Würzburg 2018 – scientific programme
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T: Fachverband Teilchenphysik
T 17: CP-Verletzung / Mischungswinkel
T 17.4: Talk
Monday, March 19, 2018, 16:45–17:00, Z6 - SR 2.007
Performance study of a novel time-dependent CP analysis of B → π0π0 and projection of the measurement of the unitarity angle φ2/α at the Belle II Experiment — •Fernando Abudinén — Max-Planck-Institut für Physik
The measurement of the time-dependent CP violation parameters of the decay channel B → π0π0 is crucial for the determination of the unitarity angle φ2. At former B-factories, only the direct CP violation parameter ACP could be measured in time-integrated studies. For the mixing-induced CP violation parameter SCP, a time-dependent analysis is required, a highly challenging task. This analysis requires a precise determination of the B0-decay vertex, which cannot be achieved in the dominant four-photons final state. Only rare events with a so-called Dalitz decay π0→ e+ e− γ or with converted photons provide information for the B0 vertex reconstruction. Thus, large samples of B0 → π0 π0 decays are needed and, at present, the size of the current B-factories data samples is insufficient.
Exploiting the capabilities of the new Belle II pixel vertex detector and the full Belle II data sample at 50 ab −1, the presented study shows that the expected uncertainty on the first measurement of Sπ0π0 is estimated to be Δ Sπ0π0 = 0.29. This results in a reduction of the current 8-fold φ2/α-ambiguity to a 2-fold considering B→ππ decays. Considering also B→ρρ decays, the final uncertainty on φ2/α is projected to be about five times smaller than the current world average.