An overview of high-p T correlations at SPS and RHIC

An overview of high-pT correlations at SPS and RHIC

Mateusz Płoskoń

24th of March 2007 High-pT at LHC 2

RAA at SPS and RHIC

p+W @ s = 19.4GeV

dNg/dy = 400-600 + Cronin + shadowingI. Vitev and M. Gyulassy, PRL 89 (2002), 252301

C. Blume

Nucl. Phys. A 783 (2007)

Energy density at s = 17.3 GeV: 0 3GeV/fm3

SPSSPS Direct photons scale with NDirect photons scale with Nbinbin

High-pHigh-pT T hadrons are suppressedhadrons are suppressed

At SPS: At SPS: Interplay between Cronin Interplay between Cronin enhancement and possibleenhancement and possible

jet quenching effectsjet quenching effects


STAR, Phys Rev Lett 91, 072304

Azimuthal Correlationstrigger

associate 1

associate 2

parton 1

parton 2

1

2

near side

away side

Medium(?)

A+A

p+p

4 < pt,trig < 6 GeV and pt,assoc > 2 GeV

In A+A collisions away-side structure In A+A collisions away-side structure modified due to interaction with the mediummodified due to interaction with the medium

Two-particle correlations

at SPS


2 Silicon Drift (SiDC) detectors, 2 RICH detectors, TPC : p/p = ((2%)2 + (1% p (GeV/c)2)1/2

Acceptance: 8o < < 15o (2.1 < < 2.65), full azimuthData set: 30 mln Pb+Au events (year 2000 run)Centrality selection: 5%, 5-10%, 10-20% most central

CERES Spectrometer with the TPC


Pioneering plots: 2-pion azimuthal correlation- pre-TPC CERES analysisTwo-particle azimuthal correlations of pions with pT > 1.2 GeV/c - centrality dependent.

CERES Collaboration, G. Agakichev, et al. Phys. Rev. Lett. 92 (2004) 032301

21 - 26 %

J. Bielcikova, PhD thesis Prague/Heidelberg 2003

< 6.16.1 - 10.6 %

10.6 - 15.1 %15.1 - 19.3 %

19.3 - 24.2 %24.2 - 30.0 %

9 - 13 %The full line - Gaussian fits to semi-hard components on top of elliptic flow modulated background (dashed line)

Broadening of the away-side component with centrality


Procedure (PHENIX: nucl-ex/0507004):

1. Accumulate: YAB()=A-B (A != B)

2. Accumulate: Ymixed()=A-Cmixed

3. Divide normalized yields:

4. Assume:

5. Fix (C0) and subtract the flow (ZeroYieldAtMinimum(*))6. Normalize and extract J

- jet associated particles(pairs) per trigger

)()(

)()(

d

dN

dY

dY

Y

YC

AB

same

mixed

mixed

same

)()cos(21)( 220 JvvCC BA

A

ABABJetDi

trig N

N

dC

J

d

dN

N

)()´(

)(

)(

1 )(

NA – number of triggersNAB – pairsAssuming AB=AB the trigger efficiency cancels out

Azimuthal angular 2-particle correlations - the recipe

mrad10min


A Monte Carlo exampleLets generate:- a trigger jet at = 0- scattered jet (left or right) at = - on top of flow

SIMULATION

A note on the ZYAM condition

The di-jet yield is nowhere ZERO

ZYAM condition may overestimatethe background contribution in caseswhere the (di-)jet yields/widths overlap

JET-T

JET-A

JET-Bdifferent event


2-particle correlations from Pb+Au at 158 GeV/cAll charged particles with 1.0 < pT

assoc < 2.5 < pTtrigg < 4.0 GeV/c

Flow (v2) from the reaction plane analysis: nucl-ex/0510057 and refs there

Strongly modified away-side in near central collisions as compared to a (expected) Gaussian-like shape. Modifications centrality dependent.


Trigger-associated charge selection

Normalized to the total number of triggers (no charge selection)

All charged with 1.0 < pTassoc < 2.5 < pT

trigg < 4.0 GeV/c

Indication (near-side) for charge ordering in the fragmentation process.“Reversed yields” on the away side – correlated (di-)fragmentations(?) – global-di-jet charge conservation(?).

MP

, Nuc

l. P

hys.

A 7

83 (

2007

)

STAR 200 GeV/cSTAR 200 GeV/c


Charge-charge correlations - unfolded /geom = 0 - 5 %

S. Kniegenucl-ex/0703008

Independent of the trigger yield is dominated by the positive particles (in the fragmentation constrained to the pT-associated range) – PYTHIA calculations indicate isospin effects – not observed at RHIC nor at LHC.

localminimum ?

CERES data: Pb+Au at 158 GeV/c

Selected correlations at RHIC


Medium on the near side ?STAR preliminary 0-10% Au+Au3 < pt,trigger < 4 GeV, pt,assoc. > 2 GeV

Jet spectra

Yie

ld (

pt,

ass

oc

> p

t,as

so

c,c

ut)

pt,assoc,cut

inclusive

STAR preliminary

Ridge spectra

Yie

ld (

pt,

ass

oc

> p

t,as

so

c,c

ut)

pt,assoc,cut

inclusive

STAR preliminary

Radiated gluons, broadened byLongitudinal flow, Armesto et al, PRL 93 (2004) QCD magnetic fields, Majumder et al, hep-ph/0611035Anisotropic plasma, P. Romantschke, PRC,75014901 (2007)

Medium heating + recombinationChiu & Hwa, PRC72, 034903

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

Unfortunately not accessible at SPS experiments due to limited Unfortunately not accessible at SPS experiments due to limited acceptance) acceptance)


Away-side at RHIC

STAR, Phys Rev Lett 95, 152301

pTtrigger>8 GeV/c

Yie

ld p

er tr

igge

r

STAR, nucl-ex/0604018

PHENIX, QM05 and nucl-ex/0507004

Shape evolving Shape evolving with centralitywith centrality

Away-side pAway-side pTT evolution: evolution:Clear narrow peak:Clear narrow peak:

Punch throughPunch throughFlat:Flat:

Jet quenching – meltingJet quenching – meltingDouble-peak structure:Double-peak structure:

Mach cones shock wavesMach cones shock waves+ more…+ more…

Broad cosine-like structure:Broad cosine-like structure:thermalized gluons thermalized gluons + momentum conservation+ momentum conservation

Low-pLow-pTT

High-pHigh-pTT


Similar pT at RHIC… and SPS

PHENIX Au+Au at sqrt(s) = 200 GeV/c

1.0 < pTassoc < 2.5 < pTtrigg < 4.0 GeV/c

PHENIX, nucl-ex/0507004 nucl-ex/0511048

Au+Au at 62.4 GeV/c

Similar away-side structure (AND) evolving with centrality…… similar mechanism(s) at work at RHIC and SPS?

CERES Pb+Au at sqrt(s) = 17.32 GeV/c

nucl-ex/0511043


Possible scenarios for the origin of the modified away-side

Double peak structure arising from Mach cone shock waves:H. Stöcker, Nucl. Phys. A 750, 121 (2005),J. Casalderrey-Solana, E. V. Shuryak and D. Teaney, Nucl. Phys. A 774, 577-580 (2006).

Induced gluon radiation:I. Vitev, Phys. Lett. B 630, 78 (2005).

Cherenkov-like radiation:V. Koch, A. Majumder and X.-N. Wang, Phys. Rev. Lett. 96, 172302 (2006).

Medium-induced radiative energy loss:A. D. Polosa, C. A. Salgado hep-ph/0607295

?

Punch-throughPossible broadening

Strongly non-GaussianModified shapes

T. RenkT. RenkK.J. EskolaK.J. EskolaJ. RuppertJ. Ruppert

QM´06QM´06

0-5%0-5%5-10%5-10%

??

0-5%0-5%5-10%5-10%10-20%10-20%

??


Hydrodynamical Study of Jet Energy Loss

t = 0 fm/ct = 0 fm/cMedium Medium

in the mixed phasein the mixed phase

EoS with 1st order phase transitionEoS with 1st order phase transition

masseless QGP: cmasseless QGP: css ~ 0.57 ~ 0.57 θ = 1.0 radθ = 1.0 rad hadronic matter: chadronic matter: css ~ 0.3 ~ 0.3

11stst order phase transition: c order phase transition: css ~ 0 ~ 0

θ = 1.3 radθ = 1.3 rad

θ = 1.5 radθ = 1.5 rad

• vvjetjet depends on the mass of the leading quarks depends on the mass of the leading quarks

F. Wang, QM06

Emission Angle of the Mach ConesEmission Angle of the Mach Cones

cos θ = cs / vjet ~ 60 – 90 deg

B. Betz, Talk at DPG 2007B. Betz, Talk at DPG [email protected]@th.physik.uni-frankfurt.de

t = 12.8 fm/ct = 12.8 fm/c

Three-particle correlations


Considering different scenarios with Monte Carlo Jets

Di-jet correlation function – generated jets:• exactly back-to-back• smeared away side (randomized deflection)• away side scattered either left or right• conical away side pattern

• leading to a double peak structure within the same event

Different mechanisms may lead to similar structures in 2-particle correlations. 3-particle correlations provide additional topology information.


3-particle correlations – studying the jet-jet correlations - an example case

JJJFFFFJFJFJ ))()(())()((

A-T vs B-T

SIMULATION


Measured 3-particle correlations –

Preliminary resultsRaw correlation function

Reconstructed signal


geom : 7%Trigger pt : (2.5-4.0) GeV/c Associate pt : (1.0-2.5) GeV/c

Subtraction of two particle correlations ( soft*soft , hard*soft )

Similar to

J. G. Ulery and F. Wang nucl-ex/0609016

b=1 (Ulery and Wang)b=1 (Ulery and Wang)No assumption NNo assumption N22

2-part2-part=N=N3-part3-part


Measured 3-particle correlations –

Preliminary resultsRaw correlation function

Reconstructed signal

Possible topology

Cone-like emission

Possible topology

“Deflection”


geom : (0.0-5.0)%Trigger pt : (2.5-4.0) GeV/c Associate pt : (1.0-2.5) GeV/c

Projection onto 2-part. Projection onto 2-part. rror of the projection (3-part. correl.)rror of the projection (3-part. correl.)not indicated (but >> 0)not indicated (but >> 0)


3-Particle Correlations - DATAat RHIC and

SPS

CE

RE

SC

ER

ES

STAR preliminarySTAR preliminaryQM’06QM’06

QM’06QM’06

Au+Au 0-12%Au+Au 0-12%

Alongation:Alongation:SPS:no(?)SPS:no(?)RHIC: yesRHIC: yes


Another method for 3-particle correlations Study angular correlations between the associated particles on the away

side

trigger norm

norm

S ( )

B (C )

)(

associate1 associate2

pt : (1.0-2.5) GeV/c pt : (2.5-4.0)

GeV/c S: trigger and accociates from the same event

B: trigger, accociate1, associate2 from different events

Orientation of angles with respect to the trigger

0°

180°

cut on associate with respect to trigger

trig<->ass> 1.0

trigger

Phase SpacePhase Space

Count angles: 0-360 degCount angles: 0-360 deg


Monte Carlo studies of the background

flow*flow

flow*jet +flow*flow

data

flow comp.subtracted

•Monte Carlo construction of non jet-jet contributions to the measured data •based on the 2 particle conditional yield and measured elliptic flow.

Yield of away side pairs

a.u.

normalized bysteeply falling

distribution

Indication of cone structure on the away side ? needs further investigation

C(

Preliminary

Preliminary

Preliminary

No trigger separation cut

geom : (0.0-5.0)%

Trigger pt : (2.5-4.0) GeV/c Associate pt : (1.0-2.5) GeV/c

C(

Project the 2D plot into 1D * plot at * that gives maximum correlation at away side

Mach ConeDeflected Jet

* *

PHENIX MC - PHENIX MC - Chun Zhang QM’06


Sructure on the away side also seen with cut around the trigger region

TA 1.0

a.u.

trigger sep. cut TA>1.0

Yield of away side pairs

TPreliminary

Indication of cone structure on the away side ? needs further investigation

??


Summary At intermediate pT 2-particle correlations show strong

modifications of the away-side structure as compared to p+p collisions – both at RHIC and SPS

Near- and away-side yields are sensitive to the trigger-associated charge combinations – near side: both at RHIC and SPS – away side: only SPS

Preliminary analysis of the 3-particle correlations indicates possible cone-like emission – further analysis in progress – both at RHIC and SPS… ;)

LHC? : Looking forward for the first data…


CERES CollaborationD. Adamova, G. Agakichiev, D. Antończyk, A. Andronic, H. Appelshäuser,

V. Belaga, J. Bielcikova, P. Braun-Munzinger, O. Busch, A. Castillo, A. Cherlin, S. Damjanovic, T. Dietel, L. Dietrich, A. Drees, S. Esumi, K. Filimonov, K. Fomenko,

Z. Fraenkel, C. Garabatos, P. Glässel, G. Hering, J. Holeczek, S. Kniege, V. Kushpil, B. Lenkeit, W. Ludolphs, A. Maas, A. Marin, J. Milosevic, A. Milov, D. Miśkowiec, R. Ortega,

Yu. Panebrattsev, O. Petchenova, V. Petracek, A. Pfeiffer, M.Płoskoń, S. Radomski, J. Rak, Ravinovich, P. Rehak, W. Schmitz, J. Schukraft, H. Sako, S. Shimansky,

S. Sedykh, J. Stachel, M. Sumbera, H. Tilsner, I. Tserruya, G. Tsiledakis, T. Wienold, B. Windelband, J.P. Wessels, J.P. Wurm, W. Xie, S. Yurevich, V. Yurevich

NPI ASCR, Rez, Czech RepublicGSI Darmstadt, Germany

Frankfurt University, GermanyHeidelberg University, Germany

JINR Dubna, RussiaWeizmann Institute, Rehovot, Israel

SUNY at Stony Brook, USACERN, SwitzerlandBNL, Upton, USA

Münster University, GermanyMPI Heidelberg, Germany


PYTHIA and UrQMD testswithin CERES

acceptance

UrQMD – special customized setup(!): Pb+Au @ 160 AGeV, b<5.8fmPythia called for hard-scatterings with Ecm > 10 GeV, short formation time to allow multiple interactions

Standard PYTHIA sqrt(s) = 17.32 GeV2-track resolution cut appliedCeres TPC geometrical acceptance

5% central


Pythia (red) and UrQMD (blue)

ALL LIKE-SIGN

UNLIKE-SIGN


3 Particle correlations : two particle contributions

- (..+..+.. ) =

yieldraw correlations


More MC studies (?)No dip at pi in 2-part. correl.No dip at pi in 2-part. correl.Dip at pi in 2-part. correl. – not data-likeDip at pi in 2-part. correl. – not data-like


Pure correlation function !!!No flow subtraction , No normalisation

C(

like signall unlike sign

correlations on top of a steeply falling background

(due to orientation of angleswith respect to the trigger)

background

a.u.

(Very) preliminary results


correlations among the associates

trigger separation cut TA>1.0

no trigger separation cut

all unlike sign like sign

all unlike sign like sign

Trigger pt : (2.5-4.0) GeV/c Associate pt : (1.0-2.5) GeV/c

Preliminary Preliminary

Preliminary Preliminary Preliminary

Preliminary

geom : (0.0-5.0)%

geom : (0.0-5.0)%


Energy scan – eta +-1


Energy scan – wide eta


Data and Pythia and UrQMD


3-particle correlations – CERES data Limiting factor – statistics:

Example from Au+Au central at RHIC: Typical S/B = 1/30 For 3-particle correl: S/B~10-3

Systematic precision of the order of 10-4

Estimations for SPS: number of particles in the

associated pT range is 10 on average

most of them are from background(!)

S/B is of about 1/150 S/B for 3-particle correlations is

squared!

Only correlation function – no background subtraction

PRELIMINARY


Transverse momentum spectra

NUCL-EX/0407019

Preliminary

Rapidities 2-2.6Corrected for efficiency only

h_

Measured with TPC-year 2000 data -~7% centralityNo corrections at all

2.1 < < 2-65

Preliminary

Present correlationsstudies :pT 1-4 GeV/c

Mixed event stat. problemNot resolution effect

An overview of high-p T correlations at SPS and RHIC

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