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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 l.jpg
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

Slide3 l.jpg

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 l.jpg
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 l.jpg
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 l.jpg
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 l.jpg
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 l.jpg




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 l.jpg
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)

Summary l.jpg

  • 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.