Conical Correlations inHeavy-Ion Collisions
Barbara Betz
Thanks to: Miklos Gyulassy, Jorge Noronha, Dirk Rischke, Giorgio Torrieri
Phys. Rev. C 79, 034902 (2009), Phys. Lett. B 675, 340 (2009), Nucl. Phys. A 830, 777c (2009), arXiv:1005.5461
2 09/13/10 MIT Seminar, Boston Barbara Betz
Conical Correlations in HICWhat are „conical correlations in heavy-ion collisions“?
Correlations revealing the creation of Mach cones???
Experiment:
Review on experimental studies
Conclusions and Outlook
Theoretical approaches:
Jets & hydrodynamics
Different energy-loss mechanisms
What could they tell us about the medium created?
Fluctuating initial conditions, v3(carrying coals to Newcastle)
Why we need to study heavy-flavor tagged jets
Deflection of wakes due to transverse flow „Conical“ signal
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HIC Facilities
initial state
pre-equilibrium
expanding fireball
hadronization
hadronic phaseand freeze-out
S. Bass, Talk Quark Matter 2001
RHIC
FAIR
LHC
09/13/10 MIT Seminar, Boston Barbara Betz
RHIC, BNL: 2000 – … p+p, d+Au, Cu+Cu,
Au+Au LHC, CERN: 2008/9 - … p+p, Pb+Pb FAIR, GSI: ~2016 - … accelerates ions from p
to U
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2 Major RHIC Results
09/13/10 MIT Seminar, Boston Barbara Betz
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Reproducing the elliptic flow v2
P. Romatschke and U. Romatschke, Phys. Rev. Lett. 99,172301 (2007)
Medium behaves like an almostideal fluid
/s
BNL press release, April 18 2005.
09/13/10 MIT Seminar, Boston Barbara Betz
Particles don‘t interact,
expansion independent
of initial shape
Particles interact,expansion
determined by density gradient
„dust“ fluid
Data can be described by hydrodynamics
with small
Fluid-like Medium
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Jet Quenching• Like in medicine, hard probes can be
used to investigate the medium properties
• If created matter is opaque, a jet depositing its energy should eventually disappear jet suppression
STAR, Phys. Rev. Lett. 91 (2003) 072304
4 < pTtrigger < 6 GeV/c
pTassoc > 2 GeV/c
What can the energy lost tell us about the medium properties?
Trigger particle
University Wuppertal, “Schul-Vorlesungen zur Physik”
09/13/10 MIT Seminar, Boston Barbara Betz
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Jets in HIC I
By observation: Confirm fast
thermalization Study EoS of the fluid
Mach cone angle sensitive to EoS
Can energy lost by jets tell us something about medium properties?
IF the medium behaves like a fluid:
Mach cones have to occur because of
fluid dynamics
4 < pTtrigger < 6 GeV/c
0.15 < pTassoc < 4 GeV/cAu+Au / p+p
= 200 GeVs
PHENIX, Phys. Rev. C 77, 011901 (2008)
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Jets in HIC II
STAR, Nucl. Phys. A 774, 129 (2006)
Reflect interaction of jet with medium
• Redistribution of energy to lower pT-particles
• Re-appearance of the away-side for low and intermediate pT
assoc
H. Stöcker, Nucl. Phys. A 750, 121 (2005), J. Casalderrey-Solana et al. Nucl. Phys. A 774, 577 (2006)
09/13/10 MIT Seminar, Boston Barbara Betz
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Experimental Studies
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STAR, Phys. Rev. C 82, 024912 (2010)see also PHENIX, Phys. Rev. C 77, 011901 (2008)
Position of away-side
peaks does not change
strongly with pTassocNot due to
Cherenkov gluonradiation
What happens to larger pT
trigger?
Jet - Studies in HIC I
09/13/10 MIT Seminar, Boston Barbara Betz
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Investigation of path length dependence:Double-peaked structure becomes
more
pronounced out-of-plane
A. Sickeles [PHENIX], Eur. Phys. J. C 61, 583 (2009)
Jet - Studies in HIC II
09/13/10 MIT Seminar, Boston Barbara Betz
Could be due to deflection
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Centrality dependence:
double-peaked structure for central collisions
one peak structure for very peripheral collisions
PHENIX, Phys. Rev. Lett. 97, 052301 (2006)
J. Jia, Eur. Phys. J. C 62, 255 (2009)
Jet - Studies in HIC III
Energy Scan:
double-peaked structure occurs at about the same angle for different collision energies Mach cone???09/13/10 MIT Seminar, Boston Barbara Betz
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Some caveats
09/13/10 MIT Seminar, Boston Barbara Betz
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Background Subtraction
How can one proof/disproof
the two-source model?J. Ulery [STAR], PoS LHC07, 036 (2007)
D. d’Enterria and BB., Springer Lecture Notes (2008)
09/13/10 MIT Seminar, Boston Barbara Betz
Assumption (Two-source model) :
No correlations between flow anisotropy
and jets
ZYAM (Zero Yield At Minimum)
Subtraction of:estimated elliptic flow modulatedbackground
can leads to:double peaked structure
Background:Particle
correlation from elliptic flow
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3-Particle Correlations
J. Ulery [STAR], Int. J. Mod. Phys. E 16, 2005 (2007)
ptrigT=3 – 4 GeV, passoc
T=1 – 2 GeV Three-particle correlations
seem to corroborate Mach cone idea
- What’s the effect of ZYAM?
- No agreement with 3-particle cumulant method
C. Pruneau, Phys. Rev. C 79, 044907 (2009)
09/13/10 MIT Seminar, Boston Barbara Betz
Deflected jet
Mach Cone
ptrigT>3 GeV, passoc
T=1 – 2 GeV
C. Pruneau, Talk at the Workshop on ‘Critical Asessment of Theory and Experiment on Correlations at RHIC’, BNL, February 2009
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Theoretical Approach
09/13/10 MIT Seminar, Boston Barbara Betz
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Modelling of Jets
STAR, Phys. Rev. Lett. 95, 152301 (2005)
residue of energy and momentum given by the jet
• Assumption of isochronous/isothermal freeze-
out
• No interaction afterwards
mainly flow driven
Conversion into particles Freeze-out:
Jets can be modelled using (ideal) hydrodynamics:
e+p v.
Medium created in a HIC can be described using hydrodynamics
09/13/10 MIT Seminar, Boston Barbara Betz
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The Static Medium
09/13/10 MIT Seminar, Boston Barbara Betz
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Stopped Jet IApplying a static medium and an ideal Gas EoS for massless
gluons
Assume: Near-side jet is not modified by mediumMaximal fluid
response
Jet decelerating from v=0.999according to Bethe-Bloch
formalism
a=-1.36 GeV/fm
Simplest back-reaction from the medium
Bragg Peak
adjusts path length
BB et al., Phys. Rev. C 79, 034902 (2009)
09/13/10 MIT Seminar, Boston Barbara Betz
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Stopped Jet II
Mach cone forsound waves Diffusion
wake
dE dM GeV(0) v (0) 1.5
dt dt fm= =
t=4.5/v fmdE GeV dM GeV
(0) 1.5 (0) 0dt fm dt fm
= =
BB et al., Phys. Rev. C 79, 034902 (2009)
09/13/10 MIT Seminar, Boston Barbara Betz
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Stopped Jet III
Diffusion wake causes peak in jet direction
Normalized, background-subtracted isochronous Cooper-Frye at mid-rapidity
Energy Flow Distribution
Assuming: Particles in subvolume will be emitted into the same direction
pT = 5 GeV
BB et al., Phys. Rev. C 79, 034902 (2009)
Any conclusions about deposition mechanism???09/13/10 MIT Seminar, Boston Barbara Betz
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Stopped Jet IV• Jet stops after t=4.5/v
fm
dE GeV(0) 1.5
dt fmdM GeV
(0) 0dt fm
=
=
dE GeV(0) 1.5
dt fmdM GeV
v (0) 1.5dt fm
=
=
Vorticity conservation
tFO=4.5/v fm
tFO=6.5/v fm
tFO=8.5/v fmDiffusion wake still
present
BB et al., Phys. Rev. C 79, 034902 (2009)
09/13/10 MIT Seminar, Boston Barbara Betz
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Stopped Jet V
tFO=4.5/v fm
tFO=6.5/v fm
tFO=8.5/v fm
Diffusion wake causes peak in jet direction
Larger impact of thermal smearing
BB et al., Phys. Rev. C 79, 034902 (2009)
09/13/10 MIT Seminar, Boston Barbara Betz
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A Comparison
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BAMPS: Boltzmann Approach of MultiParton Scatterings
A transport algorithm solving the Boltzmann equations for on-shell
partons with pQCD interactions
C. Greiner, Talk at the Opening Symposium of the JET Collaboration, Berkeley, June 2010
Box scenario, no expansion, massless Boltzmann gas interactions, 2 -> 2
The shock front (Mach front) gets broader and vanish with more dissipation09/13/10 MIT Seminar, Boston Barbara Betz
Mach Cones in Transport
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Different Jet-Energy Loss Modells
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Modelling Jets using …
Conclusion about Mach cones?
pQCD
AdS/CFT
P. Chesler and L. Yaffe, Phys. Rev. D 78, 045013 (2008)
R. Neufeld et al, Phys. Rev. C 78, 041901 (2008)
Strongly-coupled theory
Pointing vector perturbation
Momentum density perturbation
Energy density perturbation
Energy density perturbation
Weakly-coupled theory
v=0.75
v=0.99955
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Non-Mach correlations caused by Neck region
Jets in AdS/CFT
J. Noronha et al., Phys. Rev. Lett. 102, 102301 (2009)
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Heavy Quark Jets
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Heavy Quark JetsCompare weakly and strongly coupled models using heavy punch-
through jet
pQCD: Neufeld et al. source for a heavy quark
AdS/CFT: Stress tables with/s=1/(4 ) R. Neufeld et al, Phys. Rev. C 78, 041901 (2008)
pT = 3.14 GeV
BB et al., Phys. Lett. B 675, 340 (2009)
No Mach-like peaks:AdS/CFT: Strong influence of the Neck region
Static medium and isochronous freeze-out needed for comparison
t=4.5/v fmS. Gubser et al, Phys. Rev. Lett. 100, 012301 (2008)
BB et al., Phys. Lett. B 675, 340 (2009)
J. Noronha et al., Phys. Rev. Lett. 102, 102301 (2009)
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The Expanding Medium
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Expanding Medium I
Consider different jet paths
b=0
• Apply Glauber initial conditions and an ideal Gas EoS for massless gluons• Focus on radial flow contribution
Experimental results based
on many eventsA. K. Chaudhuri, Phys. Rev. C 75, 057902
(2007) ,A. K. Chaudhuri, Phys. Rev. C 77, 027901
(2008)
• Two-particle correlation (Tfreeze-out < Tcrit = 130
MeV):
near-side jet
dE/dt = 1 GeV/fm
Jet 150
Etot = 5 GeV
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Expanding Medium IIEtot = 5 GeV
broad away-side peak double peaked structure
due to non-central jets
pTtrig = 3.5
GeV
PHENIX, Phys. Rev. C 77, 011901 (2008)
vjet =0.999
BB et al., arXiv: 1005.5461
09/13/10 MIT Seminar, Boston Barbara Betz
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Expanding Medium IIIEtot = 10
GeV
Strong impact of the Diffusion wake
broad away-side peak double peaked structure
Causes smaller dip for pT=2 GeV
pTtrig = 7.5
GeV
6 < pTtrigger < 10
1.5 < pTassoc < 2.5
f
Yield
Path length dependence Centrality dependence09/13/10 MIT Seminar, Boston Barbara Betz
STAR, Phys. Rev. C 82, 024912 (2010)
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Expanding Medium IV
Comparing different deposition scenarios, one sees that„cone“ angle approximately the same for different deposition
scenarios
pTassoc = 2.0 GeV: No double-peaked structure for pure energy
deposition scenario due to thermal smearking
pTtrig = 3.5
GeV pTassoc = 3.0
GeVpT
assoc = 2.0 GeV
vjet =0.999
BB et al., arXiv: 1005.5461
09/13/10 MIT Seminar, Boston Barbara Betz
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Expanding Medium V
Conical emission angle also appears for subsonic jets
Not a Mach cone
Considering a bottom quark (M=4.5 GeV), propagating at vjet < cs
(on-shell energy-momentum deposition scenario) pTassoc = 2.0
GeV
Cu+Cu: Similar away-side shoulder width, double-peak structure reappars for pT
assoc = 3 GeV
BB et al., arXiv: 1005.5461
PHENIX, PRL98, 232302 (2007)
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Some more caveats
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Hot Spots ICan fluctuating initial condition explain the 2+3-particle
correlations?Takahashi et al, PRL 103, 242301 (2009)
F. Grassi, Talk at the Glasma Workshop, BNL, May 2010
R. Andrade et al., arXiv: 0912.0803
09/13/10 MIT Seminar, Boston Barbara Betz
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Hot Spots IICheck with one single hot
spot
Heavy quark jets are not affected 09/13/10 MIT Seminar, Boston Barbara Betz
Au, De/e0=0.2
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Fluctuating Initial Conditions
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Initial Fluctuations IP. Sorensen J. Phys. G 37, 094011 (2010), B. Alver et al., Phys. Rev. C 81, 054905 (2010)
Glauber initial conditions:
due to symmetry, odd Fourier components vanish
higher Fourier components may occur
Fluctuating initial conditions:B. Alver, Talk at the Glasma Workshop, BNL, May 2010
09/13/10 MIT Seminar, Boston Barbara Betz
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Initial Fluctuations II
B. Alver et al., arXiv: 1007.5469
B. Alver et al., Phys. Rev. C 81, 054905 (2010), B. Alver et al., arXiv: 1007.5469H. Petersen et al., arXiv: 1008.0625
v3 not negligable small
• v3 is extensively studied
Calculating v3 using a viscous hydro model with initial conditions deformed
according to the eccentricities from a Glauber and a KLM (CGC) model
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Why v3 deformations cannot be the whole story
ptrigT=3 – 4 GeV, passoc
T=1 – 2 GeV
What are the consequences of triangular flow?
Do we only see fluctuating initial conditions?What is the difference of v3 and the impact of hot spots?
Study of heavy quark jets needed
120°
09/13/10 MIT Seminar, Boston Barbara Betz
- Correlation in Df1-Df2
Df1/2 120°
- No correlation in Dh1-Dh2
B. Alver et al., Phys. Rev. C 81, 054905 (2010)
Shock front??
~ 120
J. Ulery [STAR], Int. J. Mod. Phys. E 16, 2005 (2007)
Summary „Conical“ signal can be created (general effect):
by averaging over wakes created by jets in different events.There is a deflection of particles emitted due to collective
transverse flow.
Structure cannot directly be related to EoS, but is a measure for the flow
Quite insensitive to deposition mechanism, jet velocity (even
for subsonic jets), and system size
Necessary to study heavy-flavor tagged jets.
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„Conical“ correlations could arise from multiple non-Mach sourcesMach cones have to occur in heavy-ion collisions if there is a
fluid
09/13/10 MIT Seminar, Boston Barbara Betz