Jets and high-p T results from QM 2006

Jets and high-pT results from QM 2006

Marco van Leeuwen, LBNL

2M. van Leeuwen, High-pT and jets

MotivationA reminder

Use jets and high-pT particles to probe the medium

Initial production at high-pT is calculable in perturbative QCD and can be calibrated by reference measurements

Goal: measure medium properties• Density, temperature

Number of degrees of freedom• Dynamical properties

e.g. viscosity

However, we still need to calibrate our probe:• Fragmentation, hadronisation in the vacuum• … and in the medium• Calibrate/constrain energy loss mechanism• Check initial production rates


Direct at high-pT

T. Isobe

p+p year-5

RHIC is accumulating p+p stats

0-10% Au+Au

Nuclear effects + E-loss (frag )

Quark- in-medium conversions

No enhancement in Au+AuAgrees with NLO pQCD


0 in p+p, d+AuM. Russcher

2005 p+p

STAR gearing up , 0 in p+p, d+Au

Good agreement with NLO pQCD and PHENIX

PHENIX, B. Sahlmüller

RdA centrality dependence

Measures Cronin, initial state effects

nucl-ex/0610036


RAA for 0: medium density I

C. Loizideshep-ph/0608133v2

I. Vitev

PHENIX, B. Sahlmüller

W. HorowitzUse RAA to extract medium density:

I. Vitev: 1000 < dNg/dy < 2000

W. Horowitz: 600 < dNg/dy < 1600

C. Loizides: 6 < < 24 GeV2/fmq̂

Statistical analysis to make optimal use of dataCaveat: RAA folds geometry, energy loss and fragmentation


What do we learn from RAA?

~15 GeV

E=15 GeV

Energy loss distributions very different for BDMPS and GLV formalisms

But RAA similar!

Renk, Eskola, hep-ph/0610059

Wicks et al, nucl-th/0512076v2

BDMPS formalismGLV formalism

Need more differential probes


L-dependence I: azimuthal asymmetryPQM: Dainese, Loizides, Paic, Eur Phys J C38, 461 RAA, Sloss vs azimuthal angle

L(2) scaling sets in pT > 6-8 GeVv2 only described by models above pT> 6 GeV

nucl-ex/0611007

In Plane

Out of Plane

L

Au+Au 200GeV

0-10%

50-60%

V. Pantuev, D. Winter

New scaling parameter L

No significant loss for L < 2 fm Formation time effect? V. Pantuev hep-ph/0506095

Describes RAA vs angle down to lower pT


Quark vs gluon from quark energy loss

90% of p from gluons40% 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)

pT (GeV/c)

p/STAR, B. Mohanty


Energy dependence of RAA

preliminaryp+C reference

0-12.7% most central Pb+Pb

K. Reygers

Broad agreement between experiments

Lower √sNN, steeper initial spectra• More pronounced ‘Cronin’ effect• Stronger suppression

(same RAA for more dilute medium)

NA49 preliminary

Central Pb+Pb/Au+Au

NA49

PHENIX

(+ + -)/2 -0.3 < y < 0.7B. Sahlmüller

B. Mohanty

C. Blume


nucl-ex/0504001

Energy dependence of RAA

RAA at 4 GeV: smooth evolution with √sNN

J. Velkovska

Agrees with energy loss models


Single particle measurements

• Energy dependenceSPS to RHIC 200 GeV

• System size dependence– p+p and d+Au references

– RAA vs Npart

– RAA vs reaction plane, v2

• Particle type dependence

Large set of systematics becoming available

Comparisons to theory ongoing

Warrants revisiting some areas of theory?(e.g. baryon fragmentation, path length dependence)


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 v2)

3 < pt,trigger < 4 GeV

pt,assoc. > 2 GeVAu+Au 0-10%

preliminary

Two distinct questions:

Lesson: The near-side jet does interact with the medium

M. Calderon, J. Putschke

associated

trigger

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. SicklesJ. Bielcikova

Jet + Ridge

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


Subtracting the ridge IISTAR, 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 after energy loss? Or non-trivial effect hidden by exponential spectra?

1

1zT = pT,assoc/pT,trig


pT-dependence of ridge

Ridge pT-spectra are ‘bulk-like’

Ridge independent of pT,trigger

STAR, J. Putschke

Jet spectra

Yie

ld (

pt,

as

so

c >

pt,

as

so

c,c

ut)

Ridge spectra

Yie

ld (

pt,

as

so

c >

pt,

as

so

c,c

ut)

pt,assoc,cutpt,assoc,cut


What is the ridge?

A. Majumder, B. Muller, S. Bass

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

STAR, J. Putschke

dN/d

hep

-ph/0611135

Proposed explanations so far:

Ridge shape

• Radiated gluons, broadened by– Longitudinal flow, Armesto et al, PRL 93 (2004) – QCD magnetic fields, Majumder et al, hep-ph/0611035

• Medium heating + recombination,Chiu & Hwa PRC72, 034903

• Radial flow + trigger bias, Voloshin nucl-th/0312065, Nucl. Phys. A749, 287

More differential measurements possible?Jury still out Detailed predictions welcome!


Energy content of RidgeSTAR, Phys. Rev. Lett. 95 (2005) 15230

0.15 < pt,assoc < 4 GeV



“Ridge energy”

“Ridge energy”

}

}

Near-side modification in published results also due to ridge

J. Putschke talk

Energy content of ridge: few GeV


Away-side yields and energy lossC. Zhang M. Horner

|| > /2

Clear evolution of away-side suppression with pT,trig, pT,assoc

Low pT,trig, pT,assoc: enhancement

Increase Q2 for same pT,trig due to energy loss?

Caveat: shapes change non-trivially

8< pTtrig < 15 GeV, PRL 95, 152301

Preliminary

|| > 0.9


Di-hadrons: away-side shape

Preliminary2.5 < p

T,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


And at SPS

Is this still jet-fragmentation?

Compare p+p?


Away-side shape: pT,trig

dependence

0-12%

4.0 < pT

trig < 6.0 GeV/c 6.0 < pT

trig < 10.0 GeV/c3.0 < pT

trig < 4.0 GeV/c

Preliminary

0-12%

1.3 < pT

assoc < 1.8 GeV/cSTAR, M. Horner

Away-side flatter for larger pT,trigger

But broadening at low pT,assoc persist


Summary of shape evolution

Cu+Cu follows trend vs Npart

awayhump

dashed=PHENIX, solid=STAR*0.35

PHENIX, C. Zhang, A. Sickles

F. Wang

224

2

/

)(

kurtosis

rms

nn

Shape change due to yield increase away from =

System size dependence

Npart1/3


Interpretations of away-side broadening

Mach Cone/Shock wave

T. Renk, J. Ruppert

Stöcker, Casseldery-Solana et al

Cherenkov radiation Gluon rad+Sudakov

A. Polosa, C. Salgado

V. Koch, A. Majumder, X-N. Wang

Many explanations possible, need more input to conclude

Or large kT from radial flow or energy loss Fries, Armesto et al, Hwa

Also: Vitev, Phys. Lett. B630 (2005)


3-particle correlations

1

3

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-independentNon-zero 3-particle structure

Jet+background analysis:Model-dependent, more sensitiveOff-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 SPSLike sign Unlike sign

CERES, S. Kniege

ti tj

All chargebackground 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? Some other mechanism?

2.5 < pT,trig

< 4.0 GeV/c


Raw signal Raw signal


Origin of p/ enhancement: PID correlations

Preliminary Preliminary

Near side Away side

Bar

yon

/mes

on

ass

oc

Bar

yon

/mes

on

ass

oc

B/M singles

Trigger h±: 2.5 < pT < 4.0GeV/c

A. Sickles

Near side: increase with centralityMeasure particle composition of ridge?

Away-side B/M increases strongly with centrality

Need comparisons to theory for interpretation

Extended pT -range desirable


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 mediumExperimental tests pending


Away-side suppression at high pT

NLO

Theory talk, H. Z. Zhang

J. Jin, N. Grau, J. Jia, H. Pei

Data

: ST

AR

PR

L 95, 152

301

T. Renk and Eskola, hep-ph/0610059

Di-hadron suppression: smaller surface bias, potentially better

differential probe

Comparison to theory ongoing

New data: RAA IAA also in Cu+Cu

Emission pointsHydro profile


-jet measurementsJ. 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 PythiaConsistent 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


Summary/outlook

• Impressive amount of new data– Extending pT-reach for inclusives– System size, energy dependence mapped out– Detailed shapes/yields at low, intermediate pT

Some open questions:1) Intermediate pT: origin of ridge and away-side broadening2) Role of baryon fragmentation vs coalescence

(quark/gluon energy loss)

Will this constrain energy loss models?

Expect developments in near future:Baryon/meson fragmentation at higher pT

Improve on -jet measurements


Future directions-jet rates

RAA at LHC

S. Wicks, W. Horowitz

T. Renk

Slower rise in BDMPS than GLV

… and much more!

Need plot

RAA at LHC not independent of pT:more sensitive to energy loss distribution

B. Jacak, W. Vogelsang

-jet at RHIC-II and LHC


Thank youFor your attention

And to all who provided input and discussion to shape this talk!

Jets and high-p T results from QM 2006

Documents

Transcript of Jets and high-p T results from QM 2006