DOI

10.17077/etd.fxooie6m

Document Type

Dissertation

Date of Degree

Summer 2018

Degree Name

PhD (Doctor of Philosophy)

Degree In

Physics

First Advisor

Onel, Yasar

Second Advisor

Nachtman, Jane

First Committee Member

Polyzou, Wayne

Second Committee Member

Merlino, Robert

Third Committee Member

Spiegel, Leonard

Fourth Committee Member

Yi, Kai

Abstract

This thesis focuses on two parts, the evidence of a structure in a four lepton final state, and the CMS detector upgrade studies.

The first part of the thesis focuses on an unexpected structure in Υ(1S)l+l− final state, where Υ(1S) → μ+μ−, l can represent a muon or an electron and m(l+l−) is required to be below the Υ(1S) mass. Using an integrated luminosity of 25.6 fb−1 recorded in proton-proton collisions at √s = 7 TeV and √s = 8 TeV with the CMS detector at the CERN LHC, an excess in the mass distribution near 18.5 GeV of Υ(1S)l+l− is found. The mass of this enhancement is found out to be 18.4 ± 0.1 (stat.) ± 0.2 (syst.) GeV in the Υ(1S)μ+μ− channel, and 18.5 ± 0.2 (stat.) ± 0.2 (syst.) GeV in the Υ(1S)e+e− channel. For the two results combined, the enhancement is found out to be 18.4 ± 0.1 (stat.) ± 0.2 (syst.) GeV with a local statistical significance of 4.9 standard deviations and a global significance, after taking into account the look-elsewhere-effect, of 3.6 standard deviations. The width of the observed enhancement is consistent with the mass resolution of the CMS detector.

The second part of the thesis focuses on detector upgrade studies for the silicon detector. The LHC has been increasing and will increase the luminosity and collision energy. Due to radiation damage and increasing data loss, the CMS detector underwent a Phase I upgrade in 2016/2017 and will undergo a Phase II upgrade in 2018/2019. In Phase I upgrade, silicon sensors and DC-DC converters were tested at Fermilab for the CMS Forward Pixel detector. For Phase II upgrade, a gantry robot system is built for module assemble at Fermilab for the CMS Outer Tracker detector.

Keywords

CMS, Evidence, Evidence of a new particle, Exotic Mesons, Four muon excess, Tetraquark

Pages

xix, 135 pages

Bibliography

Includes bibliographical references (pages 132-135).

Comments

This thesis has been optimized for improved web viewing. If you require the original version, contact the University Archives at the University of Iowa: http://www.lib.uiowa.edu/sc/contact/

Copyright

Copyright © 2018 Suleyman Durgut

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Physics Commons

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