Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 89 for “"leptons"”.
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The first second of leptons
We study the influence of lepton asymmetries on the evolution of the early Universe. The lepton asymmetry l is poorly constrained by observations and might be orders of magnitudes larger than the observed baryon asymmetry b~O(10^{-10}), |l|/b~O(10^9). We find that lepton asymmetries large compared …
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Composite models of quarks and leptons
… constraints on composite models of quarks and leptons. Some dynamical mechanisms for chiral symmetry breaking in chiral preon models are discussed. We have constructed several "realistic candidate" chiral preon models satisfying complementarity between the Higgs and confining phases. The models …
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Probing New Physics Through Third Generation Leptons
… lepton, it has the largest coupling ( among the leptons) to the Higgs boson in the Standard Model (SM). New physics contributions to the tau-neutrino nucleon scattering were considered. Charged Higgs and W' effects to the deep inelastic scattering ντ ( [special character omitted]τ) + N → τ− (τ+) …
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A search for heavy leptons using a differential Cherenkov counter
A search for heavy leptons has been performed at the Brookhaven National Laboratory Alternating Gradient Synchrotron. Particular emphasis has been placed on the possible existence of leptons with mass slightly less than the K meson mass. The experiment used a high resolution differential Cherenkov …
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A measurement of the relative decay rate of the charm quark into leptons
The inclusive rate of leptons produced from charmed particle decays (from Z -> charm anticharm) has been measured using a data sample of four million hgadronic Z decays recorded by the ALEPH experiment at LEP from 1991 to 1995. The analysis uses a double-tag and is self-calibrating, i.e. it makes …
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Search for exotic Higgs boson decays to four leptons with the ATLAS detector
… analyses for exotic Higgs bosons decaying into leptons, which are $H\rightarrow2a\rightarrow4\mu$ and $H\rightarrow2a\rightarrow4\tau$, and target the mass ranges of $1<m_a<15\text{ GeV}$ and $15<m_a<60\text{ GeV}$. Various data-driven techniques are developed and used to estimate the background …
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Search for the Higgs boson in its decay into tau leptons at CMS
A search for the Standard Model Higgs boson in the H --> rr channel is presented. The search is performed on proton collision data collected by the Compact Muon Solenoid at the Large Hadron Collider. The data corresponds to 4.9 fb-1 of proton collisions at [square root of]s = 7 TeV and 19.5 fb-1 at …
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Measurement of Higgs couplings to top quarks and τ leptons with the ATLAS detector
… The study of Higgs decays involving τ leptons is expanded upon with the measurement of the pp → H → ττ cross section using the full Run 2 dataset, and a new method to estimate the largest background to this measurement is introduced. The improvement in the precision of pp → H → ττ …
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Identifying fake leptons in ATLAS while hunting SUSY in 8 TeV proton-proton collisions
… of SUSY; events containing two like-charge leptons (e or μ). This signature benefits from having both low Standard Model backgrounds as well as potential to observe several SUSY scenarios, par- ticularly those involving strong production processes. These include pair production of squarks …
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Search the decay of the B meson to two leptons at the Belle Experiment
The set of decays known as B⁰ → l⁺l⁻ are exceedingly rare. This thesis details procedures developed to optimize signal extraction and improve the upper limit on the measured branching fraction. When applied to 85 million BB events collected at the Belle experiment in Tsukuba, Japan, the resulting …
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Analysis of Events with Isolated Leptons and Missing Transverse Momentum in ep Collisions at HERA
A study of events with isolated leptons and missing transverse momentum in ep collisions is presented. Within the Standard Model (SM) such topologies are expected mainly from production of real W bosons with subsequent leptonic decay. This thesis continues the analysis of such events done in the …
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Two leptons, jets, and missing transverse momentum in ATLAS: yet more non-evidence for supersymmetry
Searching for new phenomena is an essential endeavour of experimental physics, and is helped by guidance from plausible theoretical predictions. This thesis presents such a search for signals of high-energy protons scattering to massive resonances with dramatic decays, which are predicted by …
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Vertex based missing mass calculator for 3-prong hadronically decaying tau leptons in the ATLAS detector
… consist of studies and analyses relating to tau leptons. The first main section contains work on the identification of hadronically decaying tau leptons, and my specific contribution the electron veto. This work involved improving the choice of variables to discriminate against electrons that had …
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Search for flavor changing neutral currents in top quark decays using a two-leptons+track selection
… t->Zq. Only the decays of the Z-boson to charged leptons and leptonic W-boson decays are considered signal. The search uses an event selection with two identified leptons (electrons and/or muons) and one lepton selected via inner-detector track requirements only (track lepton). Backgrounds to the …
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Beyond the standard model searches with b-jets and hadronically decaying τ-leptons with the ATLAS detector
… document is on the final state where both τ -leptons decay hadronically. The search is performed using 36.1 fb−1 of data collected by the ATLAS detector in proton-proton collisions at a centre-of-mass energy of 13 TeV during 2015 and 2016. The cross-section for non-resonant di-Higgs production …
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Holly Pacey and the Half-Spin Particles: Searching for new physics with leptons at the ATLAS experiment
… the Standard Model in collision events with two leptons in the final state. The first two searches seek electroweak supersymmetry, using 80.5 fb⁻¹ and the full 139.5 fb⁻¹ of the ATLAS Run 2 dataset, respectively. The first search placed the first ATLAS Run 2 limits on chargino pair production …
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Search for new physics in events with high transverse momentum leptons with the CMS detector at the LHC
En esta tesis se presentan medidas de procesos del SM y búsquedas de procesos BSM en sucesos con leptones de alto momento medidos en el detector CMS del LHC. Los estudios se realizan con datos correspondientes a colisiones protón-protón a √s=13
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Searches for supersymmetric particles in events with two opposite-sign same-flavor leptons, jets, and large missing transverse energy
… with jets (Z + jets), where Z decays to two leptons. In addition to the jet mismeasurement, the artificial MET in Z + jets events also convolves the mismeasurement of lepton energy, which becomes significantly important when the lepton is highly boosted. A data-driven method is developed …
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Electroweak physics and evidence for a Higgs boson decaying to a pair of tau leptons with the CMS detector
… electroweak interactions using final states with leptons in proton-proton collisions at the Large Hadron Collider at [square root of] s = 7 TeV, [square root of] s = 8 TeV, and [square root of] s = 13 TeV center-of-mass energies are described. Measurements of total inclusive and fiducial W and Z …
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