Jisuke Kubo

Higgs and top mass from reduction of couplings

Abstract We reduce the couplings in the standard model with one Higgs doublet and n generations and obtain for three generations 61 GeV and 81 GeV for the mass of the Higgs particle and the top quark respectively. The error is estimated to be about 10–15%.

Reduction of couplings and heavy top quark in the minimal SUSY GUT

Abstract Out of 256 independent reduction solutions that can be found within the minimal supersymmetric SU(5) GUT, there are exactly two asymptotically free solutions which can restrict the top quark mass m t and do not contradict the observed mass spectrum of the first two fermion generations. A numerical analysis shows that these two solutions lie on the same renormalization group invariant surface on which m t and the bottom quark mass m b assume relatively stable values for a given supersymmetry breaking scale m SUSY = 200 GeV with α S ( M Z ) = 0.12, α em ( M Z ) = (127.9) −1 and m τ = 1.78 GeV fixed, we find that on this surface m t and m t vary 2% and 3% around their central values 182 GeV and 5.3 GeV, respectively.

The radiative photino decay into a higgsino

Abstract The radiative decay of the photino (γ) to a higgsino (H) is calculated in the minimal supersymmetric electroweak theory coupled to N = 1 supergravity. From the recent analyses on two photon production at PETRA, we find that the possibility that m H /m γ is almost excluded, unless m γ ≳ O (20) GeV . We also calculated the cross section for e + e - → γ →γ H +γ H as a function of photon energy.

CONSTRAINTS ON FINITE SOFT SUPERSYMMETRY-BREAKING TERMS

A new solution to the requirement of two-loop finiteness of the soft supersymmetry breaking terms (SSB) parameters is found in Finite-Gauge-Yukawa unified theories. The new solution has the form of a sum rule for the relevant scalar masses, relaxing the universality required by the previously known solution, which leads to models with unpleasant phenomenological consequences. Using the sum rule we investigate two Finite-Gauge-Yukawa unified models and we determine their spectrum in terms of few parameters. Some characteristic features of the models are that a) the old agreement of the top quark mass prediction with the measured value remains unchanged, b) the lightest Higgs mass is predicted around 120 GeV, c) the s-spectrum starts above 200 GeV.

Soft Scalar-Mass Sum Rule in Gauge-Yukawa Unified Models and Its Superstring Interpretation

Abstract It is shown that a certain sum rule for soft supersymmetry-breaking scalar masses, which has been recently found in a certain class of superstring models, is universal for gauge-Yukawa unified models. To explain this coincidence, we argue that the low-energy remnant of the target-space duality invariance in the effective supergravity of compactified superstrings can be identified with the (broken) scale invariance in gauge-Yukawa unified models, and that gauge-Yukawa unification which is indispensable for the sum rule to be satisfied follows from the matching of anomalies.

Study on the nonperturbative existence of Yang-Mills theories with large extra dimensions

Pure lattice

New results in the reduction of the standard model

\mathrm{SU}(2)

Gauge-Yukawa unification in asymptotically non-free theories

Yang-Mills theory in five dimensions is considered, where an extra dimension is compactified on a circle. Monte Carlo simulations indicate that the theory possesses a continuum limit with a nonvanishing string tension if the compactification radius is smaller than a certain value

RUNNING OF SOFT PARAMETERS IN EXTRA SPACE-TIME DIMENSIONS

{R}_{M}

INFRARED BEHAVIOUR OF SOFTLY BROKEN SQCD AND ITS DUAL

which is