F-theory Yukawa couplings and supersymmetric quantum mechanics

The localized fermions on the intersection curve Σ of D7-branes, are connected to a N=2 supersymmetric quantum mechanics algebra. Due to this algebra the fields obey a global U(1) symmetry. This symmetry restricts the proton decay operators and the neutrino mass terms. Particularly, we find that several proton decay operators are forbidden and the Majorana mass term is the only one allowed in the theory. A special SUSY QM algebra is studied at the end of the paper. In addition we study the impact of a non-trivial holomorphic metric perturbation on the localized solutions along each matter curve. Moreover, we study the connection of the localized solutions to an N=2 supersymmetric quantum mechanics algebra when background fluxes are turned on.     

Model-independent determination of the top Yukawa coupling from LHC and ILC

We show how a measurement of the process pp→tt̄H⁰+X at the Large Hadron Collider (LHC) and a measurement of the Higgs boson branching ratios BR(H⁰→bb̄) and BR(H⁰→W⁺W^-) at a future linear electron positron collider (ILC) can be combined to extract a value of the top quark Yukawa coupling in a model-independent way. We find that for masses with 120 GeV/c²<m_H<200 GeV/c² a measurement precision of 15% including systematic uncertainties can be achieved for integrated luminosities of 300 fb^-1 at the LHC and 500 fb^-1 at the ILC at a centre-of-mass energy of 350 GeV.     

Strong coupling effects in binary Yukawa systems

We analyze the acoustic collective excitations in two- and three-dimensional binary Yukawa systems, consisting of two components with different masses. A theoretical analysis reveals a profound difference between the weakly and strongly correlated limits: at weak coupling the two components interact via the mean field only and the oscillation frequency is governed by the light component. In the strongly correlated limit the mode frequency is governed by the combined mass, where the heavy component dominates. Computer simulations in the full coupling range extend and confirm the theoretical results.     

Yukawa coupling structure in intersecting D-brane models

The structure of Yukawa coupling matrices is investigated in type IIA T ⁶/(Z₂ x Z₂) orientifold models with intersecting D-branes. Yukawa coupling matrices are difficult to be made realistic in conventional models in which the generation structure emerges by the multiple intersection of D-branes in the factorized T ⁶ = T ² x T ² x T ². We study the new type of flavor structure, where Yukawa couplings are dynamically generated, and show this type of models lead to non-trivial structures of Yukawa coupling matrices, which can be realistic.Received: 8 December 2004, Revised: 22 December 2004, Published online: 9 March 2005     

Fermion masses in a strong Yukawa coupling model

For strong enough Yukawa coupling the electroweak standard model fermion finds it energetically advantageous to transform itself into a bound state in the hedgehog background of the Higgs field in the semiclassical approximation. By considering that the bound states give the masses for the lepton and quark, it is found that all fermion masses can be described by the strongly Yukawa coupling constants which tend to a unitary constant.     

Measuring the top Yukawa coupling to a heavy Higgs Boson at future e(+)e(-) linear colliders

If the Higgs boson mass is greater than 350 GeV, the top quark Yukawa coupling can be determined using the Higgs resonant contribution to t&tmacr; production from W+W- fusion at high energy e(+)e(-) linear colliders. We have evaluated the significance with which the signal of a Higgs decaying to t&tmacr; pairs could be observed at future e(+)e(-) colliders, with center of mass energies of 800 GeV and 1 TeV, and an integrated luminosity of 1 ab(-1). We find that a signal significance greater than 5sigma and a relative error in the top Yukawa measurement better than 10% can be achieved at these facilities, for Higgs boson masses in the ranges of 350-500 GeV and 350-650 GeV, respectively.     

Yukawa coupling of quantum fields in two dimensions. I

A renormalization procedure is proposed. It gives rigorous mathematical meaning to the infinite cancellations in this model. A space cutoff is introduced in the interaction termV and soV has the form , but there are no momentum cutoffs inV. There is an infinite constant and an infinite boson mass renormalization in this model. The main result is that the renormalized Hamiltonian is rigorously defined as a bilinear form in the Fock Hilbert space.This work was supported in part by the National Science Foundation, GP-6165.     

F-theory and the Witten index

We connect the fermionic fields, localized on the intersection curve Σ   of two D7-branes with zero background flux, to a N=2$N=2$ supersymmetric quantum mechanics algebra, within the theoretical framework of F-theory.     

The Yukawa coupling of quantum fields in two dimensions. II

The Yukawa coupling in two dimensional space time is considered. A space outoff is introduced in the interaction termV, so that the renormalized HamiltonianH _ren is a rigorously defined bilinear form in the Fock Hilbert space. The main result is thatH _ren is positive provided the finite part of the renormalization terms are suitably chosen. As a consequence, the Schrödinger equation (i/t–H _ren)=0 can be solved.This work was supported in part by the National Science Foundation, GP — 6165.     

Testing the supersymmetric QCD Yukawa coupling in a combined LHC/ILC analysis

In order to establish supersymmetry (SUSY) at future colliders, the identity of gauge couplings and the corresponding Yukawa couplings between gauginos, sfermions and fermions needs to be verified. A first phenomenological study for determining the Yukawa coupling of the SUSY-QCD sector is presented here, using a method which combines information from LHC and ILC.      

Threshold effects in SUSY and non-SUSY GUTs

We discuss recent contributions on threshold effects in grand unfiied theories including minimal SUSY SU (5), non-SUSY modifications of the grand desert in SU(5) and SO(10), and SO(10) with single intermediate symmetires. Consequences of theorems on vanishing GUT-scale corrections to sin² θ_w in SO(10) with SU(2) _L XSU(2) _R XSU(4) _c (g_2l =g_2R ) intermediate symmetry are discussed and vanishing corrections on the inter-mediate scale are explicitly demonstrated where predictions are more precise. Threshold and higher dimensional operator effects in SUSY SU(5) recently derived by a number of authors are presented.     

An operator approach to the strong coupling transmutation of a Yukawa interaction

It is shown that the transmutation mechanism introduced in our earlier papers is both necessary and sufficient to ensure the equivalence of the Lee model and the attractive separable potential model in all sectors when the bare coupling constant of the Lee model is taken to infinity. It is demonstrated that the hamiltonian operator for the Lee model reduces to that for the separable potential. It is further demonstrated that in the same limit the finite energy eigenfunctions, and hence the scattering amplitudes and the S-matrix calculated from the two theories coincide in all sectors.     

Particle spectrum in the modified nonminimal supersymmetric standard model in the strong Yukawa coupling regime

A theoretical analysis of solutions of renormalization group equations in the minimal supersymmetric standard model, which lead to a quasi-fixed point has shown that the mass of the lightest Higgs boson in these models does not exceed 94 ± 5 GeV. This implies that a considerable part of the parameter space in the minimal supersymmetric model is in fact eliminated by existing LEPII experimental data. In the nonminimal supersymmetric standard model the upper bound on the mass of the lightest Higgs boson reaches its maximum in the strong Yukawa coupling regime when the Yukawa constants are substantially greater than the gauge constants on the grand unification scale. In the present paper the particle spectrum is studied using the simplest modification of the nonminimal supersymmetric standard model which gives a self-consistent solution in this region of parameter space. This model can give m _h ～ 125 GeV even for comparatively low values of β ≥ 1.9. The spectrum of Higgs bosons and neutralinos is analyzed using the method of diagonalizing mass matrices proposed earlier. In this model the mass of the lightest Higgs boson does not exceed 130.5 ± 3.5 GeV.