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Physics Goals of Si Vertex Detector

Physics Goals of Si Vertex Detector. Craig Ogilvie for the PHENIX Collaboration. Physics priorities latter part of this decade spin carried by gluons: D G vs x modification of gluon structure function in nuclei properties of earliest, densest stage of Au+Au Observables

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Physics Goals of Si Vertex Detector

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  1. Physics Goals of Si Vertex Detector Craig Ogilvie for the PHENIX Collaboration • Physics priorities latter part of this decade • spin carried by gluons: DG vs x • modification of gluon structure function in nuclei • properties of earliest, densest stage of Au+Au • Observables • open charm, open beauty in pp, pA, AA • over a broad range of y, pt Craig Ogilvie

  2. Strawman Craig Ogilvie

  3. GS95 DG(x) prompt photon cc bb J/ x DG Before vs After Si Vertex Before vertex upgrade After vertex upgrade • jet-axis for photon+jet-axis => constraint on x • c=>e, m displaced vertex low-x S/B, D=>Kp high-x • b=>displaced J/y low/high-x, b=>e, displaced vertexhigh -x Si vertex extends x-range with overlap => integral DG Craig Ogilvie

  4. J/y from B direct J/y z vertex (cm) Example, B=>J/y=>mm x1 pz (GeV/c) B => J/y, utilizing large acceptance muon arms requires end-disks of vertex detector Craig Ogilvie

  5. L. Frankfurt, M. Strikman Eur. Phys. J A5, 293 (99) Before Vertex detector After Vertex detector prompt photon Q = 2 GeV Q = 5 GeV Q = 10 GeV cc bb pA Charm, Beauty Production • Heavy-flavor production via gg => q+q • Extracting gluon structure function nuclei, shadowing • vertex detector provides broader range in x • into predicted shadowing region • check consistency of several observables Craig Ogilvie

  6. AA Charm, Beauty Production • Possible charm enhancement in earliest stage of reaction • High-pt heavy-quarks may lose less energy in the plasma • Kharzeev et al. predict reduced gluon Bremsstrahlung • Charm is critical baseline for J/y suppression • Charm provides key info. for di-lepton continuum • Goals require broad-range in pt and y coverage • spectra and yields of open charm, beauty • pp, pA and AA • Strategy • different decay channels => complementary pt, y ranges Craig Ogilvie

  7. Decay Channels => Different y, pt Ranges • Charm • low-pt, D=>e, m +X, displaced electrons, muons • high-pt, D=>Kp • Beauty • B=>J/y => m+m- or e+e-, displaced J/y • high-pt B=> e+X, displaced electrons Craig Ogilvie

  8. Landscape: Mid-Rapidity Sources of Electrons Sum Dalitz Charm Beauty pt of e- pp 200 GeV Pythia Suggests a strategy: Remove Dalitz via vertex cut charm pt(e) < 3 GeV/c beauty pt(e) > 3 GeV/c details next… 1 2 3 4 5 6 7 pt(e) (GeV/c) Craig Ogilvie

  9. Robust Low-pt Charm D=>eX • remove Dalitz e, DCA cut • or fit DCA distribution folded with resolution • charm yield low ptD • reduce systematic error of existing charm result PRL 88:192303,2002 • improves S/B DG at low-x Craig Ogilvie

  10. Open Charm Forward Rapidity, Si Endcaps • Inclusive D=>m+X dominated by p, K decays • insist muon comes from within 1cm of collision • removes many muons from p, K decay high-statistics, robust charm same y, pt range as J/y => critical normalization Craig Ogilvie

  11. D+ => K-p+ p+(BR 9%) Lc High-pt: Flavor Dependence Energy-loss • @ higher pt, e and m decay channels dominated by beauty • hadronic decay for high-pt charm spectra • multiple-scattering, small acceptance less problematic pt >4 GeV/c D0=>Kp p+p 30k/year Au+Au 10K/year Au+Au 4blue-book luminosity, 50 full days/year, yield Au+Au= AA*(yield p+p) Craig Ogilvie

  12. Mid-Rapidity Open Beauty Measure DCA distribution for pt (e) > 3 GeV/c e.g. with dca >120mm p+p #electrons 320K/year Au+Au #electrons 125K/year Craig Ogilvie

  13. J/y from B direct J/y z vertex (cm) Open Beauty in Endcaps Large acceptance in muon arms => high rate e.g. with z vertex > 0.1cm p+p #J/y 20K/year Au+Au #J/y 7K/year Craig Ogilvie

  14. Strawman Design • ~1% X/X0 per layer • R&D in thinning/bump-bonding, monolithic • 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 Craig Ogilvie

  15. Craig Ogilvie

  16. Vital Statistics Craig Ogilvie

  17. Electrons: Resolution Distance Closest Approach e-track dca collision vertex 50mm x 425mm pixels, full multiple scattering dca resolution (electrons) < 50 mm at moderate pt less than ct, D0: 125mm D±: 317 mm Craig Ogilvie

  18. Matching to Muon Arms • Match tracklets in Si to muon spectrometer • cut on same charge • cut on momentum before/after muon shielding • matches hit, efficiency > 90% m xhit-xproj (cm) Craig Ogilvie

  19. Other Physics • Strange baryons, L, X, W • confirm by-then-existing STAR results • Better angle measurement for m+m- pairs • improved mass resolution for all vector mesons • J/y, y’, Upsilon • Improved signal/background for J/y • J/y flow ? • …… Craig Ogilvie

  20. Summary • Physics case for vertex upgrade • gluon spin structure function broad range in x • gluon shadowing in nuclei • charm enhancement early-stage of heavy-ion collision • charm baseline for J/y suppression • energy-loss of high-pt heavy quarks • Charm, beauty in pp, pA, AA collisions • broad pt, y range • use different decay channels to reach different parts of phase space • Required R&D • described in next talk Craig Ogilvie

  21. backups Craig Ogilvie

  22. PHENIX QM02 Craig Ogilvie

  23. Electron pt Spectra from D Craig Ogilvie

  24. x2 from B=>J/y Craig Ogilvie

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