Measuring Charm and Bottom using the PHENIX Silicon Vertex Detectors

1. Measuring Charm and Bottom using the PHENIX Silicon Vertex Detectors Hubert van Hecke, Los Alamos National Laboratory for the PHENIX collaboration Outline: • Motivation • Detector requirements • Description of the detectors • Some MC results • Construction Timeline Hubert van Hecke - QM08

2. Physics Goals for the Silicon Vertex Detectors • Study production and flow mechanisms of heavy quarks • Study of production and suppression of quarkonia • Measure reaction plane • Improve p resolution • Improve high-pT tracking • q, g contribution to proton spin Signal channels: • b->B->e • c->D-> e • J/, ’->  ,e+e- • hadrons e- m+ e+ m- Hubert van Hecke - QM08

3. Separate Signal from Backgrounds The problem: backgrounds ( ->me and K-> me) overwhelm the signal Solution: Mean ,K ->me decay distance is large D, B mesons travel some distance before semileptonic decay to muons or electrons Prompt me have 0 DCA By measuring the DCA to the primary vertex, we can separate D, B decays from prompt leptons and from long-lived decays from , K Hubert van Hecke - QM08

4. Detector Specifications • Need sufficient DCA resolution (~50m central, ~100m forward) • Need occupancy low enough to find tracks in central AuAu events (<few %) • Need enough hits to reconstruct a track (>=3 hits) • Need to match tracks with Central Arm detectors =+-0.35, or with the Muon System:  = 1.2 - 2.4 • Large solid angle coverage Hubert van Hecke - QM08

5. Detectors 80 cm • . 40 cm 38 cm Forward vertex detectors (FVTX) Barrel vertex detector (VTX) Hubert van Hecke - QM08

6. Barrel: Inner 2 Pixel Layers • Inner 2 layers: • pixels: 50 x 425 m • 150 m - thick Siilicon • R = 2.5, 5.0 cm • Length = 22 cm • 1.3, 2.6M channels • Readout with ALICE1LHCb chip • Bump-bonded to detector • RL 1.44% total Hubert van Hecke - QM08

7. Barrel: Inner 2 Pixel Layers (cont’d) Test of half-ladder, extension cable, spiro board successfully completed Carbon support + cooling tube prototype Hubert van Hecke - QM08

8. Barrel: Outer 2 Layers • Outer 2 layers: stripixels • elements: 80 x 1000 m • 650 m - thick Silicon • R=10,14 cm • Length=32, 38 cm • 140K, 280K channels • Readout with SVX4 chip • RL 2.7% total Single_sided, 2D readout Hubert van Hecke - QM08

9. ReadOut Card Strip sensor Kapton Support Barrel - strip layers (contd) Strip pixel sensor wafer made by HPK ROC-3 prototype currently under study CFC Hubert van Hecke - QM08

10. 11.2mm strip Carbon backing Kapton HDI Silicon Readout chips 12.5 cm 1664 strips 13 chips 75-um strips 3.750 2.8mm strip Forward Detectors Basic unit: ‘wedge’ • 4 disks / side • 48 wedges/disk • 75 um strips, • 2.8-11.2 mm long • 1664 strips/column • 1.1M channels total • readout with FPHX chip, • derived from BTeV chip. Hubert van Hecke - QM08

11. Forward detectors (cont’d) Mechanical design ~80% done Wedges front and back Electronics chain fully prototyped Honeycomb support panel Thermally conducting silicone Hubert van Hecke - QM08

12. Barrel: Expected DCA resolution Hadron background s ~ 40 mm • Results of simulation of Au+Au collision. • After a chi**2 cut, DCA distributions of light hadrons and D0 decay are clearly separated DCA distribution for single simulated pions in 3<pT<4 GeV/c. Simulation is done with 200 micron pixel layers and 650 micron strip layer. The passive material is 1.0% per pixel layer and 2.75% per strip layer. Hubert van Hecke - QM08

13. Endcaps: Open charm, bottom signal • In the forward detectors: • Using DCA cuts, plus  and isolation cuts, we can now improve the signal/background for D,B-> D- -> B- -> S/N Hubert van Hecke - QM08

14. Improved resolution + background reduction  Simulated RHIC-II p+p run - better background . rejection - better mass resolution - separate ’ Without FVTX ’  With FVTX ’ Hubert van Hecke - QM08

15. Status and outlook - Barrel construction well underway pixel layers completion in 2009 stripixels completion 2010 - Forward detector construction started in FY08, installation in 2011 • Collaborating institutions: • KEK, RIKEN, Rikkyo, Ecole Polytechnique, Columbia U.; SUNY Stony Brook, Los Alamos, Brookhaven, Oak Ridge; U. New Mexico, New Mexico State U.; Iowa State U.; Bhabha Atomic Research Centre, India; Saclay, France; Charles University, Prague; Czech Technical University, Prague; Institute of Physics, Academy of Sciences, Prague; Kyoto University; University of Jyvaskyla, Finland; Yonsei University, Korea Hubert van Hecke - QM08

16. . backups Hubert van Hecke - QM08

17. Endcaps: DCA resolutions Since the barrel pixels are // to the beampipe (orthogonal to the FVTX mini-strips), using them greatly improves phi resolution 100 m Hubert van Hecke - QM08

18. External mount Hubert van Hecke - QM08

19. Acceptance Since the event vertex spans ~+-10 cm in z, we can use the barrel hits for some events. Hubert van Hecke - QM08

20. Can we match muon arm tracks with a FVTX track? Use the chi2 of the Kalman track fitter : 3 GeV muon: 75% correct match 9 GeV muons; 93% correct match Hubert van Hecke - QM08