João Gentil SaraivaLIP & FCUL
On behalf of the ATLAS Tile Calorimeter group
Commissioning of the ATLAS Tile Hadronic Calorimeter with Single
Beam and First Collisions
12th Topical Seminar on Innovative Particle and Radiation Detectors
Siena, Italy 7 – 20 June 2010
J G Saraiva ([email protected]) IPRD10 7 - 10 June 2010 Siena, Italy 2
Outline
1) The Tile Calorimeter :
● Detector description
● Operational status
● Calibration tools
● Signal reconstruction
2) Readiness for collisions:
● Energy and timing response with cosmic ray muons
● Timing with Single beam
3) First collisions
4) Summary and conclusions
EXTRA*EXTRA*EXTRA*EXTRA
Poster by Renato
Febbraro on signal
reconstruction and
calibration tools for the
tile calorimeter
J G Saraiva ([email protected]) IPRD10 7 - 10 June 2010 Siena, Italy 4
Tile Calorimeter (I)
● ~ 10000 channels
● Each collecting the signal from a group of tiles -> cell
● Double read-out of a cell
● Uniformity + redundancy
EBCLBC
LBA
EBA
ro = 4230 mm
ri = 2280 mm
~ 12 meters● Hadronic barrel calorimeter of ATLAS
● Sampling calorimeter :
● Iron matrix with scintillating tiles
● Light transported through wavelength shifting optical fibers to the photomultipliers
● Coverage in | η | < 1.7
J G Saraiva ([email protected]) IPRD10 7 - 10 June 2010 Siena, Italy 5
Tile Calorimeter (II)
● 3 radial layers A, B/C, D divided in cells
● Δη x Δφ :
● 0.1 x 0.1 for A and B/C
● 0.2 x 0.1 for D
● Performance from testbeam with high energy pions gave a good energy resolution (close to design!)
● Within the ATLAS physics program it will be important for:
● Top mass measurements require a 1 % precision in jet energy scale
● Physics beyond the standard model such as SuSy models require a good missing transverse energy measurement
● Quark compositness
● Still important :
● Assistance in muon measurements
● In lepton isolation e.g. H->ZZ*->4l (4μ,2e2μ)
Segmentation
Energy resolution for standalone testbeam
with pions
Performance and physics goalsNIM A 606 (2009) 362-394
● Data□ MC
J G Saraiva ([email protected]) IPRD10 7 - 10 June 2010 Siena, Italy 6
Tile Calorimeter (III)Calorimeter status
● Tile calorimeter has a total of 5182 cells
● 97.1 % of cells used in physics
● Masking (not used for physics)
– 2.9 % of masked cells
– 2.6 % of which are OFF
– Most due to LVPS failures
Noise description● Tile electronic noise has non-gaussian tails
● Important in clustering algorithms
● Double gaussian description fits well with noise and is used to separate signal from noise
Preliminary
J G Saraiva ([email protected]) IPRD10 7 - 10 June 2010 Siena, Italy 7
TileCal calibration tools
● Calibration tools of the tile calorimeter
● Charge injection system (CIS) : ADC -> pC
● Integrator : used by cesium system, dedicated monitoring during several bunch crossings (time constant of 13.9 ms)
● Laser : photomultipliers (PMT) gain stability and readout electronics linearity
● Cesium : equalize cell response to set electromagnetic (EM) scale
In testbeam 12% of the modules
calibrated with beams of high
energy particles set EM energy scale to
1.05 pC/GeV Integrator time constant 13.9 ms
A amplitude in ADC countsE
channel in GeV
J G Saraiva ([email protected]) IPRD10 7 - 10 June 2010 Siena, Italy 8
Calibration (I) ● A known charge is injected into each channel
simulating the PMT response:
● Two readout: High Gain and Low Gain
● ADC to pC conversion factors
● Time stability below 0.1 %0.7 % systematic per channel
due to injected charge uncertainty
Charge Injection System
Laser System● A calibrated light signal is injected in each PMT that
mimics the light signal produced by scintillating tiles
● Gain stability of the photomultipliers during detectors operation
● Measure the non-linearity of PMTs and front-end electronics
● 0.28 % (high gain) variations for measurements made during 50 days
● Time synchronization of Tile Calorimeter channels with a precision better than 1 ns
● Gain variation during 22 months period below 0.01 %
● Individual channel stability is better that 0.05 %
Preliminary
Preliminary Preliminary
Integrator
J G Saraiva ([email protected]) IPRD10 7 - 10 June 2010 Siena, Italy 9
Calibration (II)
● A movable 137Cs radioactive source
● Travels across each cell of the calorimeter
● Check quality and uniformity of optical response
● Adjust photomultipliers HV to set the same energy scale in all cells
● After equalization a dispersion of 0.3 %
● Cosmic ray muons, single beam used for certification.
● Stability with time
● Following approximately the decay curve of cesium sources
– The increasing trend is under investigation
Cesium System
Preliminary
J G Saraiva ([email protected]) IPRD10 7 - 10 June 2010 Siena, Italy 10
Signal reconstruction● Reconstruction performed in Read Out Driver
(ROD) boards [with Digital signal processors (DSPs)]
● After level 1 trigger accept digitized signal send from drawers to RODs
● Fast reconstruction < 10 μs
● Optimal filter algorithm
● Algorithm coefficients are time (phase) dependent:
– Several iterations for asynchronous signals (cosmics) only one during LHC
– Prior knowledge of channel time
1 2
3
4 5
6
7
After phase correctionOnline reconstruction precision
below 1% for a | τ | < 10ns
Limited Numerical resolution in DSP reconstruction
Offline vs Online reconstruction
J G Saraiva ([email protected]) IPRD10 7 - 10 June 2010 Siena, Italy 11
Commissioning with cosmic muons (I)
● Cosmic ray muons with 10 GeV/c < p < 30 GeV/c crossing the inner detector
● Tracks extrapolated to tile calorimeter radial layers to obtain crossed path length
● dE/dx (MeV/mm) is the mean after 1% high tail truncation
Energy scale check using cosmic muons
● Results per radial layer
● Systematic uncertainties on data depending on the layer and partition
– 3-4 % for LB and 5-6 % for EB
● Layer non-uniformity of 4 % at most is under investigation
● Good agreement between data and MC
● Energy scale in cavern compatible within 3% with testbeam results:
Ecosmics
Etestbeam÷MC cosmics
MC testbeam=0.99±0.03
Preliminary
J G Saraiva ([email protected]) IPRD10 7 - 10 June 2010 Siena, Italy 12
Commissioning with cosmic muons (II) : φ and η
● Good uniformity in η and φ within each radial layer
● η : within window of ± 2 % for LB and ± 3 % for EB
● φ : within window of ± 3 %
Preliminary Preliminary
J G Saraiva ([email protected]) IPRD10 7 - 10 June 2010 Siena, Italy 13
Time Synchronization (I)● Pre-LHC timing set with laser system
● Channel synchronization required for good energy precision
● Validated with cosmic muons (2008) and single beam (2008-2010)
● Using single beam in 2010 to set time to ± 1 nsResults from 2008 Cosmics
● Method uses the time of flight between cells to verify the offset
● Combines all measurements in a matrix
● Extracts the solution based on a least square minimization
● Offsets between partitions expected due to lack of partitions inter-calibration
● 2008 Single beam also saw these offsets (see next slide)
Cosmic Muons (2008) Preliminary
J G Saraiva ([email protected]) IPRD10 7 - 10 June 2010 Siena, Italy 14
Larger precision -> Combined in 2008 with laser for time synchronization
● In 2008 dependency also on partition as observed with cosmic ray muons
● The comparison of time of tile calorimeter cells from 2008 single beam and cosmic ray muons
● A agreement better than 2 ns
Time Synchronization (II)
2008 single beam
Results from 2008
Results from 2008
Single beam (2008)
Single beam vs Cosmic muons (2008)
Preliminary Preliminary
J G Saraiva ([email protected]) IPRD10 7 - 10 June 2010 Siena, Italy 15
single beam 2009-2010
● In 2010 the time synchronization is achieved successfully
● Time synchronization using 2009 single beam data
● Precision better than 1 ns
Average time in cells within ± 1 ns
+ 1 ns
- 1 ns
97% of cells used
Results from 2009
Results from 2010
Time Synchronization (III)
ATLAS Preliminary
ATLAS Preliminary
J G Saraiva ([email protected]) IPRD10 7 - 10 June 2010 Siena, Italy 16
First Collisions (I)
● After LHC repairs the start-up in October 2009
● Minimum bias trigger
● Coincidence between MB scintillators located ~3 m from interaction point
● Since then gradual increase in center of mass energy
● 900 GeV, 2.36 TeV and 7 TeV
● General agreement between data and MC for the Tile Calorimeter cell energy
J G Saraiva ([email protected]) IPRD10 7 - 10 June 2010 Siena, Italy 17
First Collisions (II) : φ and η response
φ : ● Uniformity better than 10 %
● Good agreement with MC
+10 %
-10 %
Results
for
Ecm =
7 T
eV
LB EBAEBC η :● Distinction between EB from LB
● Both regions show good agreement with MC
J G Saraiva ([email protected]) IPRD10 7 - 10 June 2010 Siena, Italy 18
Summary & Conclusions● 97.1 % of the calorimeter operational
● Accurate noise description reviewed as a double gaussian model
● Signal reconstruction algorithm set to 1 % precision
● Calibration tools operational and being used as expected
● Long commissioning with cosmic muons + single beam:
● Energy scale from cosmic muons reproduced within 3 %
● Uniformity better than 3 % for both η and φ
● Synchronizing the calorimeter and reaching an agreement better than 2ns between single beam and cosmics
● First collisions showed good response in preliminary analysis both for η and φ
TileCal is eagerly awaiting more physics challenges from LHC collisions!