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Current status

Current status. ~ 4fb -1 , ~ 50000 dileptons at the end of the analysis The statistical error on m (0.0158 pb -1 ) is smaller than the total error of PDG 98 (0.019 pb -1 ) !!!. The value of m will be kept hidden as far as all the systematic effects haven’t been understood.

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Current status

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  1. Current status • ~ 4fb-1 , ~ 50000 dileptons at the end of the analysis • The statistical error on m (0.0158 pb-1)is smaller than the total error of PDG 98 (0.019 pb-1) !!! The value of m will be kept hidden as far as all the systematic effects haven’t been understood. C. Bozzi - Status of Dilepton Mixing Analysis

  2. Systematic uncertainties (3) • Time-dependence of the mistag: • reminder: we absorb the time distribution of cascade background with a time-dependent mistag • “slope” for same-sign events • “slope”+”bump” for opposite-sign events • systematic uncertainty on Dm: difference with perfect-tagging complete fit: 2.5% (a conservative approach) • estimate with MonteCarlo is under way • might be better if cascade background is reduced. Cut tighter on NN output ? • We have to find a tradeoff C. Bozzi - Status of Dilepton Mixing Analysis

  3. Systematic uncertainties (5) • Knowledge of the resolution function: • apply the same cuts of the analysis on inclusive J/y in data and MC • data/MC agreement is good. Uncertainties: 5% on narrow gaussian width, 10% on wide gaussian width, 10% on fraction • width of wide gaussian gives 1.6% on Dm, the others give about 0.5%. • Can be reduced by improving the resolution function using the event-by-event error C. Bozzi - Status of Dilepton Mixing Analysis

  4. Summary of systematic uncertainties Source of systematic error Relative error on Dm (%) Non-BBbar Background Not measured yet Lepton Mis-ID Not measured yet Charge asymmetry (e+ e-) negligible Mistag asymmetry (h+h-) negligible Correction for h(B0) h(B+) negligible Time-dependence of the mistag 2.5 Correction of the boost approximation 0.3 y-motion of the beam spot (<20mm) negligible Resolution Function (5% on s1) 0.3 Resolution Function (10% on s2) 1.6 Resolution Function (10% on fraction) 0.6 Tails of the resolution function In progress Time-dependence of the resolution func. In progress Sensitivity to G+ (PDG 98  1s) 1.5 Sensitivity to G0 (PDG 98  1s) 1.0 Total C. Bozzi - Status of Dilepton Mixing Analysis

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