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Challenges in Lumi Measurement

Challenges in Lumi Measurement. Some studies of sensitivity to systematic uncertainties. Amsterdam 31. March ‚03. Achim Stahl DESY Zeuthen. Method. BHLUMI (Ver. 4.04) No Detector Simulation. Generate an event  calculate coordinates on calorimeter

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Challenges in Lumi Measurement

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  1. Challenges in Lumi Measurement Some studies of sensitivity to systematic uncertainties Amsterdam 31. March ‚03 Achim Stahl DESY Zeuthen

  2. 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- > 0.8 Ebeam Acol < 11.5o 30 mrad < θ+ < 75 mrad 30 mrad < θ-< 75 mrad

  3. Offset of Beams from Axis 2 107 events  stat = 2.2 10-4,  same events for each point

  4. Offset of Beams from Axis Lin. Coeff. ≈ 0 Quadratic Coeff.: Δoffset < 200 μm 2 107 new events,  same picture

  5. Inner Radius of Calorimeter ΔL/L ≈ 1.3 10-4/ μm

  6. Longitudinal Distance of Calorimeters ΔL/L ≈ -0.0033 / mm z+ - z- < 60 μm

  7. Center-of-Mass Energy ΔL/L ≈ -7 ΔE / E Not possible from spectrometer

  8. Conclusions To achieve ΔL / L ≈ 10-4: Beam Offsets: < 200 μm Inner Radius of Cal < 0.75 μm Distance of Cals < 60 μm Center-of-Mass Energy: process dependent but that‘s not all yet

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