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LAT performance studies
Results from Cracow
(by A.Kowal, B.Pawlik, L.Zawiejski)
L.Suszycki
AGH University of Science and Technology Cracow
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Forward Calorimetry Region
with new design of the Mask
LAT parameters:• distance from the IP
305-325 cm• radial dimensions
8-28 cm• angular coverage
– 26.2<<82 mrad– 0<<360 deg
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LAT detector versions
Switching the geometry:
From the conical one (TDR version)
to the cylindrical one.
Two competitive structures of the Si/W sandwich calorimeter are considered:
• Si pads • Si strips
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Simulated LAT pad-structure
Si pads/W calorimeter 16 cylinders (in r) 30 rings (in z) 24 sectors (in )=> 11520 channels analyzed angular range:
30<<78 mrad 0<<360 deg
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Simulated LAT pad-structure 2
Large statistics behaviour Angular reconstruction not
satisfactory –
Simple reconstruction bias and resolution ~0.2 - 0.3mrad,
(with 16 cylinders),
can be reduced at price of large #channels
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Stripped LAT description
• LAT consists of 30 tungsten disks
• Each disk has silicon strip detector attached
• Every second detector has either 120 radial or 64 concentric strips
• In total there is 2960 read-out channels
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Stripped LAT reconstruction Accuracy of order 0.5x10-4 radian in measuring polar angle
Measurement of 250GeV electron energy with accuracy 5GeV (ΔE~0.31√E)
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Stripped LAT - Bhabha events Measurement of the scattered electron energy with accuracy 7GeV
(ΔE~0.44√E)
Egen - Erec
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Stripped LAT - Bhabha events 2
Reconstruction of energy of the back-to-back electron pair
E (GeV)
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Stripped LAT - Bhabha events 3
Reconstruction of theta angle of the back-to-back electron pair
Gen.
Rec.
θ (mrad)
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Stripped LAT - Bhabha events 4
Acolinearity
θL – θR (mrad)
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Stripped LAT - Bhabha events 5
Angle reconstruction accuracy ~0.09 mrad
θgen – θrec (mrad)
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Beamstrahlung background
No photons are seen in LAT (θ>26 mrad)
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Beamstrahlung background 2
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Beamstrahlung background 3Pairs from beamstrahlung in LAT angular range
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Beamstrahlung background 4Energy from beamstrahlung in LAT angular range
and azimuthal angle 0/180 degrees
Background may be present at rmin
(deg)
(deg)
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Summary• LAT with pads: reconstruction
algorithm to be improved or changed completely
• Stripped LAT: seems ok
• Bhabha events: in progress
• Beamstrahlung: needs detector simulation
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The end
Thank you
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Notices
Stripped LAT: E_rec = 60.79*E_seen
Generated 20 000 events, reconstr. 9800 (26 – 86 mrad)
Beamstrahlung: TDR, FC Proposal 20-40 TeV/bx, Jeju 20 TeV
A.Stahl 500 TeV/bx photons, 100 TeV/bx pairs
(in BeamCal 5 TeV/bx and 20 TeV/bx) – Zeuthen Nov 2002
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Reconstruction results (512ch)