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 p T (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 p T region is most interesting, and ALICE has the best low p T capabilities.  Measure same observables as used at RHIC Only ALICE can measure p T ~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/  anomaly), easiest at low p T 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 ,  0, and e +/- to higher p T Increase acceptance for  (EMCal/PHOS) + jet(TPC) Allow back-to-back coincidences –  (PHOS) + jet (TPC+EMCal) –  (EMCal) + leading  0 (PHOS) –  (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 p T ” Up to ~100 GeV/c. Yes Must demonstrate that EMCAL can be used to provide an unbiased jet trigger to as low in p T 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 p T 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:  +jet, or  +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 ALICE EMCal is large enough PROBLEM: Underlying event non-jet energy: Radius Cone Energy (GeV) Jet Energy fraction within cone radius 22 0  /2  3  /2 TPC PHOS EMCal  Jet R=0.3,  0  Use “small” jet-cone, R~0.3

9 Direct Photons  Min Bias Pb+Pb  s  =5.5 TeV,  PYTHIA Calculation  pQCD NLO Calculation  Rate to about 100 GeV/c  Gluon structure functions  Compton: g+q   +q  (gluon saturation)  Jet-Tagging

10  -Tagged jets: E-Loss/Jet Fragmentation Jets tagged by  in EMCal acceptance jet  Collision axis Direct  -tagged events: E  ~E jet Measure D h/a (z) Compare AA to pp

11 Direct  /  0 Ratio Ratio  /  0 provides figure of merit for direct gamma measurement:   /  0 ~ 10% easy ~ 3-5% limit  0 suppression by factor of ~5-10 (jet quenching) would allow direct photon measurement down to a few GeV/c At high p T,  ’s from  0 ‘s merge to appear as single   Fine granularity

12 Jets in ALICE Sufficient rate to observe jets up to ~ 500 GeV/c in one ALICE “year” (~12 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  (   ) 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 14 TeV, L< cm -2 s -1 ) L~ cm-2s-1: rare observables Year 3 –p(d, L~ cm -2 s -1 : Nuclear modification of structure function Year 4 (as year 2) : L int = nb -1 /year Year 5 L~ cm -2 s -1 : energy density dependencies Options for later 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,Bottom Production in ALICE Bottom in Min bias Pb+Pb (Similar high p T 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,Z 0,DY Production 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 Q 2 in nuclei.