DOI

10.17077/etd.xefp0v0z

Document Type

Dissertation

Date of Degree

Spring 2017

Degree Name

PhD (Doctor of Philosophy)

Degree In

Physics

First Advisor

Nachtman, Jane

First Committee Member

Onel, Yasar

Second Committee Member

Wayne, Polyzou

Third Committee Member

Yi, Kai

Fourth Committee Member

Merlino, Robert L.

Abstract

This dissertation dicusses two topics; the cross section measurement of ϓ(1S) meson pair production [1] and simulation studies of High Granularity Calorimetry (HGCal). The first part of the dissertation is dedicated for the analysis of ϓ(1S) meson pair production and measurement of its cross section. The data for this analysis were collected by the CMS experiment at Large Hadron Collider (LHC) at a center-of-mass energy of 8 TeV and correspond to an integrated luminosity of 20.7 fb −1 . Simultaneous production of two ϓ(1S) mesons is observed for the first time with 38 events, corresponding to a local significance exceeding five standard deviations from the expected combinatorial background b-quark decays. Both ϓ(1S) candidates are fully reconstructed via their decays to μ + μ − . The fiducial acceptance of the detector is measured from the simulation and is defined by an absolute Υ(1S) rapidity smaller than 2.0. To minimize the model-dependence, the acceptance and efficiency corrections are calculated on an event-by-event basis using measured ϓ meson and muon momenta. The fiducial cross section of ϓ(1S) meson production, assuming both ϓ(1S) mesons decay isotropically, is measured to be 68.8 ± 12.7 (stat) ± 7.4 (syst) ± 2.8 (B) pb, where the third uncertainty comes from the uncertainty in the branching fraction of ϓ(1S) decays to μ + μ − . Different assumptions about ϓ productions imply modifications to the cross section ranging from −38% to +36%. Cross section measurement of ϓ pair production will provide better understanding of the parton vstructure of proton and enhance precision of existing particle production models. LHC is planning to increase luminosity and energy of colliding protons. Due to accumulated radiation damage and to improve detector performance CMS experiment is expected to undergo upgrade plans. Hadron calorimeter is among them, and it is planned to be replaced with better performance high granularity calorimetry (HGCal). HGCal needs to be integrated with existing components of CMS and its smooth functioning is essential. The second part of the dissertation describes simulation studies performed to validate readiness of HGCal for the Phase II upgrade.

Public Abstract

Simultaneous production of two Υ(1S) mesons is observed for the first time in proton-proton collisions at √(s) = 8 TeV by the CMS experiment. The data analyzed corresponds to an integrated luminosity of 20.7 fb−1. To reconstruct each Υ(1S) candidate two oppositely charged muons are utilized. The fiducial acceptance of the detector is constrained by the coverage of muon stations, and it is defined as an absolute Υ rapidity smaller than 2.0. The fiducial cross section of Υ(1S) pair production is measured to be 68.8 ± 12.7 (stat) ± 7.4 (syst) ± 2.8 (B) pb, where uncertainties are statistical, systematic and branching fraction of Υ(1S) decays to µ+µ, respectively. Different assumptions about Υ(1S) polarization imply modifications to the cross section ranging from −38% to +36%. Cross section measurement of Υ pair production will provide better understanding of the parton structure of proton and enhance precision of existing particle production models.

The second half of thesis is devoted for the future plans of the LHC and upgrade preparations for high-luminosity HL-LHC, specifically High Granularity Calorimeter (HGCal) studies. Rigorous studies are performed to validate simulation of HGCal geometry. Within this work automated validation package is created which allows the production of validation plots for incpection and detection any anomaly introduced in the simulation.

Keywords

CMS, Double parton scattering, Hadron calorimeter, Upsilon pair production

Pages

xiii, 88 pages

Bibliography

Includes bibliographical references (pages 82-88).

Copyright

Copyright © 2017 Maksat Haytmyradov

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Physics Commons

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