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Simulation issue. Y. Akiba. Main goals stated in LOI. Measurement of charm and beauty using DCA in barrel c  e + X D  K p , K pp , etc b  e + X B  J/ y  ee Measurement of Jets in barrel Reconstruction of “jets” from charged tracks in barrel

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main goals stated in loi
Main goals stated in LOI
  • Measurement of charm and beauty using DCA in barrel
    • c e + X
    • D  Kp, Kpp, etc
    • b  e + X
    • B  J/y  ee
  • Measurement of Jets in barrel
    • Reconstruction of “jets” from charged tracks in barrel
  • Measurement of charm and beauty using DCA in end-cap
    • c m+ X
    • b  m + X
    • B  J/y  mm
  • Physics goals
    • Au+Au: Probing hot dense matter using heavy quarks
    • d+Au: Measurement of gluon shadowing in small x
    • p+p: Measurement of DG(x) in wide x range
Strawman Design
  • 1.5% X/X0 per layer
  • b) 1st layer as close to beam-pipe as possible
  • c) rely on PHENIX central + muon arms for PID, momentum
  • d) 4 layers => accurate, redundant DCA
critical questions
Critical Questions
  • How much conversion background the Si detector will generate to the central arm?
    • Effects on LVL1 trigger on p+p
      • “thick converter” data in RUN-3 may give the answer
    • Effects on offline analysis
      • RICH occupancy
      • Single electron background
      • Di-electron background
  • How well “external tracks” can be connected to the tracks in SVT
    • Central arm track to SVT barrel
    • Muon arm track to SVT end-cap
  • Purity of charm/beauty candidates with DCA cuts
    • purity has a major impact how well DG(x) can be measured
  • How effective DCA cuts for a given beam spot size
    • Present beam spot size of RHIC sx ~ sy ~ 500m. This is larger or comparable to ct of D0(123m), D+(315m), B0(462m), and B+(502m).
    • Beam size in RHIC-II will be smaller (s ~ 150 m?)

These questions should be answered at least by very realistic simulation

background issue
Background issue
  • Effective radiation length in present PHENIX:
    • 0.8%(Dalitz)+0.3%(beam pipe)+1%(MVD) = 2.1%
    • 1.1 % without MVD (a possible configuration in RUN-4)
  • Effective radiation length with SVT
    • 0.8%(Dalitz)+0.3%(beam pipe)+4×1.5%(Si)+0.3%(?)(Enclosure)=7.4%
    • 1.4 to 1.8 % if conversion electron in the SVT is removed by requiring a hit in the inner-most layer of the SVT.
      • Here I assume that Si sensor part is placed in the inner half of the Si layer.
      • Unique association of electron track and SVT track is required
  • If the conversion in the SVT are not removed by offiline 
    • Combinatorial background of di-electron pairs will increase by a factor of > 10. This will makes low mass measurement impossible, and this will seriously compromise the measurement of J/Y and y(2S) in the most central collision.
    • The background can conflict another upgrade plan (TPC+HBD)

This question of the conversion background should be clarified in CDR

example impact on j y
Example: impact on J/Y
  • RUN-2 Au+Au (0-20%) (7/mb of data)
    • Background: ~40 counts
    • Signal: < 10 (90%CL)
      • Expected signal is 10% to 70% of the upper limit. See left plot
  • Au+AuJ/Yee in RUN-4
    • ~300 /ub in RUN-4
    • Combinatorial Background can be reduced by 50% with narrower mass cut

 Background: ~ 900 (with narrow mass cut)

Signal: <40 (QGP suppression)

~270 (statistical model)

  • PHENIX very likely wants to continue J/Y measurement beyond RUN-4. If conversion from SVT is not removed, this measurement becomes very difficult.
  • It is important to demonstrate that the background from SVT does not compromise the J/Y measurement
what are needed to be done
What are needed to be done
  • Realistic implementation of SVT geometry and material in PISA
  • Implementation of SVT response chain in PISA
    • Efficiency
    • Noise level
  • Local track reconstruction code for simulated SVT
  • Global tracking (SVT track  DC track (PHENIX reco track))
  • New simulation reconstruction code should be implemented as a new classes of PHENIX reconstruction code
  • Simulation study of
    • Full Hijing event or parameterized Au+Au event
    • p+p event
    • with realistic vertex distribution (sr ~ 500 m, sz ~ 30 cm)
    • Study of
      • Reconstruction efficiency
      • Di-electron background (after SVT tracking)
      • DCA resolution
      • Purity of charm/beauty track candidate
      • “Jet” reconstruction in SVT
more detaled list



150 to 200µm



150 to 200µm


carbon fiber support

More detaled list
  • Structures like shown in the right should be implemented in PISA
  • New “GHIT” from SVT (one each for Si pixel, Si strip, and Si end cap)
  • New class in response chain that produces new (calibrated) “HIT” from “GHIT” and relation table between them for Si pixel, Si strip, and Si end-cap
  • Geometry objects that describes SVT geometry in reco chain
  • SVT barrel local tracking class (barrel HIT  barrel track)
  • Barrel track  central arm track global tracking class
  • SVT end cap local tracking class (end cap HIT  end cap track)
  • End cap track  muon track global tracking class
  • All code should be implemented in the current framework of PISA and PHENIX reconstruction/analysis chain
very rough estimates of man power and time
Very rough estimates of man-power and time
  • Man power need for software development
    • PISA geometry implementation: 1 to 2 man month (dedicated)
    • PISA response chain: 1 to 2 man month (dedicated)
    • SVT local tracking and Global tracking
      • Barrel + central tracks: 2-3 man months minimum
      • End-cap + muon arm track: 2-3 man months minimum
    • Need volunteer for the work:
      • 1-2 person for PISA geometry + response chain
      • 1-2 person each for tracking for (barrel+central) and (end-cap+muon)
      • 1 Coordinator of the effort
  • If we start strong effort on the simulation/reconstruction project, the first version of software can be available by end of summer
  • Simulation production RUN (>1 month, in Fall 2003?)
    • 100K Au+Au central events (10 min/event?)  1 weeks x 100 CPU
    • 100K Au+Au min. bias events (3 min/event?)  a few days x 100 CPU
    • 1M p+p charm/beauty events
    • Real time can be longer by factor 2 to 3
  • Analysis of fully simulated events (>1 months. Fall to winter 2003)
  • There are several, unanswered, critical questions on SVT
    • Performance in central Au+Au collisions
    • Conversion background and its influence to electron pair measurement
    • Compatibility with TPC/HBD project
  • They needed to be answered (at least) by a very realistic simulation and reconstruction of the simulated data.
  • This is a major effort, and requires > half year of concentrated effort of several dedicated people.
  • Need to start now to get result by the end of year.