1 Wolf G. Holzmann Will review critical aspects of jet medium interaction at RHIC (with emphasis on...
Transcript of 1 Wolf G. Holzmann Will review critical aspects of jet medium interaction at RHIC (with emphasis on...
1
Wolf G. HolzmannWolf G. Holzmann
Will review critical aspectsWill review critical aspectsof jet medium interaction at of jet medium interaction at RHIC (with emphasis onRHIC (with emphasis onPHENIX results)… PHENIX results)…
… … then discuss potential forthen discuss potential forstudying the medium studying the medium response to jet quenchingresponse to jet quenchingwith the ATLAS detector at with the ATLAS detector at the LHCthe LHC
2
dy
dE
RT
Bj0
2
11
τπε =
εBjorken~ 5 - 15 GeV/fm3
~ 35 – 100 ε0
high energydensities quark dof
Evidence for stronglyEvidence for stronglyinteracting partonic matterinteracting partonic matteris compelling !is compelling !
Strongly Interacting Matter at RHIC
stronglycoupled
3
Jets as a tomographic probe of the medium
coneRFragmentation:
hadron
parton
pz
p≡
Jets in h+h Jets in h+h collisionscollisions
coneRFragmentation:
hadron
parton
pz
p≡
Jets in HI Jets in HI collisionscollisions
Gyulassy et al., nucl-th/0302077
Jet modification sensitive to gluon densities, path length, …Jet modification sensitive to gluon densities, path length, ….Jets as Tomographic Probes of the Medium!
4
Phys. Rev. Lett. 90, (2003)
STAR
Jets via:Two Particle Correlations
Jets via:Nuclear Modification Factor
( )( )Events ppin Yield
EventsAu Auin Yield
+•
+=
BARAA
High pT Jet Modification in Au+Au
Strong jet modification observed in Au+AuStrong jet modification observed in Au+Au
How is the energy taken up by the medium ?
5
nucl-ex/0507004
T. Renk, J. Ruppert hep-ph/0509036
Strong centrality dependent modification Strong centrality dependent modification of away-side jet in Au+Auof away-side jet in Au+Au
Possible mechanismsPossible mechanismsmach-cone scenariomach-cone scenario
nucl-th/0406018 Stoeckerhep-ph/0411315 Casalderrey-Solana, et al
Not the only explanation:Not the only explanation:
Cherenkov gluon radiation: nucl-th/0507063 Koch, Majumder, X.-N. Wang
Jets and Flow couple: hep-ph/0411341 Armesto,Salgado,Wiedemann
Intermediate pT Jet induced Correlations
Can two particle correlationsCan two particle correlationsprovide constraints for theseprovide constraints for theseconjectures?conjectures?
6
D D
Characterize away-side shape via:
RMS : measures width of away-side peak
Kurtosis : <(π)4>/RMS2, the 4th central moment, measures “gaussian-ness” of peak (= 3 for
Gaussian)
D : distance between away-side peak and π from double gaussian fit -> approximates peak-position
Let’s take a closer Look at these Shapes
7
Shape modification apparently largely independent of system Shape modification apparently largely independent of system size and beam energy in range root(s) ~ 64 -200 GeV !size and beam energy in range root(s) ~ 64 -200 GeV !
Energy and System Size Dependence of Shape Parameters
8
But medium not too different over this range …
Consistent with intermediate pConsistent with intermediate pT T shape modification shape modification
being dominated by medium response to jetbeing dominated by medium response to jet
9
PHENIX Preliminary
[1] Majumder, Wang, nucl-th/0507062
[2] Koch, Majumder, Wang, nucl-th/0507063
Weak pWeak pT T dependence poses dependence poses
challenges for earlychallenges for earlygluon Cherenkov radiation gluon Cherenkov radiation models which predicted a models which predicted a
strong trend with pstrong trend with pTT
pT Dependence of Shape Parameters
10
MesonMeson vs. vs. BaryonBaryon associated partner (for fixed Hadron associated partner (for fixed Hadron trigger)trigger)
PHENIX Preliminary
Jet associated mesons and baryons Jet associated mesons and baryons show similar shape modification show similar shape modification
Jet Associated Identified Particle Correlations
11
If away-side parton is deflectedIf away-side parton is deflectedin medium, followed by normalin medium, followed by normaljet fragmentation, expect little jet fragmentation, expect little change in the away-side jet change in the away-side jet particle species compositionparticle species composition
Particle ratios inside jet can give insight!Particle ratios inside jet can give insight!
Can PID dependent jet correlations constrain deflection?
12
MesonMeson vs. vs. BaryonBaryon associated partner (for fixed Hadron associated partner (for fixed Hadron trigger)trigger)
Jet Associated Baryon to Meson Ratio
Baryon/meson ratio trend in jets qualitatively similar to Baryon/meson ratio trend in jets qualitatively similar to baryon/meson ratio trend of bulk matter.baryon/meson ratio trend of bulk matter.
Same mechanism?Same mechanism?
13
Remember …
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Single particle baryon/meson ratio well described by Single particle baryon/meson ratio well described by recombination models.recombination models.
Constituent quark scaling of elliptic flow.Constituent quark scaling of elliptic flow.
Greco & Konucl-th/0405040
14
coneR
Data is not inconsistent with a picture where Data is not inconsistent with a picture where partons from shock wave “remember” jet direction.partons from shock wave “remember” jet direction.The jet and it’s medium excitation are correlated.The jet and it’s medium excitation are correlated.
Jet quenching can introduce 2-Jet quenching can introduce 2-body correlations between the body correlations between the jet and the medium:jet and the medium:
R. Fries, S. Bass and B. Mueller nucl-th/0407102
One Possible Scenario
15
Can we do energy calibrated studies of the medium response?
• Normal dijet (πo-h):
– Trigger bias: Eπ < Ejet,, <z>~0.75
– Possible surface bias
• Direct tagged jet:
– No fragmentation: E ~ Ejet
– No strong interaction, sensitive
to the whole medium
Proposed in hep-ph/9605213Proposed in hep-ph/9605213~10 years ago~10 years ago
Fix maximum jet energy that Fix maximum jet energy that can be transferred to the can be transferred to the medium, check for consistencymedium, check for consistencyin medium response.in medium response.
16
generate incl. generate incl. -h per trigger yield-h per trigger yield
Methodology in a Nutshell
generate decay generate decay -h per trigger yield-h per trigger yield
(Use pair by pair waiting with MC factor (Use pair by pair waiting with MC factor for prob. That for prob. That ππ at given p at given pT T decays todecays to
in pin pT T range of interest)range of interest)
p+psubtract decay subtract decay -h per trigger yield-h per trigger yieldfrom from -h per trigger yield-h per trigger yield
# inclusive # inclusive ##decay decay
R=R=
€
Ydir−h
= 1R−1
RYinc−h−Ydec−h( )
17
PHENIX Preliminary PHENIX Preliminary
• data PYTHIA PYTHIA 6.1 kT = 2.5 GeV
-h Correlations in p+p
M. Nguyen (Stony Brook)
Reasonable agreement between data and PYTHIAReasonable agreement between data and PYTHIA
18
Black: Au+Au Red: p+p
1/N
trigd
N/d
(rad) Jiamin Jin (Columbia)
-h Correlations in Au+Au
We have the tools,We have the tools,we just need the statistics…we just need the statistics…
19
Possible Modification of Jet Topology
hep-ph/0411315 Casalderrey-Solana,Shuryak,Teaneynucl-th/0406018 Stoeckerhep-ph/0503158 Muller,Ruppert
Wake Effect or “sonic boom”
nucl-th/0507063 Koch, Majumder, X.-N. Wang
Cherenkov Gluon Radiation
wrong pwrong pTT dependence? dependence?
wrong particle composition in jet?wrong particle composition in jet?
Two-Particle Correlation data does not proof mach-cone Two-Particle Correlation data does not proof mach-cone but it seems consistent with it.but it seems consistent with it.
Bending Jets
20
Jet tomography at LHC
Can (and will) do RHIC type studies with better statisticsCan (and will) do RHIC type studies with better statistics
Can (and will) do high pCan (and will) do high pTT jet reconstruction jet reconstruction
(event-by-event jet tomography, event-by-event medium (event-by-event jet tomography, event-by-event medium response opposite reconstructed jet…)response opposite reconstructed jet…)
How can jet studies at the LHC improve on the situation?How can jet studies at the LHC improve on the situation?
Truly high pTruly high pTT jets will be jets will be
produced copiously in produced copiously in Pb+Pb collisions at the LHCPb+Pb collisions at the LHC
21
My personal detector wish-list for studying medium My personal detector wish-list for studying medium response to jet quenching at the LHC:response to jet quenching at the LHC:
Full azimuth and large pseudorapidity coverage toFull azimuth and large pseudorapidity coverage tostudy event shapes opposite a reconstructed jetstudy event shapes opposite a reconstructed jet
Excellent capabilities to study global medium propertiesExcellent capabilities to study global medium properties
Excellent calorimetry for full event-by-event jet Excellent calorimetry for full event-by-event jet reconstructionreconstruction
The ATLAS Detector has all these capabilities!The ATLAS Detector has all these capabilities!
Based on the previous slides …
Excellent photon identification capabilityExcellent photon identification capability
22
ATLAS Calorimetery Hadronic Barrel
Hadronic EndCap
EM EndCap
EM Barrel
Forward
Finely segmented calorimeter coverage over full rangeand large range
The ATLAS Calorimeter
23
(Di)jets from PYTHIA (Di)jets from PYTHIA in Calorimter Towersin Calorimter Towers
embedded in embedded in HIJING eventHIJING event
Measuring Jets in The ATLAS Calorimeter
Energetic jets clearly visible over the heavy ion backgroundLarge coverage is important
24
Jet
Background
Jet
Background
All too wide for single photons
x = 0.0028 x 0.1
– Segmentation of first EM sampling layer so fine that heavy ion background is ~ negligible (unique at LHC)
– Fine -> rejection of neutral hadron decays
– Clean 1st sampling-> prompt isolation
Taking a closer look
25
Two Approaches to Jet Reconstruction in ATLAS
A) Seeded Cone Algorithm
Original cellsOriginal cells Cloned cellsCloned cells
Original towersOriginal towers
Subtracted cellsSubtracted cells
New towersNew towers
Reconstructed jetsReconstructed jets
Layer-by-layersubtraction(exclude seeds)
Currently also lookingCurrently also lookingat methods to improveat methods to improvealgorithm: seed selection,algorithm: seed selection,background subtraction, …background subtraction, …
First approach: First approach: use standard p+p cone algorithm use standard p+p cone algorithm with background subtractionwith background subtraction
26
Jet Energy Resolution with Seeded Cone Algorithm
Study of different event samples embeddedinto central Pb+Pb HIJING (b=0-2 fm)
Results obtained from standard p+p Results obtained from standard p+p cone algorithm w/ backgr.- subtractioncone algorithm w/ backgr.- subtractionSome recalibration still needed.Some recalibration still needed.
27
B) KT Algorithm clusters particles close in phase-space:
dij = min(k2ti,k2
tj)R2 , where R2=(i-j)2+(i-j)2
Kt algorithm purposefully mimics a walk backwardsalong the fragmentation
chain
for all possible combinations: O(N3)
Cacciari et al: “Fast” Kt optimization to O(NlogN)
Two Approaches to Jet Reconstruction in ATLAS
diB = k2ti
28
How fast is fast?
“Fast” Kt algorithm outperforms cone algorithm,Becomes feasible in heavy ion environment!
M. Cacciari et al, hep-ph/0512210
29
Real Jets appearas narrow towers
“Fake” Jetsappear flat and broad
UseUse jet topology to discriminate between jets and backgroundjet topology to discriminate between jets and background!!
“Fast” Kt Finder: Discriminating Jets and Background
30
3 4
21
34
1
2
Initial look seems promising.Initial look seems promising.Other variables can also be Other variables can also be constructed. constructed.
E T,max = maximum ET in calo cell
<E T > = average ET in calo cell
Discriminating Jets and Background: A First Look
31
Can we control the flowing background?
Presampler Layer 1 Layer 2 Layer 3
Yes! Can measure dN/dϕ in different layers
(and sections) of calorimeters e.g. EM Barrel
η
ϕ ϕ ϕ ϕ
ϕ ϕ ϕ ϕ
η η η
32
Reaction Plane Resolution
ATLAS has excellent reaction plane resolution!ATLAS has excellent reaction plane resolution!
33
PYTHIA + jet (75 GeV) superimposed on b=4 fm HIJING Pb+Pb event, full GEANT
Jet
+Jet in ATLAS
34
EM
Layer
1 E
T
(GeV
)
Isolated photon gives clean signal in EM first sampling layer
Even in central Pb+Pb !
One (of 64) rows in barrel EM calorimeter 1st sampling layer
Δη×Δϕ = 0.003x0.1
+Jet in ATLAS
35
PYTHIA + jet (75 GeV) superimposed on b=4 fm HIJING Pb+Pb event, full GEANT
Background subtracted
Jet
+Jet in ATLAS
36
+Jet in ATLAS
Direct triggered angularcorrelationsenergy calibrated: - jet studies - mach cone studies
Photon bremsstrahlung injet cone?
Many interesting possibilities: let your imagination run wild :-)
37
Summary
Di-hadron away-side modification at intermediate pT at RHIC showscharacteristics of medium response to jet quenching
Consistent with (but no proof of) mach cone type scenario, pT and PID dependent correlations can provide constraints for models
ATLAS detector uniquely suited to study jet medium interactionsat the LHC
Lots of ground work on jet and flow reconstruction in heavy ion Environment (seeded cone algorithm, fast Kt algorithm, different Background subtraction schemes, etc…) being done in ATLAS
Studies shown only an “amuse gueule”, see N. Grau’s talk on Sunday
New collaborators are welcome!
38
★★ ★★★
★★
★
★
M. Baker, R. Debbe, A. Moraes, R. Nouicer, P. Steinberg, H. Takai, F. Videbaek, S. WhiteBrookhaven National Laboratory, USA
J. Dolejsi, M. SpoustaCharles University, Prague
A. Angerami, B. Cole, N. Grau, W. Holzmann, M. LelchoukColumbia Unversity, Nevis Laboratories, USA
A. Olszewski, B. Toczek, A. Trzupek, B. Wosiek, K. WozniakIFJ PAN, Krakow, Poland
L. RosseletUniversity of Geneva, Switzerland
J. Hill, A. Lebedev, M. RosatiIowa State University, USA
G. Atoian, V. Issakov, H. Kasper, A. Poblaguev, M. ZellerYale University, USA
A. DenisovIHEP, Russia
P. Chung, J. Jia, R. Lacey, N N.. AjitanandChemistry Department, Stony Brook University, USA
V. PozdnyakovJINR, Dubna, Russia
S. TimoshenkoMePHI, Moscow, Russia
ATLAS HI Working Group
39
40
DELPHI
Baryon yield dependence Baryon yield dependence consistent with jet physicsconsistent with jet physics
in e-e collisionsin e-e collisions
Baryon yield dependence Baryon yield dependence consistent with jet physicsconsistent with jet physics
in e-e collisionsin e-e collisions
41
i.e. Zero Yield At Minimum (ZYAM)
( ) ( ) ( )
0
HarmoC Jet Functiorrelation Function onic n
C a H Jφ φφ⎡ ⎤
ΔΔ⎢ ⎥Δ = +⎢ ⎥⎣ ⎦
64 6 748 876 7 8
( ) ( ) ( )0
0
Jet Function
JC a H
aφ
φ φΔ
Δ − Δ⎡ ⎤⎣ ⎦=6 7 8
( )min 0J φΔ =
a0 is obtained without putting any constraint on the Jet shape by requiring
Two source model : Flow (H) & Jet (J)
N.N. Ajitanand et al.N.N. Ajitanand et al.Phys. Rev. C 72, 011902 (2005)Phys. Rev. C 72, 011902 (2005)
2
vary
~ 0
out
c
Operational Demonstration
untill v
Unconstrained harmonic
Constrained
High pt particle constrainedperpendicular to RP
Constraint byte
Rψ
1 (A) LP
2 (B)
12
c
Decomposition of Flow and Jet Signals
Subtraction Extinction
Reliable Decomposition of Flow and Jet Reliable Decomposition of Flow and Jet
Signals via two separate MethodsSignals via two separate Methods
42
Test of Ansatz
Simulation
Strong Away-Side Modification in Au+Au Revealed via Both MethodsStrong Away-Side Modification in Au+Au Revealed via Both Methods
ZYAM subtracted J(ZYAM subtracted J())
Flow extinguished C(Flow extinguished C() = J() = J())
Data
Both Methods Agree!
Phys. Rev. C 72, 011902 (2005)Phys. Rev. C 72, 011902 (2005)
43
∑ ∑ = )(/)(0 φφ CJaJPFJet-Pair Fraction:
BtB
tAt
ABt n
nn
nJPFCY ×
××=Efficiency corrected
Conditional yield (CY):
BtBA
AB
nnn
nJPFCY ×
××=Efficiency corrected
Conditional yield (CY):
Eff. Corrected pair rate
Eff. Corrected Singles yields
Recorded values
( ) ( ) ( )
0
HarmoC Jet Functiorrelation Function onic n
C a H Jφ φφ⎡ ⎤
ΔΔ⎢ ⎥Δ = +⎢ ⎥⎣ ⎦
64 6 748 876 7 8Two Source Model
44
One approach: One approach: fix fix εε via N via Npartpart, ,
vary path length by vary path length by looking in and out of looking in and out of
reaction planereaction plane
One approach: One approach: fix fix εε via N via Npartpart, ,
vary path length by vary path length by looking in and out of looking in and out of
reaction planereaction plane
What are the relative influences of:What are the relative influences of:Energy-densityEnergy-density
Path-length (L, LPath-length (L, L22, L, Laa))
What are the relative influences of:What are the relative influences of:Energy-densityEnergy-density
Path-length (L, LPath-length (L, L22, L, Laa))
nucl-ex/0409015
Need to look at problem in several different ways to pin down mechanisticdetails!
D. Winter, WWND2006STAR, PRL 93 (2004) 252301
Mechanistic Details of Jet Modification
45
No striking difference in modification pattern observed for Au+Au No striking difference in modification pattern observed for Au+Au and Cu+Cu at the same Npart! Small differences in yield canand Cu+Cu at the same Npart! Small differences in yield can
cerve to constrain path length dependent modelscerve to constrain path length dependent models
Energy density major actor!Energy density major actor!Energy density major actor!Energy density major actor!
Per Trigger Yields can give additional constraints
46
47
48
Jet Position Resolution with Seeded Cone Algorithm
Results obtained from standard p+p Results obtained from standard p+p cone algorithm w/ backgr.- subtractioncone algorithm w/ backgr.- subtractionSome recalibration still needed.Some recalibration still needed.
Resolutions in and for <ET>~50 GeV
49
Jet
Background
Jet
Background
All too wide for single photons
x = 0.0028 x 0.1
– Segmentation of first EM sampling layer so fine that heavy ion background is ~ negligible
– Fine -> rejection of neutral hadron decays
– Clean 1st sampling-> prompt isolation
The ATLAS Calorimeter
50
The ATLAS Calorimeter
Δη×Δϕ in LAr Barrel:Layer 1: 0.003x0.1Layer 2: 0.025x0.025Layer 3: 0.05x0.025
Finely segmented calorimeter coverage over full rangeand large range
51
Infrared and collinear safe
Exceptionally suited to study jet sub-structure: - modification of jet topology in Pb+Pb - hard radiation within the jet
New ways to distinguish jets and background
Systematic cross-check to cone algorithm
Advantages of “Fast” Kt Algorithm
52
Possible Modification of Jet Topology
hep-ph/0411315 Casalderrey-Solana,Shuryak,Teaneynucl-th/0406018 Stoeckerhep-ph/0503158 Muller,Ruppert
Wake Effect or “sonic boom”
nucl-th/0507063 Koch, Majumder, X.-N. Wang
Cherenkov Gluon Radiation
hep-ph/0411341 Armesto,Salgado,Wiedemann
Jets and Flow couple
Can we use jets to probe the equation of state at RHIC?Can we use jets to probe the equation of state at RHIC?
53
Particle species dependent properties of bulk matter
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
54
coneR
R. Fries, S. Bass and B. Mueller nucl-th/0407102
55
MesonMeson vs. vs. BaryonBaryon associated partner (for fixed Hadron associated partner (for fixed Hadron trigger)trigger)
Jet Associated Identified Conditional Yields
Different pT trends of jet associated mesons and baryonsDifferent pT trends of jet associated mesons and baryons
56
System size and energy dependence
central peripheral
57
dNdNchch/d/d very similar for Au+Au and Cu+Cu at the same N very similar for Au+Au and Cu+Cu at the same Npartpart ! !
At RHIC almost all transverse energy At RHIC almost all transverse energy goes into particle productiongoes into particle production
Complementary opportunity for jet-tomography:Complementary opportunity for jet-tomography:-> fix energy density-> fix energy density-> vary path length -> vary path length
nucl-ex/0409015
Energy Density versus Path Length Effects
58
No striking difference in modification pattern observed for Au+Au No striking difference in modification pattern observed for Au+Au and Cu+Cu at the same Npart!and Cu+Cu at the same Npart!
Energy density major actor!Energy density major actor!Energy density major actor!Energy density major actor!
π
Jets via:Nuclear Modification Factor
( )( )Events ppin Yield
EventsAu Auin Yield
+•
+=
BARAA
Jets via:Two Particle Correlations
Jet Modification in Au+Au and Cu+Cu
59
We can use three parameters to characterize away side shape1. RMS : <(-π)2>, the width of the
distribution, the 2nd central moment.2. Kurtosis : <(-π)4>/RMS2, the 4th
central moment, equals to 3 if Gaussian.
3. D : half distance between the double peaks, a double gaussian fit.
D D
0-10% 30-40% 60-90%