d.v. perepelitsa reconstructed jet results introduction in p ......p+p fragmentation d+au kt...
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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