$SU(4)_L \times U(1)_X$ models with little Higgs (2009)
Nam, Soo-hyeon, Lee, Kang Young, Keum, Yong-Yeon
We discuss the aspects of the fermions and gauge bosons in $SU(4)_L \times U(1)_X$ models with little Higgs. We introduce a set of fermions which ensures the cancellation of gauge anomaly, and...
Propagation of Neutrinos through Magnetized Gamma-Ray Burst Fireball (2009)
Sahu, Sarira, Fraija, Nissim, Keum, Yong-Yeon
The neutrino self-energy is calculated in a weakly magnetized plasma consists of electrons, protons, neutrons and their anti-particles. By using this we have calculated the neutrino effective...
Neutrino Oscillation in Magnetized Gamma-Ray Burst Fireball (2009)
Sahu, Sarira, Fraija, Nissim, Keum, Yong-Yeon
Neutrinos of energy about 5-20 MeV are produced due to the stellar collapse or merger events that trigger the Gamma-Ray Burst. Also low energy MeV neutrinos are produced within the fireball due to...
Cosmological Signatures of the Interaction between Dark-Energy and Massive Neutrinos (2008)
Ichiki, Kiyotomo, Keum, Yong-Yeon
We investigate whether interaction between massive neutrinos and quintessence scalar field is the origin of the late time accelerated expansion of the universe. We present cosmological perturbation...
Neutrino Mass Bounds from Neutrinoless Double Beta Decays and Large Scale Structures (2008)
Keum, Yong-Yeon, Ichiki, Kiyotomo, Kajino, Taka
We investigate the way how the total mass sum of neutrinos can be constrained from the neutrinoless double beta decay and cosmological probes with cosmic microwave background (WMAP 3-year results),...
Neutrino Masses from Cosmological Probes in Interacting Neutrino Dark-Energy Models (2008)
Ichiki, Kiyotomo, Keum, Yong-Yeon
We investigate whether interaction between massive neutrinos and quintessence scalar field is the origin of the late time accelerated expansion of the universe. We present explicit formulas of the...
Ichiki, Kiyotomo, Keum, Yong-Yeon
We present cosmological perturbation theory in neutrinos probe interacting dark-energy models, and calculate cosmic microwave background anisotropies and matter power spectrum. In these models, the...
We present cosmological perturbation theory in neutrino probe interacting dark-energy models, and calculate cosmic microwave background anisotropies and matter power spectrum. In these models, the...
A_4 flavour symmetry breaking scheme for understanding quark and neutrino mixing angles (2005)
He, Xiao-Gang, Keum, Yong-Yeon, Volkas, Raymond R.
We propose a spontaneous A_4 flavour symmetry breaking scheme to understand the observed pattern of quark and neutrino mixing. The fermion mass eigenvalues are arbitrary, but the mixing angles are...
Perturbative SO(10) Grand Unification (2004)
Chang, Darwin, Fukuyama, Takeshi, Keum, Yong-Yeon, Kikuchi, Tatsuru, Okada, Nobuchika
We consider a phenomenologically viable SO(10) grand unification model of the unification scale $M_G$ around $10^{16} $ GeV which reproduces the MSSM at low energy and allows perturbative...
Phenomenological Application of $k_T$ factorization (2004)
We discuss applications of the perturbative QCD approach in the exclusive non-leptonic two body B-meson decays. We briefly review its ingredients and some important theoretical issues on the...
Phenomenological Application of $k_T$ factorization (2004)
We discuss applications of the perturbative QCD approach in the exclusive non-leptonic two body B-meson decays. We briefly review its ingredients and some important theoretical issues on the...
Nonfactorizable contributions to $B \to D^{(*)} M$ decays (2003)
Keum, Yong-Yeon, Kurimoto, T., Sanda, A. I.
While the factorization assumption works well for many two-body nonleptonic $B$ meson decay modes, the recent measurement of $\bar B\to D^{(*)0}M^0$ with $M=\pi$, $\rho$ and $\omega$ shows large...
Determination of weak phases $\phi_2$ and $\phi_3$ from $B\to \pi\pi,K\pi$ in the pQCD method (2002)
We look at two methods to determine the weak phases $\phi_2$ and $\phi_3$ from $B \to \pi\pi$ and $K\pi$ decays within the perturbative QCD approach. We obtain quite interesting bounds on $\phi_2$...
Determination of weak phases $\phi_2$ and $\phi_3$ from $B\to \pi\pi,K\pi$ in the pQCD method (2002)
We look at two methods to determine the weak phases $\phi_2$ and $\phi_3$ from $B \to \pi\pi$ and $K\pi$ decays within the perturbative QCD approach. We obtain quite interesting bounds on $\phi_2$...
Perturbative QCD analysis of $B \to \phi K^* $ decays (2002)
Chen, Chuan-Hung, Keum, Yong-Yeon, Li, Hsiang-nan
We study the first observed charmless $B\to VV$ modes, the $B\to\phi K^*$ decays, in perturbative QCD formalism. The obtained branching ratios $B(B\to\phi K^*)\sim 15 \times 10^{-6}$ are larger than...
B -> J/psi K^* Decays in QCD Factorization (2001)
Cheng, Hai-Yang, Keum, Yong-Yeon, Yang, Kwei-Chou
The hadronic decay B -> J K^* is analyzed within the framework of QCD factorization. The spin amplitudes A_0, A_\parallel and A_\perp in the transversity basis and their relative phases are studied...
Perturbative QCD analysis of $B \to \phi K$ decays and Power counting (2001)
Chen, Chuan-Hung, Keum, Yong-Yeon, Li, Hsiang-nan
We investigate exclusive nonleptonic $B$ meson decays $B\to\phi K$ in perturbative QCD formalism. It is shown that the end-point (logarithmic and linear) singularities in decay amplitudes do not...
Nonleptonic charmless B decays: factorization vs perturbative QCD (2000)
Keum, Yong-Yeon, Li, Hsiang-nan
We compare the factorization approach, the perturbative QCD approach and the Beneke-Buchalla-Neubert-Sachrajda approach to nonleptonic charmless $B$ meson decays. We discuss their treatments of...
Fat penguins and imaginary penguins in perturbative QCD (2000)
Keum, Yong-Yeon, Li, Hsiang-nan, Sanda, A. I.
We evaluate $B\to K\pi$ decay amplitudes in perturbative QCD picture. It is found that penguin contributions are dynamically enhanced by nearly 50% compared to those assumed in the factorization...
Probing penguin coefficients with the lifetime ratio tau(B_s)/tau(B_d) (1997)
Keum, Yong-Yeon, Nierste, Ulrich
We calculate penguin contributions to the lifetime splitting between the B_s and the B_d meson. In the Standard Model the penguin effects are found to be opposite in sign, but of similar magnitude as...