118081166
Renormalization in supersymmetric models
There are reasons to believe that the Standard Model is only an effective theory, with new Physics lying beyond it. Supersymmetric extensions are one possibility: they address some of the Standard Model's shortcomings, such as the instability of the Higgs boson mass under radiative corrections. In this thesis, some topics related to the renormalization of supersymmetric models are analyzed. One of them is the automatic computation of the Lagrangian and the renormalization group equations of these models, which is a hard and error-prone process if carried out by hand. The generic renormalization group equations themselves are extended so as to include those models which have more than a single abelian gauge factor group. Such situations can occur in grand unified theories, for example. For a wide range of SO(10)-inspired supersymmetric models, we also show that the renormalization group imprints on sparticle masses some information on the higher energies behavior of the models. Finally, in some cases these theories introduce charged lepton flavor violating interactions, which can change the ratio $\Gamma\left(K\rightarrow e\nu\right)/\Gamma\left(K\rightarrow\mu\nu\right)$. In light of experimental bounds on other observables, our analysis shows that any change over the Standard Model prediction must be smaller than the current experimental sensitivity on this observable.
118680546
Revisiting the $\Gamma(K \to e \nu)/\Gamma(K \to \mu \nu)$ ratio in supersymmetric unified models
It has been pointed out that supersymmetric extensions of the Standard Model can induce significant changes to the theoretical prediction of the ratio $\Gamma(K\rightarrow e\nu)/\Gamma (K\rightarrow\mu\nu)\equiv R_{K}$, through lepton flavour violating couplings. In this work we carry out a full computation of all one-loop corrections to the relevant $\nu\ell H^{+}$ vertex, and discuss the new contributions to $R_{K}$ arising in the context of different constrained (minimal supergravity inspired) models which succeed in accounting for neutrino data, further considering the possibility of accommodating a near future observation of a $\mu\to e\gamma$ transition. We also re-evaluate the prospects for $R_{K}$ in the framework of unconstrained supersymmetric models. In all cases, we address the question of whether it is possible to saturate the current experimental sensitivity on $R_{K}$ while in agreement with the recent limits on $B$-meson decay observables (in particular BR($B_{s}\to\mu^+\mu^-$) and R($B_{u}\to\tau\nu$)), as well as BR($\tau\to e \gamma$) and available collider constraints. Our findings reveal that in view of the recent bounds, and even when enhanced by effective sources of flavour violation in the right-handed $\tilde{e}-\tilde{\tau}$ sector, constrained supersymmetric (seesaw) models typically provide excessively small contributions to $R_{K}$. Larger contributions can be found in more general settings, where the charged Higgs mass can be effectively lowered, and even further enhanced in the unconstrained MSSM. However, our analysis clearly shows that even in this last case SUSY contributions to $R_{K}$ are still unable to saturate the current experimental bounds on this observable, especially due to a strong tension with the $B_{u}\to\tau\nu$ bound.
31040253
Calculating the renormalisation group equations of a SUSY model with Susyno
Susyno is a Mathematica package dedicated to the computation of the 2-loop renormalisation group equations of a supersymmetric model based on any gauge group (the only exception being multiple U(1) groups) and for any field content. Supersymmetry (SUSY) is an elegant and well known extension of the Standard Model (SM) which aims at solving or softening some of the SM theoretical and experimental shortcomings. Supersymmetric models based on Grand Unified Theories (GUTs) offer the appealing feature of being described by a unique gauge group and coupling constant; furthermore, the potential new superfields, as well as their dynamics, can provide answers to fundamental problems. For example SO(10) based models offer a natural explanation for neutrino masses and mixings via a type-I seesaw. This occurs since the spinor representation of the group contains a SM singlet superfield (with the appropriate quantum numbers). Even larger and/or more complex groups are often considered, for example E6 in string inspired models. The analysis of the theoretical and phenomenological implications of SUSY GUT models requires a careful study of the evolution of the fundamental parameters from the high-energy scale down to the electroweak scale, at which observables are computed and constraints applied. As such, knowledge of the renormalisation group equations (RGEs) is necessary. Although the RGEs of several models (e.g., MSSM, NMSSM) are already known [1, 3], for other SUSY extensions of the SM complicated general equations must be used [1, 2]. Here we describe Susyno, a Mathematica-based package that addresses this issue. The program takes as input the gauge group, the representations (i.e., the chiral superfield content), the number of flavours/copies 1 of each representation, and any abelian discrete symmetries (e.g., R-parity). Susyno then constructs the most general superpotential and soft SUSY breaking Lagrangian consistent with the field content and symmetries imposed. Once these elements have been derived, Susyno then computes the 2-loop �-functions of all the parameters of the model, which is its main output.
199681250
Running soft parameters in SUSY models with multiple U(1) gauge factors
The two-loop renormalization group equations for the parameters of softly broken supersymmetric gauge theories given in the literature are generalized to the case when the gauge group contains more than a single abelian factor. This contribution to the proceedings of the DISCRETE 2012 symposium is based on reference [1].
18372583
Interpenetrating Plasma Shells: Near-Equipartition Magnetic Field Generation and Nonthermal Particle Acceleration
We present the first three-dimensional fully kinetic electromagnetic relativistic particle-in-cell simulations of the collision of two interpenetrating plasma shells. The highly accurate plasma-kinetic particle-in-cell (with the total of 108 particles) parallel code OSIRIS has been used. Our simulations show (1) the generation of long-lived near-equipartition (electro)magnetic fields, (2) nonthermal particle acceleration, and (3) short-scale to long-scale magnetic field evolution, in the collision region. Our results provide new insights into the magnetic field generation and particle acceleration in relativistic and subrelativistic colliding streams of particles, which are present in gamma-ray bursters, supernova remnants, relativistic jets, pulsar winds, etc.
28592387
Ion motion in self-modulated plasma wakefield accelerators.
The effects of plasma ion motion in self-modulated plasma-based accelerators are examined. An analytical model describing ion motion in the narrow beam limit is developed and confirmed through multidimensional particle-in-cell simulations. It is shown that the ion motion can lead to the early saturation of the self-modulation instability and to the suppression of the accelerating gradients. This can reduce the total energy that can be transformed into kinetic energy of accelerated particles. For the parameters of future proton-driven plasma accelerator experiments, the ion dynamics can have a strong impact. Possible methods to mitigate the effects of the ion motion in future experiments are demonstrated.
90988
Near-GeV acceleration of electrons by a nonlinear plasma wave driven by a self-guided laser pulse.
The acceleration of electrons to approximately 0.8 GeV has been observed in a self-injecting laser wakefield accelerator driven at a plasma density of 5.5x10(18) cm(-3) by a 10 J, 55 fs, 800 nm laser pulse in the blowout regime. The laser pulse is found to be self-guided for 1 cm (>10zR), by measurement of a single filament containing >30% of the initial laser energy at this distance. Three-dimensional particle in cell simulations show that the intensity within the guided filament is amplified beyond its initial focused value to a normalized vector potential of a0>6, thus driving a highly nonlinear plasma wave.
205893777
Implementation of a hybrid particle code with a PIC description in r-z and a gridless description in ϕ into OSIRIS
For many plasma physics problems, three-dimensional and kinetic effects are very important. However, such simulations are very computationally intensive. Fortunately, there is a class of problems for which there is nearly azimuthal symmetry and the dominant three-dimensional physics is captured by the inclusion of only a few azimuthal harmonics. Recently, it was proposed 1 to model one such problem, laser wakefield acceleration, by expanding the fields and currents in azimuthal harmonics and truncating the expansion. The complex amplitudes of the fundamental and first harmonic for the fields were solved on an r-z grid and a procedure for calculating the complex current amplitudes for each particle based on its motion in Cartesian geometry was presented using a Marder's correction to maintain the validity of Gauss's law. In this paper, we describe an implementation of this algorithm into OSIRIS using a rigorous charge conserving current deposition method to maintain the validity of Gauss's law. We show that this algorithm is a hybrid method which uses a particles-in-cell description in r-z and a gridless description in �. We include the ability to keep an arbitrary number of harmonics and higher order particle shapes. Examples for laser wakefield acceleration, plasma wakefield acceleration, and beam loading are also presented and directions for future work are discussed.
53520094
Acceleration in perpendicular relativistic shocks for plasmas consisting of leptons and hadrons
We investigate the acceleration of light particles in perpendicular shocks for plasmas consisting of a mixture of leptonic and hadronic particles. Starting from the full set of conservation equations for the mixed plasma constituents, we generalize the magnetohydrodynamical jump conditions for a multi-component plasma, including information about the specific adiabatic constants for the different species. The impact of deviations from the standard model of an ideal gas is compared in theory and particle-in-cell simulations, showing that the standard MHD model is a good approximation. The simulations of shocks in electron-positron-ion plasmas are for the first time multi-dimensional, transverse effects are small in this configuration, and one-dimensional (1D) simulations are a good representation if the initial magnetization is chosen high. 1D runs with a mass ratio of 1836 are performed, which identify the Larmor frequency {omega}{sub ci} as the dominant frequency that determines the shock physics in mixed component plasmas. The maximum energy in the non-thermal tail of the particle spectra evolves in time according to a power law {proportional_to}t{sup {alpha}} with {alpha} in the range 1/3 < {alpha} < 1, depending on the initial parameters. A connection is made with transport theoretical models by Drury and Gargate and Spitkovsky, whichmore » predict an acceleration time {proportional_to}{gamma} and the theory for small wavelength scattering by Kirk and Reville, which predicts a behavior rather as {proportional_to}{gamma}{sup 2}. Furthermore, we compare different magnetic field orientations with B{sub 0} inside and out of the plane, observing qualitatively different particle spectra than in pure electron-ion shocks.« less