The track finding algorithm of the Belle II vertex detectors

The Belle II experiment is a high energy multi purpose particle detector operated at the asymmetric e+e-- collier SuperKEKB in Tsukuba (Japan). In this work we describe the algorithm performing the pattern recognition for inner tracking detector which consists of two layers of pixel detectors and four layers of double sided silicon strip detectors arranged around the interaction region. The track finding algorithm will be used both during the High Level Trigger on-line track reconstruction and during the off-line full reconstruction. It must provide good efficiency down to momenta as low as 50 MeV/c where material effects are sizeable even in an extremely thin detector as the VXD. In addition it has to be able to cope with the high occupancy of the Belle II detectors due to the background. The underlying concept of the track finding algorithm, as well as details of the implementation are outlined. The algorithm is proven to run with good performance on simulated Y (4S) â\u86\u92 BB events with an efficiency for reconstructing tracks of above 90% over a wide range of momentum

Status of the BELLE II Pixel Detector

The Belle II experiment at the super KEK B-factory (SuperKEKB) in Tsukuba, Japan, has been collecting $e^+e^−$ collision data since March 2019. Operating at a record-breaking luminosity of up to $4.7×10^{34} cm^{−2}s^{−1}$, data corresponding to $424 fb^{−1}$ has since been recorded. The Belle II VerteX Detector (VXD) is central to the Belle II detector and its physics program and plays a crucial role in reconstructing precise primary and decay vertices. It consists of the outer 4-layer Silicon Vertex Detector (SVD) using double sided silicon strips and the inner two-layer PiXel Detector (PXD) based on the Depleted P-channel Field Effect Transistor (DePFET) technology. The PXD DePFET structure combines signal generation and amplification within pixels with a minimum pitch of $(50×55) μm^2$. A high gain and a high signal-to-noise ratio allow thinning the pixels to $75 μm$ while retaining a high pixel hit efficiency of about $99$. As a consequence, also the material budget of the full detector is kept low at $≈0.21$$\frac{X}{X_0}$ per layer in the acceptance region. This also includes contributions from the control, Analog-to-Digital Converter (ADC), and data processing Application Specific Integrated Circuits (ASICs) as well as from cooling and support structures. This article will present the experience gained from four years of operating PXD; the first full scale detector employing the DePFET technology in High Energy Physics. Overall, the PXD has met the expectations. Operating in the intense SuperKEKB environment poses many challenges that will also be discussed. The current PXD system remains incomplete with only 20 out of 40 modules having been installed. A full replacement has been constructed and is currently in its final testing stage before it will be installed into Belle II during the ongoing long shutdown that will last throughout 2023

The Belle II vertex detector alignment studies and prompt sin 2 phi analysis

This thesis is focused on the alignment studies of the vertex detector during first years of the Belle II detector operation and the first prompt sin 2ϕ1 analysis using the first rel- evant data collected by the detector. Firstly, the Belle II detector and the SuperKEKB accelerator is introduced. Secondly, the software framework and tools operation is ex- plained, then the alignment procedure and developed validation procedures are described in detail. Fourth section reports about the first years of the detector operation. Next three sections are related to different alignment studies during thee different periods of the vertex detector operation: the Phase 2, VXD Commissioning and beginning of the Phase 3 early. The last section covers the time-dependent CP Violation and mixing measurements performed using the data collected prior to the 11en of May 2020.

Simulace fyzikalních procesů v experimentu Belle II a testovaní kvality rekonstrukčního softwaru

Táto práca je venovaná štúdiu alignmentu vrcholových polovodičových detektorov experimentu Belle II. Je rozdelená do niekoľkých častí. Prvá časť predstavuje experiment Belle II ako B-továreň novej generácie, s jej ambicióznymi plánmi naberania dát a fyzikálnej analýzy. Na to nadväzuje popis vrcholových detektorov a softwarových nástrojov určených na kalibráciu a alignment detektorov. Ťažiskovou časťou je štúdia fyzikálnych procesov, využívaných pre kalibráciu detektora, spojená s hľadaním najvhodnejšieho riešenia pre priebežnú aplikáciu počas zberu nameraných dát. Následne boli testované softwarové nástroje na rozladenej geometrii, aby sme zistili ich odolnosť voči rozladeniu geometrie. Bola prevedená aj štúdia vplyvu rozladenia geometrie (misalignmentu) na pozorovateľné parametre pri analýze vybraných fyzikálnych procesov. V poslednej časti popisujeme vývoj monitorovacieho nástroja pre priebežnú diagnostiku rozladenia geometrie alebo konfigurácie detektora. Takýto nástroj bude sledovať nepresnosti v rekonštrukcii fyzikálnych pozorovateľných a signalizovať, ak táto nepresnoť prekročí nastavené medze. Powered by TCPDF (www.tcpdf.org)This thesis is about the alignment of vertex semiconductor detectors of the Belle II experiment. It is divided into several sections. The first part introduces the Belle II experiment as a new generation B- factory, with its ambitious plans of data taking and physical analysis. The second part follows with a more detailed description of Belle II detector and software tools designed for their alignment and calibration. The central part of the thesis describes physical processes used for calibration of the vertex detector, connected with the search of an optimal solution for run-time monitoring and calibration of the detector. We also tested the effect of misalignment on the Belle II tracking software. The following part gives results of the study of misalignment effects on physical observables related to analysis of selected physical channels. The last part describes the development of a data quality monitoring tool for the tracking system. The tools has to provide a run-time diagnostic of misalignment and miscalibration by monitoring the precision and accuracy of reconstruction of physical observables. Powered by TCPDF (www.tcpdf.org)Ústav částicové a jaderné fyzikyInstitute of Particle and Nuclear PhysicsMatematicko-fyzikální fakultaFaculty of Mathematics and Physic

The Belle II vertex detector alignment studies and prompt sin 2 phi analysis

This thesis is focused on the alignment studies of the vertex detector during first years of the Belle II detector operation and the first prompt sin 2ϕ1 analysis using the first rel- evant data collected by the detector. Firstly, the Belle II detector and the SuperKEKB accelerator is introduced. Secondly, the software framework and tools operation is ex- plained, then the alignment procedure and developed validation procedures are described in detail. Fourth section reports about the first years of the detector operation. Next three sections are related to different alignment studies during thee different periods of the vertex detector operation: the Phase 2, VXD Commissioning and beginning of the Phase 3 early. The last section covers the time-dependent CP Violation and mixing measurements performed using the data collected prior to the 11en of May 2020.