arXiv subjects

Sin Kyu Kang

Publications and source records attributed to Sin Kyu Kang.

At least 109 records · Page 6Linked to original sources

arXiv2000

Majorana Neutrino Masses and Neutrino Oscillations

We examine some patterns of Majorana neutrino mass matrix which is compatible with the phenomenological lepton flavor mixing matrix and non-observation of neutrinoless double beta decay. Imposing $(M_ν)_{ee}=0$ for the Majorana neutrino mass matrix in the leading order, we obtain a relationship between the solar mixing angle and the neutrino masses $m_1$ and $m_2$. Additional possible texture zeros are assigned to the mass matrix so as for the nonvanishing $θ_{13}$ to be predictable in terms of neutrino masses. We also show how three neutrino masses can be predicted from the solar mixing angle and the experimental results of $Δm^2_{sol}$ and $Δm^2_{atm}$ in this framework, and we discuss naturality of the forms of the mass matrix found in our work.

hep-ph↗

arXiv2000

CP violating supersymmetric contributions to the electroweak $ρ$ parameter

Effects of CP violation on the supersymmetric electroweak correction to the $ρ$ parameter are investigated. To avoid the EDM constraints, we require that arg$(μ)<10^{-2}$ and the non-universal trilinear couplings $A_f=(0,0,A_0)$ and also assume that gluinos are heavier than 400 GeV. The CP phase $ϕ_t=$ arg($A_0$) leads to large enhancement of the relative mass splittings between $\tilde{t}_2$ and $\tilde{b}_L(\tilde{t}_1)$, which in turn reduces the one-loop contribution of the stop and sbottom to $Δρ$. For small $\tan β$, such a CP violating effect is prominent. We also study how much the two-loop gluon and gluino contributions are affected by the CP phase. Possible contributions to the $ρ$ parameter arising from the Higgs sector with CP violation are discussed.

hep-ph↗

arXiv2000

Neutrino Masses and Leptonic CP Violation

Neutrino oscillations as solutions of the solar neutrino problems and the atmospheric neutrino deficits may restrict neutrino mass squared differences and mixing angles in three-neutrino mixing scheme. Currently we have several solutions depending on the interpretations of the solar neutrino problems. Combining the neutrino oscillation solutions and a mass matrix ansatz, we investigated the neutrino mass bounds and found possible leptonic CP-violating rephasing-invariant quantity $J^{l}_{\tiny CP} \leq 0.012$ for large mixing angle MSW and just-so vacuum oscillations solutions, and $J^{l}_{\tiny CP} \leq 0.0013$ for small mixing angle MSW solution.

hep-ph↗

arXiv2000

Baryogenesis and Degenerate Neutrinos

We bring the theoretical issue of whether two important cosmological demands, baryon asymmetry and degenerate neutrinos as hot dark matter, can be compatible in the context of the seesaw mechanism. To realize leptogenesis with almost degenerate Majorana neutrinos without severe fine-tuning of parameters, we propose the hybrid seesaw mechanism with a heavy Higgs triplet and right-handed neutrinos. Constructing a minimal hybrid seesaw model with SO(3) flavor symmetry for the neutrino sector, we show that the mass splittings for the atmospheric and solar neutrino oscillations which are consistent with the requirements for leptogenesis can naturally arise.

hep-ph↗

arXiv2000

One-loop Corrected Neutrino Masses and Mixing in the Supersymmetric Standard Model without R-parity

We provide, in the R-parity violating supersymmetric standard model, a comprehensive analysis for sneutrino minimization from the one-loop effective scalar potential, and also for one-loop renormalized neutrino masses and mixing by calculating the effective neutrino mass matrix in the weak basis. Applying our results to theories with gauge mediated supersymmetry breaking, we show how atmospheric and solar neutrino oscillations can be accommodated simultaneously in this framework. It is observed that the one-loop correction to sneutrino vacuum expectation values leads to a significant effect on the determination of the neutrino masses and mixing.

hep-ph↗

arXiv1999

Radiative Splitting of Three Degenerate Neutrinos

We propose a radiative origin of the two mass splittings of three degenerate Majorana neutrinos. It can be achieved by extending the standard model to have the usual effective dimension 5 operators generating SO(3)-invariant tree-level masses, and a charged scalar singlet coupling with the leptons preserving the U(1) subgroup of SO(3). The mass splittings for the atmospheric and solar neutrino oscillations then arise from one-loop corrections due to the charged scalar singlet coupling and the usual tau Yukawa coupling, respectively.

hep-ph↗

arXiv1999

Lepton flavor mixing and baryogenesis

Recently a new general class of quark mass matrix ansatz has been proposed, which originates from some flavor symmetry. We extend that symmetry to the lepton sector and study the neutrino mass matrix and address the question of the baryon asymmetry of the universe in this model.

hep-ph↗

arXiv1999

Neutrino Oscillations and R-parity Violating Collider Signals

R-parity and L violation in the MSSM would be the origin of the neutrino oscillation observed in Super-Kamiokande. A distinctive feature of this framework is that it can be tested in colliders by observing decay products of the destabilized LSP. We examine all the possible decay processes of the neutralino LSP assuming the bilinear contribution to neutrino masses dominates over the trilinear one which gives rise to the solar neutrino mass. We find that it is possible to probe neutrino oscillations through colliders in most of the R-parity conserving MSSM parameter space.

hep-ph↗

arXiv1999

Higgs Boson Bounds in Three and Four Generation Scenarios

In light of recent experimental results, we present updated bounds on the lightest Higgs boson mass in the Standard Model (SM) and in the Minimal Supersymmetric extension of the Standard Model (MSSM). The vacuum stability lower bound on the pure SM Higgs boson mass when the SM is taken to be valid up to the Planck scale lies above the MSSM lightest Higgs boson mass upper bound for a large amount of SUSY parameter space. If the lightest Higgs boson is detected with a mass M_{H} < 134 GeV (150 GeV) for a top quark mass M_{top} = 172 GeV (179 GeV), it may indicate the existence of a fourth generation of fermions. The region of inconsistency is removed and the MSSM is salvagable for such values of M_{H} if one postulates the existence of a fourth generation of leptons and quarks with isodoublet degenerate masses M_{L} and M_{Q} such that 60 GeV < M_{L} < 110 GeV and M_{Q} > 170 GeV.

hep-ph↗

arXiv1999

Higgs Bounds in Three and Four Generation Scenarios

hep-ph↗

arXiv1999

Bounds and Implications of Neutrino Magnetic Moments from Atmospheric Neutrino Data

The neutral current effects of the future high statistics atmospheric neutrino data can be used to distinguish the mechanisms between a $ν_μ$ oscillation to a tau neutrino or to a sterile neutrino. However, if neutrinos possess large diagonal and/or transition magnetic moments, the neutrino magnetic moments can contribute to the neutral current effects which can be studied by the single $π^0$ production events in the Super-K data. This effect should be included in the future analyses of atmospheric data in the determination of $ν_μ$ to tau or sterile neutrino oscillation.

hep-ph↗

arXiv1998

Bi-maximal Lepton Flavor Mixing Matrix and Neutrino Oscillation

Recently, many authors showed that if the solar and atmospheric neutrino data are both described by maximal mixing vacuum oscillations at the relevant mass scale, then there exists a unique bi-maximal lepton mixing matrix for three neutrino flavors. We construct the lepton mass matrices from the symmetry principle so that maximal mixings for the atmospheric and the solar neutrino vacuum oscillations are naturally generated. Although the hierarchical patterns of the lepton sector are quite different from each other, we show how two different mass matrices suggested in this work can be generated in a unified way. We also give comments on possible future tests of the bi-maximal lepton mixing matrix.

hep-ph↗

arXiv1998

Bounds on the lightest Higgs boson mass with three and four fermion generations

We present lower bounds on the Higgs boson mass in the Standard Model with three and four fermion generations SM(3,4), as well as upper bounds on the lightest Higgs boson mass in the minimal supersymmetric extension of the SM with three and four generations MSSM(3,4). Our analysis utilizes the SM(3,4) renormalization-group-improved one-loop effective potential of the Higgs boson to find the upper bounds on the Higgs mass in the MSSM(3,4) while the lower bounds in the SM(3,4) are derived from considerations of vacuum stability. All the bounds increase as the degenerate fourth generation mass increases, providing more room in theory space that respects the increasing experimental lower limit of the Higgs mass.

hep-ph↗

arXiv1998

Mass Matrix Ansatz for Degenerate Neutrinos Consistent with Solar and Atmospheric neutrino Data

We suggest mass matrices for neutrinos and charged leptons that can explain solar and atmospheric neutrino data. The resulting flavor mixing matrix $V_ν$ has a property that $(V_ν)_{13}=0$, thus making $ν_e \leftrightarrow ν_μ$ and $ν_μ \leftrightarrow ν_τ$ oscillations to be effectively a two-channel problem. Phenomenological consequences of the lepton mass matrix ansatze are consistent with the current data on various type of neutrino oscillation experiments except the LSND measurement. %and that three neutrinos are almost degenerate in mass. Three neutrinos, being almost degenerate with $\sum | m_{ν_i} | \lesssim 1 $ eV, can be a part of hot dark matter without any conflict with the constraint from neutrinoless double beta decay experiments. The $ν_μ \leftrightarrow ν_τ$ oscillation, $\sin^2{2θ_{μτ}}$, is predicted to be 0.86-0.97 with $Δm^2_{μτ}\simeq 2 \times 10^{-3} {eV}^2$, which is consistent with the atmospheric neutrino data and can be tested further at the planned MINOS and K2K experiments searching for $ν_μ \to ν_τ$ oscillation.

hep-ph↗

arXiv1998

Neutrino Oscillations and Lepton Flavor Mixing

In view of the recent announcement on non-zero neutrino mass from Super-Kamiokande experiment, it would be very timely to investigate all the possible scenarios on masses and mixings of light neutrinos. Recently suggested mass matrix texture for the quark CKM mixing, which can be originated from the family permutation symmetry and its suitable breakings, is assumed for the neutrino mass matrix and determined by the four combinations of solar, atmospheric and LSND neutrino data and cosmological hot dark matter bound as input constraints. The charged-lepton mass matrix is assumed to be diagonal so that the neutrino mixing matrix can be identified directly as the lepton flavor mixing matrix and no CP invariance violation originates from the leptonic sector. The results favor hierarchical patterns for the neutrino masses, which follow from the case when either solar-atmospheric data or solar-HDM constraints are used.

hep-ph↗

arXiv1998

Neutrino Mass Matrix, Mixing and Oscillation

We investigate the phenomenological consequences of lepton mass matrices originated from the family permutation symmetry and its suitable breakings. Adopting the recently proposed new mass matrix for the charged lepton mass matrix and the Majorana neutrino mass matrix considered before, we find that the resulting lepton flavor mixing matrix is consistent with the current data on various type of neutrino oscillation experiments except the Chlorine data and LSND measurement and that three neutrinos are almost degenerate in mass. Numerically the three neutrinos can account for about 50% of the hot dark matter(HDM) when the neutrino mass matrix is constrained by the small angle MSW solution for the solar neutrino problem, atmospheric neutrino data of the Super-Kamiokande group, and the limitation on the electron-type neutrino mass due to non-observation of neutrino-less double beta decays.

hep-ph↗

arXiv1998

New Class of Quark Mass Matrices and the Flavor Mixing Matrix

We discuss a new general class of mass matrix ansatz that respects the fermion mass hierarchy and calculability of the flavor mixing matrix. This is a generalization of the various specific forms of the mass matrix that is obtained by successive breaking of the maximal permutation symmetry. By confronting the experimental data, a large class of the mass matrices are shown to survive, while certain specific cases are phenomenologically ruled out.

hep-ph↗

arXiv1997

The minimal supersymmetric standard model and precision of W-boson mass and top quark mass

We argue that the present value and accuracy of $M_W$ and $m_t$ measurements tend to favor the MSSM over the SM. By speculating that a precision of the order 40 MeV and 3 GeV respectively for $M_W$ and $m_t$ will be achieved at LEP2 and Tevatron, we show that the prospect for the MSSM will be further enhanced as long as the central values of $M_W$ and $m_t$ do not decrease below the present values. In addition we discuss how this scenario can constrain the Higgs boson mass and distinguish the Higgs boson of the MSSM type from that of the SM.

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