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Improved Geometry Setups for Luminosity Measurement in Forward Calorimetry

This presentation discusses the options for improving the angle measurement of Bhabha scattered electrons in order to achieve precise luminosity measurement using forward calorimetry. The standard setup and alternative geometry setups are compared, including the flat LAT and stripped LAT configurations. Preliminary results and conclusions are discussed.

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Improved Geometry Setups for Luminosity Measurement in Forward Calorimetry

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  1. LAT calorimeter options L.Suszycki, Cracow Forward Calorimetry WG, Amsterdam, 31 March 2003

  2. LAT luminosity measurement Essential for precise luminosity measurement is a precise angle measurement of the Bhabha scattered electrons. L/L = 10-4 needs min = 1.4 rad The standard (TDR) setup enables only 0.2 – 0.3 mrad accuracy (Prague, Nov 2003) with the price of 13440 channels. We try • Tthe standard setup improvements and to consider alternative geometry setups: • Flat LAT • Stripped LAT

  3. Improvements comparing to the Prague results: 1. Silicon sensors arranged in planes 2. Non-projective cylinders of equal height Improved LAT geometry

  4. Angle reconstruction using All sensors – =~0.9 mrad Every 4th sensor - =~1.1 mrad Every 10th sensor - =~1.5 mrad It is resonable to apply fine segmentation to a fraction of cylinders only Improved LAT angle reconstruction

  5. All cylinders start at z=136 cm 7, 14, 18 or 56 cylinders assumed Conical projective geometry is kept (TDR) Flat LAT geometry

  6. Cell size and number of cells depend on number of cylinders Flat LAT calorimeter cellsSergey Kananov, Tel Aviv

  7. Angle bias and angular resolution as a functions of number of cylinders Gain in angle resolution = 2.5at price of increasing #channels of factor 56/14=4! Flat LAT angle reconstructionSergey Kananov, Tel Aviv

  8. Only rings near the shower maximum at ring #8 are taken for theta reconstruction: 1, 3, 5, 7, 10, 16 or 20 „active” rings One can reach better angular resolution with similar #channels: Uniform: 14 x 30 x 24 = 10080=> 0.18 mrad 5 rings 2-fold granulated: 11760=> 0.13 mrad 5 rings 4-fold granulated: 15120=> 0.09 mrad Flat LAT shower maximum methodSergey Kananov, Tel Aviv

  9. Sillicon strips crossed for more precise r-measurement Stripped LAT viewBogdan Pawlik, Cracow

  10. Stripped LAT geometryBogdan Pawlik, CracowSilicon 1mm strips arranged in 20 cones to read r and z x 256 strips + 20 cones to read φ x 72 strips => 6560 channels in total

  11. Stripped LAT polar angle reconstruction (1)Bogdan Pawlik, CracowReconstruction in the first(left) and in the 9th(right) layers

  12. Systematic error =gen - rec (radians) versus strip layer („cylinder”)  = ~0.9mrad at 9st layer Stripped LAT polar angle reconstruction (2)Bogdan Pawlik, Cracow

  13. Error =gen - rec (degrees) versus strip layer („cylinder”) Stripped LAT azimuthal angle reconstruction Bogdan Pawlik, Cracow

  14. LAT conclusions • Preliminary results on alternative LAT geometry obtained • Much more MC work necessary to get closer to the required acurracy of the angle measurement • Still awaiting for the Flat Mask decision

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