theoretical predictions of jet suppression: a systematic comparison with rhic and lhc data
DESCRIPTION
Theoretical predictions of jet suppression: a systematic comparison with RHIC and LHC data Magdalena Djordjevic Institute of Physics Belgrade, University of Belgrade. Jet suppression. Light and heavy flavour suppressions are excellent probes of QCD matter. - PowerPoint PPT PresentationTRANSCRIPT
M. Djordjevic 1
Theoretical predictions of jet suppression: a systematic comparison
with RHIC and LHC dataMagdalena Djordjevic
Institute of Physics Belgrade, University of Belgrade
M. Djordjevic 2
Jet suppression
Light and heavy flavour suppressions are excellent probes of QCD matter.
Suppression for a number of observables at RHIC and LHC has been measured.
Comparison of theory with the experiments allow testing our understanding of QCD matter.
M. Djordjevic 3
1) Initial momentum distributions for partons2) Parton energy loss3) Fragmentation functions of partons into hadrons4) Decay of heavy mesons to single e- and J/psi.
Jet suppression
hadrons
1)
production
2)
medium energy loss
3)
fragmentation
partons e-, J/psi
4)
decay
Dynamical energy lossComputed radiative and collisional energy loss in finite size dynamical QCD medium of thermally
distributed massless quarks and gluons.
Abolishes approximation of static scatterers.M. D. PRC 80:064909 (2009), M. D. and U. Heinz, PRL 101:022302 (2008).
Finite magnetic mass effects. M. D. and M. Djordjevic, PLB 709:229 (2012)
Includes running couplingM. D. and M. Djordjevic, arXiv:1307.4098 (PLB, in press)
M. Djordjevic 5
Numerical procedure• Light flavor production Z.B. Kang, I. Vitev, H. Xing, PLB 718:482 (2012)
• Heavy flavor production M. Cacciari et al., JHEP 1210, 137 (2012)
• Path-length fluctuations A. Dainese, EPJ C33:495,2004.
• Multi-gluon fluctuations M. Gyulassy, P. Levai, I. Vitev, PLB 538:282 (2002).
• DSS fragmenation for light flavor D. de Florian, R. Sassot, M. Stratmann, PRD 75:114010 (2007)
• BCFY and KLP fragmenation for heavy flavor M. Cacciari, P. Nason, JHEP 0309: 006 (2003)
• Decays of heavy mesons to single electron and J/psi according to
M. Cacciari et al., JHEP 1210, 137 (2012)
• Temperature T=304 MeV for LHC and T=221 MeV for RHIC. M. Wilde, Nucl. Phys. A 904-905, 573c (2013) (ALICE Collab.) A. Adare et al., Phys. Rev. Lett. 104, 132301 (2010) (PHENIX Collab.)
M. Djordjevic 6
Generating predictions• Provide joint predictions across diverse probes charged hadrons, pions, kaons, D mesons, non-photonic single electorns, non-prompt J/psi M. D. and M. Djordjevic, arXiv:1307.4098 (PLB, in press)• Puzzles (apparently surprising data) Measured charged hadron vs. D meson supression M.D., PRL 112, 042302 (2014) • Concentrate on all centrality regions M. D., M. Djordjevic and B. Blagojevic, arXiv:1405.4250 All predictions generated
By the same formalismWith the same numerical procedureNo free parameters in model testing
M. Djordjevic 7
Comparison with LHC data (central collision)
Very good agreement with diverse probes!
M. D. and M. Djordjevic, arXiv:1307.4098 (PLB, in press)
M. Djordjevic 8
Heavy flavor puzzle at LHC
Significant gluon contribution in charged hadrons
Much larger gluon suppression
RAA (h±) < RAA (D)
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Charged hadrons vs D meson RAA
RAA (h±) = RAA (D)Excellent agreement
with the data!Disagreement with the qualitative expectations!
M.D., PRL 112, 042302 (2014)
ALICE data
M. Djordjevic 10
Hadron RAA vs. parton RAA
D meson is a genuineprobe of bare charm quark suppression
Distortion by fragmentation
Charged hadron RAA = (bare) light quark RAA
M.D., PRL 112, 042302 (2014)
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Puzzle explanation
RAA (D) = RAA (charm)RAA (light quarks) = RAA (charm)
RAA (h±) = RAA (D)
Puzzle explained!
RAA (h±) = RAA (light quarks)
M.D., PRL 112, 042302 (2014)
M. Djordjevic 12
Comparison with RHIC data (central collisions)
Very good agreement!
RHIC
M. Djordjevic 13
Non central collisions @ LHC (fixed centrality and charged hadrons)
An excellent agreement for different centrality regions!M. D., M. Djordjevic and B. Blagojevic, arXiv:1405.4250
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Non central collisions @ LHC (fixed centrality and D mesons)
Excellent agreement!
Predictions for upcoming measurements.
M. D., M. Djordjevic and B. Blagojevic, arXiv:1405.4250
M. Djordjevic 15Also a good agreement for RHIC!
Non central collisions @ RHIC (fixed centrality and neutral pions)
M. D., M. Djordjevic and B. Blagojevic, arXiv:1405.4250
M. Djordjevic 16
RAA vs. Npart for RHIC and LHC
Very good agreement for both RHIC and LHC and for whole set of probes!
M. D., M. Djordjevic and B. Blagojevic, arXiv:1405.4250
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Assessing medium model
A robust agreement with suppression data, for different probes, experiments and centrality regions.
Predictions are generated with the same model, parameter set and with no free parameters.
NOTE: We use a sophisticated energy loss model, but do not explicitly include the medium evolution
(i.e. we take average/effective medium parameters).
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PROPOSAL: Medium evolution may not be a major effect in hard probe (>10 GeV) suppression.
HYPOTHESIS: High energy jets sense only the average (effective) medium conditions.
CONSEQUENCE: May significantly simplify both generating predictions and analyzing
phenomena behind experimental data.
Acknowledgement
Ministry of Science and Education in Serbia
FP7 Marie Curie International
Reintegration grant
L’Oreal UNESCOFor Women in Science
Serbia
Many thanks to:• M. Djordjevic and B. Blagojevic for collaboration on this project.• I. Vitev and Z. Kang for providing the initial light flavor distributions and
useful discussions. • M. Cacciari for useful discussions on heavy flavor production and decay
processes. • ALICE Collaboration for providing the preliminary data• M. Stratmann and Z. Kang for help with DSS fragmentation functions.
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Main results
The dynamical energy loss can simultaneously explain central-collision measurements for a
diverse set of probes at LHC and RHIC.The formalism can explain puzzling data
(“the heavy flavor puzzle at LHC”).We obtain a very good agreement with the non-
central collision data as well.Results suggest that the medium evolution is not a
major effect for suppression of hard probes.
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The end
M. Djordjevic 22
The dynamical energy loss formalism is based on HTL perturbative QCD, which requires zero magnetic mass.
Finite magnetic mass
However, different non-perturbative approaches show a non-zero magnetic mass
at RHIC and LHC.
Can magnetic mass be consistently included in the dynamical energy
loss calculations?
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Generalization of radiative jet energy loss to finite magnetic mass
M.D. and M. Djordjevic, Phys.Lett.B709:229,2012
zero magnetic mass
From our analysis, only this part gets modified.
2 2
2 2 2 2( )( )E M
E Mq q
Finite magnetic mass: , where .0.4 0.6M
E
24
A simple constraint on the magnetic massIf magnetic mass is larger than electric mass, the quark jet would, overall, start
to gain (instead of lose) energy in this type of plasma.
An apparent violation of the second law of thermodynamics.
It is impossible to observe a plasma with magnetic mass larger than electric
Various non-perturbative approaches suggest that, at RHIC and LHC,
0.4 < μM/μE < 0.6.
M.D. and M. Djordjevic, Phys.Lett.B709:229,2012
M. Djordjevic 25
Running couplingCollisional energy loss Radiative energy loss
k,c
q,a p
p
q
2( )vQ
2( )kQ
2( )E
2( )vQ
2( )E
2 2~ ( ) ( )coll v EE Q
2 2 2~ ( ) ( ) ( )rad k v EE Q Q
M. D. and M. Djordjevic, arXiv:1307.4098