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Search for Charged Lepton Flavor Violating Z/Z' Boson Decays at the CMS Experiment
Search for Charged Lepton Flavor Violating Z/Z' Boson Decays at the CMS Experiment
상세정보
- 자료유형
- 학위논문 서양
- 최종처리일시
- 20250211153026
- ISBN
- 9798346857112
- DDC
- 593.7
- 서명/저자
- Search for Charged Lepton Flavor Violating Z/Z Boson Decays at the CMS Experiment
- 발행사항
- [Sl] : Northwestern University, 2024
- 발행사항
- Ann Arbor : ProQuest Dissertations & Theses, 2024
- 형태사항
- 325 p
- 주기사항
- Source: Dissertations Abstracts International, Volume: 86-06, Section: B.
- 주기사항
- Advisor: Velasco, Mayda.
- 학위논문주기
- Thesis (Ph.D.)--Northwestern University, 2024.
- 초록/해제
- 요약The search for lepton flavor violation has a long history in particle physics, starting from the search for µ → eγ after the discovery of the muon. Lepton flavor was a conserved quantity in the Standard Model until the discovery of neutrino flavor oscillations showed that neutrinos are not massless, and consequentially lepton flavor conservation is violated in nature. Despite this, lepton flavor violation has never been observed in the charged sector and the predicted rates of flavor violation in the charged lepton sector are well below the observable level at any current or future high energy experiment due to the small neutrino masses.Many models beyond the Standard Model predict measurable rates of charged lepton flavor violation (CLFV), where the observation of such a process would be unambiguous evidence of new physics. This thesis presents a search for CLFV Z boson decays at the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC). The search utilizes the Run 2 dataset of 13 TeV center-of-mass energy proton-proton collisions, corresponding to an integrated luminosity of 138 fb−1. The Z → eµ, Z → eτ , and Z → µτ decays are each separately searched for. The Z → eµ decay search is performed using exclusive categories defined using machine learning techniques to create signal enriched regions, where the eµ invariant mass distributions are simultaneously fit. The Z → eτ and Z → µτ searches use different-flavor leptonic and hadronic tau decay categories, where machine learning techniques are used to create an observable per category that is simultaneously fit in the tau final state categories for each search. The Z → eµ search is extended into a search for a new Z-like (Z' ) boson resonance in the eµ data within the mass range 110 to 500 GeV/c2. The measured (expected) 95% CLS upper limits on these CLFV decay branching fractions are: B(Z → eµ) 1.9 (2.0) x 10−7, B(Z → eτ ) 13.8 (11.4) x 10−6, and B(Z → µτ ) 12.0 (5.3)x10−6. The observed Z → eµ limit is the most stringent limit to date on this process. No significant Z' → eµ resonance signature is observed within the 110 to 500 GeV/c2 mass range, placing a 95% confidence level exclusion limit of 0.5 − 10 fb on the total σ(Z' )·B(Z' → eµ) cross section within this range. All three CLFV Z decay searches found rates of CLFV consistent with the Standard Model, though the Z → µτ search observed a notable 2.7σ excess. This observation motivates further testing utilizing the Run 3 CMS dataset, where the Run 2+3 combined dataset corresponds to more than double the integrated luminosity of the Run 2 dataset alone.
- 일반주제명
- Particle physics
- 일반주제명
- Nuclear physics
- 일반주제명
- Physics
- 키워드
- Neutrinos
- 키워드
- Boson resonance
- 기타저자
- Northwestern University Physics and Astronomy
- 기본자료저록
- Dissertations Abstracts International. 86-06B.
- 전자적 위치 및 접속
- 로그인 후 원문을 볼 수 있습니다.
MARC
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■006m o d
■007cr#unu||||||||
■020 ▼a9798346857112
■035 ▼a(MiAaPQ)AAI31634150
■040 ▼aMiAaPQ▼cMiAaPQ
■0820 ▼a593.7
■1001 ▼aMacKenzie, Michael.▼0(orcid)0000-0002-5836-4611
■24510▼aSearch for Charged Lepton Flavor Violating Z/Z' Boson Decays at the CMS Experiment
■260 ▼a[Sl]▼bNorthwestern University▼c2024
■260 1▼aAnn Arbor▼bProQuest Dissertations & Theses▼c2024
■300 ▼a325 p
■500 ▼aSource: Dissertations Abstracts International, Volume: 86-06, Section: B.
■500 ▼aAdvisor: Velasco, Mayda.
■5021 ▼aThesis (Ph.D.)--Northwestern University, 2024.
■520 ▼aThe search for lepton flavor violation has a long history in particle physics, starting from the search for µ → eγ after the discovery of the muon. Lepton flavor was a conserved quantity in the Standard Model until the discovery of neutrino flavor oscillations showed that neutrinos are not massless, and consequentially lepton flavor conservation is violated in nature. Despite this, lepton flavor violation has never been observed in the charged sector and the predicted rates of flavor violation in the charged lepton sector are well below the observable level at any current or future high energy experiment due to the small neutrino masses.Many models beyond the Standard Model predict measurable rates of charged lepton flavor violation (CLFV), where the observation of such a process would be unambiguous evidence of new physics. This thesis presents a search for CLFV Z boson decays at the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC). The search utilizes the Run 2 dataset of 13 TeV center-of-mass energy proton-proton collisions, corresponding to an integrated luminosity of 138 fb−1. The Z → eµ, Z → eτ , and Z → µτ decays are each separately searched for. The Z → eµ decay search is performed using exclusive categories defined using machine learning techniques to create signal enriched regions, where the eµ invariant mass distributions are simultaneously fit. The Z → eτ and Z → µτ searches use different-flavor leptonic and hadronic tau decay categories, where machine learning techniques are used to create an observable per category that is simultaneously fit in the tau final state categories for each search. The Z → eµ search is extended into a search for a new Z-like (Z' ) boson resonance in the eµ data within the mass range 110 to 500 GeV/c2. The measured (expected) 95% CLS upper limits on these CLFV decay branching fractions are: B(Z → eµ) 1.9 (2.0) x 10−7, B(Z → eτ ) 13.8 (11.4) x 10−6, and B(Z → µτ ) 12.0 (5.3)x10−6. The observed Z → eµ limit is the most stringent limit to date on this process. No significant Z' → eµ resonance signature is observed within the 110 to 500 GeV/c2 mass range, placing a 95% confidence level exclusion limit of 0.5 − 10 fb on the total σ(Z' )·B(Z' → eµ) cross section within this range. All three CLFV Z decay searches found rates of CLFV consistent with the Standard Model, though the Z → µτ search observed a notable 2.7σ excess. This observation motivates further testing utilizing the Run 3 CMS dataset, where the Run 2+3 combined dataset corresponds to more than double the integrated luminosity of the Run 2 dataset alone.
■590 ▼aSchool code: 0163.
■650 4▼aParticle physics
■650 4▼aNuclear physics
■650 4▼aPhysics
■653 ▼aCharged lepton flavor violation
■653 ▼aProton-proton collisions
■653 ▼aNeutrinos
■653 ▼aBoson resonance
■653 ▼aLarge Hadron Collider
■690 ▼a0798
■690 ▼a0756
■690 ▼a0605
■71020▼aNorthwestern University▼bPhysics and Astronomy.
■7730 ▼tDissertations Abstracts International▼g86-06B.
■790 ▼a0163
■791 ▼aPh.D.
■792 ▼a2024
■793 ▼aEnglish
■85640▼uhttp://www.riss.kr/pdu/ddodLink.do?id=T17164643▼nKERIS▼z이 자료의 원문은 한국교육학술정보원에서 제공합니다.
