Chris Parkes CERN LHCb VErtex LOcator Displaced Vertex

Chris Parkes, CERN LHCb VErtex LOcator & Displaced Vertex Trigger u Vertex Detector n n u Displaced Vertex Trigger n n u Design Test Beam Results Algorithm Test Beam Emulation Conclusions n n Beauty ‘ 99 Summary Future Plans

LHCb Detector Beauty ‘ 99 Chris Parkes

Resolution u Secondary Vertices u B tagging u Rejection of background u Primary vertex resolution 40 m Beauty ‘ 99 Chris Parkes

Geometry series of discs Detectors separated 6 cm during injection small overlap 10 cm Beauty ‘ 99 Chris Parkes

Vertex Locator • Detector Length 1 m • Station spacing varying from 4 - 12 cm • Phi Overlap of detectors • Each Station has an R and a Phi measuring detector • Stereo angle between successive Phi Detector layers Beauty ‘ 99 Chris Parkes

Prototype Design r-detectors r-measuring detectors -detectors Beauty ‘ 99 -measuring detectors 5 ° “stereo” tilt Both detectors utilize a double metal layer to readout inner strips whilst keeping electronics outside active area. Chris Parkes

New Design u 180 degree R & Phi Detectors u 2048 strips u Smooth variation in pitch u u 16 chip Hybrid Ready in Autumn Beauty ‘ 99 Chris Parkes

Mechanics Beauty ‘ 99 Chris Parkes

Vacuum Vessel manipulators vessel Top Half window primary vacuum 100 cm detectors RF shield vacuum barrier Beauty ‘ 99 Chris Parkes

Radiation Environment u Including effects of walls, vessel High doses at tips n u Detectors Irradiated n u (1/r 2) Test-Beam September n+ on n Silicon as base solution Dose after 1 yr 1014 1 Me. V equivalent neutrons/cm 2 u station 6 1013 1 Beauty ‘ 99 2 3 cm 4 5 6 Chris Parkes

Modelling u Cooling Required u Electric Field Distortions u Radiation Response Beauty ‘ 99 Chris Parkes

Software u LHCb will use C++ BUT Technical Proposal work was in FORTRAN u Test Beam used to gain experience with new language and Root All reconstruction software in C++ Cluster Making, Event Display, Track Fit, Alignment, Noise Studies. . . u Software Designed for future use both useful code, and class design Beauty ‘ 99 Chris Parkes

Trigger Levels Beauty ‘ 99 Chris Parkes

Second Level Trigger Vertex Algorithm u IDEA l u AIM l u l Input event rate of 1 MHz or 2 Gbytes/second. Average execution time of about 250 microseconds. Implementation l Beauty ‘ 99 Minimum bias retention of less than 4% and a signal efficiency of more than 50%. Boundary Conditions l u Separation of minimum bias events and B events by using the signature of displaced secondary vertices. benchmark results show can be performed by 120 1000 MIP processors Chris Parkes

Present Algorithm 2 d u n Track finding using triplets of r-clusters l n Primary vertex reconstruction, x y z, by crossing tracks of opposite phi-sectors l n n track search starts in inner r sector x y - resolution given by phi-sector Selection of tracks with large impact parameter Rejection of pile-up events r z Beauty ‘ 99 Chris Parkes

Algorithm cont. u 3 d n Add phi info. for large impact parameter tracks l l n n find two track combinations which are close calculate probability that one of the two tracks originate from the primary vertex l l n Beauty ‘ 99 ambiguities resolved by stereo angle and impact parameter in xy-projection based on impact parameter and geometry calculate total L 1 probability by multiplying the individual probabilities Chris Parkes

Present Performance 2 d and 3 d track reconstruction efficiency of 98% and 95%. Primary vertex resolution of 80 micron and 20 micron for z and x/y. Beauty ‘ 99 Chris Parkes

Test Beam Spring ‘ 98 12 Silicon Planes Slow Electronics Beauty ‘ 99 Chris Parkes

Vertex Trigger Peformance u u Use Targets to simulate Primary Vertex Resolution n n u Simulation 80 m Test Beam Extrapolated 80 m Assess sensitivity to detector misalignments Beauty ‘ 99 Chris Parkes

Artificial B events u Virtual B ! n Five events form one target l “minimum bias” n One From next target l B event u Good Performance Beauty ‘ 99 Chris Parkes

u. Analogue readout FE Rad. Hard >2 Mrad/yr Overview of the readout scheme u. FADC + L 1 Front End Chip buffers 10 m away DMILL- SCTA u. Processing in DSPs after L 1 accept Beauty ‘ 99 or 0. 25 m CMOSBEETLE Chris Parkes

LHC Speed Readout Chip Test-Beam Spring ‘ 99 Aim Evaluate performance of detector equipped with SCT 128 A 40 MHz FE chip u Setup 6 plane Telescope + 2 Test Detectors u Beauty ‘ 99 Chris Parkes

Test-Beam Results u u Clear Signal Observed Correlated with reference Telescope Beauty ‘ 99 Chris Parkes

Time Response Rise Time ~ 25 ns Pulse Remaining after 25 ns ~ third of Signal 40% of LHCb events are preceded by an event simulation of B Trigger efficiency drops above 30% overspill Signal: Noise ~ 20: 1 Beauty ‘ 99 Chris Parkes

Conclusions u Prototype Detectors Tested u New Design u Displaced Vertex Trigger u Future Work …. . So far the project is flying. . . Beauty ‘ 99 Chris Parkes

Milestones u 2000 : Full Half station at 40 MHz u 2001 : Technical design Report u 2003 : Construction u 2004 : Commissioning u 2005 : Start Data Taking But there is still a long way to cycle…. . Beauty ‘ 99 Chris Parkes