Physics Revealed at Intermediate p T Rudolph C. Hwa University of Oregon Quark Matter 2008 Jaipur, India February 6, 2008

Physics Revealed at Intermediate pT

Rudolph C. HwaUniversity of Oregon

Quark Matter 2008

Jaipur, India

February 6, 2008

2

pT2 6

low intermediate

high

pQCDhydro

no rigorous theoretical framework

But that is where the action is, albeit experimental.

What can we learn from the abundant data?

3

OverviewSingle particle distributionpT

Two particle correlation data

Near side Away side

Ridge Jet Double bump

Three particle correlation

(1 or 2 triggers)

Auto-correlation

(no trigger)

RCPdAu

decrease with

Huge p/ at =3.2

B/M ~ 1RCPp > RCP

(dAu)

RCPΛ,Ξ > RCP

K ,φ

v2

nq

ETnq

⎛

⎝⎜

⎞

⎠⎟ univers

alquark number scaling&

breaking

4

OverviewSingle particle distributionpT

RCPdAu

decrease with

Huge p/ at =3.2

Two particle correlation data

Near side Away side

Ridge Jet Double bump

Three particle correlation

(1 or 2 triggers)

Auto-correlation

(no trigger)

B/M ~ 1RCPp > RCP

(dAu)

RCPΛ,Ξ > RCP

K ,φ

v2

nq

ETnq

⎛

⎝⎜

⎞

⎠⎟ univers

alquark number scaling&

breaking

5

p T

R

JS

Recombination at Intermediate

pT

partons

hadronsReco

What partons?

Medium effects

u, d, sg converted

to qc,b,t primordial

6

pT

Λ/K

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

STAR4

3

2

1

0

in recombination/coalescence model (Reco)

Baryon/Meson ratios

“Baryon anomaly”On the contrary, high B/M ratio is a signature of Reco. Baryons need less quark momenta than

mesons.

implies that fragmentation is normal.

7

Elliptic flow

v2M (pT )=v2

T q1( ) + v2T q2( ) v2

B (pT )=v2T q1( ) + v2

T q2( ) + v2T q3( )

M: TT + TS + SS B: TTT + TTS + TSS + SSS

Ifq1 =q2 =q3 =pT / 3

M:

B:

q1 =q2 =pT / 2 then

v2M

2

pT2

⎛⎝⎜

⎞⎠⎟;

v2B

3pT

3⎛⎝⎜

⎞⎠⎟



0.1

0.05

v2 / nq

pT → KET

Molnar & Voloshin, PRL91,(2003)

quark number scaling(QNS)

a property of naïve recombination

8



RH&CBY,0801.2183

STAR, PRC75,054906(07)

minbias

However, at larger KET

M: TT + TS + SS B: TTT + TTS + TSS + SSS

v2M (pT )≈v2

T q1( ) + v2S q2( ) v2

B (pT )≈v2T q1( ) + v2

T q2( ) + v2S q3( )

q1 ≠q2v2T ≠v2

S

v2M

2

pT2

⎛⎝⎜

⎞⎠⎟≠

v2B

3pT

3⎛⎝⎜

⎞⎠⎟

QNS is broken, but hadronization is still by recombination

pΛ

K

9

BRAHMS, nucl-ex/0602018Au+Au at 62.4 GeV Forward production

TT

TS

TTT

xF = 0.9

xF = 0.8

xF = 1.0

Shower partons are suppressed at the kinematical boundaryFew

antiquarks at large

mainly p produced

10



BRAHMS(preliminary)

Comments at the end, if asked.

11

Ridgeology

Putschke, QM06

J+R

R

J

Correlation on the near side

STAR

ridge R Jet J

Properties of Ridge YieldDependences on Npart, pT,trig, pT,assoc, trigger B/M ratio in the ridge

12

Jet+Ridge ()

Jet ()

Jet)

Putschke, QM06

R

1. Dependence on Nparton pT,trig2.

pt,assoc. > 2 GeVSTAR preliminary

Ridge is correlated to jet production. Surface bias of jet ridge is due to medium effect near the surface

Medium effect near surface

Ridges observed at any pT,trig

Ridge yield 0as Npart 0

depends on medium

13

3. Dependence on trigger

QuickTime™ and aTIFF (Uncompressed) decompressor


STAR (preliminary)

A. Feng

20-60%, 3-4:1.5-2

| 1RP

s

T

Ridge develops by radial flow near the jet axis

Mismatch of T and the direction of radial expansion.

has more ridge yield than

Ridge yield decreases with increasing s

Comments at the end, if asked.

14

Ridge

Putschke, QM06

4. Dependence on pT,assoc

Yet Ridge is correlated to jet production; thermal does not mean no correlation.

Ridge is from thermal source enhanced by energy loss by semi-hard partons traversing the medium.

Ridge is exponential in pT,assoc slope independent of pT,trigExponential behavior

implies thermal source.

STAR

15

5. B/M ratio in the ridge

Ridge hadrons are formed by recombination

Large B/M

Bielcikova, WWND07

K

Λ+Λ

Λ + ΛK

: 2

pt,assoc. > 2 GeV

Au+Au 0-10%

Putschke, QM06p

2-4p(R) / p(J )

(R) / (J )

STAR

16

Medium effect near surface coordinated with radial flow

SS

trigger

TT ridge (R)

associated particles

These wings are useful to identify the RidgeBut of interest below is

mainly the distribution.

Ridge is from enhanced thermal source caused by semi-hard scattering.

Recombination of partons in the ridge

ST

peak (J)

17

What are the consequences of Ridgeology?

1. Jet correlation at low and intermediate pT

2. Effect on single particle spectra

3. Effect on elliptic flow

18



PHENIX

2.5<pT,trig<4 GeV/c

1.8<pT,assoc<2.5

PH

EN

IX,

PLB

64

9,3

59

(07

)Peak is referred to as jet

1. Jet correlation at intermediate pT

Not seeing the ridge does not mean that it is not there.

J

R

Correlation in J is different from correlation in R

Does not see the ridge

||<0.35

19

STAR preliminary

Jet

STAR preliminary

Jet + RidgePHENIX, PLB 649,359(07)

SS TS

TT

Not un-correlated. Ridge would not be there without semi-hard scattering.

How can intermediate-pt Jet yield be independent of centrality?

0.35

20

PHENIX data cannot be properly understood without taking Ridge into account

2.5<pT,trig<4.0 GeV/c

PHENIX 0712.3033

J

R

: 1 2

2p(R) / p(J )

(R) / (J )

pt,assoc. > 2 GeV

Au+Au 0-10%

Putschke, QM06p

STAR

21

2. Effect of Ridge on single-particle spectra

Semi-hard scattering at kT~2-3 GeV/c is pervasive.

Ridges are present with or without triggers.

STAR, PRC 73, 064907 (2006)

Auto-correlation without triggers.

0.15<pt<2.0 GeV/c, ||<1.3, at 130 GeV

22







Bulk+Ridge

TT

Semi-hard partons generating ridge

TS

Fragments from hard partons

SS

(fragmentation)

T includes enhanced thermal partons --- Ridge

23

sss

How can we see better the TT component?

Remove the TS and SS components, if possible.

production: Au+Au + anything

(sss) s quark suppressed in shower



pt

dN

/ptd

pt

(log

sc

ale

)

TTS

TTT

uud

Exposes the long exponential behavior in production

24

spectrum is exponential (thermal)




are needed to see this picture.Chiu & Hwa, PRC76,024904(2007)



How can it have correlated partners? --- the puzzle.

STAR

Resolution: Both and its associated hadrons are in the Ridge.

Prediction: there is no peak (J) in the distribution --- only R

R only

25

= cos-1(b/2R)

If the semi-hard jets are soft enough, there are many of them, all restricted to || < .

A semi-hard scattering near the surface gives rise to a jet, whose direction, on average, is normal to the surface.

Initial configuration

There is a layer of ridges at the surface without triggers.

3. Effect of Ridge on elliptic flow

26

In momentum space

B

B+R

dN

pTdpTdφ=B(pT ) + R(pT )Θ(φ)

v2 (pT )= cos2φ =sin2(b)

B(pT ) / R(pT ) + 2(b)

Relate ridgeology to v2 Hwa, 0708.1508

Use data on B(pT) and R(pT)

bow tie region

27



Elliptic flow at low pT

v2 driven by Ridge



Made no assumption about rapid thermalization.

28

Elliptic flow at intermediate pT

v2 dominated by TS recombination





Hwa & CB Yang, 0801.2183

29

Away-side correlation

PHENIX 0705.3238 & .3060

Double-bump first observed by STAR

STAR, PRL 95, 152301 (05)

has been studied extensively --- experimentally and theoretically.

Mach conegluon radiation

Cherenkov radiation deflected jets …

Is there any connection between the double bumps and ridge w/o peak(J)?

2D

mild dependence of D on pt,assoc favors

30

Possible relationship between ridge and bump (Renk, Jia)

Near side Away side

Ridge Bump

Generated by semi-hard scattering

Mach cone, deflected jet,--- due to recoil of semi-hard parton

Due to recombination of enhanced thermal partons

What is partonic structure of the Mach-shock-wave?

Exponential pt,assoc Distribution in pt,assoc ?

Large B/M ratio B/M ratio is also large.

31

Papers submitted to the session on: “Response of Medium to Jets”

Experimental

Netrakanti (STAR)Wenger (PHOBOS)McCumber (PHENIX)Suarez (STAR)Feng (STAR)Adare (PHENIX)Barannikova (STAR)Catu (STAR)Daugherity (STAR)Pei (PHENIX)Haag (STAR)Szuba (NA49)G. Ma (STAR)Wang (STAR)Noferini (ALICE)Chetluru (UIC)

TheoreticalMajumder

C.Y.Wong

Gavin

Mizukawa, Hirano, Isse, Nara, Ohnishi

Pantuev

Lokhtin, Petrushanko, Snigirev, Sarycheva

Levai, Barnafoldi, Fai

Betz, Gyulassy, Rischke, Stoecker, Torrieri

Molnar

Asakawa, Mueller, Neufeld, Nonaka, Puppert

Schenke, Dumitru, Nara, Strickland

BauchlePlenary session X Ulery

Jia

32

On to LHCMany predictions made (see arXiv:0711.0974)

Those with existing codes can make extrapolations.



Eskola et al (EKRT model)

Is there new physics that cannot be obtained by extrapolation?

SS

hard parton

hadron

energy loss

p/>>1

Density of semi-hard partons is high at LHC.

SS

semi-hard partons

SS or SSS recombination to form or p.

33

What is the bulk background at LHC?

Since SS and SSS recombination of semi-hard partons are uncorrelated, they occur in mixed events.

Thus they belong to the background.

But those partons are not thermal, not in hydro.

Can Ridge be identified in association with a high pT trigger --- pT,trig > 20 GeV/c?

The ridge may not stand out among the background that consists of TT, TS, SS, TTT, TTS, TSS, SSS hadrons.

Physics at intermediate pT at LHC may be very different from that at RHIC ----- cannot be obtained by extrapolation.

So there is a mismatch between bg and hydro.

34

Summary

p T

R

JS

Physics revealed by phenomena observed at intermediate pT

soft & semi-hard partons

35

T S

Large B/M ratio

QN scaling and breaking

Exponential pT at large

v2

Ridge

Jet

Double bump

Reco at LHC

36

Backup slides

37

At large xF, proton can be formed by leading quarks from different nucleons. dxi

xii=1

3

∏⎛

⎝⎜⎞

⎠⎟∫ Fνu(x1)Fν

u(x2 )Fνd(x3)Rp(x1,x2 ,x3,x)

p x can exceed 1

Antiquarks at low xi are affected by the regeneration of that depends on .qq

Pions are suppressed due to the lack of antiquarks at large xi.



BRAHMS (preliminary)

should be larger less degradation more protons less increase of pions larger p/ ratio

~0.75 Hwa & CBYang, PRC76,104901(2007)

momenta degraded survival probability

“baryon stopping”

Forward production

38

QuickTime™ and aTIFF (Uncompressed) decompressor


STAR (preliminary)

A. Feng

20-60%, 3-4:1.5-2

| 1

3. Dependence on trigger

RP

s

T

Ridge develops by radial flow near the jet axis

Ridge yield decreases with increasing sMismatch of T and the direction of radial expansion.

has more ridge yield than

Documents

Physics Revealed at Intermediate p T Rudolph C. Hwa University of Oregon Quark Matter 2008 Jaipur, India February 6, 2008