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The LHCb Vertex detector

The LHCb Vertex detector. Physics Goals Properties and consequences LHCb Overview of the detector Vertex Specifications Silicon stations Overview Details Radiation hardness Read-out chip developments Conclusions & Prospects.

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The LHCb Vertex detector

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  1. The LHCb Vertex detector • Physics • Goals • Properties and consequences • LHCb • Overview of the detector • Vertex • Specifications • Silicon stations • Overview • Details • Radiation hardness • Read-out chip developments • Conclusions & Prospects Vertex2003, Sander Klous (on behalf of the LHCb collaboration) 15/9/2003

  2. Bs Dsp h g b r 0 1 Bs DsK Accessible by LHCb Current status PhysicsGoals • Investigate difference between Matter and Antimatter • CP violation in standard model • Rotation between mass eigenstates and weak eigenstates (CKM matrix) • Expressed with Wolfenstein parameterization • One of the 6 Unitary Triangles • Order l or l2 for all sides

  3. b P P b P P b b PhysicsProperties and consequences • You want B decays! • B’s are heavy • Results from B – factories • LHCb offers • Bs production • Higher yield • Over constrained triangle • LHC Production channel • Gluon fusion ~ 1012 bb pairs a year • Boosted system (decay length) Angular coverage • 15–300 mrad in bending plane • 15-250 mrad in non-bending plane

  4. LHCbOverview of the experiment Luminosity: 2 . 1032 cm-2s-1

  5. Vertex detectorSpecifications • Forward detector • Detectors only 8 mm from beam • 360º coverage in f • overlapping detectors • Low number of pp interactions per event • In level-0 trigger (40 MHz) • Pile – Up detector • Trigger on high pt displaced tracks • In level-1 trigger (1 MHz) • Standalone track reconstruction • Use stray field to select high pt • Identify Bs oscillations • Vertex resolution: 17 mm + 32mm/pt 44 fs (Dsp) • 5s sensitivity to Bs oscillations with: Dms = 68 ps-1 • Tight material budget

  6. y y pitch from 40 to 103 mm x x Second metal layer Interaction region s = 5.3cm Vertex has standalone track and vertex reconstruction (Projection in R-z plane) 45º segments 8 mm 42 mm Pile - Up stations A 21 + 2 Highest x-y resolution naturally closest to interaction region Stereo -20° and 10° R 250 mrad 1meter z 15 mrad A AA Vertex detectorSilicon stations Trigger: Talk on Wednesday, Thomas Schietinger Temperature -5 ºC CO2 Cooling system Thickness 220 mm

  7. Retractable detector halves for beam injection Silicon stations in vacuum R detector Phi detector Beam Thin exit foil Vertex detectorOverview Detector on X-Y tables

  8. Bellows to accommodate retractable detector halves • Thin separation between silicon stations and beam • Secondary vacuum • RF shield • Wakefield guide • Controlled pressure • 250 mm thick • Complex shape (overlapping detectors) • Super plastic, hot gas formation Vertex detectorDetails

  9. Middle station Far station Vertex detectorRadiation hardness Radiation hardness • Replace detectors every 4 years • Maximum irradiation per station 5 x 1012 to 1.3 x 1014 neq/cm2/year • Detector could have undepleted layer after irradiation • Resolution of p on n detector degrades fast • Undepleted layer insulates strips from bulk • n on n ~100% efficient for only 60% depletion depth

  10. Pipeline cells Front-ends Read-out (Beetle)Introduction • Beetle was selected in January 2003 • Used in Vertex Detector and Silicon Trackers • 0.25 mm CMOS technology • Intrinsically radiation hard • Single Event Upsets • Triple redundant logic • Analogue and digital output • Digital output used in level-0 • Analogue output used in level-1 to comparator (digital out) Vpre Vsha Readout x 186 Out In Mux Ipre Isha Ibuf x 128 Pipeline Front-end

  11. Beetle1.1 • Tested in SPS beam • 16 chips on 1 hybrid • PR02-R p-on-n detector 90% Rise time Spill over 10% 25 ns Read-out (Beetle)Analogue specifications • 40 MHz clock frequency • 1 MHz read-out • Signal / Noise > 14 • Rise time < 25 ns • Spill over < 30 %

  12. Peak 3 ns Signal snoise Baseline 3 ns Spill over point Read-out (Beetle) Analysis Convolution of Landau and Gaussian • Goal • Optimize performance • Check chip behavior • 16 chips on 1 hybrid • Test beam environment • Mimic LHCb operation • Sampling mode • Sampling rate • Took 10 million events

  13. m m Efficiency enc (e-) Threshold = 14 Hits from previous bunch crossing Read-out (Beetle)Results Average capacitance: 10 pF Signal/Noise = 17.4  0.2 Spill over = 36.1 %  1 Rise time = 23.5 ns  0.5 ENC = 500 + 50 e-/pF Detector capacitance : 6 - 14 pF Resulting S/N range: 14.5 - 21.5

  14. No deteriorating effects were found Test beam mode: 19.7  0.2 Single time sample: 19.6  0.2 Test beam mode: 18.7  0.2 High trigger rate: 18.7  0.2 Note: comparison with other settings Mimic sampling rate Occupy read-out circuit Send test pulses at high rate Mix with physics triggers Let ADC only read physics triggers Test beam mode Time 2 3 4 5 6 1 7 0 Time sample Continuous beam LHCb sampling mode Time 2 3 4 5 6 1 7 0 1 Time sample Read-out (Beetle)Mimic sampling mode/rate

  15. Silicon and Read-outTo do Beam test with irradiated Czochralski silicon To do: • Analysis of beam tests • Irradiated Czochralski silicon • Single Beetle1.2 chip • Beam test with new hybrid • 16 Beetle1.2 or 1.3 chips on hybrid • Thinner detectors • 3D detectors ??? • High resistance • High oxygen content

  16. Conclusions • LHCb is a next generation experiment for CP violation measurements • The vertex detector for LHCb is a mechanically challenging project • Production has started • The silicon and hybrid developments are in their final phase • Results from the beam test with irradiated Czochralski silicon are coming • The new hybrid will be tested in the test beam with 16 Beetle1.2 chips • The Beetle read-out chip developments are in their final phase as well • Version 1.1 is extensively tested and complies almost with specifications • Version 1.2: a single chip is just tested in the test beam • Version 1.3 is the final version and is submitted on a MPW run in June • Next year, system tests will start • The construction of the LHCb vertex detector is on track

  17. Level-0 trigger combines High pt info from calorimeters and muon detectors Pile - Up information from Pile – Up detector Counts number of primary vertices per event 2 dedicated stations in the vertex detector Digital read-out at 40 MHz Outside acceptance Level-1 trigger Identify displaced tracks at 1 MHz Low occupancy High efficiency R/Phi configuration Match with high pt tracks B A Station: RA/RB = ZA/ZB = k RB RA Vertex ZA ZB LHCbVertex and Trigger Trigger: Talk on Thursday, Thomas Schietinger

  18. b + g b dg g - 2dg b P P b g P P b b PhysicsProperties and consequences • You want B decays! • B’s are heavy • Results from B – factories • LHCb offers • Bs production • Higher yield • Over constrained triangle • LHC Production channel • Gluon fusion ~ 1012 bb pairs a year • Boosted system

  19. For Bssdecay is in the order of a few mm LHCbSpecifications • Angular coverage • 15–300 mrad in bending plane • 15-250 mrad in non-bending plane • Trigger on displaced vertices • Excellent vertex resolution • Single pp interactions • Particle identification • K/p separation • Flavor tagging • 1 – 150 GeV

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