University of Minnesota
School of Physics & Astronomy

Elementary Particle Physics Seminar

Wednesday, January 10th 2018
Speaker:  Jaebak Kim, Korea University
Subject:  Search for CP violation using T-odd correlations in D0 → K+K−π+π− decay / The 3-dimensional level one track trigger for the Belle II experiment

We search for CP violation using T-odd correlation in the singly Cabbibo suppressed D0 -> K+K-pi+pi- decay at the KEKB asymmetric e+e- collider. The D+- particles are reconstructed to tag the D0 particles and a triple product using the momentum of the D0's daughter particles is calculated. Cuts and vetos are applied to the reconstructed sample. A two dimensional simultaneous fit using four sub-samples depending on the triple product and D0 flavor while using the invariant mass of D0 and the invariant mass difference between D+ and D0 particles as the two dimensions is performed. The T-odd correlation and systematics are calculated.

The next generation e+ e- collision experiment called Belle II will start colliding particles this year. It will search for new physics using high precision measurements which were not possible before. The precision will be achieved by using a high luminosity beam. Due to the luminosity of the beam, there must be an fast and efficient trigger system in order to record the physics relevant data. The Belle II level 1 trigger system is a combination of sub-trigger FPGA based systems, where the main triggers are the central drift chamber (CDC) trigger and electromagnetic calorimeter detector trigger (ECL) trigger. Between them the CDC trigger finds the momentum and vertex position of charged tracks. These precise information will then be used to determine whether the event has
interesting physics or not. If the event is determined to be physics relevant, the DAQ system will record the detector data to disk. The level 1 CDC trigger consists of 7 types of boards. They are the Frontend boards, Merger boards, TSF boards, 2D finder board, Event time finder board, 3D tracker boards, and Neural Network boards. Each board has a specific function that makes tracking charged track possible with high precision.

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