The ALICE EMCal Physics Performance Report Organization, Status, Plans

1
The ALICE EMCal Physics Performance Report-
Organization, Status, Plans -

• Rene Bellwied
• (Wayne State University)
• ALICE U.S. Collaboration Meeting, October 3rd,
  2008

2
Purpose of the document

• Originally requested by the Department of Energy
  and to be completed by Dec.31st, 2008, in order
  to formulate the physics scope of the U.S.
  contribution to ALICE.
• Based on discussions with ALICE the EMCal PPR
  will become an official addendum to the existing
  ALICE PPR.
• We will ask for an extension until June 2009 (see
  later slides).

3
Organization

• Report coordinator Rene Bellwied (Wayne State)
• Six prioritized sub groups with group
  coordinators
• 1.) jet reconstruction (Joern Putschke)
• 2.) EMCal triggering (Mateusz Ploskon)
• 3.) photons and gamma jets (Gustavo Balbastre)
• 4.) electron and heavy quark tagging (Mark Heinz)
• 5.) particle identified jet measurements (Rene
  Bellwied)
• 6.) jet correlations (Claude Pruneau)
• Initially groups 1 and 6 will be merged until the
  jet reconstruction algorithm is optimized.
• Bi-weekly EVO meetings.
• Several face-to-face meetings planned around
  ALICE weeks, ALICE-US collaboration meetings,
  EMCal meetings
• web-page http//alice.physics.wayne.edu
• Report to PWG-3, PWG-4 and ALICE Physics Board
  regularly (either the group coordinators or the
  report coordinator)

4
Working groups

• Presently 36 members, almost evenly distributed
  over the groups, with priority to the first four
  groups.
• Contributors from 14 institutions
• Yale, LBNL, Nantes, Wayne State, Grenoble, CERN,
  Jyvaskyla, ORNL, Tennessee, Creighton, Purdue, UT
  Austin, LLNL, Frascati

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.
• 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
How to define physics goals

• Measure parameters that determine energy loss
  mechanism (e.g. qhat)
• Determine level of medium response through
  correlation analysis (jet broadening, jet shape,
  particle correlations). Specify medium parameters
  (viscosity, speed of sound etc.)
• Determine relative strength of recombination and
  modified fragmentation as a function of
  transverse momentum. Explores hadronization.
• Determine light / heavy quark energy loss and
  hadronization differences.
• Determine medium modification of resonances in
  jets and medium and relate to chiral symmetry

7
Main goals for group 1 jet reconstruction

• 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
  (kTJet, JetAn, FastJet)
• Optimize quenching simulations, estimate effects
  elliptic and radial flow, hadron corrections,
  electron conversions, jet-energy correction

8
Group 1 goals / plans

• Jet spectra for different jet finders (LOCone vs.
  FastJet)
• Jet resolution for different jet finders (area
  vs. rec. energy)
• Fragmentation function for different jet finders
• Jet/kT distributions
• Medium modification of sub-jet population
• Effect of v2, radial flow, missing neutral
  energy, hadronic energy double counting, energy
  calibration

9
Main goals for group 2 jet triggering

• Attempt to extend the trigger efficiency for jet
  energies of 50-100 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

10
Group 2 goals / plans

• Extending LVL-1 reach to lower jet energies
  through mapping implementation and further
  simulation studies.
• Implementation of basic EMCal components into HLT
  framework
• Assessing possible impact from EMCal-HLT trigger
  through
• TPC-HLT particle tracking for pt gt 0.7 GeV/c
• TRD-HLT particle tracking, first stansalone then
  matching to TPC
• Final ITS-TRD-TPC-HLT matching

11
Main goals for group 3direct photons and
gamma-jets
Isolation cut study, PbPb quenched

• Simulate effect of p0 suppression on direct
  photon measurement
• Optimize shower shape algorithms, isolation cuts

12
Group 3 goals / latest results

• The modification of the fragmentation function
  can be measured for 30 GeV photons in the range
  of 0.5 lt x lt 3.2.
• HI Background is the main source of error. Need
  more studies on bkg area, min pT cut, jet-jet
  bkg, photon Isolation

Ratio pp / PbPb
13
Main goals for group 4heavy quark tagging with
electrons

• Show electron to heavy meson correspondence in AA
  collisions.
• Optimize e/h discrimination
• Simulate signed DCA method for B-mesons

14
Group 4 goals / plans

• Revisit rate calculations with higher statistics
• Re-check e-ID with newer AliRoot
• Electron and Electron-Jet Trigger Rates and
  backgrounds?
• Electron Spectra/RAA studies
• Investigate electron ? heavy meson (Charm/Bottom)
  correspondence in AA
• Compare to TPC alone and TPCTRD vs. with EMCAL
• D/B Spectra/RAA studies
• DVM method for B-mesons through eD
• Displaced vertex reconstruction of B through
  J/psiK
• Compare to electron RAA
• B-jet studies
• DVM B-jet selection
• Effect of mis-identified electron/hadrons?
• W rejection
• Study of alternative tagging methods/algorithms
• Combine DVM method and electron ID with JETAN
• Cone and FastJet objects
• FF performance for B-jets
• Effect of mis-identified B-jets on FF

Effect of mis-identified electron/hadrons?
15
Main goals for group 5particle identified jet
measurements

• Correlate high momentum PID measurements (rdE/dx,
  V0, hadronic resonances) to triggered jet rates
  for single hadron or resonance and di-hadron
  correlation measurements in jets and between
  di-jets.
• Determine neutral energy in jet by measuring
  protons (neutrons) and K0s (for K0L) very
  precisely.

16
Group 5 goals / plans

• Determine statistics and resolution of identified
  particle measurements in away-side jet cone (non
  EMCal info) under EMCal trigger assumption.
  Measure fragmentation functions and form hadron
  ratios.
• Compare to models
• Recombination
• L. Maiani et al. (hep-ph/0606217)
• Quenched Fragmentation
• Sapeta/Wiedemann (arXiv0707.3494)
• For resonances
• Possible chiral effects due to differing
  formation time for jet and bulk resonances.
  Determine statistics and resolution in quadrants
  (arXiv0807.1509).

17
Main goals for group 6 jet correlations
di-jet angle
di-jet energy correlation di-jet
energy balance

• Simulate possibility of acoplanarity and jet
  shape measurements based on jet reconstruction
  resolution.
• Compare jet axis correlations to leading particle
  correlations.

18
Group 6 goals / plans

• Acoplanarity kTx,kTy,Dj
• Can be done
• Multi-jet effects important
• How large are medium effects?
• Pt vs Pt
• Can be done
• Background effects? Jet splitting?
• How large are medium effects?
• Away Side Jet
• Enrich sample of modified jet. Bias of
  reconstruction?

19
Progress since beginning (June 2008)

• Physics contribution to EMCal TDR (largely based
  on very thorough CD-2 document)
• FastJet implementation in AliRoot
• Clear definition of achievable physics and
  simulation goals. Defined money plots for PPR
• Expansion of physics goals through identified
  particle and correlation studies.
• Ready to go.

20
Arguments for PPR delay

• Four main categories of arguments
• Physics based event generators (qPYTHIA and
  JEWEL) will be available soon. Much better
  description of quenching effect
• Systematic error studies have to be more specific
  and detailed. Needs STAR input.
• Calibration of ALICE detectors is ongoing.
  Detector response in physics simulations will not
  rely on simulated response any longer
• New analysis ideas for specific physics goals can
  be explored

21
Summary

• A dedicated effort to define the physics scope
  enhancement due to the EMCal in ALICE is
  underway.
• We hope to complete the document within six to
  nine months in close collaboration with the
  existing PWGs in ALICE.
• We are on our way, but we need to stay
  aggressively on timeline. Everybody needs to get
  involved. All institutions needs to set up for
  running ALICE simulations and analyzing ALICE
  data. Need dedicated resources.