arXiv subjects

Kyungsik Kang

Publications and source records attributed to Kyungsik Kang.

At least 37 records · Page 2Linked to original sources

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.

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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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arXiv1997

New Class of Quark Mass Matrix and Calculability of 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 and justification of the various specific forms of the mass matrix 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. Also the CP-violation turns out to be maximal, when the phase of the (1,2) element of the mass matrix is $π/2$.

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arXiv1997

Simple Model for Total Cross Sections

Adopting the philosophy à la Donnachie and Landshoff that simple pole exchanges could account for all data of total, elastic and diffractive scattering cross sections to present energies, we show that such simple pole fits to $pp$ and ${\bar p}p$ total cross sections are indeed very successful. We assess the uncertainties of the various parameters by making careful statistical analysis of the data and their correlations. In particular, the pomeron intercept which controls total cross sections and the real part of the elastic amplitude at high energies is shown to lie anywhere between 1.07 and 1.11, with a preferred value 1.096.

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arXiv1997

Field Theory for the Standard Model

We review the origin of the standard electroweak model and discuss in great detail the on-shell renormalization scheme of the standard model as a field theory. One-loop radiative corrections are calculated by the dimensional regularization and the dominant higher-order corrections are also discussed. We then show how well the standard model withstands the precision test against the LEP and SLD data along with its prediction on the indirect bound of the Higgs boson mass $m_H$. The uncertainty in $m_H$ and in $Z-$decay parameters due to the experimental uncertainties in $m_t, M_W$ and QED and QCD couplings is also discussed.

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arXiv1996

Almost maximally broken permutation symmetry for neutrino mass matrix

Assuming three light neutrinos are Majorana particles, we propose mass matrix ansatz for the charged leptons and Majorana neutrinos with family symmetry $S_{3} $ broken into $S_{1}$ and $S_{2}$, respectively. Each matrix has three parameters, which are fixed by measured charged lepton masses, differences of squared neutrino masses relevant to the solar and the atmospheric neutrino puzzles, and the masses of three light Majorana neutrinos as a candidate for hot dark matter with $\sum |m_ν| \sim 6 eV$. The resulting neutrino mixing is compatible with the data for the current upper limit, $ < m_{ν_e} >_{th} < 0.8 eV$, of neutrino-less double beta decay experiments, and the current data for various types of neutrino oscillation experiments. One solution of our model predicts that $ν_μ \rightarrow ν_τ$ oscillation probability is about $< 0.008$ with $Δm^{2} \sim 10^{-2} eV^2$, which may not be accessible at CHORUS and other ongoing experiments.

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arXiv1996

A simple modification of the maximal mixing scenario for three light neutrinos

We suggest a simple modification of the maximal mixing scenario (with $S_3$ permutation symmetry) for three light neutrinos. Our neutrino mass matrix has smaller permutation symmetry $S_{2}$ ($ν_μ \leftrightarrow ν_{e}$), and is consistent with all neutrino experiments except the $^{37}$Cl experiment. The resulting mass eigenvalues for three neutrinos are $m_{1} \approx (2.55-1.27) \times 10^{-3} eV, m_{2,3} \approx (0.71-1.43) eV$ for $Δm_{LSND}^{2} = 0.5 - 2.0 eV^2$. Then these light neutrinos can account for $\sim (2.4-4.8)% (6.2-12.4 %)$ of the dark matter for $h = 0.8 (0.5)$. Our model predicts the $ν_μ \rightarrow ν_τ$ oscillation probability in the range sensitive to the future experiments such as CHORUS and NOMAD.

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arXiv1996

Critical Review of The Electroweak Precision Tests

There have been a great deal of works on the precision test of the standard model (SM) because of the incredibly precise data obtained at the LEP and the new measurements of $M_W$ and $m_t$ at the Fermilab Tevatron as well as the recent theoretical progress in the higher order radiative corrections. We will discuss some of the hidden inputs and theoretical uncertainties involved in making the predictions of the observables in the SM. From the minimal $χ^2$-fit to the experimental Z-decay parameters (with the aid of a modified ZFITTER program) in a scheme where $M_Z$, $G_μ$ and $α(M_Z)$ are taken as inputs, we can predict $M_W$ for given values of $m_H$ and $m_t$. The current world average value of $M_W$ definitely favor nonvanishing electroweak radiative corrections and is consistent with a heavy $m_t$ as measured by the recent CDF report but with a heavy Higgs scalar of about 500 GeV within the context of the minimal SM. The sensitivity of and the errors in the best fit solutions due to the uncertainties in the gluonic coupling $α_s(M_Z)$ and $α(M_Z)$ are examined carefully and any trace of new physics beyond the SM implied by the data, in a particular $R_b$ and $R_c$, is also touched upon. In addition we discuss how the future precision measurements of $M_W$ and $Z$ decay parameters can determine the Higgs boson mass and distinguish the SM with radiative corrections from the minimal supersymmetric standard model (MSSM) and other extended model.

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arXiv1995

Remarks on the UA4/2 dσ/dt and on the Asymptotic σ_T(s) Behavior

We find that the UA4/2 measurements on the real part of the forward $p \bar p$ scattering amplitude and total cross section are consistent with each other and also with the standard picture of the Pomeron of either ${\it ln} ^2 s$ or ${\it ln} s$ type. However the asymptotic $σ_T (s)$ behavior obtained from the {\it ad hoc} parametrization fit to the $p \bar p$ total cross sections as quoted in the Review of Particle Properties is consistent with the analysis of the class of the analytic amplitude models that contain the ${\it ln} ^2 s$ type Pomeron term.

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arXiv1995

Status of High Energy Foward Elastic Scattering

We present the results of fitting all data for $pp$ and $\bar pp$ scattering at $\sqrt s \geq 9.7$ Gev and up to the collider energy with various analytic parametrizations of the elastic forward scattering amplitudes based on the derivative dispersion relation. It is found that the model containing the Pomeron and Reggeon terms with 8 parameters has the most preferred $χ^2/d.o.f = 1.3$, while the Donnachie and Landshoff model with 5 parameters has $χ^2/d.o.f = 2.16$ for a data set of 111 experimental points. The current data however make no clear preference between the $\ell n s$ and $\ell n^2 s$ type Pomerons.

hep-ph↗

arXiv1995

The W-Boson Mass and Precision Tests of the Standard Model

We have examined the electroweak radiative corrections in the LEP precision data in view of the new measurements of $M_W$ and $m_t$ as well as the recent progress in the higher order radiative corrections. From the minimal $χ^2$-fit to the experimental Z-decay parameters (with the aid of a modified ZFITTER program), we predict that $M_W=80.29(4)(2)$ GeV where the first error is due to the uncertainty in the fitted $m_t$ for a fixed $m_H$ and the second error comes from the $m_H$ in the range of $60-1000$ GeV, which is to be compared with the current world average $M_W=80.23(18)$ GeV. The current world average value of $M_W$ and the 1994 LEP data definitely favor nonvanishing electroweak radiative corrections and are consistent with a heavy $m_t$ as measured by the recent CDF report but with a heavy Higgs scalar of about 400 GeV within the context of the minimal standard model. The sensitivity of and the errors in the best fit solutions due to the uncertainties in the gluonic coupling $α_s(M_Z)$ and $α(M_Z)$ are also studied carefully. In addition we discuss how the future precision measurements of $M_W$ can provide a decisive test for the standard model with radiative corrections and give a profound implication for the measurement of t-quark and Higgs masses.

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arXiv1995

Consequences of Recent Electroweak Data and W-mass for the Top Quark and Higgs Masses

We critically reexamine the precision tests of the standard model by coupling the current world average value of $M_W$ with the recent LEP electroweak data with the aid of a modified ZFITTER program to include the dominant two-loop and QCD-EW mixed terms. The results show a clear evidence of nonvanishing electroweak radiative corrections. The recent CDF $m_t$ is a solution of the minimal $χ^2$-fits to the recent LEP data set and $M_W=80.23(18)~$ GeV but with a heavy Higgs scalar, i.e., $m_t=179~$ GeV and $m_H=300~$ GeV. We discuss how sensitive $m_t$ and $m_H$ are depending on the exact value of $M_W$ even within the present uncertainty, as well as on $α_s$ and $α(M_Z)$. We show how the future improvements on $M_W$ can discriminate different values of $m_t$ and $m_H$ from the electroweak data and provide a crucial and decisive test for the standard model.

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arXiv1994

Electroweak Physics at LEP

We have examined the evidence for the electroweak radiative corrections in the LEP precision data sets of 1993 and 1994 along with the intriguing possibility that the QED corrections only may be sufficient to fit the data within the framework of the minimal standard model. We find that the situation is very sensitive to the precise values of $M_W$. The current world average value of $M_W$ and the improved 1994 LEP data strongly favor nonvanishing electroweak radiative corrections and are consistent with a heavy $m_t$ as reported by CDF but with a heavy Higgs scalar of about 400 GeV. We discuss how future precision measurements of $M_W$ and $m_t$ can provide a decisive test for the standard model with radiative corrections.

hep-ph↗

arXiv1994

High Energy Hadron-Hadron Scattering

The elastic hadron-hadron scattering at high energies is one of the most fundamental subjects of all particle physics problems and yet is least understood in spite of many advances in quantum chromodynamics (QCD) at the conceptual level. We review here the recent theoretical and experimental status of the subject as well as the rigorous results of the high energy hadron-hadron scattering. Surprisingly enough, the high-energy models for the elastic and diffractive scattering abstracted from the Regge-Pomeron field theory is still {\it phenomenologically} successful to explain the high-energy scattering data though no rigorous derivation out of the QCD is yet available.

hep-ph↗

arXiv1994

Electroweak Radiative Corrections, Born Approximation, and Precision Tests of the Standard Model at LEP

We have examined the evidence for the electroweak radiative corrections in the LEP precision data along with the intriguing possibility that the QED corrections only may be sufficient to fit the data. We find that the situation is very sensitive to the precise value of $M_W$. While the world average value of $M_W$ strongly favors nonvanishing electroweak radiative corrections, the QED corrections alone can account for the data within $2σ$ in the context of the standard model. We discuss how the precision measurements of $M_W$ can provide a decisive test for the standard model with radiative corrections and give a profound implication for the existence of t-quark and Higgs scalar.

hep-ph↗

arXiv1994

LEP Electroweak Physics

This is an overview of the electroweak physics achieved at LEP. After a brief review of the standard model and the calculation of the radiative corrections both in the MS and on-shell schemes, we introduce the Z decay parameters around the resonance energy and discuss the status of the standard model fits for them, along with some selected highlights of the measurements as well as new particle searches.

hep-ph↗

arXiv1993

The $η_6$ at LEP and TRISTAN

The $η_6$ is a ``heavy axion'' remnant of dynamical electroweak symmetry breaking by a color sextet quark condensate. Electroweak scale color instanton interactions allow it to be both very massive and yet be responsible for Strong CP conservation in the color triplet quark sector. It may have been seen at LEP via its two-photon decay mode and at TRISTAN via its hadronic decay modes.

hep-ph↗

arXiv1993

Color--Sextet Quark Condensation in QCD

We suggest that the sextet color condensation model is not only the simplest and most attractive scheme to modify the standard model but also may already have some ``experimental" support. The crucial test may be to observe a short-- lived axion--like $η_6$ of mass around 60 GeV/$c^2$ that can produce high energy photon pairs diffractively at hadron colliders and also radiatively from $Z^0$ at high energy $e^+ e^-$ colliders. Here we show how high--energy forward scattering can be affected by diffractive production of the $η_6$. Presented to the DPF-92 meeting.

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