The ATLAS Experiment: Status and Recent Results

CERN-RRB-2004-152
The ATLAS Experiment: Status and Recent Results
Henry Lubatti
M ay 24, 2010
INT, Seattle workshop New Results from LHC and
May 24, 2010
RHIC
ATLAS
1
ATLAS Collaboration
May 24, 2010
INT, Seattle workshop - New Results from LHC and RHIC
Henry Lubatti
2
ATLAS
May 24, 2010
INT, Seattle workshop - New Results from LHC and RHIC
Henry Lubatti
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ATLAS Inner Detector (ID)
 Pixel Detector (Three layers - double sided)
•|η| < 2.5 with σρφ ~ 10 µm, σz ~ 115 µm (80M channels)
 Semiconductor Tracker (SCT): single sided Si strips
• stereo pairs
• Four barrel layers and 2x9 end-cap disks stereo
• |η| < 2.5 with σrφ ~ 17 µm, σz ~ 580 µm (6.3M channels)
 Transition Radiation Tracker (tracking and e/π separation)
• 73 barrel straw layers and 2x160 end-cap radial layers
• |η| < 2.0 with σrφ ~ 130 µm (350k channels)
• Average of 32 hits/track
 The ID is inside a 2 Tesla solenoidal magnetic field
May 24, 2010
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Inner Detector
Tracks for one of the first 2009
stable beam runs
About 98% live channels
for all three subsystems
Pixel Detector
5.05 < r < 12.25 cm
10 µm (rφ) 115 µm (z)
Silicon Strip Detector
25.5 < r < 54.9 cm
17 µm (rφ) 580 µm (z)
Transition Radiation Tracker
55.4 < r < 108.2 cm
σρφ ~ 130 µm, particle ID
e’s from conversions for
γ > 1000; low γ all tracks
selected tracks in event
used with mπ assumed
May 24, 2010
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Calorimeters
• Electromagnetic
Calorimeter (ECAL)
– Lead accordion with
liquid argon
• Hadronic Calorimeter
(HCAL)
– Iron plates with
polystyrene
• Barrel Dimensions
– ECAL 1.1m < r < 2.25m
– HCAL 2.25m < r < 4.25m
8m
12 m
May 24, 2010
INT, Seattle workshop - New Results from LHC and RHIC
Henry Lubatti
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ATLAS
Muon
Spectrometer (MS)
MUON
SPECTROMETER
•
•
•
•
Precision Measurements with
Monitored Drift Tubes (MDT) in
barrel and most of endcap
Cathode Strip Chambers (CSC’s) for
2.0 < η < 2.7
Toroidal Magnetic Field (air core
toroid)
Resolution goal σpT/pT = 10%
at pT = 1 TeV
 Trigger Chambers
•
•
•
RPC’s in barrel region
|η|<2.4
TGC’s in Forward region
2.0 < |η|< 2.7
Trigger covers |η|<2.4
May 24, 2010
INT, Seattle workshop - New Results from LHC and RHIC
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ATLAS Trigger System
Level 1 (hardware)
2.5ms
Latency
40 MHz
Uses Calo cells with reduced
granularity and muon chambers
e, µ, γ, τ, jet candidates
Defines Regions of Interest (RoI)
75 kHz
Seeded by LVL 1 RoI
Full granularity of the detector
Performs Calo-track matching
10ms
Execution Time
Level 2
2 kHz
Event Filter O(1900Cs)
200 Hz
May 24, 2010
1s
Offline-like algorithms
Refines LVL2 decision
Full event building
INT, Seattle workshop - New Results from LHC and RHIC
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ATLAS
• Level 1
– Corse CAL & Muon Spectrometer
granularity and no ID tracking
– Identifies Regions of Interest (RoI)
for further processing at Level 2
Regions of Interest (RoI)
• Level 2
– The full detector granularity in RoI
– Full tracking in RoI and all tracks
required to connect to the
Interaction Point
– Only one muon per RoI is
reconstructed
May 24, 2010
INT, Seattle workshop - New Results from LHC and RHIC
Areas selected by
Level 1 Trigger
Henry Lubatti
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ATLAS – Collisions Begin
•
November 23 first pp collisions
•
December 6 stable beam operation
at √s = 0.9 TeV
–
–
•
•
All ATLAS systems on
Collect min. bias data √s = 0.9 TeV
December 8, 14, 16 √s = 2.36 TeV
run that ends 09 operation
2010 run begins March 30 with
collisions at √s = 7 TeV
May 24, 2010
INT, Seattle workshop - New Results from LHC and RHIC
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10
ATLAS – initial beam trigger
 Triggers on particles produced close to beam axis
• Peripheral interactions beam gas interactions and beam halo
•
BPTX: Electrostatic beam
pick up timing devices at
± 175 m from IP
•
MBTS: Minimum bias Trigger
Scintillators mounted on LAr
calo-end caps at ± 3.56m
from IP
–
16 Scintillators per disk
covering 2.1 < η < 3.8
 Used for 2009 and 2010 data taking
May 24, 2010
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Accumulated Interactions
•
LHC Operations in 2009 and 2010
–
–
–
–
–
–
November 20, 2009 Beam splash observed
November 23, 2009 First collisions at √s = 900 GeV
December 6, 2010
Stable beam – all systems on
December 8, 2010
Collisions at √s = 2.36 TeV
March 30, 2010
Collisions at √s = 7 TeV begin
April 1, 2010
First W candidate observed
April 1
May 24, 2010
April 1
April 1
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ATLAS is Recording Events
First stable 900
GeV beams in LHC
on Dec 6, 20009
ATLAS recorded
collisions until
December 16, 2009
2009 minimum bias run begins
May 24, 2010
INT, Seattle workshop - New Results from LHC and RHIC
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ATLAS 2009 Results
Comparison of 900 GeV data with ATLAS Non Diffractive Minimum Bias MC
Pixel Detector
Pixel Detector
May 24, 2010
SCT Detector
Very good agreement between
data and Monte Carlo
INT, Seattle workshop - New Results from LHC and RHIC
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ATLAS 900 GeV Data
Tracking efficiency from ATLAS MC
Vertical bars represent the statistical uncertainty and the
shaded areas the statistical and systematic uncertainties
(dominated uncertainties of material distribution in the
inner detector) are added in quadrature
May 24, 2010
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Pixel dE/dx
Energy loss dE/dx as a function of
reconstructed momentum for all primary
tracks in the 900 Gev data
Simulation: pions, kaons and protons bands fit with
Bethe-Bloch (lines with their 1 σ error bands)
MC
simulation
normalized
to data
Invariant mass
distribution of the
positive and negative
track pairs in the kaon
band for |η| < 2.5
m(K+K-)
May 24, 2010
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ATLAS – 900 GeV results
 Invariant mass distribution of two track
vertices found with the ATLAS standard
vertex finding code.
 Vertex fit has no mass constraint applied
pL along pV0 direction
 Observe KS and Λ at correct
mass with good resolution
 Observed mass distributions in
good agreement with MC
May 24, 2010
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Di-Jets at 900 GeV
• QCD di-jet produced in
early 900 GeV data
• Kinematic balance well
described by MC
May 24, 2010
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ATLAS Conversion Results
Conversions of γ to e+epairs maps/validates the
distribution of material in
the detector
Brem ?
Conversion point
Pixel
Layers
2
3
SCT Layer 1
Beam pipe
1
Converts on 1st SCT layer
PT(e-) = 0.79 GeV
PT (e+) = 1.75 GeV
MC agrees well with data
Beam pipe
May 24, 2010
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19
γγ Mass Spectrum
Good agreement
between data and MC
May 24, 2010
MC simulation normalized to
number of events
INT, Seattle workshop - New Results from LHC and RHIC
No EM clusters with a
matched IP track
Henry Lubatti
20
B Tagging
B tagging important
 SM Physics (W, ttbar,..)
 SUSY and Higgs searches
 New Physics
B is Long Lived
(decays via weak force)
Impact Parameter (d)
Hard Scatter
B
Decay Length (Lxy)
Impact Parameter d/σ(d)
Resolution
Decay Length
Resolution
May 24, 2010
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Lxy/σ(Lxy)
Henry Lubatti
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Secondary Vertices
•
Secondary vertex in 900 GeV data
Tracks with pT > 500
MeV shown traversing
the three layers of the
barrel pixel detector
•
B-jet candidate event in 7 TeV
–
b-jet has 19 GeV measured at EM scale
Secondary vertex
surrounded by red box; The
main vertex has 3 jets with
pT > 15 GeV (EM scale) of
which two are seen in top
left projection
May 24, 2010
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ATLAS b-tagging – 900 GeV Data
 Distribution of the
transverse impact
parameter d0 with
respect to the
primary vertex for
tracks passing btagging quality cuts
Sign with respect
to jet axis
MC normalized to
data
Decay length significance
with respect to the
calorimeter primary vertex
for all reconstructed
secondary vertices
May 24, 2010
INT, Seattle workshop - New Results from LHC and RHIC
Henry Lubatti
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ATLAS Missing ET Resolution
 Missing Et central to…
• SM physics, (W, ttbar)
• SUSY and Higgs searches
• New Physics
 MC predictions agree well with data
at both 900 GeV and 2.36 GeV
 MET stable to within ± 3% during
900 GeV run
May 24, 2010
INT, Seattle workshop - New Results from LHC and RHIC
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ATLAS 7 TeV Results
7 TeV Collisions – Preliminary Results
May 24, 2010
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ATLAS – 2010 run
•
All subsystems operating at high efficiency
Subdetector
Number of Channels
Subsystem Operation Efficiency
Pixels
80 M
97.5%
SCT Silicon Strips
6.3 M
99.3%
TRT Transition Radiation Tracker
350 k
98.0%
LAr EM Calorimeter
170 k
98.5%
Tile Calorimeter
9800
97.3%
Hadronic endcap LAr calorimeter
5600
99.9%
Forward LAr calorimeter
3500
100%
LVL1 Calo trigger
7160
99.8%
LVL 1 Muon RPC trigger
370 k
99.7%
LVL 1 Muon TGC trigger
320 k
100%
MDT Muon Drift Tubes
350 k
99.7%
CSC Cathode Trip Chambers
31 k
98.5%
RPC Barrel Muon Chambers
370 k
97.3%
TGC Endcap Muon Chambers
320 k
98.8%
•
Muons do not include the EE chambers (installation ongoing)
May 24, 2010
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First W Candidate
First candidate
for a W  µν
decay from 7
TeV collisions
observed in
2010 running
Blue boxes are
Muon Chambers
traversed by the
muon
Gold tubes are
muon drift tubes
hit by the muon
May 24, 2010
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27
Second W Candidate
Recent candidate for a W  eν decay from 7 TeV collisions in 2010 running
Electron energy
deposited in first
two layers of EM
Calorimeter
Electron track
shown yellow
May 24, 2010
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28
Third W Candidate
W  eν decay from 7 TeV collisions in 2010 running
May 24, 2010
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Fourth W Candidate
Muon in the
endcap muon
spectrometer
Gold tubes are
muon drift tubes
hit by the muon
May 24, 2010
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30
ATLAS First Zee Event
Z  e+e- decay Candidate
Electron
energy
deposited in
first two
layers of EM
Calorimeter
Electron track
shown yellow
May 24, 2010
INT, Seattle workshop - New Results from LHC and RHIC
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31
ATLAS
Z  µ+µ- decay Candidate
One muon (µ−)
in barrel and
one (µ+) in
endcap
May 24, 2010
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ATLAS Di-Jet Event
May 24, 2010
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ATLAS - Jets
Event with two muons and
several hadronic jets
observed in first 7 TeV fill
March 30 2010
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Di-Jets at 7 TeV
Jet energies
about 300 GeV
Min bias triggers, 350 µb-1 integrated luminosity,
uncorrected electromagnetic-scale and pT > 20 GeV
(EM-scale) -normalized to the total number of jets.
∆φ difference between the two highest pT
May 24, 2010
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35
Jets and Missing ET
May 24, 2010
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ATLAS – Muon Spectrometer
Event with track
traversing the
barrel muon
chambers – blue
boxes in figure
Struck muon
drift tubes
shown in red
May 24, 2010
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37
ATLAS - pile-up events
An example of a
simple pile up
event observed
at start of 7
TeV run.
As luminosity
increases most
events will have
several pile up
events
May 24, 2010
INT, Seattle workshop - New Results from LHC and RHIC
Henry Lubatti
38
ATLAS - J/Ψ Observed
•
Di-muon invariant mass distribution (J/Ψ)
–
–
–
–
Minimum bias trigger at 7 TeV (320µb-1)
Fit track to common vertex in IT and
select muons > 3 GeV
One muon required to be a “combined
muon”: reconstructed in both IT and MS
Fit is un-binned ML fit using each
di-muon calculated mass error
 The entire mass region
shown in the plot is fit.
 Signal and background are
computed in a mass range of
2.82- 3.30GeV (3 σ around peak)
May 24, 2010
Fit Results
Gaussian-mean mass: 3.06±0.02 GeV
Resolution: 0.08±0.02 GeV
Number of signal events: 49±12
Number of background events: 28±4
INT, Seattle workshop - New Results from LHC and RHIC
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ATLAS – Vertex Reconstruction
Excellent Primary Vertex Reconstruction
7 TeV
900 GeV TeV
Longitudinal Plane
distribution for
events with at
least 10 tracks
Transverse Plane
distribution for
events with at
least 10 tracks
May 24, 2010
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40
Tracking Efficiency
Preliminary Tracking efficiency from 7 TeV data
The total
uncertainties on
each point shown
as shaded boxes
and the
vertical error
bars represent
the statistical
uncertainty
The contribution from secondary charged
particles is shown in shaded green, the
sum of the primary and secondary
particles is shown in red and compared to
the data (black points). The primary and
secondary track distributions are obtained
from Monte Carlo.
May 24, 2010
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41
Charged Particle Multiplicities
• Measured Charged Particle Multiplicities of inelastic events at
900 GeV and preliminary results at 7 TeV
– Data (track) selection
•
•
•
•
•
•
nch >1
|η| < 2.5 and pT > 500 MeV (extension to 100 MeV in progress)
Pixel hits ≥ 1
SCT hits ≥ 6
|d0| < 1.5 mm
Primary mean life time τ > 0.3x10-10 s
– Compare results with various simulations
– Trigger and vertex corrections obtained from data
• Events triggered by Minimum Bias Trigger (MBTS)
• The 900 GeV results have been published in Phys. Lett. B688, 1,
(2010) p. 21-42
May 24, 2010
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42
Charged Particle Distributions
The 900 GeV η and pT spectrum compared to simulation
Systematic uncertainties dominated by material distribution uncertainties
May 24, 2010
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43
Charged Particle Distributions
The 7 TeV η and pT spectrum compared to simulation
May 24, 2010
INT, Seattle workshop - New Results from LHC and RHIC
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44
Charged Particle Distributions
Charged particle multiplicities comparing 7 TeV and 900 GeV
The 7 TeV results are preliminary
May 24, 2010
INT, Seattle workshop - New Results from LHC and RHIC
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45
Charged Particle Distributions
Comparing (1/pT)dNch/dpT with CMS and UA1
 Good agreement with CMS within
uncertainties when convert ATLAS to
CMS NSD result
 UA1 results are approximately
about 20% higher at low pT
 Expected: UA1 used doublearm scintillator trigger
that rejected low charged
particle multiplicity events
May 24, 2010
INT, Seattle workshop - New Results from LHC and RHIC
Henry Lubatti
46
ATLAS
• ATLAS is operational – all detector systems and DAQ
running with good efficiency
– Excellent agreement between data and Monte Carlo
– We understand the material distribution
• First Physics results have been published and more
are almost ready to submit
• The LHC is operating reliably
– 2010-2011 running will provide much data and for some
channels we will have more sensitivity than the
Tevatron accumulated results
• An exciting moment well worth almost 20 years of
much hard work!
May 24, 2010
INT, Seattle workshop - New Results from LHC and RHIC
Henry Lubatti
47
ATLAS
Back-up Slides
May 24, 2010
INT, Seattle workshop - New Results from LHC and RHIC
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48
ATLAS
• LHC Operation
– Commissioning phase since start-up
• Ensure all safety systems are working well – provide needed protection
• Train people on shift to run the LHC safely
– Plan calls for a step-wise increase of intensity (factor 2 to 4)
followed by operation periods of ~14 weeks at constant intensity
– Current physics operation mode with β* = 2 m
• Machine protection systems, collimator and absorbers setup and
validated for β* of 2 m.
• Current operating conditions
– Present parameters for collisions
•
•
•
•
May 24, 2010
Number of bunches, 6
β*=2 m
Protons per bunch: 2x1010
3 colliding pairs per IR
– Peak L ~ 6×1028 cm-2s-1
INT, Seattle workshop - New Results from LHC and RHIC
Henry Lubatti
49
ATLAS
Average pT versus number of charged particles
The 7 TeV results are preliminary
May 24, 2010
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50
ATLAS
ATLAS LAr Calorimeter
Barrel
End-cap
Barrel Segmentation
May 24, 2010
Cumulative Material in units of X0
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Henry Lubatti
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ATLAS
May 24, 2010
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