone shock waves, not simple Cerenkov gluon radiation.

- Cone angle:  ~ 1.45 ~ 80o
- 	cos() ~ 0.12  =??? cS

- Jason Ulery (STAR), QM’06 poster, arXiv:0704.0224 [nucl-ex]

- 1/Ntrig d2N/d1d2

## 3-particle signal strength

- 1/Ntrig d2N/d1d2

- Away

- Cone

- Deflected
- + Cone

- J.G. Ulery (STAR), HP’06, nucl-ex/0609047; J.G. Ulery (STAR), QM’06, arXiv:0704.0224.

- signal / radian2

- Cone signal in pp, d+Au, peripheral Au+Au consistent with zero; increases rapidly in central Au+Au.

## Flow systematics

- Flow is varied between the modified reaction plane result and the 4- particle cumulant result.
- Result is robust with the variation in v2.

- Jason Ulery (STAR), Hard Probes 2006.

## Background normalization systematic

- Normalization within |Δ±1|<0.175 assuming zero yield at minimum.
- Default uses a normalization range of 0.35.
- Normalization range of 0.70 used to check systematic.
- Result is robust with respect to normalization range.

- default

- wide norm. region

- Jason Ulery (STAR), Hard Probes 2006.

## Slide 18

##  PHENIX polar coord. analysis

**Polar plot**

-  PHENIX polar coord. analysis

**Normal Jet**

**along radius**

**Hi pT(1)**

## PHENIX deflected and cone jet similations

**Deflected jet sim**

**3-Particle  di-jet correlations allow a distinction between different mechanistic scenarios !**** **

**Mach Cone sim**

** ****2-particle Correlations  matched **** **

**High pT(1)**

**High pT(1)**

## PHENIX 3-particle correlation result

- Strong away side modification in both total and true 3-particle jet correlations

**Radial section**** **

- Total 3-particle jet correlation:
- Jet x Jet + (Jet x Bkgd + Bkgd x Jet)

- True 3-particle jet correlation:
- Jet x Jet

## PHENIX 3-particle correlation: S/B ratio

- PHENIX, PRL 97, 052301 (2006):

- Total 3-particle jet correlation:
- Jet x Jet + (Jet x Bkgd + Bkgd x Jet)

- True 3-particle jet correlation:
- Jet x Jet

## Summary

**conical emission of back-side particles**

- Evidence of conical emission in central AA.
- Consistent with Mach-cone shock waves.
- Speed of sound? EOS?Cone angle  ~ 1.45 ~ 80ocos() ~ 0.12 =??? cS

**Notes:**
partons mean quarks and gluons

## extra slides

## 3-particle signal strength

- Major sources of systematic errors: flow, background normalization.
- Mach cone signal in central Au+Au collisions.
- Contribution from deflected jets present.

- J.G. Ulery (STAR), Hard Probes 06, nucl-ex/0609047; QM’06 poster # 44.

- 1/Ntrig d2N/d1d2

## polar coord. analysis

- N.N. Ajitanand (PHENIX), poster # 39.

- Background from mixed-events.
- Background subtracted.
- 3-particle correlation in PHENIX acceptance, consistent with MC.

## STAR 3-Particle Cumulant

- Clear evidence for ***finite 3-Part Correlations***
- Observation of flow like and jet like structures.
- Evidence for v2v2v4 contributions

- C. Pruneau (STAR), QM’06, nucl-ex/0703010

## 3-Cumulant vs. centrality

- Au + Au  80-50%

- 30-10%

- 10-0%

- kT?  Interplay of jet & flow?

- C. Pruneau (STAR), QM’06, nucl-ex/0703010

## toy model simulations

- Cone case

*k**T** *case

**ZYAM/Purdue normalisation**

**Cumulant normalisation**

- 4-peak structure for conicalemission
- 2-peak for kT-smearing

- Valleys and peaks due to different normalisation

- 4-peak/2-peak difference also visible

- Caveat: soft-soft term ignored (see next slides)

**Valley-peak strength similar: ****0.2 in both cases**

- Signal seen in both schemes. Both schemes distinguish between conical emission and kT effect

- Marco van Leeuwen, Hard Probes 2006.

## cumulant vs jet-like with no flow

- J.G. Ulery, FW, nucl-ex/0609017.

## cumulant vs jet-like with flow

- J.G. Ulery, FW, nucl-ex/0609017.