1. The ALICE EMCal-PPR strategy / progress
Rene Bellwied
Wayne State University
EMCal Software / PPR Meeting, Frascati
May 19-21, 2009

2. Purpose of the document
Originally requested by the Department of Energy (to be completed by June 2009) in order to formulate the physics scope of the EMCal for ALICE.
Based on discussions with ALICE the EMCal PPR will become an official addendum to the existing ALICE PPR.
We aim for official (J.Phys.G ?) publication along the lines of the original ALICE-PPR
Working on an extension until October 2009

3. Organization Report coordinator: Rene Bellwied (Wayne State)
Five prioritized sub groups with group coordinators
1.) jet reconstruction (Joern Putschke)
2.) EMCal triggering (Mateusz Ploskon)
3.) photons and gamma jets (Gustavo Balbastre Conesa)
4.) electron and heavy quark tagging (Jennifer Klay)
5.) particle identified jet measurements (Rene Bellwied)
Bi-weekly EVO meetings, face-to-face meetings planned around ALICE weeks, ALICE-US collaboration meetings, EMCal meetings. Next meeting during ALICE week, late June)
web-page:
Report to PWG-3, PWG-4 and ALICE Physics Board regularly (either the group coordinators or the report coordinator)

4. Define calorimeter driven physics goals
Measure parameters that determine energy loss mechanism (e.g. transport coefficient, color charge density, as)), energy flow (r/R), jet cross section (jet RAA)
Jet reconstruction of hadron jets and gamma jets
Determine level of medium response through correlation analysis (jet broadening, jet shape, particle correlations). Specify medium parameters (viscosity, speed of sound etc.)
Jet correlation measurements
Determine relative strength of recombination and modified fragmentation as a function of transverse momentum. Explore hadronization, jet flavor conversion.
Identified particle measurements in jets
Determine light / heavy quark energy loss and hadronization differences.
Jet reconstruction of electron jets
Determine medium modification in jets related to chiral symmetry
Identified resonance measurements in jets

5. General strategy
For jet reconstruction, triggering, photon, and electron physics improve on the existing simulations as shown in the CD-2 final physics report and recent EMCal TDR.
For particle identified jet measurements and jet correlations develop a performance report and interface with multiple other detector components in ALICE (TPC,TRD, ITS, PHOS)

6. EMCal PPR – proposed Table of Content
1.) EMCal Physics - theoretical overview
2.) EMCal Detector Layout
3.) Simulation Framework and MC Generators
4.) EMCal Detector Performance
Energy resolution
Jet energy resolution
Trigger performance
Jet trigger
Photon trigger
Electron trigger
Gamma/pi0 identification
Hadron/electron discrimination
5.) EMCal Physics Performance

7. EMCal PPR – Physics Performance Breakdown
A.) Jet reconstruction
Comparison of jet algorithms
Jet reconstruction corrections
hadronic energy corrections
neutral energy correction
final jet energy resolution
effects of v2 and radial flow
Jet reconstruction in pp
jet energy and yield
jet axis and width
Jet reconstruction in AA
Fragmentation functions in pp
Fragmentation functions in AA
Constraints on energy loss models
jet broadening measurements
sub-jet distribution
modified fragmentation functions
Constraints on medium response models
jet correlation measurements
B.) Photon and gamma-jet reconstruction
Photon reconstruction
Isolation cuts
Gamma-jet reconstruction
Comparison to PHOS physics performance
Photon-tagged jet analysis
fragmentation functions
constraints on models
C.) Electron and heavy flavor jet reconstruction
Electron reconstruction
Electron-jet reconstruction
Heavy quark energy loss
Heavy quark fragmentation functions
D.) Identified particle studies in jets
High momentum PID in ALICE
Identified jet yields and ratios
Identified fragmentation functions in pp
Identified fragmentation functions in AA
Constraints on fundamental QCD processes
Constraints on energy loss and
medium response models
Resonances in jets

8. Specific Strategies since TDR
Use more realistic event generators, in particular for in-medium modification (tool 1)
Use better jet algorithms in particular fast-jet package (tool 2)
Use data driven detector performance benchmarks (based on test beam and calibration)
Use data driven analysis tools (based on STAR)

9. Tool 1: ‘Realistic Event-generators’
Monte Carlo Implementations:
PYQUEN (Lokhtin, Snigriev):
PYTHIA afterburner reduces energy of final state partons and adds radiated gluons according to BDMPS expectations.
PQM (Dainese, Loizides, Paic):
MC implementation of BDMPS quenching weights
HIJING (Gyulassy, Wang):
jet and mini-jet production with induced splitting
JEWEL (Zapp, Ingelman, Rathsman, Stachel, Wiedemann):
parton shower with microscopic description of interactions with medium
q-PYTHIA (Armesto, Cunquiero, Salgado, Xiang):
includes BDMPS-like radiation in modified splitting function
YaJeM (Renk):
medium increases virtuality of partons during evolution

10. Tool 2: Jet Reconstruction Algorithms (FastJet Package)
seed
Seed Cone:
‘seed’ (E>Ethreshold)
iterative approach
Seedless Cone (SIS cone):
all the particles used as seeds
Splitting/Merging applied
fragmentation
tracks or towers
Cone Algorithms
outgoing parton
Rcone
seed
R=√(Δφ2+Δη2)
[Cacciari, Soyez, arXiv: ]
Seedless, not bound to a circular structure
kT: starts from merging low pT particles close in the phase-space
Anti-kT: starts from merging high pT particles close in the phase-space
Recombination Algorithms
[Cacciari, Salam, Soyez, arXiv: ]

11. Status Detector Performance Jet reconstruction (Joern Putschke)
Trigger (Mateusz Ploskon)
Photons (Gustavo Balbastre Conesa)
Electrons (Jennifer Klay)
Identified Particles /Resonances (Francesco Blanco, Renaud Vernet, Christina Markert, RB)

12. Jet energy resolution from STAR data in pp collisions (H.Caines QM09)

13. Jet energy resolution from STAR data in pp collisions (H.Caines QM09)

14. Jet reconstruction in TDR
Attempt to extend the reliability of jet finding algorithm to jet energies below 100 GeV. Important for single jets, crucial for jet correlations.
Optimize jet finding algorithm through comparison (FastJet)
Optimize quenching simulations, estimate effects elliptic and radial flow, hadron corrections, electron conversions, jet-energy correction

15. Example: Sensitivity to transport coefficient Most asked question: Can you, based on your simulation, tell us how sensitive you are to qhat within the ASW approach ?

16. Fake jet subtraction Different approaches shown at QM by:
E. Bruna (STAR): use C&S with off-axis ‘jet’ spectrum
M. Ploskon (STAR): part of spectrum unfolding (event mixing)
Y.S. Lai (PHENIX): Gaussian filter
Additional publications by:
Cacciari & Salam (Phys.Lett. B659, 119 (2008)): s / sqrt(<A>)
ATLAS HI (arXiv: ): SjT

18. I.Vitev et al. (arXiv:0810.2807) Jet shapes

19. Related results (ALICE-PPR)
No EMCal, PYTHIA jets in HIJING background (jet data challenge)

20. Jet cross sections Related STAR result (M.Ploskon, QM09)
Theory prelim.STAR data
STAR Preliminary
RAA for jet cross section evolves continuously by varying cone size and acceptance cut.
Contrast: single result for leading particle
Limits: RAA approaches to single hadron suppression with very Rmax and large ωmin

21. T. Renk (arXiv:0808.1803) medium modified fragmentation function
This is a
calculation for
RHIC energies
but Thorsten
could certainly
provide a
comparable
simulation for
the LHC

22. Medium modified fragmentation function Related STAR result (E
Medium modified fragmentation function Related STAR result (E. Bruna, QM09)
“recoil” jet
“trigger” jet
pT(trigger)>20 GeV Ptcut=2 GeV
pT(recoil)>25 GeV (reduce fake jets to <10%) Ptcut=0.1 GeV
No major modification without any pTcut on tracks and towers

23. Recent studies of jet triggering
Attempt to extend the trigger efficiency for jet energies of GeV. Check effect of jet quenching
Optimize LVL-1 algorithm by taking altering patch size/geometry based on new mapping manipulations (elelctronics).
Optimize HLT based on EMCal

24. Triggered jet yields in one LHC year
Jet yield in 20 GeV bin
Another factor 5 is possible by triggering TPC at 500 Hz instead of 100 Hz and using EMCal L1/HLT to cut recorded rate down to 100 Hz

25. Jet trigger and wrong slope extrapolation can make large difference in particle yield estimates
EMCal PPR Original ALICE-PPR
Reach out to 12 GeV/c or 30 GeV/c per year ?

26. Direct photons and gamma-jets
Shower shape study,
PbPb quenched
Isolation cut study,
PbPb quenched
Optimize shower shape algorithms, isolation cuts

27. R. Fries et al. (arXiv:0801.0453): jet-photon conversions
Annihilation (q-qbar to  or q-qbar to  g) or Compton (q g to  q)

28. Latest gamma-jet simulations
Ratio pp / PbPb
The modification of the fragmentation function can be measured for 30 GeV photons in the range of 0.5 < x < 3.2.
HI Background is the main source of error. Need more studies on: bkg area, min pT cut, jet-jet bkg, photon Isolation
Comparison: PYTHIA / HERWIG / NLO pQCD

29. W. Horowitz (arXiv:0710.0595) heavy quark energy loss in the strong and weak coupling limit

30. Activities Matrix – group 4
Task
Sub-topics/ Physics
Plots
Manpower 1
Revisit rates
(higher stats)
1.1) Electron rates and backgrounds
1.2) B-jet rates and backgrounds
1.3) Hadron rejection requirement
E-rates from different sources
B-jet rates for electron selection
Hadron/electron ratio
Jenn 2
Re-check e-ID
2.1) Track-matching in PYTHIA/HIJING
2.2) p/E cut study
2.3)  rejection vs. pT for given efficiency levels
Matching efficiency + Fakes
p/E example distributions
Rejection vs. efficiency
Josh 3
Spectra/RAA (single electrons)
3.1) Investigate heavy flavor production via non-photonic electron measurement – Cross-check with NLO predictions
3.2) Investigate HF suppression in heavy ion collisions via R_AA (parton suppression)
Electron Spectra in p-p Collisions for PID with: (1) TPC, (2) TPC+TRD, (3) TPC+TRD+EMCAL
Electron Spectra in Pb-Pb (Hijing) Collisions for PID with: (1) TPC, (2) TPC+TRD, (3) TPC+TRD+EMCAL
Inclusive electrons vs non-photonic electrons
Irakli + Ken
Task
Sub-topics/ Physics
Plots
Manpower 4
B-jets
5.1) Event-by-Event B-tagging (using Jet-Finder + Displaced Vertex Method (DVM))
5.2) Event-by-Event B-tagging (using Jet-Finder + Transverse IP significance)
5.3) Measurement of B-jet Fragmentation function (statistical using Jet-Finder + tagging algorithm)
B-jet efficiency and false identification rate vs. pT for DVM, other tag methods
Rejection rates for non-B-jet vs. pT for DVM, other tag methods
B-jet Fragmentation Function sensitivity for various Jet-reco algorithms in p+p
5.1) Jenn, Brandon, Chris
5.2) Alberto & Mauro
5.3) Yale
Udara

31. Simulation run status
Discussions with Latchezar Betev, Peter Hristov, Federico Carminati
Jennifer Klay, Gustavo Balbastre Conesa, Magali Estienne
HIJING more time consuming than jet runs

32. Production cycle status (5/16/09)

33. FastJet / JetAn status Andreas’ latest modifications
Fastjet packages including cgal are now on the grid:
Test example is in (alien) /alice/cern.ch/user/m/morsch/fastjet/
Andreas prepared a special JETAN.par

34. JetAn / FastJet status Magali’s latest modifications
JETAN now uses charged + neutral information.
Jet finder now has options (UA1, FastJet, SISCone), can look for jets including "neutrals".
Hadron correction based on Geant 3 included (no FLUKA).
No electron correction part yet.
Both corrections (hadronic and electron) are applied at the level of the reader of the code.
Background subtraction includes the possibility to work on a limited EMCal acceptance (cut on eta and phi in the eta/phi grid).
Possibility of smaller resolution parameter R is not yet included.

35. Summary & Outlook
Work plans and strategies for an effective PPR are in place.
The effort needs to be focused, and largely based on the existing STAR software for jet reconstruction.
We need to effectively utilize the simulation datasets on the GRID, the Fastjet as well as qPYTHIA emulations in ALICE need to be available and used as the standard for jet algorithms and quenching simulations
We will have in parallel a PPR writing team and PPR simulation team.

36. Update on Identified particles in jets (hadro-chemistry, chirality)

37. Particle identified jet measurements e. g. Sapeta/Wiedemann (Eur. Phys
Particle identified jet measurements e.g.Sapeta/Wiedemann (Eur.Phys.J. C55 (2008) 293): The hadro-chemistry will change in medium
medium
modification
medium
modification

38. ALICE primary track analysis using TPC rdE/dx
Based on:
tracking efficiency
rdE/dx efficiency
rdE/dx purity
discuss rdE/dx issues tomorrow
(Francesco Blanco)

39. Efficiency and acceptance corrected spectra
original efficiency & acceptance relative
corrected error L k0 p k

40. Accuracy of measurement compared to Sapeta-Wiedemann predictions
SW predictions
(MLLA plus
JEWEL-type
medium
modifications)
Scaled PYTHIA
reconstructed
in ALICE jets
(one LHC year
Statistics)

41. K/p ratio in STAR (p+p and A+A)
STAR preliminary
pT (GeV/c)
K/ (Au+Au) > K/ (p+p)
consistent with in-medium fragmentation
(Sapeta-Wiedemann, arXiv: ) 41 41

42. modified FF for identified particles (see Christina’s talk)

43. Fries & Ko (arXiv:0711.0974): quark-gluon conversions

44. Jet-flavor conversions (A.Timmins, STAR, QM09)
STAR preliminary
pT (GeV/c)
Fries et al., arXiv:
At RHIC the s-quark is supposed to show the effect as well.
At ALICE s-quark production is too abundant though

45. Formation Time of Resonances in LHC QGP (C. Markert et al., arXiv:0807.1509)45

46. Probe chirality through resonances in jets (C. Markert et al
Probe chirality through resonances in jets (C. Markert et al., arXiv: )
CDF underlying event analysis
partonic
medium
hadrons/
resonances
a mixed d.o.f. system
side 1
side 2
near
away
Jet triggered
quadrant analysis
= very similar to

47. Probe chirality through resonances in jets (C. Markert et al
Probe chirality through resonances in jets (C. Markert et al., arXiv: )
side 1
side 2
near
away
In Jet-Plane Same Side near
In Jet-Plane Away Side away
e.g. STAR results:Trigger pT > 4GeV, f(1020) <pT>~ 0.9 GeV
All angles
Out of Jet-Plane side1 + side2
M inv (K+ K-)
Systematic errors
not included !

48. Hadronic resonance reconstruction (example: ALICE-PPR K*)