No description available.

No description available.

No description available.

This thesis considers the search of charged Higgs bosons, which are predicted by several extensions of the Standard Model of particle physics. Light charged Higgs bosons (below the top quark mass) can appear in top quark decays and are assumed to decay exclusively to tauons. Two discriminating variables are presented that are sensitive to such a process taking place in top-antitop events with two final state leptons. Distributions of these variables are computed for Monte Carlo simulations and for 35/pb of data from 7 TeV proton-proton collisions recorded in 2010 by the ATLAS experiment at the LHC. Monte Carlo simulations are found to agree well with data, validating the use of these discriminating variables, but no conclusions about the existence of charged Higgs bosons can be made at this point.

No description available.

Thesis (M.S.)--Rochester Institute of Technology, 1989. / Includes bibliographical references.

No description available.

A fundamental problem in astrophysics is the interaction between space plasmas and energetic particles. Plasmas form the vast majority of space and can be found in any astrophysical environment, from the plasma of the solar wind to the interstellar medium for example. When plasmas stream through space, they give rise to turbulent magnetic fields. In addition, space is populated by energetic particles whose origins could be interplanetary, such as solar energetic particles generated by explosions on the surface of the Sun, or Galactic, such as cosmic rays generated by supernova remnants. As these particles propagate through interplanetary or interstellar space, they experience scattering due to magnetic turbulence. Describing these scattering effects, through the calculation of diffusion coefficients, is crucial to understanding several important processes in astrophysics. Such processes include particle acceleration at interplanetary shocks, solar modulation and space weather studies, and the motion of cosmic rays through galaxies. A test-particle code is developed to simulate the interaction of charged particles with turbulent magnetic fields. Diffusion coefficients along and across the mean magnetic field are calculated and compared with analytical theories and space mission measurements. Turbulence models with reduced dimensionality and full three-dimensional corresponding to different space settings are considered, including reproducing the magnetic turbulence in the solar wind and the interstellar medium. Wave propagation, dynamical effects, and unique turbulence setups such as noisy hydrodynamic models are also considered. We show that the influence of turbulence properties and various space regimes on transport parameters is minor and not as strong as originally thought. This points toward a universal transport behaviour of charged particles which motivates the employment of a comprehensive diffusion formula for different space settings. In addition, we were able for the first time to accurately describe the interaction between Galactic cosmic rays and dynamical solar wind turbulence to reproduce observational results of mean free paths. The validity of certain asymptotic limits for the parallel and perpendicular diffusion coefficients are examined. It is shown that only two parameters control those limits, namely the fundamental length scale of magnetic turbulence and the ratio of turbulence strength to the mean field. / February 2017

Collisionless turbulence is common in astrophysical magnetic fields and plasmas. The determination of the transport of high-energy charged particles both parallel and perpendicular to the average magnetic field in such a system is of considerable interest. It is recognized that the turbulent magnetic field has important effects on the transport of charged particles and that the properties of different turbulence models may significantly affect the resulting transport properties. A number of different magnetic turbulence models have been proposed in the last several decades. We present here the results of a study of charged particle transport in two new turbulent magnetic field models that have not been previously considered and include newly described characteristics. We investigate the effect of energetic charged particle motion in these new models. We use a method (D A Roberts, 2012) that optimizes phase angles of a set of circularly polarized, transverse modes with Kolmogorov power-law enveloped amplitudes to construct magnetic field fluctuations with nearly constant |B| but with large variances in the components Bx, By, Bz, as is observed in the Solar Wind. Charged particle scattering coefficients are determined through computer simulations. The results are compared with those from previous isotropic and composite turbulence models. We studied charged particle transport in the turbulent magnetic field with global anisotropy and compared with the isotropic turbulence. We found that the magnetic turbulence with global anisotropy and isotropy have similar effects on charged particle transport from 1𝑀𝑒𝑉 up to 10𝐺𝑒𝑉. We proposed a general framework for a multi-scale synthesis with the scale- dependent, localized anisotropic feature incorporated. We run test particle simula- tions in the field by the two-scale algorithm to calculate the transport coefficients for charged particles with different energies. We found that the local anisotropy has the significant difference from the previous model in the effect on charged particle transport. The parallel transport (𝑘∥) decreases while the perpendicular transport (𝑘⊥) increases compared with the isotropic and globally anisotropic field models, the difference is enhanced as the local anisotropy is enhanced, and there is an order of magnitude increase in the ratio of perpendicular to parallel transport coefficients. We proposed a simple power spectrum synthesis method based on the Fourier analysis to extract the large and small scale power spectrum from any single space- craft observation with a long enough period and a high sampling frequency. We applied the method to the solar wind measurement by the magnetometer onboard the ACE spacecraft and reconstructed the large scale isotropic 2D spectrum and the small scale anisotropic 2D spectrum.

<p>Conventional searches for the charged Higgs boson using its production in association with Standard Model (SM) quarks is notoriously weak in the mid-tanB range. Hoping to find an alternate channel to fill this gap, the production of the charged Higgs boson in association with supersymmetric squarks is studied. Using Monte Carlo generators the production at the LHC is simulated within the non universal Higgs mass model (NUHM). If the six parameters of the model (m₀, m_1/2, A₀, tanB, u, m_A) induce small masses of the stop, sbottom and charged Higgs, the production cross section can be of the order pb. Through scans of the input parameter the cross section is maximized, with the requirement that the stop decays directly to a neutralino - simplifying detection, in the point (m₀, m_1/2, A₀, tanB, u, m_A) = (190, 187, -1147, 179, 745, 13.2) where the cross section is 559 fb.</p><p>The production is compared to the irreducible backgrounds stop, stop, t, tbar and t, tbar + 2 jets. The former poses no severe constraints and can be easily removed using appropriate cuts. The latter, SM background, has a cross section almost 1000 times larger and strong cuts must be imposed to suppress it. Neglecting hadronization and systematic effects, we show that a 5 sigma discovery is possible at 133 fb^-1. In this range, mH+ = 194 GeV and tanB = 13.2, other channels have little or no prospects of detecting the charged Higgs and the studied process shows good prospects for complementing charged Higgs searches at the LHC in the mid-tanB range.</p>