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Dielectron Spectrum Analysis

This document outlines the action items and considerations regarding the analysis of dielectron spectrum shapes and efficiency features observed in the data. Key tasks include identifying specific cuts that may distort mass and pT distributions, investigating isolation factors, and optimizing electron cuts for improved signal efficiency. Attention is drawn to the distinct efficiency features at different cuts and the necessity to analyze efficiency for barrel versus endcap regions. Further steps involve consulting relevant literature and external authors for additional insights on the observed phenomena.

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Dielectron Spectrum Analysis

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  1. Dielectron Spectrum Analysis J. Leonard 16 Sept. 2009

  2. Today • Action items from e-mail • Identify which cut is causing the strange shape in mass and pt. • Check all cuts in sequence one at a time till you find the cut that is a problem. • See later slides • Though first try removing the isolation. Isolation looks like it might be the source of part of the problem. • Part of the problem, but only part -- see later slides • If it is the source of all the problems move to relative isolation. • Investigate relative isolation with a floor • Optimize final cuts • Probably we want to use tighter electron cuts.

  3. Signal efficiency vs. invariant mass at each step • Features appear separately • Fall-off at low end appears after 10-GeV pT cut • Peak and dip/plateau below peak start to appear after electron ID cuts (ii, in) • Dip and high-end fall-off more pronounced after isolation cuts • Efficiencies defined with respect to initial step

  4. Efficiency features: electron ID or isolation? • Main idea: • Switch electron ID and isolation steps • If features due mainly to electron ID, should not show up until electron ID step (after isolation step) • Features already present in isolation step (before electron ID) • Dip and high-end drop-off pronounced • Electron ID step reduces general efficiency, flattens area ~50 GeV • Efficiencies defined with respect to initial step

  5. Signal efficiency: electron ID • Plateau/peak structure appears with each cut (ii and in) separately • Possibility the problem is -dependent -- endcap vs barrel. To investigate • Efficiencies defined with respect to initial step

  6. Signal efficiency: isolation • Dip ~70 GeV appears clearly in ECAL-only curve • Drop-off at high end has no clear culprit • Efficiencies defined with respect to initial step

  7. Next Steps • Further investigate efficiency features • Analyze separately for barrel/endcap • See how eID/iso variables themselves vary with pT/invariant mass • Ask authors of Zee note if they’ve seen this issue or know anything about it • Investigate relative isolation • May help efficiency (especially at high end) • See what optimization algorithm from Zee note can do for us • What to optimize: S/B, or something else

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