PHENIXJet Results

(1/ 19)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Cu+Cu

d+Au

nPDF effects

Outlook

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

at 200 GeV from PHENIX

Dennis V. PerepelitsaColumbia University

for the PHENIX Collaboration

Hard Probes 2012Cagliari, Sardinia, Italy

31 May 2012

PHENIXJet Results

(2/ 19)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Cu+Cu

d+Au

nPDF effects

Outlook

Jets in Heavy Ion Collisions

0 0.5 1

Eve

nt F

ract

ion

0.1

0.2 =7.0 TeVspp

PYTHIA

CMS -1L dt = 35.1 pb∫

, R=0.5TAnti-k

(a)

0 0.2 0.4 0.6 0.8 1

Eve

nt F

ract

ion

0

0.1

0.2

20-30%

(d) 0.2 0.4 0.6 0.8 1

0.1

0.2 =2.76 TeVNNsPbPb

PYTHIA+DATA

50-100%

(b)

Iterative Cone, R=0.5

-1bµL dt = 6.7 ∫

)T,2

+pT,1

)/(pT,2

-pT,1

= (pJA0.2 0.4 0.6 0.8 1

0.1

0.2

10-20%

(e) 0.2 0.4 0.6 0.8 1

0.1

0.2

30-50%

(c)

> 120 GeV/cT,1

p

> 50 GeV/cT,2

p

π32 >

12φ∆

0.2 0.4 0.6 0.8 1

0.1

0.2

0-10%

(f)

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/ 19)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Cu+Cu

d+Au

nPDF effects

Outlook

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

⇒ hard probes analyses from Cu+Au and U+U in progress!

PHENIXJet Results

(4/ 19)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Cu+Cu

d+Au

nPDF effects

Outlook

PHENIX detector

I Drift Chamber (DC), Pad Chambers (PC) and Ring ImagingČerenkov 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/ 19)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Cu+Cu

d+Au

nPDF effects

Outlook

Gaussian Filter algorithm

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

pjetT ≡ max{∫ ∫

dη′dφ′pT(η′, φ′

)e−(∆η

2+∆φ2)/2σ2}

I Developed for use in heavy ion collisions.

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

I Stabilizes the jet axis in the presence of background

PHENIXJet Results

(6/ 19)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Cu+Cu

d+Au

nPDF effects

Outlook

Fake jet rejection

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

I Similar to “angularly-weighted” pT which rewards jets with a tightcore of energy and punishes diffuse jets.

⇒ efficient saturation with reconstructed pT⇒ trade reconstruction efficiency for sample purity⇒ data-driven approaches set threshold

PHENIXJet Results

(7/ 19)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Cu+Cu

d+Au

nPDF effects

Outlook

Energy Scale

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

(8/ 19)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Cu+Cu

d+Au

nPDF effects

Outlook

Jets in p+p at√s = 200 GeV

I Demonstration of PHENIX jet reconstruction and gaussian filteralgorithm capability:

I comparison with NLO pQCD across ten orders of magnitude.

I Fragmentation function (z = pparticle|| /pjet) measurement:

I required development of n-dimensional generalization of

SVD unfolding in GURU!

PHENIXJet Results

(9/ 19)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Cu+Cu

d+Au

nPDF effects

Outlook

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

(10/ 19)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Cu+Cu

d+Au

nPDF effects

Outlook

Suppression without de-correlation in Cu+Cu

I Suppression of reconstructed jet RAA:

⇒ over a wide pT range

⇒ increasing suppression in more central collisions

I Reconstructed di-jet ∆φ distributions unmodified:

⇒ no angular de-correlation in central collisions!

PHENIXJet Results

(11/ 19)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Cu+Cu

d+Au

nPDF effects

Outlook

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 relative to peripheral collision baselineI pT-feeding from modest underlying event evaluated with

embedding procedure and unfolded

I Suppression effect consistent with single-particle π0 measurement.

⇒ cold nuclear matter energy loss?⇒ impact parameter dependence of nPDFs?

PHENIXJet Results

(12/ 19)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Cu+Cu

d+Au

nPDF effects

Outlook

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 Multiple cone sizes provide additional control against effects ofunderlying event

I RCP exhibits increasing suppression with decreasing impactparameter

I Ongoing improvements to analysis will produce:

I RdA

I lower pT behavior

I results at ptruthT scale

PHENIXJet Results

(13/ 19)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Cu+Cu

d+Au

nPDF effects

Outlook

nPDF effects in d+Au RCP

I Nuclear PDF sets do not parameterize impact parameterdependence:

⇒ K. Eskola, Plenary 4B and I. Helenius, Parallel VC

I Leading-order toy study with EPS09 parameters

(nucl-th/1011.4534):

⇒ quadratic b-dependence of Au nPDF from PHENIX J/ψdata, (PRL 107, 142301 (2011))

⇒ suppression from nPDF effects underpredicts data

PHENIXJet Results

(14/ 19)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Cu+Cu

d+Au

nPDF effects

Outlook

Outlook

I Jet reconstruction efforts at PHENIX are ongoing.

I Preliminary results from d+Au jet reconstruction:

⇒ suppression effect at high-pT⇒ consequences for interpretation of A+A results!

I PHENIX capability for jet measurements improving:

⇒ VTX (silicon vertex tracker) and FVTX (forward siliconvertex tracker)

PHENIXJet Results

(15/ 19)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Cu+Cu

d+Au

nPDF effects

Outlook

BACKUP

PHENIXJet Results

(16/ 19)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Cu+Cu

d+Au

nPDF effects

Outlook

Backup Plots I

(GeV/c)T

p0 2 4 6 8 10 12 14 16 18 20

A

A R

00.20.40.60.8

11.21.4

1.61.8

22.22.4 = 200 GeV, 0-10% most centralNNsPHENIX Au+Au,

(arXiv:1205.5759)γdirect (PRL101, 232301)0π

(PRC82, 011902)η (PRC83, 024090)φ

p (PRC83, 064903)

0-20% cent. (PRL98, 232301)ψJ/ 0-20% cent. (PRC84, 044902)ω

(PRC84, 044905)HF±e (PRC83, 064903)+K

PHENIXJet Results

(17/ 19)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Cu+Cu

d+Au

nPDF effects

Outlook

Backup Plots II

gσdis(η, φ) ≡∑

i∈fragment

(pT )2i exp

(−(∆η2 + ∆φ2)/2σ2dis

)

PHENIXJet Results

(18/ 19)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Cu+Cu

d+Au

nPDF effects

Outlook

Backup Plots III

(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/cdAuT

p⊗ > 13.3 GeV/c dAuT

p

> 5 GeV/cdAuT

p⊗ 10-13.3 GeV/c ∈ dAuT

p

> 5 GeV/cdAuT

p⊗ 8-10 GeV/c ∈ dAuT

p

> 5 GeV/cdAuT

p⊗ 6.7-8 GeV/c ∈ dAuT

p

> 5 GeV/cdAuT

p⊗ 5-6.7 GeV/c ∈ dAuT

p

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/cdAuT

p⊗ > 6 GeV/c dAuT

p

PHENIX Preliminary

/4π < 5φ∆/4 < π3

pout (= 〈kT 〉) ≡ (pT)low · sin ∆φ

PHENIXJet Results

(19/ 19)

D.V. Perepelitsa

Introduction

Jets in PHENIX

Gaussian Filter

Analysis Techniques

p+p

Cu+Cu

d+Au

nPDF effects

Outlook

Backup Plots IV

(GeV/c)Tp2 4 6 8 10 12 14 16

dA

R0.8

1

1.21.4

1.60-20 %

0.8

1

1.2

1.4

1.620-40 %

0.8

1

1.2

1.4

1.640-60 %

0.8

1

1.2

1.4

1.660-88 %

(GeV/c)Tp0 2 4 6 8 10 12 14 16

0.6

0.81

1.2

1.4

1.6min bias

π η0

Phys. Rev. Lett. 98, 172302 (2007)

IntroductionJets in PHENIXGaussian FilterAnalysis Techniques

p+pCu+Cud+AunPDF effects

Outlook