Matching Items (7)

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True muonium on the light front

Description

The muon problem of flavor physics presents a rich opportunity to study beyond standard model physics. The as yet undiscovered bound state (μ+μ-), called true muonium, presents a unique opportunity

The muon problem of flavor physics presents a rich opportunity to study beyond standard model physics. The as yet undiscovered bound state (μ+μ-), called true muonium, presents a unique opportunity to investigate the muon problem. The near-future experimental searches for true muonium will produce it relativistically, preventing the easy application of non-relativistic quantum mechanics. In this thesis, quantum field theory methods based on light-front quantization are used to solve an effective Hamiltonian for true muonium in the Fock space of |μ+μ-> , |μ+μ-γ> , |e+e->, |e+e-γ>, |τ+τ-> , and |τ+τ-γ> . To facilitate these calculations a new parallel code, True Muonium Solver With Front-Form Techniques (TMSWIFT), has been developed. Using this code, numerical results for the wave functions, energy levels, and decay constants of true muonium have been obtained for a range of coupling constants α. Work is also presented for deriving the effective interaction arising from the |γγ sector’s inclusion into the model.

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  • 2016

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Faint relics of violent high energy physics in the early universe

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The work presented in this dissertation examines three different nonequilibrium particle physics processes that could play a role in answering the question “how was the particle content of today’s universe

The work presented in this dissertation examines three different nonequilibrium particle physics processes that could play a role in answering the question “how was the particle content of today’s universe produced after the big bang?” Cosmic strings produced from spontaneous breaking of a hidden sector $U(1)_{\rm X}$ symmetry could couple to Standard Model fields through Higgs Portal or Kinetic Mixing operators and radiate particles that contribute to the diffuse gamma ray background. In this work we calculate the properties of these strings, including finding effective couplings between the strings and Standard Model fields. Explosive particle production after inflation, known as preheating, would have produced a stochastic background of gravitational waves (GW). This work shows how the presence of realistic additional fields and interactions can affect this prediction dramatically. Specifically, it considers the inflaton to be coupled to a light scalar field, and shows that even a very small quartic self-interaction term will reduce the amplitude of the gravitational wave spectrum. For self-coupling $\lambda_{\chi} \gtrsim g^2$, where $g^2$ is the inflaton-scalar coupling, the peak energy density goes as $\Omega_{\rm GW}^{(\lambda_{\chi})} / \Omega_{\rm GW}^{(\lambda_{\chi}=0)} \sim (g^2/\lambda_{\chi})^{2}$. Finally, leptonic charge-parity (CP) violation could be an important clue to understanding the origin of our universe's matter-antimatter asymmetry, and long-baseline neutrino oscillation experiments in the coming decade may uncover this. The CP violating effects of a possible fourth ``sterile" neutrino can interfere with the usual three neutrinos; this work shows how combinations of various measurements can help break those degeneracies.

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Date Created
  • 2016

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Cosmological and astrophysical probes of physics beyond the standard model

Description

Cosmology, carrying imprints from the entire history of the universe, has emerged as a precise observational science over the past 30 years. It can probe physics beyond the Standard Model

Cosmology, carrying imprints from the entire history of the universe, has emerged as a precise observational science over the past 30 years. It can probe physics beyond the Standard Model at energy scales much higher than the weak scale. This thesis reports on some important probes of beyond standard model physics derived in a cosmological setting - (I) It is shown that primordial gravitational waves left over from inflation carry unique detectable CMB signatures for neutrino masses, axions and any other relativistic species that may have been present. (II) Higgs Inflation, the most popular and compelling inflation model with a higgs boson is studied next and it is shown that quantum effects have so far been incorrectly incorporated. A spurious gauge ambiguity arising from quantum effects enters the canonical prediction for observables in Higgs Inflation that must be addressed. (III) A new novel mechanism for generating the observed baryon asymmetry of the universe via decaying gravitinos is proposed. If the Supersymmetry (SUSY) breaking scale is high, then in the presence of R-parity violation, gravitinos can successfully reproduce the baryon asymmetry and evade all low energy constraints. (IV) The final chapter reports on a new completely general analysis of simplified models used in direct detection of dark matter. This is useful to explore what high energy physics constraints can be obtained from direct detection experiments.

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Date Created
  • 2015

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Direct dark matter detection phenomenology

Description

The identity and origin of dark matter is one of the more elusive mysteries in the fields of particle physics and cosmology. In the near future, direct dark matter detectors

The identity and origin of dark matter is one of the more elusive mysteries in the fields of particle physics and cosmology. In the near future, direct dark matter detectors will offer a chance at observing dark matter non-gravitationally for the first time. In this thesis, formalisms are developed to analyze direct detection experiments and to quantify the extent to which properties of the dark matter can be determined. A range of non-standard assumptions about the dark matter are considered, including inelastic scattering, isospin violation and momentum dependent scattering. Bayesian inference is applied to realistic detector configurations to evaluate parameter estimation and model selection ability.

A complete set of simplified models for spin-0, spin-1/2 and spin-1 dark matter candidates are formulated. The corresponding non-relativistic operators are found, and are used to derive observational signals for the simplified models. The ability to discern these simplified models with direct detection experiments is demonstrated. In the near future direct dark matter detectors will be sensitive to coherent neutrino scattering, which will limit the discovery potential of these experiments. It was found that eleven of the fourteen non-relativistic operators considered produce signals distinct from coherent scattering, and thus the neutrino background does not greatly affect the discovery potential in these cases.

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  • 2016

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Precision measurement of the radiative decay mode of the free neutron

Description

The theory of quantum electrodynamics predicts that beta decay of the neutron into a proton, electron, and anti-neutrino should be accompanied by a continuous spectrum of photons. A recent experiment,

The theory of quantum electrodynamics predicts that beta decay of the neutron into a proton, electron, and anti-neutrino should be accompanied by a continuous spectrum of photons. A recent experiment, RDK I, reported the first detection of radiative decay photons from neutron beta decay with a branching ratio of (3.09 ± 0.32) × 10-3 in the energy range of 15 keV to 340 keV. This was achieved by prompt coincident detection of an electron and photon, in delayed coincidence with a proton. The photons were detected by using a single bar of bismuth germanate scintillating crystal coupled to an avalanche photodiode. This thesis deals with the follow-up experiment, RDK II, to measure the branching ratio at the level of approximately 1% and the energy spectrum at the level of a few percent. The most significant improvement of RDK II is the use of a photon detector with about an order of magnitude greater solid angle coverage than RDK I. In addition, the detectable energy range has been extended down to approximately 250 eV and up to the endpoint energy of 782 keV. This dissertation presents an overview of the apparatus, development of a new data analysis technique for radiative decay, and results for the ratio of electron-proton-photon coincident Repg to electron-proton coincident Rep events.

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Created

Date Created
  • 2012

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Measurement of the branching ratio of Klong to pi0 nu nubar

Description

A search for Klong to pi0 nu nubar was performed on the initial Physics data taken by the KOTO collaboration by the 30-GeV proton synchrotron at JPARC, located in Tokai,

A search for Klong to pi0 nu nubar was performed on the initial Physics data taken by the KOTO collaboration by the 30-GeV proton synchrotron at JPARC, located in Tokai, Japan. The detector used in the experiment is an upgraded version of the E391 detector, KOTO's predecessor experiment performed at KEK. The analysis was performed on 2.49 E+11 ± (0.91%)stat ± (2.50%)syst kaon decays. The analysis uses Klong to 3pi0, Klong to 2pi0, and Klong to 2 gamma; for normalization and Monte Carlo validation. Based on my independent analysis, the single event sensitivity was determined to be 1.31 E-8 ± (1.22%)stat ± (7.12%)syst, comparable with the E391 result. An upper limit of 5.12 E-8 was measured for the Klong to pi0 nu nubar branching ratio at a 90% confidence level.

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Date Created
  • 2015

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Phenomenology of the N=3 Lee-Wick Standard Model

Description

With the discovery of the Higgs Boson in 2012, particle physics has decidedly moved beyond the Standard Model into a new epoch. Though the Standard Model particle content is now

With the discovery of the Higgs Boson in 2012, particle physics has decidedly moved beyond the Standard Model into a new epoch. Though the Standard Model particle content is now completely accounted for, there remain many theoretical issues about the structure of the theory in need of resolution. Among these is the hierarchy problem: since the renormalized Higgs mass receives quadratic corrections from a higher cutoff scale, what keeps the Higgs boson light? Many possible solutions to this problem have been advanced, such as supersymmetry, Randall-Sundrum models, or sub-millimeter corrections to gravity. One such solution has been advanced by the Lee-Wick Standard Model. In this theory, higher-derivative operators are added to the Lagrangian for each Standard Model field, which result in propagators that possess two physical poles and fall off more rapidly in the ultraviolet regime. It can be shown by an auxiliary field transformation that the higher-derivative theory is identical to positing a second, manifestly renormalizable theory in which new fields with opposite-sign kinetic and mass terms are found. These so-called Lee-Wick fields have opposite-sign propagators, and famously cancel off the quadratic divergences that plague the renormalized Higgs mass. The states in the Hilbert space corresponding to Lee-Wick particles have negative norm, and implications for causality and unitarity are examined.

This dissertation explores a variant of the theory called the N = 3 Lee-Wick

Standard Model. The Lagrangian of this theory features a yet-higher derivative operator, which produces a propagator with three physical poles and possesses even better high-energy behavior than the minimal Lee-Wick theory. An analogous auxiliary field transformation takes this higher-derivative theory into a renormalizable theory with states of alternating positive, negative, and positive norm. The phenomenology of this theory is examined in detail, with particular emphasis on the collider signatures of Lee-Wick particles, electroweak precision constraints on the masses that the new particles can take on, and scenarios in early-universe cosmology in which Lee-Wick particles can play a significant role.

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Date Created
  • 2015