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(based on a discussion between H. Haggerty, H.Wieman and SNW)

“The Virtues of Pileup” (not my title) “Can PHENIX use STAR APS with ~5 ms readout?” (my title). (based on a discussion between H. Haggerty, H.Wieman and SNW). Si Pixel goal is to extract Charm via secondary vertex We do not plan to use Si pixel in any trigger

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(based on a discussion between H. Haggerty, H.Wieman and SNW)

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  1. “The Virtues of Pileup” (not my title) “Can PHENIX use STAR APS with ~5 ms readout?” (my title) (based on a discussion between H. Haggerty, H.Wieman and SNW)

  2. Si Pixel goal is to extract Charm via secondary vertex • We do not plan to use Si pixel in any trigger • PHENIX differs from STAR in high rate DAQ and • small cross section triggers but…. • High data rate Pixel readout = High power • Is it nuts to think of hybrid == High bandwidth PHENIX • Central Arms + 5 ms readout Pixel layer(s)? • There are many precedents: ie emulsion neutrino • experiments which trade spatial resolution for • time resolution

  3. Invariant mass reconstruction of D0s k (preliminary simulation in STAR and following slides from H.Wieman) D0 S B M (GeV) Because A+A at RHIC produces very high multiplicity events the vertex detector must be exceptionally good to reduce B Number of events required to get a statistically significant result

  4. Background depends strongly on thickness of inner layer(STAR) Shows effects of first layer SI thickness, includes contribution from 760 m beam pipe. Preliminary GEANT simulation B Si thickness reduction 300 m 50 m reduces beam time by factor 19 Si thickness (m)

  5. The options • ATLAS style hybrid • Thick ~ 300 m Si • High power 800 W/cm2 – requires liquid cooling, more thickness • CCDs • Very thin • Power vs speed ? • Rad soft • Active Pixel Sensors (APS) • Very thin • Rad hard enough • Slow? But good potential with low power • New technology with normal uncertainties

  6. APS Compromises • Short, does not cover diamond • Most running not luminosity limited so not an issue unless run with a very good trigger • Slow, contains multiple events • Background rejection is pileup tolerant

  7. tracking in cone of uncertainty SVT, or Si strips real hits pileup hits inner vertex detector pileup causing false rejection primary vertex rejection cut False rejection by pileup • Purpose of vertex detector – remove primary tracks before calculating invariant mass • 40 x design luminosity, 5 ms readout • 400 hits/cm2 • 1.4% pixels filled • false rejection 0.5% • 40 X design luminosity, 20 ms readout • 1500 hits/cm2 • 5.3% pixels filled • false rejection 2.9%

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