Marco Delmastro 23 /02/2006 Status of LAr EM performance andmeasurements fro CTB 1 Status of LAr EM Status of LAr EM performance and performance and measurements for CTB measurements for CTB Overview Overview Data - MC comparison Data - MC comparison Uniformity and energy resolution Uniformity and energy resolution 3x3 cluster corrections Longitudinal weights Linearity Linearity Different amounts of material VLE electrons ID – LAr alignment ID – LAr alignment Conclusions and perspectives Conclusions and perspectives on behalf of the LAr EM CTB Group Marco Delmastr Marco Delmastr o o
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Marco Delmastro 23/02/2006 Status of LAr EM performance andmeasurements fro CTB 1
Status of LAr EM Status of LAr EM performance and performance and
measurements for CTBmeasurements for CTB
OverviewOverview
Data - MC comparisonData - MC comparison
Uniformity and energy resolutionUniformity and energy resolution 3x3 cluster corrections Longitudinal weights
LinearityLinearity Different amounts of material VLE electrons
ID – LAr alignmentID – LAr alignment
Conclusions and perspectivesConclusions and perspectives
on behalf of the LAr EM CTB Group Marco DelmastrMarco Delmastroo
Marco Delmastro 23/02/2006 Status of LAr EM performance andmeasurements fro CTB 2
OverviewOverview
The preliminary calibration of the LAr detector (Pedestals, The preliminary calibration of the LAr detector (Pedestals, Ramps, OFC) has been completed, the analysis has entered Ramps, OFC) has been completed, the analysis has entered the interesting stage where detailed physics effects and the interesting stage where detailed physics effects and combined performances are studied…combined performances are studied…
Full list of analysis topics can be found at:Full list of analysis topics can be found at: http://atlas.web.cern.ch/Atlas/GROUPS/LIQARGON/Comb_TB/
CBT_Barrel/Analysis/summer2005.html
The LAr EM CTB Group meets regularly, please find the details The LAr EM CTB Group meets regularly, please find the details of the analysis in:of the analysis in: http://agenda.cern.ch/displayLevel.php?fid=65
A list of foreseen CTB e-gamma papers can be found at A list of foreseen CTB e-gamma papers can be found at https://uimon.cern.ch/twiki/bin/view/Atlas/
EgammaCombinedTestBeam
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ConfigurationsConfigurationsSeveral MC configurations…Several MC configurations… 13.35 mm of Al far
upstream (beam line)… Additional material in fron
of the calorimeter:• 15mm of Al• 0mm of Al
Runs with/without charge corrections
6 Energies: • 9, 20, 50, 100, 180,
250 GeVThroughout the PS energy in Throughout the PS energy in the MC was scaled with 11/13the MC was scaled with 11/13X-talk between strips is still X-talk between strips is still under study, affects strip under study, affects strip normalisation...normalisation...
Yellow: MC
Points: data
Note: used one overall scale factor for MC and X-talk correction
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Electrons Data-MC comparison:Electrons Data-MC comparison: Presampler and StripsPresampler and Strips
No material added on top of 13.35mm of Al far upstream + PS scaled in data by 0.89 (cross talk correction usually 0.93) + MC scale overall 0.957
MC with extra material need a more reasonable MC with extra material need a more reasonable x-talk correction; x-talk correction; L1/L2 is then better, but PS is L1/L2 is then better, but PS is off...off...
MC without extra material would require MC without extra material would require 10% x-10% x-talk to get good agreement... too much?talk to get good agreement... too much?
Can the effect be explained by material between Can the effect be explained by material between PS and Strips?PS and Strips?
... or does it really come from X-talk?... or does it really come from X-talk?
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Sensitivity on material between Sensitivity on material between Presampler and StripsPresampler and Strips
nominal
5% more X0 between PS and strips
Difference: ~20% increase in energy loss
Beam energy (GeV)
Very strong sensitivity on the amount Very strong sensitivity on the amount of material between the PS and the of material between the PS and the stripsstripsApproximately 5%XApproximately 5%X00 between PS and between PS and strips raise signal in strips by 2-3%strips raise signal in strips by 2-3%with less than 10%Xwith less than 10%X00 more material more material between PS and strips our material between PS and strips our material problem could be solved…problem could be solved…… … but also cross-talk stil needs to be but also cross-talk stil needs to be measured for CTB2004! (work is measured for CTB2004! (work is ongoing…)ongoing…)
Possible candidates for Possible candidates for explanationexplanationss are… are…
• Cross-talk• Material in front of PS• Material between PS and
strips• Description of energy
collection in electrodes fold in MC?
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Electrons Data-MC comparison:Electrons Data-MC comparison: Summary of current situation with CTB Summary of current situation with CTB
material in front of ID and of LAr EMmaterial in front of ID and of LAr EMEM sharing between Strips and layer 2 requires about 15% XEM sharing between Strips and layer 2 requires about 15% X00 additional just in additional just in front of PS…front of PS… 15% X0 just in front not really identified yet:
• Rohacell LAr excluder? Recent measurements seem to exclude…• Material between Presampler and Strips? Sensitivity can be very high…• X-talk? Realistic treatment is needed, detailed measurement from data is ongoing…
… … and about 15% Xand about 15% X00 additional further upstream. additional further upstream. 15% X0 very far upstream identified…
• but within magnetic part of beam, so unclear how much of it is relevant (was found to be relevant in 2002)
• Detailed simulation of the beamline ongoing…
ID material itself understood to better than 10% from multiple scattering ID material itself understood to better than 10% from multiple scattering studies…studies… Tail of reconstructed momentum spectrum in ID for electrons of 9 GeV
apparently does not support the hypothesis of 15% X0 additional material far upstream distorting the electron spectrum itself…
More studies in progress on all sides with next meeting foreseen in three More studies in progress on all sides with next meeting foreseen in three weeks' time and progress on convergence reported by trigger/physics week… weeks' time and progress on convergence reported by trigger/physics week…
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From “raw” to “calibrated” energy:From “raw” to “calibrated” energy: 3x3 cluster corrections (1)3x3 cluster corrections (1)
Position corrections – f(E, Position corrections – f(E, ηη)) S shape in the middle & strips
Eta modulations – f(EEta modulations – f(E)) Due to the finite size of the
clusterPhi modulations – no obvious Phi modulations – no obvious dependence on E, dependence on dependence on E, dependence on ηη to be checkedto be checked Due to the accordion geometry
Three sets of the energy: single Three sets of the energy: single electrons at 50GeV, 180GeV and 250 electrons at 50GeV, 180GeV and 250 GeVGeVEta range 0-1.2Eta range 0-1.2Implementation in Athena…Implementation in Athena… CaloClusterCorrection
Phi modulationsa+b*X+c*X²+d*sin(16pX+e)
Eta modulationsParabola fixed at 1 in the middle of the cell
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E=250GeV E=50GeV
E u
pstr
eam
Eps
Calibration formula in LArCTBLongWeights:a + b*Eps + c* sqrt(Eps*Estr) + d*Eacc +
Eleak
EpsE u
pstr
eam
E=250GeV
E lost
betw
een
Ep
s-s
trip
s
Sqrt(Eps.Estrips)
From “raw” to “calibrated” From “raw” to “calibrated” energy:energy:
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UniformityUniformity
Global constant term:Global constant term:total energy resolution: 0.7%total energy resolution: 0.7%
RMS/<E> = O.52%
22 cells
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Energy resolutionEnergy resolution
Electronic noise in cluster subtractedElectronic noise in cluster subtractedAll corrections are applied:All corrections are applied: S shape, Out of cone, Longitudinal weights, eta and phi modulation
Different wrt Lar standalone TB because ofDifferent wrt Lar standalone TB because of more material in front of calorimeter beam spread
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Linearity and resolution with Linearity and resolution with different amounts of materialdifferent amounts of material
• Errors on linearity comes from uncertainty of the beam energy
• Noise term fixed to 200 MeV
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VLE beam – Energy MeasurementVLE beam – Energy Measurement
A medium energy beam hits a secondary target about 50m upstream of our set-upA medium energy beam hits a secondary target about 50m upstream of our set-up VLE spectrometer – Energy selection with the last magnets in the spectrometer B7, and B8
(deflection angle θ=120mrad), the currents are in the DB for each run Calculated p=q*Bdl(I)/θ Estimated momentum spread (defined by collimator C12) about 5%
Analysis to extend linearity study below 9 GeV has recently started…Analysis to extend linearity study below 9 GeV has recently started…
Run# Nominal Energy (GeV/c) B8 current (A) Bdl (Tm) Energy error Real Energy (Gev/c)2102101 1 71.699 0.3600 ~ 1.39% 0.899372102117 2 140.699 0.7801 ~ 0.71% 1.944862102098 3 208.000 1.2000 ~ 0.48% 2.997912102104 5 349.799 1.9900 ~ 0.28% 4.971532102103 9 807.200 3.6010 ~ 0.12% 8.99370
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Inner Detector – LAr alignment (1)Inner Detector – LAr alignment (1)
Track-cluster matching…Track-cluster matching…
Phi-misalignment checked with Phi-misalignment checked with 50GeV and 80GeV50GeV and 80GeV Same results within 8%
In reality not all the LAr samplings In reality not all the LAr samplings will show the same offset…will show the same offset… Coming from the accordion
shape – offset different in each layer
Phi
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Inner Detector – LAr alignment (2)Inner Detector – LAr alignment (2)
Same study done for Eta misalignment with 150 GeV muonsSame study done for Eta misalignment with 150 GeV muonsTracker has worse resolution in eta…Tracker has worse resolution in eta…It was found that the existing alignment correction overdoes the phi-correction It was found that the existing alignment correction overdoes the phi-correction and does rather well in etaand does rather well in etaNew corrections will be implemented…New corrections will be implemented… But systematic in phi-measurement of LAr has to be understood better…
Eta
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Conclusions and perspectivesConclusions and perspectives
Energy reconstruction in LAr EM calorimeter for CTB is well Energy reconstruction in LAr EM calorimeter for CTB is well advanced:advanced: Cell calibration, cluster corrections, longitudinal weights, …
Data-MC agreement is good…Data-MC agreement is good… … but still no definite conclusions on material upstream,
studies are ongoing LAr realistic X-talk corrections are mandatory…
Uniformity, resolution and linearity studies show good Uniformity, resolution and linearity studies show good performances…performances… Will be extended to…
• Full eta range• VLE energy (<9 GeV)
Many physics studies are advancing, combined analysis Many physics studies are advancing, combined analysis started:started: Combined tracking… Photon conversion…
