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The Next Round of Proposal Preparation

The Next Round of Proposal Preparation. The NSAC/DOE report endorsed the importance of the LHC physics program - “LHC participation should be comparible with the two RHIC detector upgrade projects”. We don’t need to spend much time selling the LHC program.

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The Next Round of Proposal Preparation

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  1. The Next Round of Proposal Preparation • The NSAC/DOE report endorsed the importance of the LHC physics program - “LHC participation should be comparible with the two RHIC detector upgrade projects”. • We don’t need to spend much time selling the LHC program. • The next round of proposals will be do or die for the EMCAL in ALICE. • The next proposal must do the following clearly and convincingly: • Must demonstrate that EMCAL in ALICE brings unique and important physics that will not be done by CMS or ATLAS. • Presumably jet physics • Provide a realistic and defensible cost estimate • We cannot have the committee think it’s really 50% more than we quote. • Present arguments for design cost/performance tradeoffs • Segmentation, sampling, acceptance, etc choices • What’s the “killer” EMCAL argument? • Arguments we’ve been making (to DOE) on following 3 slides

  2. I. Why ALICE? • Designed for soft physics of RHI -> Limitations imposed by physics (multiplicities) not performance (occupancies). • A “complete” experiment -> Full range of RHI observables. • Better suited to most interesting “semi-hard” region where jet quenching effects expected to be most visible. • Detailed jet-fragmentation studies -> lower pT (z), particle ID, strangeness, charm, B content,... • “The HI experiment” at the LHC, -> no concern about priorities.

  3. II. Why Jets in ALICE: • Why is ALICE the most interesting LHC experiment for jet measurements? Answer: Because the low to intermediate pT region is most interesting, and ALICE has the best low pT capabilities. • Measure same observables as used at RHIC Only ALICE can measure pT ~5 GeV/c of RHIC as well as jets up to ~300 GeV/c. • Lower x, where Gluon Saturation effects will be greatest • Energy-loss effects will be most apparent • Study of Jet composition is important (RHIC p/p anomaly), easiest at low pT and ALICE has best PID capability. • Large rate, therefore acceptance is not so important.

  4. III. Why Large EMCal in ALICE? • Measure neutral energy of jets • Improves jet energy resolution, ~30% -> ~15% • PHOS is too small to contain jet • Extend PHOS measurements g, p0, and e+/- to higher pT • Increase acceptance for g (EMCal/PHOS) + jet(TPC) • Allow back-to-back coincidences • g (PHOS) + jet (TPC+EMCal) • g (EMCal) + leading p0 (PHOS) • g (EMCal/PHOS) + e+/- from D,B decay (heavy q jet) (PHOS/EMCal) • Significant and highly visible US contribution to ALICE • Attracts interest of US collaborators

  5. Peter’s Complaint(s)- • Must make stronger case for EMCAL in next round of proposal than in NSAC/DOE report - • We are arguing to take ~$10M+ from RHIC for EMCAL, therefore proposal must make very convincing argument of need for EMCAL. • Must demonstrate that EMCAL in ALICE brings unique physics that will not be done by CMS or ATLAS • Do not dilute proposal with ALICE capabilities, even if unique, that do not need EMCAL • Should lay out a detailed LHC program of jet studies (Peter volunteers!) • It’s argued that PID is essential to jet studies and unique to ALICE, but is was not convincingly demonstrated why this is so. • Peter believes that little will be learned by conventional jet measurements. Particle correlations are better. • Maybe so, if true, it is a strong argument for ALICE against CMS and ATLAS. Can it be convincingly demonstrated?

  6. Peter’s Suggestions - • Jet energy range : “Low pT” Up to ~100 GeV/c. Yes • Must demonstrate that EMCAL can be used to provide an unbiased jet trigger to as low in pT as possible. Use EMCAL with HLT. Yes • Peter doesn’t give much credit to what has been done so far… • Jet energy resolution. Need to discuss more about improvement with EMCAL. ??? • But why emphasize if jet energy measurements are not very useful? • Intermediate pT is most interesting. Yes • PID important and particle correlations powerful. Yes, we’ve said it too, now demonstrate it! • Direct photons important. Yes, Yes! • TCA: g+jet, or g+particle may be the killer argument • Drives detector granularity

  7. Peter’s Concerns - • p+p, p+A : What does EMCAL bring? • Acceptance of EMCAL? • Minimum size? Why not half as large? • Staging scenarios? • Trigger bias? • Further investigations with lower L1 thresholds and rejection followed by HLT rejection. • Computing costs • For later discussion • Other costs • Common fund, M&O, Travel • Should get DOE guidance so quoted similarly for all 3 proposals.

  8.  JetR=0.3,0.5 0.9 0 PHOS EMCal TPC -0.9 3/2 /2  2 0  ALICE EMCal is large enough PROBLEM: Underlying event non-jet energy: Radius Cone Energy (GeV) 0.7 750 0.5 380 0.3 140 0.1 15 Jet Energy fraction within cone radius Use “small” jet-cone, R~0.3

  9. Direct Photons • Min Bias Pb+Pb • s1/2 =5.5 TeV, • PYTHIA Calculation • pQCD NLO Calculation • Rate to about 100 GeV/c • Gluon structure functions • Compton: g+q ->g+q • (gluon saturation) • Jet-Tagging

  10. jet Collision axis g g-Tagged jets: E-Loss/Jet Fragmentation Jets tagged by g in EMCal acceptance • Direct g-tagged events: Eg~Ejet • Measure Dh/a(z) • Compare AA to pp

  11. Direct g/p0Ratio • Ratio g/p0 provides figure of merit for direct gamma measurement: • g/p0 ~ 10% easy ~ 3-5% limit • p0 suppression by factor of ~5-10 (jet quenching) would allow direct photon measurement down to a few GeV/c • At high pT, g’s from p0‘s merge to appear as single g • Fine granularity

  12. Jets in ALICE • Sufficient rate to observe jets up to ~ 500 GeV/c in one ALICE “year” (~12 days @50% design luminosity). • But, essential to trigger on jets or lose factor of ~100 if limited to ALICE DAQ rate. • Electromagnetic calorimeter can provide a clean jet trigger.

  13. Triggering on Jets using EMCal Trigger efficiency vs jet energy for factor of 20 central event suppression • Investigating simple “overlapping tile” thresholded energy sum. • A single g (p0) 4x4 tile, as used in WA98, PHENIX, and planned for PHOS, works well. • Must investigate bias (against high z charged jets).

  14. ALICE-USA (partial) Joblist • Need to become a fully approved project. • Proposal writing, CD0, CD1, etc. • Further simulations: • Directed towards detector optimization: segmentation vs cost, acceptance compromises, depth, etc • Physics performance for proposal. • Mock data analysis as part of ALIROOT effort. • Detector component tests and optimization • Scintillator, WLS fiber, APDs, Preamp, Assembly,… • Prototype production and testing • Test beam measurements and data analysis • Integration into ALICE • Engineering, Suitability of PHOS FEE, Trigger+DAQ, Services,…

  15. ALICE-USA (partial) Joblist • Production: • EMCal module assembly • APD, preamp, FEE preparation and QA • Initial module testing and calibration after assembly • Module installation and testing. • Datataking shifts • Software development, calibrations, and data analysis • Participation in other ALICE subsystems • PHOS • Muons • A new forward detector?

  16. Heavy Ion Running Scenario • Year 1 (2007?) • pp: detector commissioning & physics data • PbPb physics pilot run: global event-properties, observables with large cross-section • Year 2 (in addition to pp @ 14 TeV, L< 5.1030 cm-2s-1 ) • PbPb @ L~ 1027 cm-2s-1: rare observables • Year 3 • p(d, a)Pb @ L~ 1029 cm-2s-1 : Nuclear modification of structure function • Year 4 (as year 2) : Lint = 0.5-0.7 nb-1/year • Year 5 • ArAr @ L~ 1027 -1029 cm-2s-1 : energy density dependencies • Options for later • pp @ 5.5 TeV, pA (A scan to map A dependence), AA (A scan to map energy-density dependence), PbPb (energy-excitation function down towards RHIC), ….

  17. Jet-Quenching Observables The parton loses energy, but the jet does not! • Small change in radial distribution of energy within jet. • The greatest effect is on the distribution of fragments within the jet • Fragmentation Function

  18. Jet Measurement using EMCal Jet-finding algorithm studies: Cone sizes, thresholds, TPC tracking info, background subtraction,…-> resolution, efficiency TPC+EMCal Jet energy resolution: pp~18%, PbPb~25-29% Accurate measurement of jet fragmentation Reconstructed= Input Jet quenching example

  19. Charm,BottomProduction in ALICE • Bottom in Min bias Pb+Pb • (Similar high pT charm rate) • EMCal gives robust e trigger. • Assists TRD e identification • Use high energy electron to tag jets containing charm or bottom to study energy-loss of heavy quarks.

  20. W,Z0,DYProduction in ALICE EMCal • Min bias Pb+Pb • (PYTHIA pn scaled to Pb+Pb) • Robust e trigger • Assist TRD e identification • Exceeds C,B e yield above ~25GeV/c • Unique information on • quark structure functions at low x, high Q2 in nuclei.

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