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Heavy Quark Energy Loss. William Horowitz Columbia University June 6, 2006. With many thanks to Simon Wicks, Azfar Adil, Miklos Gyulassy, Magdalena Djordjevic, and Brian Cole. Azfar Adil. Simon Wicks. Glue and Lights. Charm and Bottom. R AA ( j )=R AA (1+2v 2 Cos(2 j )+…). - PowerPoint PPT Presentation
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RHIC & AGS Annual Users’ Meeting ‘06 1
6/6/06 William Horowitz
Heavy Quark Energy Loss
William HorowitzColumbia University
June 6, 2006
With many thanks to Simon Wicks, Azfar Adil, Miklos Gyulassy, Magdalena
Djordjevic, and Brian ColeSimon Wicks Azfar Adil
RHIC & AGS Annual Users’ Meeting ‘06 2
6/6/06 William Horowitz
RAA()=RAA(1+2v2Cos(2)+…)• Glue and Lights • Charm and
Bottom
•Correlations of back-to-back jets, etc.
RHIC & AGS Annual Users’ Meeting ‘06 3
6/6/06 William Horowitz
Jets as a Tomographic Probe
• Tomography requires precision measurements AND precision, pQCD theory
Probe the unknown QGP with energy loss
Quark or Glue Jet probes: (, pT, - reac, MQ) init
Hadron jet fragments: (, pT, – reac ) final
RHIC & AGS Annual Users’ Meeting ‘06 4
6/6/06 William Horowitz
to understand the medium
• If pQCD makes the correct predictions, we can use
Jets as a Tomographic Probe (cont’d)
•Otherwise, jet suppression is just another non-perturbative anomaly of A+A collisions (like J/ suppression)
RHIC & AGS Annual Users’ Meeting ‘06 5
6/6/06 William Horowitz
Before the e- RAA, the picture looked pretty good:
– Null Control: RAA()~1
– Consistency: RAA()~RAA()
– GLV Prediction: Theory~Data for reasonable fixed L~5 fm and dNg/dy~dN/dy
Y. Akiba for the PHENIX collaboration, hep-ex/0510008
RHIC & AGS Annual Users’ Meeting ‘06 6
6/6/06 William Horowitz
But with Hints of Trouble:
• Theory v2 too small
• Fragile Probe?
A. Drees, H. Feng, and J. Jia, Phys. Rev. C71:034909 (2005)(first by E. Shuryak, Phys. Rev. C66:027902 (2002))
K. J. Eskola, H. Honkanen, C. A. Salgado, and U. A. Wiedemann, Nucl. Phys. A747:511:529 (2005)
RHIC & AGS Annual Users’ Meeting ‘06 7
6/6/06 William Horowitz
What Can Heavies Teach Us?
• Provide a unique test of our understanding of energy loss– Mass => Dead Cone => Reduction in E
loss
Bottom Quark =
(Gratuitous Pop Culture Reference)
RHIC & AGS Annual Users’ Meeting ‘06 8
6/6/06 William Horowitz
Entropy-constrained radiative-dominated loss FALSIFIED by e- RAA
Problem: Qualitatively, RAA~ e- RAA
RHIC & AGS Annual Users’ Meeting ‘06 9
6/6/06 William Horowitz
Inherent Uncertainties in Production Spectra
M. Djordjevic, M. Gyulassy, R. Vogt, S. Wicks, Phys. Lett. B632:81-86 (2006)
How large is bottom’s role?
– Vertex detectors could de-convolute the e- contributions
N. Armesto, M. Cacciari, A. Dainese, C. A. Salgado, U. A. Wiedemann, hep-ph-0511257
RHIC & AGS Annual Users’ Meeting ‘06 10
6/6/06 William Horowitz
The BDMPS-Z-WS Approach
• Increase to 14 to push curve down
• Fragility in the model allows for consistency with pions
N. Armesto, M. Cacciari, A. Dainese, C. A. Salgado, U. A. Wiedemann, hep-ph-0511257
RHIC & AGS Annual Users’ Meeting ‘06 11
6/6/06 William Horowitz
What Does Mean?
We believe it’s nonperturbative:– = .5 => dNg/dy ~ 13,000
R. Baier, Nucl. Phys. A715:209-218 (2003)
“Proportionality constant ~ 4-5 times larger than perturbative estimate”
K. J. Eskola, H. Honkanen, C. A. Salgado, and U. A. Wiedemann, Nucl. Phys. A747:511:529 (2005)
“Large numerical value of not yet understood”
U. A. Wiedemann, SQM 2006
RHIC & AGS Annual Users’ Meeting ‘06 12
6/6/06 William Horowitz
Is this Plausible? Maybe• Flow nonperturbative at low-pT
• v2 possibly nonperturbative at mid-pT
• Asymptotic Freedom MUST occur– But at what momentum?
WH, nucl-th/0511052 D. Winter, QM2005
RHIC & AGS Annual Users’ Meeting ‘06 13
6/6/06 William Horowitz
But what if we Neglected an Important Effect?
M. Mustafa, Phys. Rev. C72:014905 (2005) S. Wicks, WH, M. Gyulassy, and M. Djordjevic, nucl-th/0512076
RHIC & AGS Annual Users’ Meeting ‘06 14
6/6/06 William Horowitz
Elastic History
(a) J. D. Bjorken, FERMILAB-PUB-82-059-THY (Quantal)(b) M. H. Thoma and M. Gyulassy, Nucl. Phys. B351:491-506 (1991) (Classical)(c) E. Braaten and M. H. Thoma, Phys. Rev. D24:2625-2630 (1991) (Quantal)(d) P. Romatschke and M. Strickland, Phys. Rev. D71:125008 (2005) (Quantal)
People have thought about Elastic Loss for a long time, and in different ways—all assume parton starts in asymptotic past
Bottom Charm
Most correct (infinite time) elastic loss calculation approximately bounded by BT and TG curves
RHIC & AGS Annual Users’ Meeting ‘06 15
6/6/06 William Horowitz
Include Path Length Fluctuations with Realistic
Geometry– For fixed L~5 fm, Collisional+Radiative leads to pion overquenching
– Use Woods-Saxon density• hard production ~ TAA
• medium ~ participant
– This allows a self-consistent pion prediction
without “fixed L”approx
S. Wicks, WH, M. Gyulassy, and M. Djordjevic, nucl-th/0512076
RHIC & AGS Annual Users’ Meeting ‘06 16
6/6/06 William Horowitz
Our Extended Theory
• Convolve Elastic with Inelastic energy loss fluctuations
• Include path length fluctuations in diffuse nuclear geometry
• Separate calculations with BT and TG collisional formulae provide a measure of the elastic theoretical uncertainty
RHIC & AGS Annual Users’ Meeting ‘06 17
6/6/06 William Horowitz
Conservative Results
S. Wicks, WH, M. Gyulassy, and M. Djordjevic, nucl-th/0512076
•Elastic loss improves quench•keeping dNg/dy = 1000 s = .3• and No change in c or b production cross sections•Extended Theory is consistent with data for pT > 7 GeV
RHIC & AGS Annual Users’ Meeting ‘06 18
6/6/06 William Horowitz
Consistency Test with Pions
Not flat, which requires a balance of many competing effects (Cronin, EMC, etc.) but not at odds with data
S. Wicks, WH, M. Gyulassy, and M. Djordjevic, nucl-th/0512076
RHIC & AGS Annual Users’ Meeting ‘06 19
6/6/06 William Horowitz
El+Rad+Geom NOT a Fragile Probe
• Why? First, experimental error bars have shrunk considerably since 2004. Second, el < rad
WH, S. Wicks, M. Gyulassy, M. Djordjevic, in preparation
RHIC & AGS Annual Users’ Meeting ‘06 20
6/6/06 William Horowitz
Why Widths are Vital
– The whole distribution is important: , but el < rad
S. Wicks, WH, M. Gyulassy, and M. Djordjevic, nucl-th/0512076
RHIC & AGS Annual Users’ Meeting ‘06 21
6/6/06 William Horowitz
Elastic Objections• All derivations start parton at asymptotic
past: are there formation time effects?– Peigne et al. (Classical):
– This is unintuitive: one expects effects to disappear by L ~ 1/D ~ .5 fm, the screening scale; but perhaps there is a hidden factor
• What about interference effects?
S. Peigne, P.-B. Gossiaux, and T. Gousset, JHEP0604:011 (2006)
They claim NO elastic loss until L > 10 fm!
RHIC & AGS Annual Users’ Meeting ‘06 22
6/6/06 William Horowitz
Adil et al. Classical Refutation of Peigne et al.
Two issues:– Peigne et al. do not disentangle
known radiative effects• small
– Peigne et al. neglect a term intheir classical current, therebyviolating current conservationand resulting in a spurious A. Adil, M. Gyulassy, WH, and S.
Wicks, nucl-th/0606010
subtraction of the (negative) binding energy of the quark-antiquark pair
•HUGE
RHIC & AGS Annual Users’ Meeting ‘06 23
6/6/06 William Horowitz
Classical Finite Time Results
A. Adil, M. Gyulassy, WH, and S. Wicks, nucl-th/0606010
By L ~ 1/D, stable field reaches ~ 90% of the asymptotic10 GeV Charm 10 GeV Charm
RHIC & AGS Annual Users’ Meeting ‘06 24
6/6/06 William Horowitz
Quantal Finite Time Results
Again, formation effects negligible beyond 1/D
X. N. Wang, nucl-th/0604040M. Djordjevic, nucl-th/0603066
No one as yet fully combines El+Rad with interference
RHIC & AGS Annual Users’ Meeting ‘06 25
6/6/06 William Horowitz
Heavy Quark Tomography of the LHC
• Additional systematic tests of the energy loss theory– 2-3 times RHIC
medium densities
– Enormous pT range• At very high momenta,
GLV and BDMPS-Z-WS results converge, but elastic effects persist! WH, S. Wicks, M. Gyulassy, M. Djordjevic, in preparation
RHIC & AGS Annual Users’ Meeting ‘06 26
6/6/06 William Horowitz
LHC Predictions
WH, S. Wicks, M. Gyulassy, M. Djordjevic, in preparation
RHIC & AGS Annual Users’ Meeting ‘06 27
6/6/06 William Horowitz
Conclusions
– Fantastic new RHIC data challenging, surprising• Better understanding of heavy quark loss
mechanisms, production critical for interpreting experimental results
– Large uncertainties in ratio of charm to bottom contribution to non-photonic electrons• Direct measurement of D spectra would help
separate the different charm and bottom jet dynamics
• FONNLL would provide better information on theoretical production error
RHIC & AGS Annual Users’ Meeting ‘06 28
6/6/06 William Horowitz
Conclusions (cont’d)
– BDMPS-Z-WS:• IF extreme is assumed• IF elastic loss is assumed to vanish• IF they assume fragility• Then not inconsistent with data• No hope for tomography
RHIC & AGS Annual Users’ Meeting ‘06 29
6/6/06 William Horowitz
Conclusions (cont’d)
– DGLV: • Include elastic, inelastic, and path
length fluctuations
• Consistent results for high-pT e- RAA
• Pion RAA predictions agree well with data over large momentum range, are sensitive to changes in medium density, consistent with multiplicity constraints
RHIC & AGS Annual Users’ Meeting ‘06 30
6/6/06 William Horowitz
Conclusions (cont’d)
– Far from finished:• Coherence and correlation effects between elastic
and inelastic processes that occur in a finite time over multiple collisions must be sorted out
• Fixed must be allowed to run; the size of the irreducible error due to integration over low, nonperturbative momenta, where > .5, needs to be determined
• Where will e- RAA data and theoretical calculations settle down as research progresses and error bars are reduced over time?
RHIC & AGS Annual Users’ Meeting ‘06 31
6/6/06 William Horowitz
Conclusions (cont’d)
– AMY: a third approach?
• Produced a pion RAA; no calculation of e- RAA, a crucial consistency check
– The LHC will provide an excellent new testing ground for systematic study (falsification?) of energy loss theory
– Jet tomography is an elusive, but achievable goal
P. Arnold, G.D. Moore, and L. Yaffe, JHEP 011:057 (2001)S. Turbide, C. Gale, S. Jeon, G. D. Moore, Phys. Rev. C72:014906 (2005)
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RHIC & AGS Annual Users’ Meeting ‘06 33
6/6/06 William Horowitz
Backup Slides
RHIC & AGS Annual Users’ Meeting ‘06 34
6/6/06 William Horowitz
WH, S. Wicks, M. Gyulassy, M. Djordjevic, in preparation
RHIC & AGS Annual Users’ Meeting ‘06 35
6/6/06 William Horowitz
S. Wicks, WH, M. Gyulassy, and M. Djordjevic, nucl-th/0512076
RHIC & AGS Annual Users’ Meeting ‘06 36
6/6/06 William Horowitz
WH, S. Wicks, M. Gyulassy, M. Djordjevic, in preparation
RHIC & AGS Annual Users’ Meeting ‘06 37
6/6/06 William Horowitz
WH, S. Wicks, M. Gyulassy, M. Djordjevic, in preparation
RHIC & AGS Annual Users’ Meeting ‘06 38
6/6/06 William Horowitz
WH, S. Wicks, M. Gyulassy, M. Djordjevic, in preparation
RHIC & AGS Annual Users’ Meeting ‘06 39
6/6/06 William Horowitz
K. J. Eskola, H. Honkanen, C. A. Salgado, and U. A. Wiedemann, Nucl. Phys. A747:511:529 (2005)
A. Dainese, C. Loizides, G. Paic, Eur. Phys. J. C38:461-474 (2005)
RHIC & AGS Annual Users’ Meeting ‘06 40
6/6/06 William Horowitz
N. Armesto, M. Cacciari, A. Dainese, C. A. Salgado, U. A. Wiedemann, hep-ph-0511257
A. Dainese, C. Loizides, G. Paic, Eur. Phys. J. C38:461-474 (2005)
RHIC & AGS Annual Users’ Meeting ‘06 41
6/6/06 William Horowitz
A. Dainese, C. Loizides, G. Paic, Eur. Phys. J. C38:461-474 (2005)
RHIC & AGS Annual Users’ Meeting ‘06 42
6/6/06 William Horowitz
S. Wicks, WH, M. Gyulassy, and M. Djordjevic, nucl-th/0512076
