Transcript The ATLAS Experiment: Status and Commissioning • Introduction • Characteristics of the ATLAS Experiment. • Installation and commissioning • The ATLAS inner detector. • The ATLAS calorimeters • The ATLAS MUON Spectrometer • Present.

The ATLAS Experiment:
Status and Commissioning
• Introduction
• Characteristics of
the ATLAS
Experiment.
• Installation and
commissioning
• The ATLAS inner
detector.
• The ATLAS
calorimeters
• The ATLAS MUON
Spectrometer
• Present planning
for closing.
• Conclusions
11/6/2015
G. Mikenberg on behalf of the
ATLAS Collaboration
Introduction
•
B-physics: CP violation, rare
decays, B0 oscillations (use
Leptons)
•
Precise measurement of W mass
(need of Leptons and missing E(t))
Precise measurement of Top mass,
couplings and decay properties
(Leptons, b-tagging, E(jet), missing
E(t))
Z’ and W’ discoveries (Leptons,
missing E(t))
Measurement of Higgs properties
(Leptons, b tagging, Tau tagging,
missing E(t), E(jet)).
•
•
•
ATLAS Characteristics
• Main emphasis in the ATLAS design has been on:
– High resolution and high acceptance MUON measurements, by
measuring P (not P (t)) using an Air-Core Toroid (to avoid large
energy loss), with rapidity coverage up to 2.7.
– High resolution and acceptance for electrons, by using a high
granularity L-Ar calorimeter (with longitudinal sampling),
complemented with a TRT detector. The above allows also very
good two photon separation (important for H->2 photons).
– High hermeticity, with calorimetric coverage down to rapidity of 5
and non-pointing gap (with longitudinal sampling for pi/e
corrections) for high resolution measurements of missing E(t) and
E(jet).
– Good vertex resolution (with 3 layers of pixel), to permit the
detection of secondary vertices, even in a high background
environment (important for b and Tau tagging, in various searches
for various Higgs production modes).
Inner Detector Fully installed and
Operational
One of the most serious problems
for such a system with a large number
of channels is the number of services
and
the required cooling.
•
The Inner Detector (ID) is
organized
into four sub-systems:
Once the main decision of introducing the
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•
Pixels
TRT, for improving electron identification,
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•
Silicon Tracker (SCT)
(6 10E6 channels)
•
Transition Radiation Tracker
(TRT)
(4 10E5 channels)
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•
(0.8 10E8 channels)
was taken, there is little room to maneuver
between the number of layers
in Pixel and Si detector.
Calorimeters fully Installed and
operational
•
Albeit some initial problems
with power supplies, that were
corrected, the full detector was
ready to take data on
September 10th.
LAr and Tile Calorimeters
Tile barrel
Tile extended barrel
L-Ar
Acordeon
module
LAr hadronic
end-cap (HEC)
LAr EM endcap (EMEC)
fibre
tiles
LAr EM barrel
A TileCal Module
64 Barrel
2x64 Ext. Barrel
LAr forward calorimeter (FCAL)
Expect excellent resolution for E(T)
By using the various samples in depth
To correct for EM/HAD
MUON Spectrometer fully installed (except
for staged detectors) and operational
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•
All 1.5 10E6 channels were operational
on Sept. 10th, as well as the alignment
systems.
Following single beam and cosmic data
allowed for debugging and
commissioning.
And we have not only managed to construct
such a detector, but it even started to run
• First single beam event taken in Sept. 10th
• Followed by 1.5 months of cosmic MUON’s, permits first
look at performances
Short run with single beam was useful for timing
BPTX
(175m)
Collimators
(~147m)
10 September
ATLAS
C
A
12 September
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Within 2 days of single
beam, most of the timing
was set correctly.
Time of flight is an
important element for
single beam and cosmics
But most of the Commissioning
results come from cosmic rays
•
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•
To simulate real collisions in terms of timing, one needs to trigger
in lower sectors.
Most of the data was taken with full detector operational (see
arrows) with and without magnetic field.
For the barrel (after opening the End-Caps, the amount of
accumulated data has been doubled (not yet analyzed).
Inner Detector
Status: TRT
•
TRT is running with its operational gas
(Xe).
•
Transition Radiation function is
operational.
•
Less than 2% of non-operational channels
Inner Detector
Status: Pixel
• Vey small number of noisy channels.
• First look at cosmic data, after
alignment and bowing corrections,
starts to approach target values.
• Very high efficiency for each layer
Inner Detector
Status: SCT
• Very high efficiency.
• Very good results after alignment is introduced
L-Ar Calorimeter
Status
LAr wave 15GeV cosmics
Measured
Predicted
Difference
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Very small # of non-working channels.
During 2008 run one HEC power supply not
working.
Very stable pedestals.
Although cosmics deposit little Energy, enough
data was taken to check parameterization.
Timing is already set to within a few ns for real
collisions.
Tile calorimeter
Status
•
•
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•
Only very few problematic channels (<1.4%) that are being fixed during the
shut-down.
Timing has been set for all modules at the level of a few ns.
Energy response for cosmic MUONs is uniform across the full calorimeter.
Good position matching is being achieved between Tile-LAr and ID tracks.
MUON Spectrometer
Status
• System composed of:
– Magnets
– Tracking chambers (MDT and CSC)
– Alignment system (Barrel and End-Cap)
– Trigger Chambers (RPC and TGC)
Magnetic Field
knowledge
• Magnetic field was measured
with probes on chambers to
determined where the coils
are located to within 1mm.
Status of the
alignment
•
By comparing track intersection in middle layer with expected chamber
position after alignment, one can check the quality of the alignment:
– For the End-Caps, one obtains that the distribution are centered at 40 microns.
– For the large Barrel chambers at better than 250 microns, while for the Small
chambers (no direct projective lines), it is still at the 1mm level.
Status of MUON
Tracking Chambers
MDT eff.:
Find segment in 3rd
Station using other 2
99%
•
CSC started operation
rates), with
•
Track residuals in barrel and End-Cap
(red after alignment corrections)
Sigma~135microns, goal 80 microns
(still some readout problem at high
initial resolutions at the mm level.
The main tracking detectors (MDT) operating close to
the expectations, with less than 1.5% of problematic
channels.
Status of the RPC
Trigger Chambers
• More than 50% of the RPC towers have been timed-in
• Efficiency of individual layers and of coincidence is reaching its
expected level.
• Good matching between tracking and trigger chambers for finding
the tracks.
Status of TGC
Trigger Chambers
TGC track extrapolated
MDT
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All TGC detectors have been timed-in for collisions.
The efficiency for each individual plane is as expected for cosmics (not well defined
time of arrival).
Although without final TGC alignment, matching with MDT tracks is good.
0.03% of noisy channels and 0.1% of problematic planes.
And ATLAS works as an integrated
Experiment
• Momentum measurements of cosmics in the Inner
Detector are well correlated to those measured with the
MUON Spectrometer.
• The Energy loss of the Cosmic MUON’s in the
Calorimeters matches the measurement of the tracking
detectors
What has been achieved with little
beam time a lot of cosmic events
• Timing of the various detectors to within a few ns.
• The MUON Spectrometer is providing trigger and
tracking with close to its final resolution for the full (<2.7)
rapidity range.
• The TRT has shown its Transition Radiation
characteristics to perform its share in electron
identification.
• The calorimeters are providing the full coverage, with the
expected performance (for cosmics), and a negligible
number of non-working channels.
• The Inner Detector, with all its complexity, is approaching
its expected performance.
2008/2009 Shutdown
11/10/08
M.Nessi
Activities during the Shut-Down
• Fix various electronics/LV problems on the calorimeters
• Consolidation work on the ID cooling and environment gas systems
(fix some
loops if possible, fix/improve distribution racks, thermal
analysis at the
level of the id end plate, fix some optical
readout problems,…)
• Turn on and check the SW chambers, in particular TGCs, access
possible
damages, change 3 EIL4 broken TGC chambers
• Fix as much as possible all gas leaks in the RPC and MDT
chambers (1 tower is problematic), finish barrel hardware
commissioning for RPCs
• Change to RADHARD the optical fibers in the MDT wheels, this
requires
opening the wheels. Start installing un-staged EE
chambers
• Fix small problems in all systems. Improve on the temperature
gradient
Conclusions
• With its 100,000,000 detector channels, ATLAS is one of
the most complex scientific endeavors ever constructed.
• By the strong dedication of 1000’s of scientists,
engineers and technicians, all its elements were
practically ready to take p-p collision data on September
10th.
• The few days of beam have been extremely useful to
time the various components to the few ns level.
• Using a long cosmic run, one has been able to debug
the majority of the components, to show that one can
reach the expected performances.
• The moment the LHC switches on again in 2009, it will
be take little time to start producing new Physics results.