PHENIXJet Results

(1/ 22)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Fragmentation

d+Au

kT Broadening

Cu+Cu

∆φ broadening

Outlook

Jets at RHIC

Acknowledgements

Reconstructed Jet Resultsin p+p, d+Au and Cu+Cu collisions

at 200 GeV from PHENIX

Dennis V. PerepelitsaColumbia University

for the PHENIX Collaboration

28th Winter Workshop on Nuclear DynamicsDorado del Mar, Puerto Rico

8 April 2012

PH ENIX

PHENIXJet Results

(2/ 22)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Fragmentation

d+Au

kT Broadening

Cu+Cu

∆φ broadening

Outlook

Jets at RHIC

Acknowledgements

Introduction

Jets in PHENIXGaussian FilterAnalysis Techniques

p+pFragmentation

d+AukT Broadening

Cu+Cu∆φ broadening

OutlookJets at RHIC

Acknowledgements

PHENIXJet Results

(2/ 22)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Fragmentation

d+Au

kT Broadening

Cu+Cu

∆φ broadening

Outlook

Jets at RHIC

Acknowledgements

Jets in Heavy Ion Collisions

I Jet reconstruction is being done in heavy ion collisions at RHICand the LHC:

I Reconstruct full fragmenting parton kinematics at LO.I Sensitive probe of suppression/quenching effects.

PHENIXJet Results

(3/ 22)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Fragmentation

d+Au

kT Broadening

Cu+Cu

∆φ broadening

Outlook

Jets at RHIC

Acknowledgements

Why Jets at RHIC?

I Complementary set of measurements from two high statisticscolliders!

I Can measure jet modification at:

I lower energies due to smaller underlying event

I different x and Q2 (different mixture of quark and gluon jets)

I Versatility of collision species provides:

I ability to vary system size, energy density, geometry

I control against cold nuclear matter effects

⇒ Cu+Au, U+U collisions in the next 1-2 months!

PHENIXJet Results

(4/ 22)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Fragmentation

d+Au

kT Broadening

Cu+Cu

∆φ broadening

Outlook

Jets at RHIC

Acknowledgements

PHENIX detector

West Beam View

PHENIX Detector 2008

East

MPC RxNP

PbSc PbSc

PbSc PbSc

PbSc PbGl

PbSc PbGl

TOF-E

PC1 PC1

PC3

PC2

Central Magnet TEC

PC3

BB

RICH RICH

DC DC

Aerogel

TOF-W

I Drift Chamber (DC), Pad Chambers (PC) and Ring ImagingCerenkov Detector (RICH) measure charged hadrons and electrons

I Electromagnetic Calorimeter (EMCal) clusters photons, π0’s,(some) neutral hadrons

I EMCal/RICH Trigger (ERT) and the high PHENIX DAQ rateallow complementary Minimum Bias and high-pT triggereddatasets

PHENIXJet Results

(5/ 22)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Fragmentation

d+Au

kT Broadening

Cu+Cu

∆φ broadening

Outlook

Jets at RHIC

Acknowledgements

Gaussian Filter algorithm

1. Seedless, cone-like algorithm with a Gaussian angular weighting(nucl-ex/0806.1499)

pjetT ≡ max

{∫ ∫dη′dφ′pT

(η′, φ′

)e−(∆η2+∆φ2)/2σ2

}

2. Focuses on the energetic core of the jet, optimizing S/B

3. Stabilizes the jet axis in the presence of background

PHENIXJet Results

(6/ 22)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Fragmentation

d+Au

kT Broadening

Cu+Cu

∆φ broadening

Outlook

Jets at RHIC

Acknowledgements

Fake jet rejection

I Technique to separate low-pT jets from underlying eventfluctuations in HI collisions on a jet by jet basis.

I g -discriminant (with σdis < typical distance between underlyingevent particles):

gσdis(η, φ) ≡∑

i∈fragment

(pT )2i exp

(−(∆η2 + ∆φ2)/2σ2

dis

)I Similar to “angularly-weighted” pT which rewards jets with a tight

core of energy and punishes diffuse jets.

PHENIXJet Results

(7/ 22)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Fragmentation

d+Au

kT Broadening

Cu+Cu

∆φ broadening

Outlook

Jets at RHIC

Acknowledgements

Fake jet rejection

gσdis(η, φ) ≡∑

i∈fragment

(pT )2i exp

(−(∆η2 + ∆φ2)/2σ2

dis

)

I Require gσdis > gmin:

⇒ efficient saturation with reconstructed pT⇒ trade reconstruction efficiency for sample purity

I Data-driven approaches used to set fake jet rejection thresholdgmin.

PHENIXJet Results

(8/ 22)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Fragmentation

d+Au

kT Broadening

Cu+Cu

∆φ broadening

Outlook

Jets at RHIC

Acknowledgements

Energy Scale

I In PHENIX, energy “resolution” driven by tracking inefficiency,loss of n,K 0

L neutral energy, edge of acceptance effects.

I PYTHIA Tune A 2→ 2 QCD events from Q2 = 0.5 to 64 GeV.

⇒ Cross-checks with HERWIG, other PYTHIA tunes

⇒ Embedding into real heavy ion background.

I NLO calculation + hadronization correction in progress that willallow proper comparison to data.

PHENIXJet Results

(9/ 22)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Fragmentation

d+Au

kT Broadening

Cu+Cu

∆φ broadening

Outlook

Jets at RHIC

Acknowledgements

Jets in p+p at√s = 200 GeV

I Demonstration of PHENIX jet reconstruction capability.

I Comparison with NLO pQCD across ten orders of magnitude.

I residual differences from jet definition

I Analysis being finalized, moving towards publication.

PHENIXJet Results

(10/ 22)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Fragmentation

d+Au

kT Broadening

Cu+Cu

∆φ broadening

Outlook

Jets at RHIC

Acknowledgements

Jets in p+p: Fragmentation Function

I Proof of principle measurement of fragmentation function(z = pparticle

|| /pjet)

I n-dimensional generalization to GURU SVD unfoldingimplementation:(

pparticle|| , pjet

T

)rec→(pparticle|| , pjet

T

)truth

PHENIXJet Results

(11/ 22)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Fragmentation

d+Au

kT Broadening

Cu+Cu

∆φ broadening

Outlook

Jets at RHIC

Acknowledgements

Jets in d+Au at√s = 200 GeV

(GeV/c)recT

p0 10 20 30

CP

R

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6 = 200 GeVNNsd+Au 0-20%/60-88%

0πPHENIX 2007

(PRL 98 172302)

Preliminary

jetTR=0.3 anti-k

(GeV/c)recT

p0 10 20 30

CP

R

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6 = 200 GeVNNsd+Au 40-60%/60-88%

0πPHENIX 2007

(PRL 98 172302)

Preliminary

jetTR=0.3 anti-k

I anti-kT jet reconstruction with R = 0.3, 0.5

I Reconstructed jet RCP at the p+p reconstructed scale.

I pT-feeding from modest underlying event evaulated with

embedding procedure and unfolded

I Suppression effect consistent with single-particle π0 measurement.

⇒ Cold nuclear matter energy loss?

⇒ Centrality dependent nPDF modification?

PHENIXJet Results

(12/ 22)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Fragmentation

d+Au

kT Broadening

Cu+Cu

∆φ broadening

Outlook

Jets at RHIC

Acknowledgements

Jets in d+Au at√s = 200 GeV

(GeV/c)recT

p15 20 25 30 35

CP

R

0.6

0.8

1

1.2

1.4

1.6

1.8

2

PHENIX Preliminary

= 200 GeVNNsd+Au

jetTR=0.3 anti-k

0-20%/60-88%CPR

20-40%/60-88%CPR

40-60%/60-88%CPR

(GeV/c)recT

p15 20 25 30 35

CP

R

0.6

0.8

1

1.2

1.4

1.6

1.8

2

PHENIX Preliminary

= 200 GeVNNsd+Au

jetTR=0.5 anti-k

0-20%/60-88%CPR

20-40%/60-88%CPR

40-60%/60-88%CPR

I Systematic change in RCP with centrality selection

I Consistency between cone sizes

I Ongoing improvements to analysis will produce:

I RdA

I lower pT behavior

I results at ptruthT scale

⇒ critical for refining our understanding of Au+Au results!

PHENIXJet Results

(13/ 22)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Fragmentation

d+Au

kT Broadening

Cu+Cu

∆φ broadening

Outlook

Jets at RHIC

Acknowledgements

Jets in d+Au: kT Broadening

I Reconstructed di-jets can be used to examine multiple scatteringeffects in the cold nuclear medium.

I Search for possible broadening by examining:

pout (= 〈kT 〉) ≡ (pT)low · sin ∆φ

(rad)φ∆0 1 2 3 4 5 6

)φ∆)(

dN

/dd

i-je

t/Nπ

(2

0

2

4

6

8

10

12

14

φ∆ di-jet TR=0.3 anti-k

d+Au 0-20%

> 5 GeV/cdAu

T p⊗ > 13.3 GeV/c dAu

Tp

> 5 GeV/cdAu

T p⊗ 10-13.3 GeV/c ∈ dAu

Tp

> 5 GeV/cdAu

T p⊗ 8-10 GeV/c ∈ dAu

Tp

> 5 GeV/cdAu

T p⊗ 6.7-8 GeV/c ∈ dAu

Tp

> 5 GeV/cdAu

T p⊗ 5-6.7 GeV/c ∈ dAu

Tp

PHENIX Preliminary

(GeV/c)out

p0 1 2 3 4 5 6

)o

ut

)(d

N/d

pd

i-je

t (

1/N

0

0.1

0.2

0.3

0.4

0.5

0.6

0-20%

20-40%40-60%60-88%

di-jetsTR=0.3 anti-k

> 6 GeV/cdAu

T p⊗ > 6 GeV/c dAu

Tp

PHENIX Preliminary

/4π < 5φ∆/4 < π3

I Kinematic requirements on away-side jet removes combinatorialcontribution.

⇒ constraint on centrality-dependent broadening.

PHENIXJet Results

(14/ 22)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Fragmentation

d+Au

kT Broadening

Cu+Cu

∆φ broadening

Outlook

Jets at RHIC

Acknowledgements

Jets in Cu+Cu at√s = 200 GeV

I pT-feeding from underlying event:

I subtraction of centrality- and z-vertex parameterized average

background

I pT-smearing from UE fluctuations:

I evaluated through embedding p+p jets into Cu+Cu

minimum bias events

I results shown here unfolded to p+p reconstructed scale

PHENIXJet Results

(15/ 22)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Fragmentation

d+Au

kT Broadening

Cu+Cu

∆φ broadening

Outlook

Jets at RHIC

Acknowledgements

Jets in Cu+Cu at√s = 200 GeV

I Suppression of reconstructed jet RAA:

⇒ over a wide pT range

⇒ systematic with centrality

⇒ comparable to single-particle suppression

I Potential out-of-cone radiation or other jet modification?

PHENIXJet Results

(16/ 22)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Fragmentation

d+Au

kT Broadening

Cu+Cu

∆φ broadening

Outlook

Jets at RHIC

Acknowledgements

Jets in Cu+Cu: ∆φ broadening

I Changes in the width of ∆φ distribution would be a possiblesignal of cold nuclear matter effects.

⇒ No centrality-dependent broadening observed within

sensitivity.

PHENIXJet Results

(17/ 22)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Fragmentation

d+Au

kT Broadening

Cu+Cu

∆φ broadening

Outlook

Jets at RHIC

Acknowledgements

OutlookI Jet reconstruction efforts are ongoing.

I Current set of measurements being finalized!

I PHENIX capability for jet measurements improving:

I VTX (silicon vertex tracker) and FVTX (forward silicon

vertex tracker) to provide superior tracking and b/c

separation

I “sPHENIX” upgrade plan:

I dedicated jet detector with acceptance, hermiticity, hadronic

calorimetryI see A. Hanks talk, Tuesday 6:30pm

PHENIXJet Results

(18/ 22)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Fragmentation

d+Au

kT Broadening

Cu+Cu

∆φ broadening

Outlook

Jets at RHIC

Acknowledgements

Jets at RHIC Study

I In support of the sPHENIX program:

I “Jet - Underlying Event Separation Method for Heavy IonCollisions at the Relativistic Heavy Ion Collider”(nucl-ex/1203.1353)

I Test ability to associate truth jets with reconstructed jets at

RHIC energies.

I Proof of principle that reconstructed jets produced at RHIC

rates can be separated from fake jets.

I 0.75× 109 Au+Au HIJING events at√sNN = 200 GeV

I ∆η ×∆φ = 0.1× 0.1 segmented “ideal” calorimeter withφ ∈ (0, 2π) , η ∈ (−1,+1)

PHENIXJet Results

(19/ 22)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Fragmentation

d+Au

kT Broadening

Cu+Cu

∆φ broadening

Outlook

Jets at RHIC

Acknowledgements

Jets at RHIC Study

I Iterative background subtraction evolved from ATLAS procedure:

I exclusion of jet energy from background determination

I proper v2 modulation

PHENIXJet Results

(20/ 22)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Fragmentation

d+Au

kT Broadening

Cu+Cu

∆φ broadening

Outlook

Jets at RHIC

Acknowledgements

Jets at RHIC Study

[GeV] T,trueE10 20 30 40 50 60

jets

N

0

500

1000

1500

2000

2500

> = 18.61TTrue <E

= 0.745(S+B)

S

Au+Au @ 200 GeV, 0 - 10%

JetsTR = 0.2 Anti-k

= 20-25 GeVTReco E

[GeV] T,trueE10 20 30 40 50 60 70

jets

N

0

20

40

60

80

100

120

140

160

180

200

220

240

> = 23.7TTrue <E

= 0.802(S+B)

S

Au+Au @ 200 GeV, 0 - 10%

JetsTR = 0.3 Anti-k

= 30-35 GeVTReco E

I High purity of reconstructed jets:

I Appropriate regime for well-controlled unfolding to E trueT

I Before any fake jet rejection scheme!

PHENIXJet Results

(21/ 22)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Fragmentation

d+Au

kT Broadening

Cu+Cu

∆φ broadening

Outlook

Jets at RHIC

Acknowledgements

Jets at RHIC Study

[GeV] TE5 10 15 20 25 30 35 40 45 50

]

­1

[(G

eV

)T

/dE

jets

dN

even

ts1

/N

­910

­810

­710

­610

­510

­410

­310

­210

­110

1

10

HIJING True Jets

sPHENIX Recon. Jets

sPHENIX Recon. matched

sPHENIX Recon. not matched

JetsTR = 0.3 Anti­k

Au+Au @ 200 GeV, 0 ­ 10%

I Jets from hard scatterings dominate above E recoT > 20, 30, 40 GeV

for R = 0.2, 0.3, 0.4 anti-kT, respectively.

I RHIC luminosity upgrade: 1010 central Au+Au collisions / year

⇒ capitalize on high PHENIX data rate

⇒ high statistics inclusive jet, di-jet, γ-jet measurements!

I see A. Hanks talk, Tuesday 6:30pm

PHENIXJet Results

(22/ 22)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Fragmentation

d+Au

kT Broadening

Cu+Cu

∆φ broadening

Outlook

Jets at RHIC

Acknowledgements

Many Thanks To. . .

I Brian Cole, Nathan Grau, Yue-Shi Lai

I Ali Hanks, Jamie Nagle, Anne Sickles for sPHENIX discussions

I PHENIX Collaboration

I WWND12 Organizers