Higgs phenomenon in string theories

We show how to construct consistent four-dimensional string theories in the spontaneously broken, Higgs phase. The symmetry breaking scale is a free, classically undetermined parameter, due to the existence of flat directions in the scalar potential.     

Global symmetry restoration in high temperature Higgs theories

A simple high temperature expansion is developed for lattice gauge theories with scalar matter fields. The expansion is used to prove the absence of global symmetry breaking for sufficiently high temperature.Research supported in part by U.S. National Science Foundation grant PHY 8117463Research supported in part by the Department of Energy under grant No. DE-AC02-76ER03072Alfred P. Sloan Research Fellow     

Fermion and Higgs masses as probes of unified theories

The effects of Yukawa couplings of order of the gauge couplings in the SU(3) × SU(2) × U(1) renormalization group equations governing the evolution of observable parameters such as $\text{m}{}_{\mathrm{<mtext>b</mtext>}}\text{m}{}_{\mathrm{\tau }}$ and the Higgs mass are studied systematically to one-loop order. These parameters are found to give useful constraints on the mass of the t quark, and of possible heavier fermion families, in theories with SU(5)-like boundary conditions at unification energies.     

Charge quantization in theories with an adjoint representation Higgs mechanism

Gauge theories are considered in which an overall simple gauge symmetry group G is broken, by a Higgs field in the adjoint representation, to an exact symmetry with a structure locally of the form U(1)×K. Necessary and sufficient conditions on the Higgs field for K to be semisimple are given, together with an algorithm for determining K from the Dynkin diagram. The theory of weight lattices is used to show that both the electric and magnetic charges are multiples of certain basic units. These are calculated and related to each other by formulae more precise than quantization conditions given previously. It is shown that globally the exact symmetry group has the form $\text{H}\text{=(}\text{U}\text{(1)×}\text{K}\text{)/}\text{Z}$, where $\text{K}$ is simply connected (assuming G is) and Z is a cyclic group whose order can be calculated from the Dynkin diagram.     

The extended Higgs system in R-symmetric supersymmetry theories

The Higgs sector is extended in R  -symmetric supersymmetry theories by two iso-doublets R_d,u$R_{d,u}$ which complement the standard iso-doublets H_d,u$H_{d,u}$. We have analyzed masses and interactions of these novel states and describe their [non-standard] decay modes and their production channels at the LHC and e⁺e⁻$e^{+}{e}^{-}$ colliders.     

Purely transmitting defect field theories

We define an infinite class of integrable theories with a defect which are formulated as chiral defect perturbations of a conformal field theory. Such theories are massless in the bulk and are purely transmitting through the defect. The integrability of these theories requires the introduction of defect degrees of freedom. Such degrees of freedom lead to a novel set of Yang-Baxter equations. The defect degrees of freedom are identified through folding the chiral defect theories onto massless boundary field theories. The examples of the sine-Gordon theory and Ising model are worked out in some detail.     

Study on the Effects of the Light CP-odd Higgs via the Leptonic Decays of Pseudoscalar Mesons

To explain the anomalously large decay rate of Σ+→ p+μ+μ- , it was proposed that a new mechanism where a light CP-odd pseudoscalar boson of mA10 = 214.3 MeV makes a crucial contribution. Later, some authors have studied the transition π0→e+e- and Υ→γA10 in terms of the same mechanism and their result indicates that with the suggested mass one cannot fit the data. This discrepancy might be caused by experimental error of Σ+→p+μ+μ- because there were only a few events. Whether the mechanism is a reasonable one motivates us to investigate the transitions π0→e+e-; η(η′) →μ+μ- ; ηc→μ+μ- ;ηb→τ+τ- within the same framework. It is noted that for π0→e+e-, the standard model (SM) prediction is smaller than the data, whereas the experimental central value of η→μ+μ- is also above the SM prediction. It means that there should be extra contributions from other mechanisms and the contribution of A10 may be a possible one. Theoretically calculating the branching ratios of the concerned modes, we would check if we can obtain a universal mass for A10 which reconcile the theoretical predictions and data for all the modes. Unfortunately, we find that it is impossible to have such a mass with the same coupling |ge|. Therefore we conclude that the phenomenology does not favor such a light A10 , even though a small window is still open.     

Coulomb branch Hilbert series and three dimensional Sicilian theories

Journal of High Energy Physics - We find both analytical and numerical solutions of SU(2) Yang-Mills with an adjoint Higgs field within both closed and open tubes whose sections are spherical caps....     

Study on the Effects of the Light CP-odd Higgs via the Leptonic Decays of Pseudoscalar Mesons

To explain the anomalously large decay rate of Σ⁺→p+μ⁺μ^-, it was proposed that a new mechanism where a light CP-odd pseudoscalar boson of m_A1⁰=214.3 MeV makes a crucial contribution. Later, some authors have studied the transition π⁰→ e⁺e^- and r → γA₁⁰ in terms of the same mechanism and their result indicates that with the suggested mass one cannot fit the data. This discrepancy might be caused by experimental error of Σ⁺→ p+μ⁺μ^- because there were only a few events. Whether the mechanism is a reasonable one motivates us to investigate the transitions π⁰→ e⁺e^-;η(η')→ μ⁺μ^-; η_c→ μ⁺μ^-; η_b→τ⁺τ^- within the same framework. It is noted that for π⁰→ e⁺e^-, the standard model (SM) prediction is smaller than the data, whereas the experimental central value of η→μ⁺μ^- is also above the SM prediction. It means that there should be extra contributions from other mechanisms and the contribution of A₁⁰ may be a possible one. Theoretically calculating the branching ratios of the concerned modes, we would check if we can obtain a universal mass for A₁⁰ which reconcile the theoretical predictions and data for all the modes. Unfortunately, we find that it is impossible to have such a mass with the same coupling |gl|. Therefore we conclude that the phenomenology does not favor such a light A₁⁰, even though a small window is still open.     

The Higgs sector of supersymmetric theories and the implications for high-energy colliders

One of the main motivations for low-energy supersymmetric theories is their ability to address the hierarchy and naturalness problems in the Higgs sector of the standard model. In these theories, at least two doublets of scalar fields are required to break the electroweak symmetry and to generate the masses of the elementary particles, resulting in a rather rich Higgs spectrum. The search for the Higgs bosons of supersymmetry and the determination of their basic properties is one of the major goals of high-energy colliders and, in particular, the LHC, which will soon start operation. We review the salient features of the Higgs sector of the minimal supersymmetric standard model and of some of its extensions and summarize the prospects for probing them at the LHC and at the future ILC. In memoriam of Julius Wess, 1934–2007.