arXiv subjects

Eung Jin Chun

Publications and source records attributed to Eung Jin Chun.

133 records · Page 8Linked to original sources

arXiv1998

Cosmology of Light Moduli

In string/M-theory with a large compactification radius, some axion-like moduli can be much lighter than the gravitino. Generic moduli in gauge-mediated supersymmetry breaking models also have a mass far below the weak scale. Motivated by these, we examine the cosmological implications of light moduli for the mass range from the weak scale to an extremely small scale of order 10^{-26} eV, and obtain an upper bound on the initial moduli misalignment for both cases with and without a late entropy production.

hep-ph↗

arXiv1997

Gauge Unification and Dynamical Supersymmetry Breaking

Under the assumption that all the gauge groups in supersymmetric theories unify at the fundamental scale, the numbers and the mass scales of messenger quarks and leptons, as well as the beta-function coefficient of the sector for dynamical supersymmetry breaking are constrained depending on various gauge mediation mechanisms. For this, we use one-loop renormalization group equations and draw constraints on the scales in each gauge mediation model.

hep-ph↗

arXiv1996

Supersymmetry Hierarchy Problems and Anomalous Horizontal U(1) Symmetry

It is suggested that various hierarchy problems in supersymmetric standard model, i.e. the Yukawa hierarchies, the μproblem, and the suppression of dangerous baryon and/or lepton number (B/L) violating couplings, are resolved altogether in the framework of horizontal U(1) symmetry whose spontaneous breaking results in the appearance of one expansion parameter (the Cabibbo angle). Within a reasonable range of U(1) charges, there exist a few models compatible with experiments. The specific sizes of B/L violating couplings of these models are calculated and several phenomenological consequences are discussed.

hep-ph↗

arXiv1996

Proton Decay with a Light Gravitino or Axino

We consider the proton decay in supersymmetric models with a gravitino or axino lighter than the proton. This consideration leads to a stringent limit on the R parity and B violating Yukawa coupling of the superpotential operator U^c_i D^c_j D^c_k as $λ"_{112} < 10^{-15} (m_{3/2}/eV)$ for a light gravitino, and $λ"_{112} < 10^{-15} (F_a/ 10^{10} GeV)$ for a light DFSZ axino. For hadronic axino, the constraint is weakened by the factor of 10^{3}.

hep-ph↗

arXiv1996

The $μ$ problem, and B and L Conservation with a Discrete Gauge R Symmetry

We examine in a generic context how the $μ$ problem can be resolved by means of a spontaneously broken gauge symmetry. We then focus on the new scheme based on a discrete gauge R symmetry which is spontaneously broken by nonperturbative hidden sector dynamics triggering supersymmetry breaking also. The possibility to suppress the dangerous baryon and/or lepton number violating interactions by means of this discrete R symmetry is examined also together with some phenomenological consequences.

hep-ph↗

arXiv1995

Gauged R-symmetry, Fermion and Higgs Mass Problem

We consider the simplest model of $SU(3) \times SU(2) \times U(1)_Y \times U(1)_R$ gauge symmetry with one extra singlet field whose vacuum expectation value breaks the horizontal $R$-symmetry $U(1)_R$ and gives rise to Yukawa textures. The $U(1)_R$ symmetry is able to provide both acceptable fermion mass hierarchies and a natural solution to the $μ$ problem only if its mixed anomalies are cancelled by the Green-Schwarz mechanism. When the canonical normalization $g_3^2=g_2^2={5\over3}g_1^2$ of the gauge coupling constants is assumed, the Higgs mass parameter $μ\sim m_{3/2}$ can arise taking into acount the uncertainty in the ultraviolet relation $m_e m_μm_τ/m_d m_s m_b \simeq λ^q$ with $q \neq 0$. When $q=0$ is taken only a suppressed value of $μ\sim λm_{3/2}$ can be obtained.

hep-ph↗

arXiv1993

Dark Matters in Axino Gravitino Cosmology

It is suggested that the axino mass in the 1 MeV region and gravitino mass in the eV region can provide an axino lifetime of order of the time of photon decoupling. In this case, some undecayed axinos act like cold dark matters and some axino decay products (gravitinos and hot axions) act like hot dark matters at the time of galaxy formation.

hep-ph↗