1. A Novel Heavy Quark Suppression Mechanism in the QGP
Time evolution
Presentation Title Slide Notes
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Ivan Vitev, Nuclear Theory, T-16 , LANL
"Characterization of the Quark-Gluon Plasma with Heavy Quarks” Seminar
June , 2008, Bad Honnef, Germany

2. Outline of the Talk Jet tomography of the QGP
Success of jet quenching for light hadrons, QGP tomography
The heavy quark puzzle at RHIC. A space-time picture of hadronization
Collisional dissociation of hadrons in dense QCD matter
Dissociation: new approach to D- and B-mesons suppression in the QGP
Light cone wave-functions. Mesons propagation in matter
Phenomenological results for RHIC and the LHC
Heavy resonances and partial chiral symmetry restoration
Hadrons and  symmetry. Formation time of resonances in the medium
Interaction and decay of heavy resonances in matter
Experimental detection techniques
Summary and outlook
Universal modification of fragmentation functions in the QGP
Talk based upon: A.Adil, I.Vitev, Phys. Lett. B649 (2007)
Ch.Markert, R.Bellwied, I.Vitev, Phys. Lett. B to be submitted
R. Sharma, I.Vitev, in progress

3. Light Hadron Quenching
Nuclear modification factor
Predictions of this formalism tested vs
particle momentum, C.M. energy, centrality
I.V., Phys.Lett.B 639 (2006)
Constrained by the gluon rapidity (entropy) density

4. Non-Photonic Electron / Heavy Flavor Quenching
Proceed the same way to heavy flavor in A+A collisions
Single electron measurements (presumably from heavy quarks) may be
problematic
M.Djordjevic, M.Gyulassy, Nucl.Phys.A (2004)
Radiative Energy Loss using (D)GLV
(both c + b)
Radiative + Collisional + Geometry
(both c + b) (overestimated)
Deviation by a factor of two
Is it accidental or is it symptomatic?
S. Wicks et al., Nucl.Phys.A (2007)

5. The Space-Time Picture of Hadronization
In mesoscopic systems one has to account for the space-time evolution
Inside-outside cascade
J.D. Bjorken, Lect.NotesPhys.56, (1987)
Correctly accounts for the leading energy and mass dependence. Lack of control over t0
Outside-inside cascade
A. Bialas, M.Gyulassy, Nucl.Phys.B 291, (1987)
Correctly points at the reduction of tform at large values of x. Specific for Lund string fragmentation. Mass dependence obscured

6. Evaluating the Formation Times
Problem: treated in the same way as light quarks + B D
QGP extent (~5 fm)
Parton
Hadron
20 fm
1.5 fm
0.4 fm
Fragmentation and dissociation of hadrons from heavy quarks inside the QGP

7. Collisional Dissociation of D / B Mesons
Conceptually different approach to heavy flavor suppression
Time evolution
A. Adil, I. Vitev, Phys. Lett. B649, 139 (2007), hep-ph/

8. Light Cone Wave Functions
From general theory of LCWF for the lowest-lying Fock state
- Transverse momentum scale
- Longitudinal momentum fractions
S.Brodsky, D.S.Hwang, B.Q.Ma, I.Schmidt, Nucl.Phys.B 592 (2001)
Results for heavy flavor
Expansion in Fock components
LO Fock component
Mean Peaked at large x
Models such as coalescence should use
plausible wave functions, especially for heavy flavor

9. Medium-Modified Heavy Meson
Initial distribution:
Resum using GLV the multiple scattering in
impact parameter (B,b) space
Heavy meson acoplanarity: ?
Broadening (separation) the q q-bar pair:

10. Initial Conditions (Hard Parton Spectra)
Simultaneous fragmentation and dissociation call for solving a system
of coupled equations
I.V.,T.Goldman,M.Johnson,J.W.Qiu, Phys.Rev.D74 (2006)
Example:
radioactive
decay chain
Initial
conditions
Proposed back-2-back D / B
triggered correlations

11. Heavy Meson Dissociation at RHIC and LHC
Coupled rate equations
The asymptotic solution in the QGP -
sensitive to t0~0.6 fm and expansion
dynamics
Features of energy loss
B-mesons as suppressed as D-mesons
at pT~ GeV at the LHC
Unique feature
A. Adil, I. Vitev, Phys. Lett. B649, 139 (2007)

12. Quenching of Non-Photonic Electrons
Full semi-leptonic decays of C- and B-
mesons and baryons included. PDG
branching fractions and kinematics.
PYTHIA event generator
Similar to light , however, different
physics mechanism
B-mesons are included. They give a
major contribution to (e++e-)
Note on applicability
D-, B-mesons to
(e++e-) to 25 GeV

13. Areas of Improvement
Incorporate radiative and collisional energy loss at really high pT
Main criticism: what are the modifications to a fragmentation process,
modified fragmentation functions, coalscence, …
( We wanted to solve this, the hierarchy problem, GUT, the baryon asymmetry, dark matter … but we couldn’t in the same paper )
A+A
These are not “modified fragmentation functions”
A. Majumder, X.N.Wang (2008)

14. R. Sharma, I. Vitev, in prepration
A Possible Path
Definition of the fragmentation
functions
The apparent duality between
parton distribution functions
and fragmentation functions is
understandable
From D(z) parameterizations or
LCWF extract information about
matrix elements
We may gain insight of universal (T) modifications to fragmentation functions
R. Sharma, I. Vitev, in prepration

15. Effects of Partial Chiral Symmetry Restoration
Kaon
Lagrangian
Scale of chiral symmetry restoration
- Includes approximately strange quarks
Mass shifts
G. Brown, M.Rho, Rev. Mod. Phys., (2001)
Width broadening
Phi meson
L. Holt, K.Haglin, J. Phys. G31, S245 (2005)
Manifestation for baryons
L. Glozman, Phys.Lett. B475, 329 (2000)
Evidence for possible chiral
symmetry restoration
Important to include baryons
(,*) in experimental searches
at finite T

16. Motivation / Estimates - a Simple Case
Mass of heavy resonances: falls in the right region to ensure early formation
Quick evaluation ( z = 0.7 )
QGP formation (in the absence of dynamical
calculation)
Cross sections and z distributions

17. Formation Time of Resonances
Distributions
One has to approximate fragmentation functions. Normalizations cancel in the ratio
RHIC
LHC

18. In-medium Lifetime (Stronger Constraints)
Spectral function: medium broadening
Remember the dilation factor
Reduction if the lifetime is critical if any
effects are to be observed in the resonance
channel (upper pT limit)
URQMD study: any signal in pT 0-2 GeV strongly affected by hadronic rescattering of decay products (lower pT limit)
L. Holt, K.Haglin, J. Phys. G31, S245 (2005)
Phi meson
M.Bleicher et al., Phys. Lett. B530, 81 (2002)

19. Triggered Measurements
Ensure maximum medium size without changing the formation times
pT associated
pT trigger
There is always a time distribution
Many of the resonances will be dissociated. We are concerned with those that survive .

20. Summary of Open Heavy Flavor Suppression
Collisional QGP-induced B- / D-meson dissociation
Derived formation and dissociation times in the QGP. They are short
Solved the set of coupled rate equations. More sensitive to QGP
properties and formation / expansion dynamics than e-loss
Found that suppression of non-photonic electrons from heavy mesons,
including B, is large. Not inconsistent with light pions
B-mesons are as suppressed as D-mesons at pT ~ 10 GeV, unique
Toward experimental resolution of the B- / D- puzzle
Identify the B- and D-meson contribution to the inclusive electron spectra
and the suppression factor RAA separately for Bs and Ds
This will certainly motivate us to improve the calculation: modified fragmentation functions (really) and folding in energy loss.
Searches for chiral symmetry restoration
Identified the phase space and channels if those searches are to be done experimentally wit heavy resonances.

21. Outline of the Talk Jet tomography of the QGP
Success of jet quenching for light hadrons, QGP tomography
The heavy quark puzzle at RHIC. A space-time picture of hadronization
Collisional dissociation of hadrons in dense QCD matter
Dissociation: new approach to D- and B-mesons suppression in the QGP
Light cone wave-functions. Mesons propagation in matter
Phenomenological results for RHIC and the LHC
Heavy resonances and partial chiral symmetry restoration
Hadrons and  symmetry. Formation time of resonances in the medium
Interaction and decay of heavy resonances in matter
Experimental detection techniques
Summary and outlook
Universal modification of fragmentation functions in the QGP
Talk based upon: A.Adil, I.Vitev, Phys. Lett. B649 (2007)
Ch.Markert, R.Bellwied, I.Vitev, Phys. Lett. B to be submitted
R. Sharma, I.Vitev, in progress

22. I.V., M.Gyulassy, Phys.Rev.Lett. 89 (2002)
Jet Tomography
Determining the properties of the QGP:
SPS
RHIC
LHC
I.V., M.Gyulassy, Phys.Rev.Lett. 89 (2002)
F.Karsch, Nucl.Phys.A698 (2002)

23. Single inclusive pion suppression at the LHC
Running
Fixed
High pT suppression at the LHC can be
comparable and smaller than at RHIC
LHC quenching follows the steepness
of the partonic spectra
Reduced sensitivity to medium properties
S.Wicks et al., in progress

24. Direct photon at the LHC
Direct photons also have limited sensitivity: isospin effects,
cold nuclear matter e-loss
Prompt photons +
Fragmentation photons
Better jet interaction
measures?
Direct photon tagging:
can be compromised by
fragmentation photons

25. Non-Photonic Electron / Heavy Flavor Quenching
Radiative and collisional energy loss
Langevin simulation of heavy quark
diffusion
S. Wicks et al., (2005)
N. Armesto et al., (2006)
Ratio:
Opacity of the QGP
H. van Hees, R. Rapp, (2005)
G. Moore, D.Teaney (2005)
Diffusion coefficient D and eventually
Existence of heavy heavy
resonances near Tc in the QGP

26. The Path Forward An interesting idea valid physics explanation
To understand heavy flavor modification in the QGP we need direct and
separate measurements of D- and B-mesons, excellent statistics
Measurable at RHIC
Measurable at the LHC
A.Adil, I.Vitev, Phys. Lett. B (2006)
W.Horowitz, M. Gyulassy, (2007)
Meson
dissociation
PQCD,
Transport
String theory
AdS/CFT
10-15
50-100
Never
PT [GeV]

27. Heavy Flavor Elliptic Flow and Suppression
Test coalescence model fits to the v2 of
light hadrons via heavy flavor
Understand the structure of mesons
light cone wave functionsc
Sensitive to the opacity of the QGP
and its formation time
D. Molnar (2004)
A. Adil, I. Vitev, Phys.Lett.B (2007)

28. Heavy Quark Production and Correlations
Fast convergence of the perturbative
series
Possibility for novel studies of heavy
quark-triggered (D and B) jets: hadron
composition of associated yields

29. Scales in Thermalized QGP (GP)
Experimental: Bjorken expansion
Theoretical: Gluon dominated plasma
Energy density
Transport coefficients (not a good measure for expanding medium)
Define the average for Bjorken

30. Langevin Simulation of Heavy Quark Diffusion
Input in a Langevin simulation of heavy quark diffusion
H. van Hees, I.V., R. Rapp, in preparation
Drag coefficient:
Diffusion coefficient:
Equilibration is imposed by Einstein’s
fluctuation-dissipation relation:
Radiative energy loss is dominant except for b-quarks and very small systems

31. Transport + Quenching Approach
Numerical results for heavy quark diffusion
Results are preliminary
H. van Hees, I.V., R. Rapp, in preparation
The suppression and v2 are large when e-loss and q-resonance interactions are
combined
Normal hierarchy: c quarks are significantly more suppressed than b-quarks

32. Hard Probes from Factorized PQCD
xbP’ P
xaP Pd
Single and double inclusive hard production
in PQCD - applicable from photons to heavy
quarks X
Pd / zd
Pc / zc
Single and double inclusive hard production
in PQCD - applicable from photons to heavy
quarks X Pc
Power laws:
Quenching factor

33. Jet cross sections: comparison to LO and NLO PQCD
I.V., S. Wicks, in preparation
Good comparison to the shape at LO.
Meaningful K-factor
Even better comparison at NLO.

34. Jets from Factorized PQCD
Single and double inclusive hard production
in PQCD - applicable from photons to heavy
quarks P’
xbP’ P
xaP Pd X
Pd / zd
Pc / zc X Pc
For jets:
Caveat: parton-hadron duality
Jet cross sections are more inclusive and therefore more robust PQCD observables
CDF studies:
J.Collins, D.Soper, G.Sterman, Nucl.Phys.B (1983)