Elementary Particles and Fields and String Theory Commons^™

Improved Constraints On The Standard Model Higgs Self-Interaction Using A Search For Hh → 4b Via The Vector-Boson Fusion Production Mode At √S = 13 Tev In 126 Fb^-1 Of Data Collected By The Atlas Experiment, Christopher Milke

Physics Theses and Dissertations

A search for di-Higgs production via the Vector Boson Fusion mechanism decaying to 4 bottom quarks is performed using 126 fb−1 of data from Run 2 of ATLAS at √s = 13 TeV. The search was performed in the non-resonant regime, finding an upper bound on the production cross-section for the Standard Model VBF→HH→4b of about 200 times the Standard Model. Constraints are placed on both the HHVV coupling (which determines the W/Z-higgs four-point interaction strength) and HHH Higgs self-coupling scale factors at 95% confidence. The HHVV coupling scaling factor (κ2V ) is constrained to an observed interval between 0.09 …

Fast Statistical Methods For The Global Qcd Analysis Of The Proton Structure, Xiaoxian Jing

Physics Theses and Dissertations

Parton distribution functions (PDFs) quantify probabilities to find partons (quarks and gluons) in a hadron as a function of the fraction x of the hadron’s momentum carried by the parton at a given energy scale. PDFs play a critical role in precision tests of the Standard Model in Higgs boson production and other electroweak processes at the Large Hadron Collider (LHC), and in searches for physics beyond the Standard Model. PDFs are obtained by the global QCD analysis, which fits theoretical predictions to experimental measurements. PDF fitting and post-analysis are computationally intensive. This dissertation discusses fast statistical methods for the …

Constraints On Parton Distribution Functions Imposed By Hadronic Experiments, Boting Wang

Physics Theses and Dissertations

The theoretical uncertainties of the Large Hadron Collider (LHC) observables are decreasing with the increasing statistics of the LHC experiments, and it is becoming more and more important to reduce the uncertainties in the knowledge of the nucleon structure. The latest LHC high-energy experiments, future experimental proposals, and computational tools are expected to enhance the knowledge of the nucleon structure. However, the global analysis that assesses their impact on Parton Distribution Functions (PDFs) knowledge is computationally expensive due to the corresponding large size of data. I developed a new approach that can make a quick preliminary evaluation to help the …

A Search For Boosted Low Mass Resonances Decaying To The Bb̅ Final State And Produced In Association With A Jet At √S = 13 Tev With The Atlas Detector, Matthew Feickert

Physics Theses and Dissertations

A search in the high momentum regime for new resonances, produced in association with a jet, decaying into a pair of bottom quarks is presented using an integrated luminosity of 80.5 fb^-1 of proton-proton collisions at center-of-mass energy √s = 13 TeV recorded by the ATLAS detector at the Large Hadron Collider. The search was performed for low mass resonances, including the Standard Model Higgs boson and leptophobic Z' dark matter mediators, in the mass range of 100 GeV to 200 GeV. For the Standard Model Higgs boson, the observed signal strength is μH = 5.8 ± 3.1 (stat.) …

Massive Elementary Particles In The Standard Model And Its Supersymmetric Triplet Higgs Extension, Keping Xie

Physics Theses and Dissertations

In this dissertation, we focus on massive elementary particles in the Standard Model and its supersymmetric triplet Higgs extension.

In the first part, we start with a review of electroweak (EW) sector in the Standard Model. Motivated by nonzero neutrino masses, we consider triplet scalars in addition to the Standard Model. The vacuum expectation values of scalar triplets are strongly constrained by the $\rho$ parameter, extracted from electroweak precision measurements. Therefore, we introduce a custodial symmetry to weaken this constraint and obtain the well-known Georgi-Machacek (GM) Model. The GM model still requires fine-tuning to satisfy the $\rho$ parameter constraint. It …

The Impact Of Ppb W/Z Lhc Data On Ncteq15 Parton Distribution Functions With An Emphasis On Refitting The Ncteq15 Npdf Set, Eric Godat

Physics Theses and Dissertations

As the LHC experiments increase their statistics and reduce their systematics, it is in- creasingly important to reduce the theoretical uncertainties so we can perform precision com- parisons. The parton distribution functions (PDFs) which describe the hadronic structure of protons and nuclei are the critical link between the experimental data and the proposed theoretical models; hence, a better understanding of the PDFs is essential for improved pre- dictions. Nuclear PDFs, in particular, have proven valuable in this regard, especially for flavor differentiation. I introduce ”nCTEQ+LHC,” the first PDF set fit using the nCTEQ formalism to include data from the LHC. …

Muon-Neutrino Electron Elastic Scattering And A Search For The Muon-Neutrino Magnetic Moment In The Nova Near Detector, Biao Wang

Physics Theses and Dissertations

We use the NOvA near detector and the NuMI beam at Fermilab to study the neutrino-electron elastic scattering and the muon neutrino magnetic process beyond the Standard Model physics. The particle identifications of neutrino on electron elastic scattering are trained by using the multi-layer neural networks. This thesis provides a general discussion of this technique and shows a good agreement between data and MC for the neutrino-electron elastic weak scattering. By using 3.62e20 POT dataset in the NOvA near detector, we find 1.58e-9 Bohr magneton as the 90% C.L. upper limit. We also find a sensitivity of 8e-10 Bohr magneton …