1. LHCb: Towards data taking in 2008
The LHCb experiment at the
Large Hadron Collider
Developments at the PI for the LHCb
experiment
The construction and commissioning
of the LHCb experiment
Palavernachmittag, 23/07/07
Sebastian Bachmann
11/14/2018

2. The Large Hadron Collider
pp-collisions
ECMS=14 TeV
1034 cm-2s-1
First collisions expected in summer 2008
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3. Goals of the LHCb Experiment
 profits from the copious number of
B-mesons produced at LHC
(production rate ~100
 searchs for New Physics by
- high precision measurements of
CP-violating phases in decay of
B-mesons.
- searchs for rare and very rare decays
of the B-mesons
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4. Measurement of CP violating phases:
Reminder CP-transformation:
Combined application of charge (C) and parity (P) conjugation.
CP |Particle> → |Antiparticle>
If CP is a good symmetry we have e.g. for the branching ratios of
CP conjugated processes:
BR (P→f) = BR(P→f)
For K- and B-mesons it has been observed that CP is violated.
This allows to search for effects from New Physics.
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5. Measurement of CP-violating phases
Measurement of fCP is a very sensitive probe
to Physics Beyond the Standard Model
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6. An example: Bs → ΦΦ + W- H- ??? Standard model prediction
of the CP-asymmetry is very
small the (<1%)
H- ???
In many extensions of the
Standard model the decay
gets additional contributions.
 ΦCP is altered.
 CP-asymmetry might be
strongly enhanced! +
11/14/2018

7. Production and decay of B-mesonsl- π- K+ π+ B0 p
D0* p
- pp interaction rate: 40MHz
Production rate for B-mesons: 100kHz
Decay length of B0: ≈ 1cm
Charged particles in acceptance: ≈ 100
11/14/2018

8. The LHCb detector Magnet + Tracking stations Vertex RICH locator
Calorimeters +
muon
detectors
RICH
detectors
Vertex
locator
11/14/2018

9. A simulated event
VeLo
Magnet TT
T Stations
11/14/2018

10. The Outer Tracking System (OT)
Outer Tracker
Outer tracking system:
- Detector technology: Straw tubes
- 56,000 straws and wires
- 200,000 soldered joints
- arranged in 185F and
124 S modules 5m 6m
Inner tracker
In total individual, hand-made
particle detectors.
~ ¼ of them produced in Heidelberg
TT Station
11/14/2018

11. Straw tube detectors Requirements for the Outer tracking system: Track
 good spatial resolution (<200µm) over entire area (~30m²)
 high efficiency
 fine segmentation
Straw tube detectors are
- light and fine segmented (i.e. small Ø)
proportional counters with drift time
measurement
Single Double Layer
5mm straws
pitch 5.25 mm
Track e-
11/14/2018

12. Module production
C.Rummel
&
S. Rabenecker
11/14/2018

13. Detector production finished end of 2005
Detector modules
Detector production finished end of 2005
11/14/2018

14. Frontend Electronics Amplify and discriminate analog signals from
anode wires (ASDBLR)
Drift Time measurement (OTIS)
Data Serialization and optical link (GOL)
Developed
at the PI
11/14/2018

15. Frontend boxes
In total 432 frontend boxes, each
box contains
- 2 HV boards
- 8 Amplifier boards
- 4 TDC boards
- 2 GOL boards (optical link)
Production and test of TDC boards and optical links finished end of 2006
11/14/2018

16. The bridge: Support structure for the Outer Tracker.
11/14/2018

17. C-frames with detector modules
In total 12 C-frames
Frontend
electronics
Detector
modules
C-frame
11/14/2018

18. Quality control during installation
Two examples for the commprehensive
tests of C-frames and detectors performed
during installation.
Detector response:
Leak rate
Tested 60% of all wires,
21/32040 faulty wires found (0.65‰)
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19. Installation of the C-frames
11/14/2018

20. Current view to the Experiment
11/14/2018

21. Architecture of readout chain:
11/14/2018
Courtesy Rainer Schwemmer

22. Performance of FE-electronics in situ
Drift time resolution
σΔt ≈ 300ps
Courtesy Jan Knopf & Rainer Schwemmer
Long term time stability for 15hr
Stability < 100ps
Linearity of
drift time
11/14/2018

23. Another challenge: The trigger
Trigger Überblick
40 MHz
Hardware
Level-0:
High ET / pT von m, e, g , hadrons Veto for empty or too complex events
New idea:
Reconstruct two body
decays already at
L0 confirmation.
(~1ms availablê)
1 MHz (35 GB/s)
Software ~1800 CPU
HLT:
1. Confirm L0
2. Partial reconstruction of event (m, e , g, hadron-alley)
3. Complete reconstruction of event
2 kHz (70 MB/s) on tape
11/14/2018

24. Reconstruction of J/ψ → μμ
Courtesy Johannes Albrecht
Reconstructed mass peak
from J/ψ → μ+μ- .
CPU consumption reduced
from 15 ms to 3-4 ms.
Aim tCPU ≈1ms is well
within reach.
minv[GeV]
mJ/ψ
11/14/2018

25. LHCb – towards data taking in 2008: Summary
LHCb is on a good track to take first data
when the Large Hadron Collider goes into
operation in summer 2008.
The Outer Tracking System is installed, now
the focus is to commission the system.
First light (from cosmics or radioactive source)
is expected in ~September.
There are versatile contributions from the PI
to the Outer Tracking System in the field of
detector, electronics and software development.
11/14/2018

26. The LHC experiments: Alice: Atlas and CMS: LHCb: LHCf and Totem:
See talk by Rainer Schicker.
Atlas and CMS:
General purpose experiments.
Main goal: Search for new particles, e.g. the Higgs or
Supersymmetric particles.
LHCb:
Search for new physics by high precision measurements.
Study mainly B-Mesons, but also D-Mesons, τ‘s …
LHCf and Totem:
Special purpose experiments.
11/14/2018

27. Search for rare decays: Bs→μ+μ-µ- µ+ Z x
Many decays of B-mesons
are forbidden in first order
in the SM (GIM mechanism),
e.g. Bs→µ+µ-:
In higher order decays are
possible, but branching ratio
is only ~2x10-9 : b s µ- µ+ Z W t
Branching ratio might be
strongly enhanced by
contributions from New
Physics (e.g. SuSy): b s µ- µ+
H0/A0 t ~ χ
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28. The Outer Tracking System
C-Frames
Bridge
Modules
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29. Contributions for LHCb at the PI
Detector technology:
- Development, test and construction
of the Straw Tube detectors
for the Outer Tracking System*.
- Assembly and commissioning of the
Outer Tracking System at CERN**.
Electronics:
- Development and testing of an
ASIC for drift time measurements.
- Development and testing of the
optical readout chain for the OT*.
Software:
- Development of the Experiment
Control System for the OT*.
- Development of tracking &
alignment algorithms***.
- Development of trigger algorithm***.
* In collaboration
with NIKHEF and
Krakow
** in collaboration
with NIKHEF
*** in the framework
of the LHCb soft-
ware
11/14/2018

30. Performance of straw tubes
Results from a test beam experiment in 2005 at DESY with final detectors and final frontend electronics:
Efficiency, ε
Resolution (µm)
amplifier Threshold (mV)
amplifier Threshold (mV)
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31. Rasnik: Observing movements
Task:
Monitor movements
of the detectors with
Respect to reference.
On C-frame
On bridge
TopMux
Observing mask with camera allows to survey movements of the C-frames.
11/14/2018

32. Results from Rasnik y 3 2
100 µm x 1
12 days
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33. The phenomenon Gas flow Ratio Plot: I(after)/I(before)
Irradiate with 2 mCu 90Sr source
Gain loss “in the neighborhood” of the irradiation point:
Croissant? Bean? Kidney?
Upstream of gas flow
Gas flow
Courtesy Niels Tuning
11/14/2018

34. Finding the culprit Compare test modules:
Left: Production like (Use Araldite)
- 7% gain loss after 90h of irradiation
- Effect reproduced for the first time
in test modules.
Right: Trabond used
- no ageing after 393h of irradiation
With Araldite, 90h
7% gain loss
No Araldite, 393h
no ageing
source
Courtesy Tanja Haas
11/14/2018

35. Beneficial effects HV training: Flushing: Beneficial effects:
Courtesy Niels Tuning
HV training:
2nd HV training
1st HV training
3rd HV training
 Relative Gain
 Irradiation Time (hours)
Beneficial effects:
Flushing
HV Training
Heating
Flushing:
 Flushing Time (weeks)
 Gain loss (%)
11/14/2018

36. Heating procedure
Two very similar set-ups: Heidelberg and NIKHEF set-up
cover the module
with thin aluminium plates
wrap the module in
electric blankets
take a module and
flush for n days
Insulate, then keep 2 weeks at 4042C
11/14/2018

37. Heating: Results from Heidelberg set-up
Courtesy Tanja Haas
Heidelberg
20 before
20 after
7 before
7 after
27 before
27 after
NIKHEF
N123 before
N 005 before
N005 after
N058 befor
N058 after
N123 after
N058 NIKHEF
W023 before
W023 after
W2.5m before
W2.5m after
- All modules benefit, but level of
improvement varies.
Improvement is a convolution of
heating and additional flushing.
Warsaw
11/14/2018