Measuring Charm and Bottom using the PHENIX Silicon Vertex Detectors

Measuring Charm and Bottom using the PHENIX Silicon Vertex DetectorsHubert van Hecke, Los Alamos National Laboratoryfor the PHENIX collaboration Motivation Detector requirements Description of the detectors Some MC results Construction TimelineOutline:

Physics Goals for the Silicon Vertex DetectorsSignal channels: b->B->e c->D-> eJ/, -> ,e+e-hadronsm-e-e+m+ 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

Separate Signal from BackgroundsThe problem: backgrounds ( ->me and K-> me) overwhelm the signalSolution:Mean ,K ->me decay distance is large

D, B mesons travel some distance before semileptonic decay to muons or electrons

Prompt me 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

Detector Specifications Need sufficient DCA resolution (~50m central, ~100m forward) Need occupancy low enough to find tracks in central AuAu events (=3 hits) Need to match tracks with Central Arm detectors =+-0.35, or with the Muon System: = 1.2 - 2.4Large solid angle coverage

Detectors.Barrel vertex detector (VTX)Forward vertex detectors (FVTX)80 cm40 cm38 cm

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

Barrel: Inner 2 Pixel Layers (contd)Test of half-ladder, extension cable, spiro board successfully completedCarbon support + cooling tubeprototype

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

Barrel - strip layers (contd)ROC-3 prototype currently under studyCFCStrip pixel sensor wafer made by HPK

Forward DetectorsBasic 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.

Forward detectors (contd)Thermally conducting siliconeHoneycomb support panelWedges front and backMechanical design ~80% doneElectronics chain fully prototyped

Endcaps: Open charm, bottom signalIn the forward detectors:Using DCA cuts, plus and isolation cuts, we can now improve the signal/background for D,B->D- ->

B- ->

S/N

Improved resolution + background reductionSimulated RHIC-II p+p run - better background . rejection - better mass resolution - separate

Without FVTXWith FVTX

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

.backups

Endcaps: DCA resolutionsSince the barrel pixels are // to the beampipe (orthogonal to the FVTX mini-strips), using them greatly improves phi resolution

100 m

External mount

AcceptanceSince the event vertex spans~+-10 cm in z, we can use the barrel hits for some events.

Can we match muon arm tracks with a FVTX track?Use the chi2 of the Kalman track fitter :

3 GeV muon: 75% correct match9 GeV muons;93% correct match