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Challenges in Lumi Measurement

This study presents findings from a systematic analysis of luminosity measurement sensitivities to uncertainties within a particle collision experiment in Amsterdam. Using the BHLUMI method (Ver. 4.04), we conducted evaluations on event generation, calorimeter coordinate calculations, and applied systematic shifts. Results indicate stringent requirements for beam offsets and other parameters to achieve a ΔL/L of approximately 10^(-4). Key takeaways involve understanding limits on beam alignment, calorimeter inner radius, and the center-of-mass energy, underscoring the complexities in precision measurement.

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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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