A study of beam background from SuperKEKB on Belle II Silicon Vertex Detector

Sumitted to PubDB: 2019-12-06

Category: Master Thesis, Visibility: Public

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Authors	Yutaka Ushiroda
Non-Belle II authors	Hikaru Tanigawa
Date	Jan. 1, 2019
Belle II Number	BELLE2-MTHESIS-2019-023
Abstract	The Belle II experiment plans to start its full operation in March 2019 hosted by KEK in Tsukuba, Japan. The SuperKEKB accelerator has been upgraded to collide e+ and e− beams at a rate forty times higher than its predecessor. The Belle II detector detects the decay products of the particles created after e+e− annihilations to explore new areas of flavor physics. This thesis focuses on the silicon vertex detector at the core of the Belle II detector. The upgrade of SuperKEKB introduces a challenging environment for the silicon vertex detector in two ways: the high data acquisition rate leads to an unignorable dead time of its readout ASIC and the intense beam background causes detector performance to deteriorate. We developed a firmware module which emulates the data processing procedure of the readout ASIC and mini- mizes the dead time by optimal trigger-veto. We investigated the beam background condition with a subset of the detector in the commissioning phase which ran from March to July of 2018. Based on our estimation of the beam background level in full operation, the full silicon vertex detector was installed in the Belle II detector.
Conference	Tokyo