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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

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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.

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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/

anomaly), easiest at low pT and ALICE has best PID capability.

Large rate, therefore acceptance is not so important.

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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 pT

• 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

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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?

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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: +jet, or +particle may be the killer argument– Drives detector granularity

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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.

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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 15Jet Energy fraction within cone radius

20 /2 3/2

TPC

PHOS

EMCal

Jet R=0.3,0.5

0.9

-0.9

0

Use “small” jet-cone, R~0.3

Figure 5.4 Energy resolution ofreconstructed jets in central PbPb HIJINGevents (open symbols) and pp (closedsymbols) for jets of 30,50, and 100 GeV/c.For PbPb collisions, an optimum coneradius of R=0.3 is indicated.

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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

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-Tagged jets: E-Loss/Jet Fragmentation

Jets tagged by inEMCal acceptance

jet

Collision axis

• Direct -tagged events: E~Ejet

• Measure Dh/a(z)

• Compare AA to pp

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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 pT, ’s from 0‘s merge to appear as single Fine granularity

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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.

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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).

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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,…

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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?

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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), ….

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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

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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

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Charm,Bottom Production 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.

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W,Z0,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 Q2 in nuclei.