Challenges in

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Challenges in Lumi Measurement
Some studies of sensitivity to systematic
uncertainties
Achim Stahl DESY Zeuthen
Amsterdam 31. March 03
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Method
BHLUMI (Ver. 4.04) No Detector Simulation
Generate an event ? calculate coordinates on
calorimeter ? apply systematic shifts
? recalculate coordinates
? apply selection cuts
? count events ? Lumi
E, E- gt 0.8 Ebeam Acol lt 11.5o
30 mrad lt ? lt 75 mrad 30 mrad lt ?- lt 75 mrad
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Offset of Beams from Axis
2 107 events ? ?stat 2.2 10-4, ? same events
for each point
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Offset of Beams from Axis
Lin. Coeff. 0
Quadratic Coeff. ?offset lt 200 µm
2 107 new events, ? same picture
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Inner Radius of Calorimeter
?L/L 1.3 10-4/ µm
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Longitudinal Distance of Calorimeters
?L/L -0.0033 / mm z - z- lt 60 µm
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Center-of-Mass Energy
?L/L -7 ?E / E Not possible from spectrometer
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Conclusions
To achieve ?L / L 10-4
Beam Offsets lt 200 µm Inner
Radius of Cal lt 0.75 µm Distance of
Cals lt 60 µm Center-of-Mass
Energy process dependent
but thats not all yet