881293
Minimal spontaneously broken hidden sector and its impact on Higgs boson physics at the CERN Large Hadron Collider
Little experimental data bears on the question of whether there is a spontaneously broken hidden sector that has no Standard Model quantum numbers. Here we discuss the prospects of finding evidence for such a hidden sector through renormalizable interactions of the Standard Model Higgs boson with a Higgs boson of the hidden sector. We find that the lightest Higgs boson in this scenario has smaller rates in standard detection channels, and it can have a sizeable invisible final state branching fraction. Details of the hidden sector determine whether the overall width of the lightest state is smaller or larger than the Standard Model width. We compute observable rates, total widths and invisible decay branching fractions within the general framework. We also introduce the 'A-Higgs Model', which corresponds to the limit of a hidden sector Higgs boson weakly mixing with the Standard Model Higgs boson. This model has only one free parameter in addition to the mass of the light Higgs state and it illustrates most of the generic phenomenology issues, thereby enabling it to be a good benchmark theory for collider searches. We end by presenting an analogous supersymmetry model with similar phenomenology, which involves hidden sector Higgs bosons interactingmore » with MSSM Higgs bosons through D-terms.« less
9265646
The Two-loop Hemisphere Soft Function
The hemisphere soft function is calculated to order alpha_s^2. This is the first multi-scale soft function calculated to two loops. The renormalization scale dependence of the result agrees exactly with the prediction from effective field theory. This fixes the unknown coefficients of the singular parts of the two-loop thrust and heavy-jet mass distributions. There are four such coefficients, for 2 event shapes and 2 color structures, which are shown to be in excellent agreement with previous numerical extraction. The asymptotic behavior of the soft function has double logs in the CF CA color structure, which agree with non-global log calculations, but also has sub-leading single logs for both the CF CA and CF TF nf color structures. The general form of the soft function is complicated, does not factorize in a simple way, and disagrees with the Hoang-Kluth ansatz. The exact hemisphere soft function will remove one source of uncertainty on the alpha_s fits from e+e- event shapes.
118554212
One-Loop Maximally Supersymmetric Yang-Mills Scattering Amplitudes to All Orders in the Spacetime Dimension
OF THE DISSERTATION ONE-LOOP MAXIMALLY SUPERSYMMETRIC YANG-MILLS SCATTERING AMPLITUDES TO ALL ORDERS IN THE SPACETIME DIMENSION by ROBERT MORTON SCHABINGER Dissertation Director: Matthew J. Strassler In this thesis we discuss in detail computational methods and new results for one-loop virtual corrections to N = 4 super Yang-Mills scattering amplitudes calculated to all orders in , the dimensional regularization parameter. It is often the case that one-loop gauge theory computations are carried out toO( 0), since higher order in contributions vanish in the → 0 limit. We will show, however, that the higher order contributions are actually quite useful. In the context of maximally supersymmetric Yang-Mills, we consider two examples in detail to illustrate our point. First we will concentrate on computations with gluonic external states and argue thatN = 4 supersymmetry implies a simple relation between all-orders-inone-loop N = 4 super Yang-Mills amplitudes and the first and second stringy corrections to analogous tree-level N = 4 amplitudes. For our second example we will derive a new result for the all-orders-inone-loop superamplitude for planar six-particle NMHV scattering, an object which allows one to easily obtain six-point NMHV amplitudes with arbitrary external states. To make the presentation as self-contained as possible, we extensively review the prerequisites necessary to understand the main results of this thesis.