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First High p T Physics Prospects with the Photon Spectrometer at ALICE. Kenta Shigaki (Hiroshima University ) for the ALICE Collaboration 3 rd Joint Meeting of DNP’s of APS and JPS October 14, 2009 Waikoloa, Big Island, Hawaii. Most Relevant Members.

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First high p t physics prospects with the photon spectrometer at alice

First High pT Physics Prospectswith thePhoton Spectrometer at ALICE

Kenta Shigaki

(Hiroshima University )

for the ALICE Collaboration

3rd Joint Meeting of DNP’s of APS and JPS

October 14, 2009

Waikoloa, Big Island, Hawaii


Most relevant members
Most Relevant Members

  • + all PHOS and PWG4 (jet/photon) collaborators

Kenta Shigaki Aya Hiei Hisa Torii

Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki


Presentation outline
Presentation Outline

  • LHC/ALICE/PHOS status and schedule

  • high pT neutral mesons in first year of ALICE

    • statistics and pT reach

    • technical challenges and resolutions

  • first high pT physics prospects

    • p0 in Pb+Pb run in 2010

    • more work in progress

  • summary and concluding remarks

Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki


Lhc alice phos status schedule
LHC/ALICE/PHOS Status & Schedule

  • collisions in 2009/12; physics awaited in 2010

  • ALICE under commissioning

    • cosmic data taking ongoing

    • LHC beam (p and Pb) also seen

  • 3(/5) PHOS modules installed; being cooled down

September, 2009

Pb beam injection oriented

Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki


Jet quenching at lhc
Jet Quenching at LHC

  • higher pT reach + stronger suppression than RHIC

    • clearer measurement of quark energy loss

      • e.g. quark flavor/spin dependent suppression?

  • “day-1” ALICE physics program

    • enough acceptance with initial 3 PHOS modules

Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki


Statistics p t reach in 1 st p p run
Statistics + pT Reach in 1st p+p Run

  • assumptions:

    • 10 TeV p+p;

      5×1028 cm-2s-1;

      180 days×10%

    • p0 in NLO/CTEQ6M/KKP;

      particle ratios from PYTHIA

    • 3/5 PHOS geom. coverage

      (~ high pT limit) only

Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki


Statistics p t reach in 1 st pb pb run
Statistics + pT Reach in 1st Pb+Pb Run

  • assumptions:

    • 3.9 TeV Pb+Pb;

      5×1025 cm-2s-1;

      30 days×10%;

      ~ 10% central (b < 5 fm)

    • NLO pQCD×PYTHIA

      ×N-N binary scaling

      (1,150 for central Pb+Pb)

      ×suppression (0.1)

    • 3/5 PHOS geom. coverage

      (~ high pT limit) only

Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki


Lhc first year versus years at rhic
LHC First Year versus Years at RHIC

  • statistics not really an issue

Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki


And more

Technical Experiences

and More

  • multi-photon decay channels challenging

  • kinematic cut optimization to improve S/B

  • careful combinatorial background subtraction

  • PHOS: highest resolution ever in RHI experiments

PHENIX example wp0g

PHENIX wp0g

Au+Au peripheral (cent 60~92 %)

3.5 < pT < 4.5 [GeV/c]

WA98

13 GeV Pb+Pb

nucl-ex/0108006

PHENIX

200 GeV Au+Au

run 2

ALICE

14 TeV p+p

GEANT simulation

after cut optimization

S/√B (significance)

w

before cut optimization

pT(w) [GeV/c]

Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki


Feasibility evaluation ingredients
Feasibility Evaluation Ingredients

  • single particle simulation

    • NLO pQCD×PYTHIA×N-N binary scaling×suppression

    • mass reconstruction in ALICE analysis framework

      • acceptance for multi-photon decays

      • two-cluster resolution (merging effect)

      • photon identification

  • 1 M central Pb+Pb HIJING at 3.9 TeV

    • locally generated at Hiroshima

  • “hybrid” approach

    • multiplicity effects in next steps

      • embedding study by combining the two

h

p0

Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki


S b and s s b
S/B and S/(S+B)

  • better S/B, not necessarily S/(S+B), at higher pT

  • p0 in ~ 10% central Pb+Pb at 3.9 TeV; RAA = 0.1

  • 5×1025 cm-2 s-1, 30 days, 10% uptime

  • feasible up to >> 10 GeV/c

  • more species (h, w, K0s) under study

Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki


Proof of hybrid approach applicability
Proof of Hybrid Approach Applicability

  • p0 peak visible in central Pb+Pb HIJING

  • consistent S/B in NLO/HIJING hybrid evaluation

    • multiplicity effects to be tested by embedding

pT = 3 GeV/c

pT = 4 GeV/c

pT = 5 GeV/c

pT = 6 GeV/c

pT = 7 GeV/c

pT = 8 GeV/c

pT = 9 GeV/c

pT = 10 GeV/c

with gID

Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki


Summary and concluding remarks
Summary and Concluding Remarks

  • new physics prospects at very high pT at LHC

  • ALICE at LHC starting in months (finally!)

  • neutral meson yields in first year very promising

    • both for p+p and Pb+Pb runs

  • real issue: S/B ratio, significance S/(S+B)

    • especially for multi-body decays (e.g.w, K0s) in Pb+Pb

  • p0 feasible even in central Pb+Pb

  • work in progress: h, w, K0s

    • solid basis on RHIC experiences

  • physics from very beginning of LHC operation!

Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki


Famous kinematic cut asymmetry
Famous Kinematic Cut: Asymmetry

  • discard highly asymmetric pairs to reduce BG

    • background concentrated at high a ( asymmetry)

    • acceptance only at low a at low pT

    • optimized for p0: a < 0.7 at pT 3 GeV/c

    • two photon separation only at high a at very high pT

      • minimum a cut option

  • more complicated cuts for > 2 body cases

    • e.g.p0–p0 energy asymmetry in K0s case

Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki


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