1 The LHCb Vertex detector 15/9/2003 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)

2 Physics Goals Current status 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 or 2 for all sides Accessible by LHCb 0 1     B s  D s K B s  D s 

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

4 LHCb Overview of the experiment Luminosity: cm -2 s -1

5 Vertex detector Specifications Forward detector –Detectors only 8 mm from beam –360º coverage in  overlapping detectors Low number of pp interactions per event –In level-0 trigger (40 MHz) –Pile – Up detector Trigger on high p t displaced tracks –In level-1 trigger (1 MHz) –Standalone track reconstruction –Use stray field to select high p t Identify B s oscillations –Vertex resolution: 17  m + 32  m/p t  44 fs (D s  –5  sensitivity to B s oscillations with:  m s = 68 ps -1 Tight material budget

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

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

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

9 Middle station Far station Vertex detector Radiation hardness Radiation hardness Replace detectors every 4 years –Maximum irradiation per station 5 x to 1.3 x n eq /cm 2 /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 Beetle was selected in January 2003 Used in Vertex Detector and Silicon Trackers 0.25  m 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 Read-out (Beetle) Introduction x 186 x 128 V pre I pre V sha I sha I buf Mux to comparator (digital out) In Out Pipeline cells Front-ends Front-end Readout Pipeline

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

12  noise Baseline Signal 3 ns 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 Read-out (Beetle) Analysis Peak Spill over point Convolution of Landau and Gaussian

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

14 Time Time sample Continuous beam Read-out (Beetle) Mimic sampling mode/rate Mimic sampling rate 1.Occupy read-out circuit Send test pulses at high rate 2.Mix with physics triggers 3.Let ADC only read physics triggers 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 Time Time sample Test beam mode 1 LHCb sampling mode

15 Silicon and Read-out To 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

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18 Level-0 trigger combines –High p t 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 p t tracks Trigger: Talk on Thursday, Thomas Schietinger Vertex Station: A B ZAZA ZBZB RARA RBRB R A /R B = Z A /Z B = k LHCb Vertex and Trigger

19 Physics Properties and consequences     You want B decays! –B’s are heavy –Results from B – factories –LHCb offers B s production Higher yield –Over constrained triangle LHC Production channel –Gluon fusion ~ bb pairs a year –Boosted system P P b b P P b b

20 LHCb Specifications Angular coverage –15–300 mrad in bending plane – mrad in non-bending plane Trigger on displaced vertices Excellent vertex resolution Single pp interactions Particle identification –K/  separation –Flavor tagging –1 – 150 GeV For B s  decay is in the order of a few mm