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Observation of Four-Top Quark Production and Measurement of Off-Shell Higgs Boson Interactions With Top Quarks With ATLAS
Observation of Four-Top Quark Production and Measurement of Off-Shell Higgs Boson Interactions With Top Quarks With ATLAS
상세정보
- 자료유형
- 학위논문 서양
- 최종처리일시
- 20260202105001
- ISBN
- 9798288862779
- DDC
- 530
- 서명/저자
- Observation of Four-Top Quark Production and Measurement of Off-Shell Higgs Boson Interactions With Top Quarks With ATLAS
- 발행사항
- [Sl] : University of California, Berkeley, 2025
- 발행사항
- Ann Arbor : ProQuest Dissertations & Theses, 2025
- 형태사항
- 264 p
- 주기사항
- Source: Dissertations Abstracts International, Volume: 87-01, Section: B.
- 주기사항
- Advisor: Wang, Haichen.
- 학위논문주기
- Thesis (Ph.D.)--University of California, Berkeley, 2025.
- 초록/해제
- 요약The ATLAS experiment at CERN measures proton-proton collisions produced by the Large Hadron Collider at energies up to 13.6 TeV. Analysis of the Run 2 dataset, which totals an integrated luminosity of 140 fb−1 at a center of mass energy of 13 TeV, has resulted in unprecedented precision in measurements of rare processes involving the top quark and the Higgs boson, the heaviest known fundamental particles. Measuring these processes provides direct probes of the top Yukawa coupling and tests of the Standard Model fermion mass generation mechanism. The total decay width of the Higgs boson can also be accessed by comparing the rates of on- and off-shell Higgs boson production.The simultaneous production of four top quarks (tt̄tt̄) is a rare process sensitive to possible contributions from heavy new particles. Additionally, tt̄tt̄ production is sensitive to the top Yukawa coupling through contributions from off-shell Higgs bosons. Therefore, tt̄tt̄ production may be used to measure the top Yukawa coupling independently of the Higgs boson's total width.The first observation of tt̄tt̄ production in ATLAS established the tt̄tt̄ process with a statistical significance of 6.1σ. The observation of tt̄tt̄production was performed in the samesign dilepton and multilepton final states and uses a graph neural network to separate the small tt̄tt̄signal from background processes. The measured value of the tt̄tt̄production cross-section was σ = 22+6.6−5.5 fb, which is 1.9 times the Standard Model prediction. Interpretations of the observed tt̄tt̄ signal were used to set limits on the coefficients of four-fermion SMEFT operators and the Higgs oblique parameter. Further interpretations set limits on the top Yukawa coupling and its CP properties. The top Yukawa coupling was constrained to κt 1.9 at the 95% CL when considering the variation of the tt̄H background and κt 2.3 when considering only the effect on tt̄tt̄ production. Additional limits were set on the cross-section of tt̄t production, which remains unobserved.Following the observation of tt̄tt̄ production, the results were combined with measurements of on-shell Higgs boson production and decay to produce the first limits on the total width of the Higgs boson Γh based on measurements of Higgs boson couplings to fermions. The combination placed a limit of Γh 450 MeV at the 95% CL when loop-induced interactions of the Higgs boson were profiled and Γh 160 MeV when they were parameterized as functions of tree-level couplings to Standard Model Particles.
- 일반주제명
- Physics
- 일반주제명
- Particle physics
- 일반주제명
- Nuclear physics
- 일반주제명
- Energy
- 키워드
- Higgs boson
- 키워드
- Top quark
- 키워드
- Yukawa coupling
- 기타저자
- University of California, Berkeley Physics
- 기본자료저록
- Dissertations Abstracts International. 87-01B.
- 전자적 위치 및 접속
- 로그인 후 원문을 볼 수 있습니다.
MARC
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■020 ▼a9798288862779
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■040 ▼aMiAaPQ▼cMiAaPQ
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■1001 ▼aRoberts, Benjamin Ryan.
■24510▼aObservation of Four-Top Quark Production and Measurement of Off-Shell Higgs Boson Interactions With Top Quarks With ATLAS
■260 ▼a[Sl]▼bUniversity of California, Berkeley▼c2025
■260 1▼aAnn Arbor▼bProQuest Dissertations & Theses▼c2025
■300 ▼a264 p
■500 ▼aSource: Dissertations Abstracts International, Volume: 87-01, Section: B.
■500 ▼aAdvisor: Wang, Haichen.
■5021 ▼aThesis (Ph.D.)--University of California, Berkeley, 2025.
■520 ▼aThe ATLAS experiment at CERN measures proton-proton collisions produced by the Large Hadron Collider at energies up to 13.6 TeV. Analysis of the Run 2 dataset, which totals an integrated luminosity of 140 fb−1 at a center of mass energy of 13 TeV, has resulted in unprecedented precision in measurements of rare processes involving the top quark and the Higgs boson, the heaviest known fundamental particles. Measuring these processes provides direct probes of the top Yukawa coupling and tests of the Standard Model fermion mass generation mechanism. The total decay width of the Higgs boson can also be accessed by comparing the rates of on- and off-shell Higgs boson production.The simultaneous production of four top quarks (tt̄tt̄) is a rare process sensitive to possible contributions from heavy new particles. Additionally, tt̄tt̄ production is sensitive to the top Yukawa coupling through contributions from off-shell Higgs bosons. Therefore, tt̄tt̄ production may be used to measure the top Yukawa coupling independently of the Higgs boson's total width.The first observation of tt̄tt̄ production in ATLAS established the tt̄tt̄ process with a statistical significance of 6.1σ. The observation of tt̄tt̄production was performed in the samesign dilepton and multilepton final states and uses a graph neural network to separate the small tt̄tt̄signal from background processes. The measured value of the tt̄tt̄production cross-section was σ = 22+6.6−5.5 fb, which is 1.9 times the Standard Model prediction. Interpretations of the observed tt̄tt̄ signal were used to set limits on the coefficients of four-fermion SMEFT operators and the Higgs oblique parameter. Further interpretations set limits on the top Yukawa coupling and its CP properties. The top Yukawa coupling was constrained to κt 1.9 at the 95% CL when considering the variation of the tt̄H background and κt 2.3 when considering only the effect on tt̄tt̄ production. Additional limits were set on the cross-section of tt̄t production, which remains unobserved.Following the observation of tt̄tt̄ production, the results were combined with measurements of on-shell Higgs boson production and decay to produce the first limits on the total width of the Higgs boson Γh based on measurements of Higgs boson couplings to fermions. The combination placed a limit of Γh 450 MeV at the 95% CL when loop-induced interactions of the Higgs boson were profiled and Γh 160 MeV when they were parameterized as functions of tree-level couplings to Standard Model Particles.
■590 ▼aSchool code: 0028.
■650 4▼aPhysics
■650 4▼aParticle physics
■650 4▼aNuclear physics
■650 4▼aEnergy
■653 ▼aGraph neural networks
■653 ▼aHiggs boson
■653 ▼aLarge Hadron Collider
■653 ▼aTop quark
■653 ▼aYukawa coupling
■690 ▼a0605
■690 ▼a0798
■690 ▼a0756
■690 ▼a0791
■71020▼aUniversity of California, Berkeley▼bPhysics.
■7730 ▼tDissertations Abstracts International▼g87-01B.
■790 ▼a0028
■791 ▼aPh.D.
■792 ▼a2025
■793 ▼aEnglish
■85640▼uhttp://www.riss.kr/pdu/ddodLink.do?id=T17359282▼nKERIS▼z이 자료의 원문은 한국교육학술정보원에서 제공합니다.
