Searcharxiv⌕ Search

arXiv subjects

W. Namgung

Publications and source records attributed to W. Namgung.

7 recordsLinked to original sources
arXiv2001

Test of Factorization Hypothesis from Exclusive Non-leptonic B decays

We investigate the possibility of testing factorization hypothesis in non-leptonic exclusive decays of B-meson. In particular, we considered the non factorizable \bar{B^0} -> D^{(*)+} D_s^{(*)-} modes and \bar{B^0} -> D^{(*)+} (π^-, ρ^-) known as well-factorizable modes. By taking the ratios BR(\bar{B^0}-> D^{(*)+}D_s^{(*)-})/BR(\bar{B^0}-> D^{(*)+}(π^-,ρ^-)), we found that under the present theoretical and experimental uncertainties there's no evidence for the breakdown of factorization description to heavy-heavy decays of the B meson.

hep-ph↗
arXiv2000

Measurement of |V_{ub}/V_{cb}| (and |V_{ub}|) in Exclusive Nonleptonic Decays, \bar{B}^0 --> D_s^{(*)-}(π^+,ρ^+) and \bar{B}^0 --> D_s^{(*)-}D^{(*)+}

We have studied extracting $|\vub/\vcb|$ by calculating the ratios ${\cal B}(\bar{B}^0\to D_s^{(*)-}(π^+,ρ^+))/{\cal B}(\bar{B}^0\to D_s^{(*)-}D^{(*)+})$ including penguin effects within the factorization assumption. The ratios involving $\bar{B}^0\to D_s^-D^{+}$ mode have considerable penguin corrections ($\sim 15%$ at the amplitude level), but those involving $\bar{B}^0\to D_s^-D^{*+}$ mode have relatively small penguin corrections. On the other hand, the $\bar{B}^0\to D_s^-D^{+}$ mode has smaller form-factor dependance. Therefore, these ratios complement each other in measuring $\vub/\vcb$. The theoretical uncertainty from the hadronic form factors in our method is at the level of 15%, which is comparable to the model-dependence uncertainty of about 20% in the measurement of $| \vub/\vcb |$ from the exclusive semileptonic B decays. Using the newest upper limit on $B\to D_s π$ decay from CLEO, our method sets an upper limit $| \vub/\vcb | < 0.13$ which is very close to the measured values from the semileptonic B decays. We also discuss the possible breaking of factorization assumption.

hep-ph↗
arXiv1999

Search for New Physics in the Semileptonic D_{l4} Decays, D->K πl ν

New physics effects through the direct CP violation and the decay rate change are investigated in the semileptonic $D_{l4}$ decays, $D^\pm\to Kπl^\pm ν$, by including a scalar-exchange interaction with a complex coupling. In the decay process, we included various excited states as intermediate states decaying to the final hadrons, $K+π$, and found that among the intermediate states only the lowest state ($K^*$) is dominant and the other higher excited states are negligible, contrary to the $B_{l4}$ decays. We also obtained constraints on the new complex coupling within the multi-Higgs doublet model and the scalar leptoquark models.

hep-ph↗
arXiv1999

CP Violation in the Semileptonic B_{l4} (B^\pm -> pi^+ π^- l^\pm ν) Decays

Direct CP violations in $B_{l4}$ decays ($B^\pm \to π^+π^- l^\pm ν_l$) are investigated within the Standard Model (SM) and also in its extensions. In the decay processes, we include various excited states as intermediate states decaying to the final hadrons, $π^+ + π^-$. The CP violation within the SM is induced by the interferences between intermediate resonances with different quark flavors. As extensions of the SM, we consider CP violations implemented through complex scalar-fermion couplings in the multi-Higgs doublet model and the scalar-leptoquark models. We calculate the CP-odd rate asymmetry and the optimal asymmetry. We find that the optimal asymmetry can be measured at $1σ$ level with about $10^9$ $B$-meson pairs in the SM case and $10^3$--$10^7$ pairs in the extended model case, for maximally-allowed values of CP-odd parameters in each case.

hep-ph↗
arXiv1998

CP Violation in the Semileptonic $B_{l4}$ (B->D πl ν) Decays: A Model Independent Analysis

CP violation from physics beyond the Standard Model is investigated in $B_{l4}$ decays: $B\to Dπl\barν_l$. The semileptonic $B$-meson decay to a $D$-meson with an emission of single pion is analyzed with heavy quark effective theory and chiral perturbation theory. In the decay process, we include various excited states as intermediate states decaying to the final hadrons, $D+π$. The CP violation is implemented in a model independent way, in which we extend leptonic current by including complex couplings of the scalar sector and those of the vector sector in extensions of the Standard Model. With these complex couplings, we calculate the CP-odd rate asymmetry and the optimal asymmetry. We find that the optimal asymmetry is sizable and can be detected at $1σ$ level with about $10^6$-$10^7$ $B$-meson pairs, for some reference values of new physics effects.

hep-ph↗
arXiv1998

CP Violation in the Semileptonic $B_{l4}$ ($B->D πl ν$) Decays: Multi-Higgs Doublet Model and Scalar-Leptoquark Models

CP violation from physics beyond the Standard Model is investigated in $B_{l4}$ decays: $B\to Dπl\barν_l$. In the decay process, we include various excited states as intermediate states decaying to the final hadrons, $D+π$. We consider the semileptonic decay to a tau lepton family as well. The CP violation is implemented through complex scalar--fermion couplings in the multi-Higgs doublet model and scalar-leptoquark models beyond the Standard Model. With these complex couplings, we calculate the CP-odd rate asymmetry and the optimal asymmetry. We find that for $B_{τ4}$ decays the optimal asymmetry is sizable and can be detected at $1σ$ level with about $10^6$-$10^7$ $B$-meson pairs, for maximally-allowed values of CP-odd parameters in those extended models.

hep-ph↗
arXiv1994

Fermi motion parameter $p_{_F}$ of $B$ meson from relativistic quark model

The Fermi motion parameter $p_{_F}$ is the most important parameter of ACCMM model, and the value $p_{_F} \sim 0.3$ GeV has been used without clear theoretical or experimental evidence. So, we attempted to calculate the value for $p_{_F}$ theoretically in the relativistic quark model using quantum mechanical variational method. We obtained $p_{_F} \sim 0.5$ GeV, which is somewhat larger than 0.3 GeV, and we also derived the eigenvalue of $E_B \simeq 5.5$ GeV, which is in reasonable agreement with $m_B=5.28$ GeV. We also recalculated $|V_{ub}/V_{cb}|$ as a function of $p_{_F}$.

hep-ph↗