Transcript No Slide Title

Chris Parkes, CERN
LHCb VErtex LOcator &
Displaced Vertex Trigger
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Vertex Detector
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Displaced Vertex Trigger
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Design
Test Beam Results
Algorithm
Test Beam Emulation
Conclusions
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Beauty ‘99
Summary
Future Plans
LHCb Detector
Beauty ‘99
Chris Parkes
Resolution
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Secondary Vertices
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B tagging
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Rejection of
background
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Primary vertex
resolution 40 m
Beauty ‘99
Chris Parkes
Geometry
series of discs
Detectors separated
6cm during injection
small
overlap
10cm
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Chris Parkes
Vertex Locator
• Detector Length 1m
• Station spacing varying
from 4 - 12cm
• 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
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-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
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180 degree
R & Phi
Detectors
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2048 strips
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Smooth
variation in
pitch
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16 chip Hybrid
Ready in
Autumn
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Chris Parkes
Mechanics
Beauty ‘99
Chris Parkes
Vacuum Vessel
manipulators
vessel
Top
Half
window
primary vacuum
100cm
detectors
RF shield
vacuum barrier
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Chris Parkes
Radiation Environment
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Including effects of
walls, vessel
High doses at tips
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Detectors Irradiated
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(1/r2)
Test-Beam
September
n+ on n Silicon as
base solution
Dose after 1yr
1014
1 MeV equivalent neutrons/cm2
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station 6
1013
1
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2
3
cm
4
5
6
Chris Parkes
Modelling
 Cooling Required
 Electric Field Distortions
 Radiation Response
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Chris Parkes
Software
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LHCb will use C++
BUT Technical Proposal work was in FORTRAN
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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...
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Software Designed for future use
both useful code, and class design
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Chris Parkes
Trigger Levels
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Chris Parkes
Second Level Trigger
Vertex Algorithm
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IDEA
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AIM
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Input event rate of 1 MHz or 2Gbytes/second .
Average execution time of about 250 microseconds.
Implementation
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Minimum bias retention of less than 4% and a signal
efficiency of more than 50%.
Boundary Conditions
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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
2d
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Track finding using triplets of r-clusters
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Primary vertex reconstruction, x y z, by crossing
tracks of opposite phi-sectors
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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
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Chris Parkes
Algorithm cont.
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3d
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Add phi info. for large impact parameter tracks
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find two track combinations which are close
calculate probability that one of the two tracks
originate from the primary vertex
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Beauty ‘99
ambiguities resolved by stereo angle
and impact parameter in xy-projection
based on impact parameter
and geometry
calculate total L1 probability by multiplying the
individual probabilities
Chris Parkes
Present Performance
2d and 3d track
reconstruction efficiency
of 98% and 95%.
Primary vertex resolution
of 80micron and 20micron
for z and x/y.
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Chris Parkes
Test Beam
Spring ‘98
12 Silicon Planes
Slow Electronics
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Chris Parkes
Vertex Trigger
Peformance
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Use Targets to
simulate Primary
Vertex
Resolution
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Simulation 80m
Test Beam
Extrapolated 80m
Assess sensitivity
to detector
misalignments
Beauty ‘99
Chris Parkes
Artificial B events
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Virtual B !
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Five events form one target
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One From next target
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“minimum bias”
B event
Good Performance
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Chris Parkes
Analogue
readout
FE Rad. Hard
Overview
of the
readout
scheme
>2Mrad/yr
FADC + L1
Front End Chip
DMILL- SCTA
buffers 10m away
Processing in
DSPs after L1
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
SCT128A 40MHz
FE chip
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Setup
6 plane Telescope
+ 2 Test Detectors
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Beauty ‘99
Chris Parkes
Test-Beam Results
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Clear Signal Observed
Correlated with reference Telescope
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Chris Parkes
Time Response
Rise Time ~ 25ns
Pulse Remaining after
25ns ~ 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
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Chris Parkes
Conclusions
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Prototype Detectors Tested
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New Design
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Displaced Vertex Trigger
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Future Work
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…..
So far the project is flying...
Beauty ‘99
Chris Parkes
Milestones
 2000 : Full Half station at 40MHz
 2001 : Technical design Report
 2003 : Construction
 2004 : Commissioning
 2005 : Start Data Taking
But there is still a long way to cycle…..
Beauty ‘99
Chris Parkes