Search for B+ → K+ τ+ τ− at the Belle Experiment and Enabling Belle II to Improve the Search
by
Chris Ketter(University of Hawaii)
→
Pacific/Honolulu
Room 112 (Watanabe Hall)
Room 112
Watanabe Hall
32
Description
Abstract
The branching fraction for the electroweak penguin decay B → K τ τ has not been measured. Motivated by speculative physics scenarios that predict a large enhancement in the branching fraction of B → K τ τ compared to the Standard Model, and motivated further by recent success of the inclusive tagging technique, we develop an inclusive-hadronic-tagging technique for measuring the decay B+ → K+ τ+ τ− . We use simulated Belle data equivalent in size to the 711 fb−1 recorded by the Belle experiment. The goal is to show that we can improve sensitivity over existing hadronic-tagging measurements of this decay. Based on simulation, we achieve a branching-fraction sensitivity of 7.1 × 10−5 , a factor of about 30 better than the world's leading upper limit measurement. The second part of this dissertation addresses a critical weakness in τ-lepton reconstruction, which is muon identification for τ decays to muon final states. As Belle II aims to record 50 ab−1 at the Υ(4S) resonance, it is of utmost importance that this weakness is addressed now in order to enable future searches for this and other rare B-meson decays. Some of this poor muon identification can be attributed to lack of calibration and to unused features of the readout electronics for the Belle II K-Long and Muon (KLM) detector subsystem. We develop firmware that enables waveform readout of the silicon photomultipliers installed in the KLM detector. We employ a novel method for efficiently calibrating many channels at once, and we improve the hit-time granularity by a factor of four compared to the former firmware that did not use the waveform readout.
