Studying Gaugino Mass Unification at the LHC

We begin a systematic study of how gaugino mass unification can be probed at the CERN Large Hadron Collider (LHC) in a quasi-model independent manner. As a first step in that direction we focus our attention on the theoretically well-motivated mirage pattern of gaugino masses, a one-parameter family of models of which universal (high scale) gaugino masses are a limiting case. We improve on previous methods to define an analytic expression for the metric on signature space and use it to study one-parameter deviations from universality in the gaugino sector, randomizing over other soft supersymmetry-breaking parameters. We put forward three ensembles of observables targeted at the physics of the gaugino sector, allowing for a determination of this non-universality parameter without reconstructing individual mass eigenvalues or the soft supersymmetry-breaking gaugino masses themselves. In this controlled environment we find that approximately 80% of the supersymmetric parameter space would give rise to a model for which our method will detect non-universality in the gaugino mass sector at the 10% level with an integrated luminosity of order 10 inverse femptobarns. We discuss strategies for improving the method and for adding more realism in dealing with the actual experimental circumstances of the LHC

Identifying Supersymmetry at the CERN LHC and Indirect Dark Matter Detection Experiments

Supersymmetry (SUSY) remains the most well-motivated scenario for new physics beyond the Standard Model. There is strong reason to expect that if nature is supersymmetric it will be observed at the LHC. Consequently, searches for SUSY are among the primary tasks of the LHC program. However, much of this work focuses on scenarios such as mSUGRA, which include many simplifying assumptions. It is necessary, therefore, to consider the broader SUSY parameter space, and explore the implications of various other model choices on the spectrum of possible experimental signatures. This thesis addresses this phenomenologically challenging problem. We present several studies that examine the relationship between various SUSY scenarios and experimental phenomena, and introduce new techniques to extract meaningful information about fundamental parameters. First, we discuss identification of multiple top quark production from gluino decay at the LHC. We find that 4-top production can be discovered in excess of Standard Model backgrounds with ∼ 500 pb^−1 of data. We argue that statistical reconstruction of this scenario is extremely difficult due to large combinatorical uncertainty. We demonstrate a novel approach whereby information about the gluino decay fraction into top quarks may be extracted with low luminosity, thus providing early evidence for multi-top produc- tion. Next, we investigate the problem of identifying gaugino mass unification from LHC measurements. We consider mirage-mediation models, where gaugino mass universality is controlled by a single parameter α (α → 0 gives the universal limit). We show that that by utilizing a χ^2 -like metric on the signature space it is possible to detect non-universality to α ≃ 0.3 with only a few fb^−1 of data for the majority of the parameter space. Finally, we examine the excess positron flux reported by the HEAT, AMS, and PAMELA experiments. We argue that annihilation of light (200 GeV), non-thermally produced wino-like LSP WIMPs can explain the excesses. However we find this candidate does not convincingly model the recent PAMELA measurements if traditional astrophysical propagation parameters are assumed

Identifying Supersymmetry at the CERN LHC and Indirect Dark Matter Detection Experiments.

Supersymmetry (SUSY) remains the most well-motivated scenario for new physics beyond the Standard Model. There is strong reason to expect that if nature is supersymmetric it will be observed at the LHC. Consequently, searches for SUSY are among the primary tasks of the LHC program. However, much of this work focuses on scenarios such as mSUGRA, which include many simplifying assumptions. It is necessary, therefore, to consider the broader SUSY parameter space, and explore the implications of various other model choices on the spectrum of possible experimental signatures. This thesis addresses this phenomenologically challenging problem. We present several studies that examine the relationship between various SUSY scenarios and experimental phenomena, and introduce new techniques to extract meaningful information about fundamental parameters. First, we discuss identification of multiple top quark production from gluino decay at the LHC. We find that 4-top production can be discovered in excess of Standard Model backgrounds with ∼ 500 pb^−1 of data. We argue that statistical reconstruction of this scenario is extremely difficult due to large combinatorical uncertainty. We demonstrate a novel approach whereby information about the gluino decay fraction into top quarks may be extracted with low luminosity, thus providing early evidence for multi-top produc- tion. Next, we investigate the problem of identifying gaugino mass unification from LHC measurements. We consider mirage-mediation models, where gaugino mass universality is controlled by a single parameter α (α → 0 gives the universal limit). We show that that by utilizing a χ^2 -like metric on the signature space it is possible to detect non-universality to α ≃ 0.3 with only a few fb^−1 of data for the majority of the parameter space. Finally, we examine the excess positron flux reported by the HEAT, AMS, and PAMELA experiments. We argue that annihilation of light (200 GeV), non-thermally produced wino-like LSP WIMPs can explain the excesses. However we find this candidate does not convincingly model the recent PAMELA measurements if traditional astrophysical propagation parameters are assumed.Ph.D.PhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/63818/1/elementl_1.pd