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: • Physics goals • 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 • We require: • DCA resolution < 50 um for the central barrel • < 100 um for the forward detectors • Occupancy < 10% • Large solid angle coverage • || < 1.2 - barrel, standalone • || < 0.35 - barrel, matches central arms • 1.2 < || <2.4 - forward detectors, covers most of • the muon arms • Capability to match tracks with Central arm and • Muon arm tracking systems • Enough hits (>=3) to reconstruct a track • Minimal mass 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 • 200 m - thick Silicon • 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 • AuAu occupancy: 0.5, 0.2% 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 • AuAu occupancy: 4.6, 2.6% 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. Carbon backing Kapton HDI Silicon Readout chips 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. • RL 2.4% 2.8 - 11.2mm strips, 75 um wide 12.5 cm 1664 strips 13 chips Hubert van Hecke - QM08 75-um strips 3.750 2.8mm strip

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

12. Some simulation results Hubert van Hecke - QM08

13. Barrel: Expected DCA resolution Hadron background s ~ 40 mm DCA distribution for single 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. • Results of simulation of Au+Au collision. • After a chi**2 cut, DCA distributions of light hadrons and D0 decay are clearly separated Hubert van Hecke - QM08

14. 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

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

16. Status and outlook - Barrel construction well underway pixel layers completed in 2009, installed and ready for PHENIX run 10 stripixels completion 2010, insalled and ready for run 11 - Forward detector construction started in FY08, installation in 2011, ready for run 12 • 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

17. . backups Hubert van Hecke - QM08

18. 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

19. External mount Hubert van Hecke - QM08

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

21. 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