Bristol, CERN, Glasgow, Lausanne,
Liverpool, Manchester, Moscow State,
NIKHEF, Oxford, Syracuse University,
Warwick
PART I
Status of the
VErtex LOcator
Thanks to
VELO colleagues
for slides, notably
Themis Bowcock,
Silvia Borghi
PART 2
Potential for
Upgrade
1
Chris Parkes
Warwick 16th July 2009
PART I
Status of the
LHCb Vertex
Locator:
Finishing the last
spoke of the VELO
•
•
•
•
•
LHCb Intro
Velo Design
Construction
Alignment
Commissioning - Data
2
B Physics Progress
• Spectacular progress in heavy flavour physics this millenium
– Baseline measurement ACP (J/y KS)
– Bs and D Oscillation Measurements
• B Factories/Tevatron achieved much more than dreamed
LHCb Goals
• Explore Bs System
Bs  K  K 
• Charm Physics
Bs  J /y
– Discover CP violation ?
• Rare decay
Bs   


Bs  K * 
• Unitarity Triangle
Loop Discoveries:
Charm..top..Higgs(?)
Angle 
• Compare loops & trees
3
Plagiarism as flattery...Jonas from Monday
4
B Production
•LHC: pp-collisions @ 14TeV
•2 fb-1 Nominal data taking year of 107s
bb correlated
Lorentz boost
LHCb: forward spectrometer
15-250 mrad acceptance
Interactions/crossing
•Pile-up at high luminosity
•choose 2x1032 cm-2 s-1
most events have single interactions
5
LHC will reach early in run
Dedicated Flavour Experiment
•Full spectrum of B (&c) hadrons:
B , Bd,0 s, c , baryons
• Bs system,all angles, sides of both CKM s
•Lots of events !
σbb  500 μb, O (1012) bb pairs per year
Dipole magnet Tracking system
Muon system
Calorimeters
Vertex
Locator
p
10 mrad
p
RICH detectors
6
Muon
Calorimeters
RICH2
Trackers
RICH1
Magnet VELO
7
• UK
–
–
–
–
Spokesperson
Physics Co-ordinator
VELO Project Leader
20% of Collaboration
Flag Waving
• Cost
– £ Entire LHCb < Cost of ATLAS SCT
– £ VELO R&D < Cost of ATLAS spare module boxes
• Glasgow Detector Responsibilities
– RICH HPD testing
– VELO module testing
– VELO HV system
– VELO simulation & reco. software
– VELO Alignment
• Glasgow Physics
– CKM angle γ from U-spin methods
• Standard Model γ (Tree Diagrams): BD / BsDsK
• NP sensitive γ (Penguin Diagrams): B / BsKK
– Two body Decays
• Lifetime measurements (charm, BsKK)
• Rare Bhh
• time dependent two body D decays
– New Physics sensistive rare decay BK*μμ
8
Aims & Critical Components
•LHCb:
• study CP violation
• rare B decays
New Physics
•Requirements:
• efficient trigger on leptons and hadron channels
• efficient particle ID for flavour tagging and
background rejection
• good proper time resolution for time dependent
measurements of Bs decays
• good B mass reconstruction for background
rejection
9
LHCb: Triggering on B’s
10 MHz
Visible collisions
L = 2 1032 cm-2 s-1
L0: [hardware]
high Pt particles
calorimeter + muons
4 μs latency
1 MHz
HLT [software]
1 MHz readout
~1800 nodes farm
~2 kHz
On tape:
Exclusive selections
Inclusive streams
10
Velo Rôles
• Primary / b decay Vertex reconstruction
• Stand alone Tracking
– A principle tracking device for the experiment
• Second Level Trigger
– Fast tracking
1m
•In vacuum
•Retract each fill
One set of half disks
•Align each fill
11
Design
•VELO sensors as close
as possible to beam
injection
6 cm
•no beam pipe,
•sensors ~7mm away from
beam
BUT
•Injection: retraction by 30mm
y
x
stable
beams
partly overlapping
sensors
•Protect sensors against RF pickup from
LHC beam
•Protect LHC Vacuum from possible
out-gassing of detector modules
•Place sensors in a secondary vacuum in Roman pots
12
UK responsibilities:
Design , Build, Test
•Si Sensors
•Hybrids
•Thermal/ mechanical modules
•HV system
Software
•Simulation
•Reconstruction
•Pattern Recognition
•Alignment
13
VELO: Tank
14
Secondary Vacuum – RF Foil
•Made from 300m thick Al
outer corrugations
•Inner corrugations :
Minimal material before the
first sensor is hit
•Outer corrugations:
F sensors
R sensors
allow for overlap of detector
halves for full azimuthal coverage
and for alignment
inner corrugations
•Manufactured at NIKHEF
method: Hot gas Forming
vacuum tight and stiff
15
VELO: Cooling
• Biphase CO2 @ 15bar
• Low mass
16
•
•
•
•
•
•
highly segmented
n+ on n & 1 n on p
double metal layer
2048 strips/sensor
Laser cut
Two designs
VELO: Sensors
~4cm
– R-measuring
– Phi-measuring
17
Sensor Design
•R & Phi sensors
R-measuring sensor:
(concentric strips)
•Fast stand-alone tracking and
vertexing for trigger
•Design allows to optimise resolution
vs. number of channels
•Design of Sensors:
•Active area 8mm to 42 mm
•Smooth pitch variation from inner
(40m) to outer radii (100m)
•2nd metal layer to route signal to
chips
•n+-on-n DOFZ
•Analogue readout, 40MHz clock
F–measuring sensor:
(Radial strips with a stereo angle)
18
Production: Hybrid
•
•
•
•
TPG/CF core
Double sided
Populated
Pitch adaptors
– Chips
• Bonding
• Sensors
• More bonding
19
Production: Sensor Bonding
•
•
•
•
Loop heights
Row 1 = 250 µm
Row 2 = 450 µm
Row 3 = 750 µm
Row 4 = 900 µm
Chip
Pitch Adapter
The chip pads are four row bonding with small pads, making it
difficult but not impossible to do repair work.
There are 16 chips per sensor each with 128 wires a total of
4096 wires per module
20
Testing: IR Laser
•Programmed & aligned
•Noise plots
•Laser scan every strip of
every detector
21
Testing: Inspection / Burn-in
• Visual inspection
– Detailed High
Resolution
• Vacuum Burn-in
– Thermal Cycling
– 16 hour burn-in
– Noise
22
Assembly: Mounting
module bridge rotated into
position
module inserted onto
support
cooling cookies attached
experts brought
in for kapton
attachments
23
Only 41 to go …. !
24
25
Installation
Lowering into the LHCb cavern …
… ready for installation …
… insertion of one half
Installed October/November 2007
Now Commissioning
26
Readout scheme
Processor Board
in FPGAs
Analogue signals
Clusters
27
FPGA based Data Processing
• Velo Data Processing Raw -> Clusters in TELL1
RAW
•Require 1M parameters
Pedestal Following
•Optimisation critical for data
quality
Beetle Cross-talk Correction
Cable Cross-talk Filter (FIR)
Lower
priority
Common Mode Suppression (MCMS)
Beetle baseline shift
Lower
priority
Reordering
Common Mode Suppression (LCMS)
• Pedestal & Clusterisation
Thresholds most important
•Bit Perfect Emulation of
Algorithms in full LHCb
Software Framework
Clusterization
28
CLUSTERS
Material Budget / Resolution
Material
Distribution
20% X0
Resolution
Performance:
Single Hit
best 4 m
Primary vertex
42 m in Z,
10 m XY
Decay length
220 - 375 m
Test-beam
Measurement
29
• strip isolation via p-spray
• expected max dose:
-1.3 · 1014 neq/cm2/year
after 4 years [~8 fb-1]: cannot fully deplete
• LHCb VELO will
be HOT!
•VELO in construction – again !
Udep [V]
after 1 year of irradiation
[2 fb-1]
not type inverted
• inherently radiation tolerant
Radiation
type inverted
n+ in n-bulk sensors [300 m]
R [cm]
Middle
station
•Building replacement sensors:
• n-in-p
Far
station
•Radiation damage
•Beam accidents
30
Expected Performance
 = -ln tan(/2)
B decays
For typical B decay modes:
reconstructed track - hits in 3 stations
LHCb acceptance: 1.9 <  < 4.9
• primary vertex resolution:
- x,y: ~10 m, z: ~60 m
• Proper time res.: ~40 fs
• B Mass res.: 12 -25 MeV
31
Elements of Alignment
• Each detector half moved 3cm each fill
Hardware Design
Rigidity
low thermal
expansion
10m Si-Si
alignment
Measurement
Measurement
machine
Individual
modules during
assembly
Complete system
Software
BEFORE / AFTER
Alignment in
few minutes
At few m level 32
Nucl. Instr. and Meth. A596 (2008) 157-163
Nucl. Instr. and Meth. A596 (2008) 164-171
Aligning the Velo
Step 0
Step 1
Step 2
Step 3
Misaligned
VELO
Sensors
aligned in
modules
Modules
aligned in
halves
Aligned VELO
Halves aligned
•Physics tracks
•Overlap tracks
•Beam Halo tracks
•Vertices
33
Effect of Misalignment on Physics
 
B  
•
LHCb 2008-012 Impact of
misalignments on the
analysis of B decays
•50% loss of events for 15µm misalignment
34
Global Alignment Method
 Establish linear expression of residuals
as a function of mis-alignments.
Fit the tracks simultaneously with the alignment constants
xclus = ∑xtrack
ai∙di + ∑eaxj∙j
Parameters di of the tracks
(different for each track)
LOCAL PART
Residuals expressed as function of
misalignments i
GLOBAL PART
∂ c2
∂ c2
rclus = (xclus - x)
=
=0
∂ di
∂ ∆i
Alignment  minimise c2res = ∑ ∑wclus∙r2clus
 Get all track parameters and all misalignment constants
simultaneously
BUT…
 1 single system to solve.
35
 But this system is huge ! (Ntracks∙Nlocal+Nglobal equations)
Matrix Inversion
 The matrix to invert has a very special structure:
kCkglobal
…
HkT
Cklocal
0
0
0
…
Nglobal
dk
kwkak
…
0
=
…
0
…
0
kwkxk

…
…
…
Hk
Nlocal x Ntraces
 Inversion in section (implemented in the code MILLEPEDE V.Blobel - NIM. A 566), The
problem becomes only Nglobal x Nglobal
 If Nglobal  100 , the problem can be solved in seconds
36
Commissioning the VELO
 Single module operation under
Neon atmosphere – 18th March
2008.
System @ full power
 Noise level compared with
previous data taken in assembly
 Operation of 15 modules on 15th
May 2008
 Single module test of 2nd half –
from 2nd June 2008.
 Full half powered for first time –
June 10th 2008.
 First operation in vacuum – 18th
June 2008
 Full detector operated under
vacuum.
 Operated cooling fully loaded at 25C
 Modules @ -5C
Silvia Borghi
A ‘Typical’ day at the pit
37
Nucl. Instr. and Meth. A604, Issues 1-2, 1 June 2009
LHC synchronization test
in August and September 2008, June 2009
Beam dumped on injection line beam
stopper (TED)
1 shot / 48 seconds
5 109 – 5 1010 protons per shot
TED
TED is absorber at end of injection line
340m before LHCb
38
38
Results on TED data
First Event
17:3322-08-08
September 2008 – 2,000 tracks
June 2009 - 60,000 tracks
39
Silvia Borghi
39
An event with high luminosity
•25ns Bunch Structure
40
First look at the data:
ADC sum of clusters associated to a track
fitted by Landau function
Preliminary
ADC sum (ADC counts)
Signal/Noise approximately 20:1
Preliminary
ADC sum (ADC counts)
41
VELO Timing
• Timed to ~ +/- 2ns
• Data taken at 4 timing
steps: 0, 6.5, 12.5, 19 ns
• Fit pulse shapes
• Fast turn around on
procedure
42
Alignment Results
Step2: Relative Module Alignment
from 2008 data
Difference of align. constants
for X and Y translations
A side
M. = 0.4 μm
X trans
Y trans
σ = 3.2μm
C side
X trans
Y trans
☛ The detector displacement from
metrology is less than 10 m
☛ Module alignment precision is 5 m
for X and Y translation and 200 rad
for Z rotation
43
Silvia Borghi
TIPP09 - 12 March 2009
43
Step1: First Sensor-Sensor Alignment from 2009 data
44
Method for VELO half distance
• Fit tracks in two halves
separately
– constrain to same track
z
in local frame
x
Z
x
• Only works when (almost)
closed
• For collision data will also
constrain using PV fitted
VELO was almost in the close position
in two halves
Twoseparately
different positions:
x-distance
–Resolver distance between the two half of 2 mm
–Resolver distance between the two half of 2.45 mm
45
First evaluation of 2 halves distance
•Data taken at two VELO closing
Positions
Very
Preliminary
injection
X mm
y
x
2mm and 2.45 mm
Very
Preliminary
VELO was moved by 445 ± 10 chocolates
46
VELO Resolution
VELO resolution


Linear dependency on the pitch
Dependency on the track angle
Evaluation of the resolution
versus the projected angle
TED
data
Resolution evaluated integrating the
results of all sensors
47
Silvia Borghi
TIPP09 - 12 March 2009
47
Comparison with Metrology
•Sensors in module measured with smartscope
•Compare with software alignment
48
VELO Summary
• VErtex LOcator is small but complex detector
• precision tracking very close to the interaction region
• radiation tolerant design
• results from the testbeams/TED runs
– S/N: 24-29 (), 20-24 (R)
– Perpendicular track resolution: 9 -20 m
• LHCb on schedule for first beams in 2009
(mid-November…..)
49
PART 2
Potential for a Future
Upgrade
: how to turn a VELO into a
VESPA.
 Vertex Detector
with
Vertex Trigger
 Independent of SLHC
 Competitive &
complementary to e+e-
super B-factories
VElo Superior Performance Apparatus
50
Initial Phase of LHCb Operations
•
Data taking starts 2009
Defocus LHC beams
•LHCb L= 2x1032 cm-2s-1
•Factor 50 below ATLAS/CMS design L
1. Most Events have Single Interaction
Number of pp interactions/ beam crossing
Pile-up at high luminosity
• B mesons identified by
separation of primary interaction
vertex and decay vertex
(few mm)
• Displaced Vertex trigger
• 2nd level of triggering
• Multiple Interactions
• Limit Triggering
51
Initial Phase of LHCb Operations
•
•Displaced Vertex trigger
•2nd level of triggering
•Multiple Interactions
•Limit Triggering
•LHCb L= 2x1032 cm-2s-1
•Factor 50 below ATLAS/CMS design L
•Most events have single interaction
Data taking starts 2009
Defocus LHC beams
•LHCb Upgrade L= 2x1033 cm-2s-1
•Cope with 4 int./x-ing
•SLHC peak L=
8×1034
cm-2s-1
rate of pp interactions
•Baseline - 40MHz, alternate High, Low I
LHCb H
L
Select Low I for desired luminosity
GPDs
H
H
Effective 20MHz Crossing rate
52
LHCb Physics Programme
But NOT Limited by LHC
• Upgrade to extend Physics reach
– Exploit advances in detector technology
– Radiation Hard Vertex Detector
– Displaced Vertex Trigger
– Better utilise LHC capabilities
Independent of
LHC upgrade
• Timescale ? Trigger Dependent
•Start before SLHC
• Upgrade Lumi. by factor 10
•But continue running
33
-2
-1
– 2x10 cm s
during SLHC phase
• Collect ~100 fb-1 data
• Modest cost compared with existing accelerator
infrastructure
53
Upgrade Physics Programme
Examples
Complementary to ATLAS / CMS direct searches
•New particles are discovered
•LHCb measure flavour couplings though loop diagrams
• No new particles are found
•LHCb probe NP at multi-TeV energy scale
g~
B
New Physics in loops
~
b,~
s
0
s
~
b,~
s
B
0
s
b
g~
• CP Violation

– Angle  to better than 10
B D K
0
–

Bs  D K

s
c-

Tree Diagram Dominated Decays, 0.10 theory
s
•Rare Decays
Bd  K     
Angular Correlations
54
LHCb Trigger System
• Cope with approx 5 interactions / beam crossing
Existing 1st Level
Trigger
•Veto on multiple
interactions
Current 1st Level Trigger Performance




•Existing Trigger based

on:

•High pT Muons
•Calorimeter
Clusters
Events with muons Events with hadrons
Require Displaced
Vertex Trigger
At 1st level
– trigger efficient
– need improved
trigger
Full detector 40MHz readout
55
Detector Upgrade
• Critical component to achieve this physics
Radiation Hard Vertex Detector
with
Displaced Vertex Trigger
VElo Superior Performance Apparatus
56
Radiation Hard Vertex Locator
• UK responsible for Silicon Modules
• Upgrade Requires high radiation
tolerance device
>1015 1 MeV neutroneq /cm2
• Strixels / Pixels
VELO Module
8cm
57
Z Beam
Enabling Technologies
•Low-mass Thermo-Mechanical •Novel processing technologies
SiC foam
PocoFoam
(Low-mass)
ATLAS
CF, TPG
CVD Diamond
Junction
2.9m
LHCb
TEOS
Poly
TSV
Through Silicon Vias
BCB
Dielectric Layer
Radiation Hard Silicon Sensor (UK leading)
Front-End Chip Development (Timepix)
Micromachining for TSV (3D)
BCB deposition on sensors (ATLAS strip upgrade)
Mechanical systems (LHC expertise, low-mass)
Systems Expertise (ATLAS SCT, LHCb VELO)
58
3D
Detector
Structure
Array of electrode columns passing through substrate
•
• Electrode spacing << wafer thickness (e.g. 30m:300m)
• Benefits
– Vdepletion  (Electrode spacing)2
– Collection time  Electrode spacing
– Reduced charge sharing
• More complicated
fabrication - micromachining
+ve
+ve
Planar
3D
+ve
-ve
n-type
electrode
+ve
n-type
electrode
electrons
electrons
Lightly
doped
p-type
silicon
holes
300
µm
300
µm
holes
p-type
electrode
p-type
electrode
Particle
-ve
Particle
Around
30µm
59
Lateral depletion around
column (~2V in sim.)
CV
• Pad detector – 90 * 90 columns, 55μm pitch
P
+
1/Capacitance, Pad detector
5.0E+09
4.5E+09
4.0E+09
1/C (F-1)
3.5E+09
3.0E+09
2.3V
lateral
depletion
2.5E+09
2.0E+09
~9V back
surface
depletion
1.5E+09
N
+
1.0E+09
5.0E+08
Depletion to back surface from 0.0E+00
tip of column (~8V in sim.)
0.0
5.0
10.0
Bias (V)
15.0
20.0
60
3D Detectors
•3D Detectors provide extreme rad hard solution
•novel double sided processing
•Devices tested with Beetle / Medipix electronics
25000
signal [electrons]
strips pixels
20000
p-in-n
n-in-p
3D simulation
15000
140m p-FZ
10000
[1] 3D, double sided, 250m columns, 300m substrate [Pennicard 2007]
[2] p-FZ, 280m, (-30oC, 25ns), strip [Casse 2007]
[3] p-FZ, 280m, (-30oC, 25ns), strip [Casse 2004]
[4] p-MCZ, 300m, (-30OC,  s), pad [Bruzzi 2006]
[5] p-MCZ, 300m, (<0OC, s), strip [Bernadini 2007]
[6] n-MCZ, 300m, (-30OC, 25ns), strip [Messineo 2007]
[7] p-FZ, 140m, (-30oC, 25ns), strip [Casse 2007]
[8] n-EPI, 150m, (-30OC, 25ns), strip [Messineo 2007]
[9] n-epi Si, 150m, (-30oC, 25ns), pad [Kramberger 2006]
[10] n-epi Si, 75m, (-30oC, 25ns), pad [Kramberger 2006]
75m n-EPI
See also: [M. Bruzzi et al. NIM A 579 (2007) 754-761]
[H.Sadrozinski, IEEE NSS 2007, RD50 talk]
14
10
3D - Example diffraction ring
1500
150m n-EPI
5000
Double-sided 3D, 250 m, simulation! [1]
n-in-p (FZ), 280 m [2,3]
n-in-p (MCZ), 300m [4,5]
p-in-n (MCZ), 300m [6]
n-in-p (FZ), 140 m, 500V [7]
p-in-n (EPI), 150 m [8,9]
p-in-n (EPI), 75m [10]
15
10
Feq [cm-2]
10
50
1000
100
150
16
M.Moll 2007
500
200
61
250
50
100
150
200
250
0
Timepix Front-End chip
• Spin-out from HEP, now being spun back for SLHC
• Same chip developers as ALICE/LHCb pixel chip
55 x 55 μm
pixels
elongated
in periphery
TSV: Hole etched
between front & back
surfaces – sensor or chip
130nm future development,
New! demonstrated rad. hard
(Medipix 3 - 400 Mrad)
Time Over Threshold
-‘Analogue’ information
improves resolution
62
LHCb Strawman
1m
390 mrad
LHCb Pixel Upgrade Layout
modules
x
60 mrad
cross section at y=0
15 mrad
z
LHCb Pixel Module
interaction region
s = 5.3 cm
Retract During LHC Injection
Beam aperture
7mm to active silicon
Hybrid / Cooling
outside acceptance
63
Example Pixel Tile Element
•Module constructed from
common tile elements
•Thermally conductive Mechanical Support
•‘Edgeless’ Sensor to reduce guard-ring dead space
•TSV through sensor to Readout Chip
•BCB layer deposited for signal transmission
•Hybrid connected to cooling with thermal solder
64
Upgrade Summary
• Key Upgrade Elements
– Physics Studies
– Radiation Hard Vertex Detector
– With Displaced Vertex Trigger
• Independent of LHC upgrade plans
• Major Physics Programme at modest cost
– Flavour Sector of New Physics
b
B s0
?W
s





LHCb preparation in good
shape
Looking forward to first data
And an even brighter far future
s
?t
Bs0
?W
?t

b


65