arXiv subjects

C. S. Kim

Publications and source records attributed to C. S. Kim.

At least 181 records · Page 10Linked to original sources

arXiv2002

A Consistent Resolution of Possible Anomalies in B^0 --> phi K_S and B^+ --> eta' K^+ Decays

In the framework of R-parity violating (\rpv) supersymmetry, we try to find a consistent explanation for both recently measured CP asymmetry in B^0 --> phi K_S decay and the large branching ratio of B^{+/-} --> eta' K^{+/-} decay, which are inconsistent with the Standard Model (SM) prediction. We also investigate other charmless hadronic B --> PP and B --> VP decay modes whose experimental data favor the SM: for instance, recently measured CP asymmetries in B^0 --> eta^{prime} K_S and B^0 --> J / Psi K_S. We find that all the observed data can be accommodated for certain values of \rpv couplings.

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arXiv2002

Nonleptonic two-body charmless B decays involving a tensor meson in ISGW2 model

Nonleptonic charmless B decays into a pseudoscalar (P) or a vector (V) meson accompanying a tensor (T) meson are re-analyzed. We scrutinize the hadronic uncertainties and ambiguities of the form factors which appear in the literature. The Isgur-Scora-Grinstein-Wise updated model (ISGW2) is adopted to evaluate the relevant hadronic matrix elements. We calculate the branching ratios and CP asymmetries for various $B\to P(V)T$ decay processes. With the ISGW2 model, the branching ratios are enhanced by about an order of magnitude compared to the previous estimates. We show that the ratios $\calB(B\to VT)/\calB(B\to PT)$ for some strangeness-changing processes are very sensitive to the CKM angle $γ$ ($ϕ_3$).

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arXiv2002

Hadronic decays of B involving a tensor meson through a $b \to c$ transition

We re-analyze hadronic decays of B mesons to a pseudoscalar (P) and a tensor meson (T), or a vector meson (V) and a tensor meson, through a $b \to c$ transition. We discuss possible large uncertainties to branching ratios (BR's) of the relevant modes, mainly arising from uncertainties to the hadronic form factors for the $B \to T$ transition. The BR's and CP asymmetries for $B \to PT$ and VT decays are then calculated by using the form factors given in the ISGW2 model (the improved version of the original Isgur-Scora-Grinstein-Wise (ISGW) model). We find that the estimated BR's of many modes are increased by an order of magnitude, compared to the previous results calculated within the ISGW model.

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arXiv2002

Top quark Kaluza-Klein mode mixing in the Randall-Sundrum bulk Standard Model and Constraint from Δρ

Randall-Sundrum scenario with all the standard model (SM) fermions and gauge bosons in the bulk is phenomenologically studied. Even though the simple assumption of universal bulk fermion mass m_ψleads to the same Kaluza-Klein (KK) mass spectrum for all the SM fermions and thus suppresses new contributions to Flavor-Changing-Neutral-Current and the ρparameter, large Yukawa coupling of the top quark generates its KK mode mixing and breaks the degeneracy: unacceptably large contribution to Δρoccurs. With a different bulk fermion mass to SU(2) singlet bottom quark, we demonstrate that there exists some parameter space to satisfy the Δρconstraint.

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arXiv2002

Top quark Kaluza-Klein mode mixing in the Randall-Sundrum bulk Standard Model and B -> X_s gamma

We study top quark Kaluza-Klein (KK) mode mixing in the Randall-Sundrum scenario with all the SM fermions and gauge bosons in the bulk. Even though the simple assumption of universal bulk fermion mass m_psi leads to the same KK mass spectrum for all the SM fermions and thus suppresses new contributions to the flavor changing neutral current and the rho parameter, large Yukawa coupling of the top quark generates the mixing among its KK modes and breaks the degeneracy: Unacceptably large contribution to rho occurs. In order to satisfy the rho constraint, we relax the model by assigning a different bulk fermion mass to SU(2) singlet bottom quark, and demonstrate that there exists some limited parameter space where the $Δρ$ constraint is satisfied. It is also shown that the current measurement of Br(B -> X_s + gamma) can be accommodated in this modified model, and one sigma level precision constrains the effective weak scale k_{EW} such as k_{EW} ~ 3 TeV for m_psi/k=-0.4, where k_{EW} is the warp-suppressed AdS_5 curvature.

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arXiv2002

Measurement of $|V_{ub}|$ in semi-inclusive charmless $B \to πX$ decays

We study semi-inclusive charmless decays $B \to πX$, where $X$ does not contain a charm (anti)quark. The mode $\bar B^0 \to π^- X$ turns out to be be particularly useful for determination of the CKM matrix element $|V_{ub}|$. We present the branching ratio (BR) of $\bar B^0 \to π^- X$ as a function of $|V_{ub}|$, with an estimation of possible uncertainty. The BR is expected to be an order of $10^{-4}$.

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arXiv2002

Decays $B \to η^{\prime} K$ in R-parity violating supersymmetry

In light of the recent experimental data from $B$ factories, We try to explain the large branching ratio (compared to the Standard Model prediction) of the decay $B^{\pm}\to η' K^{\pm}$ in the context of R-parity violating ($\rpv$) supersymmetry. We investigate other observed $η^{(\prime)}$ modes and find that only two pairs of $\rpv$ coupling can satisfy the requirements without affecting the other $B \to PP$ and $B \to VP$ decay modes except the mode $B \to ϕK$. We also calculate the CP asymmetry for the observed decay modes affected by the new couplings.

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arXiv2002

A study of semi-inclusive charmless $B \to πX$ decays

We study semi-inclusive charmless decays $B \to πX$ in detail, such as $\bar B^0 \to π^{\pm (0)} X$, $B^0 \to π^{\pm (0)} X$, $B^{\pm} \to π^{\pm (0)} X$, where $X$ does not contain a charm (anti)quark. We find that the process $\bar B^0 \to π^- X$ ($B^0 \to π^+ X$) can be particularly useful for determination of the CKM matrix element $|V_{ub}|$. We calculate and present the branching ratio (BR) of $\bar B^0 \to π^- X$ as a function of $|V_{ub}|$, with an estimate of possible uncertainties. It is expected that the BR is an order of $10^{-4}$. Our estimation indicates that one can phenomenologically determine $|V_{ub}|$ with reasonable accuracy by measuring the BR of $\bar B^0 \to π^- X$ ($B^0 \to π^+ X$).

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arXiv2002

Charmless Non-Leptonic B Decays and R-parity Violating Supersymmetry

We examine the charmless hadronic B decay modes in the context of R-parity violating ($\rpv$) supersymmetry. We try to explain the large branching ratio (compared to the Standard Model (SM) prediction) of the decay $B^{\pm}\to η' K^{\pm}$. There exist data for other observed $η^{(\prime)}$ modes and among these modes, the decay $B^{0}\to ηK^{*0}$ is also found to be large compared to the SM prediction. We investigate all these modes and find that only two pairs of $\rpv$ coupling can satisfy the requirements without affecting the other $B\ra PP$ and $B\ra VP$ decay modes barring the decay $B\raϕK$. From this analysis, we determine the preferred values of the $\rpv$ couplings and the effective number of color $N_c$. We also calculate the CP asymmetry for the observed decay modes affected by these new couplings.

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arXiv2002

On Lepton Flavor Violation in Tau Decays

We study lepton flavor violation (LFV) in tau decays induced by heavy Majorana neutrinos within two models: (I) the Standard Model with additional right-handed heavy Majorana neutrinos, i.e., a typical seesaw-type model; (II) the Standard Model with left-handed and right-handed neutral singlets, which are inspired by certain scenarios of SO(10)models and heterotic superstring models with E_6 symmetry. We calculate various LFV branching ratios and a T-odd asymmetry. The seesaw Model I predicts very small branching ratios for LFV processes in most of the parameter space, although in a very restricted parameter region it can reach maximal branching ratios Br(tau to mu gamma) approx 10^-9 and Br(tau to 3mu) approx 10^-10. In contrast, Model II may show branching ratios Br(tau to e gamma) approx 10^-8 and Br(tau to 3e) < 10^-9, over a sizable region of the parameter space, large enough to be tested by experiments in the near future.

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arXiv2002

Longitudinal polarization asymmetry of leptons in the pure leptonic B decays

Longitudinal lepton polarization asymmetry in B_q -> l l (q = d, s$ and l = e, mu, tau) decays is investigated. The analysis is done in a general manner by using the effective operators approach. It is shown that the longitudinal lepton polarization asymmetry would provide a direct search for the scalar and pseudoscalar type interactions, which are induced in all variants of Higgs-doublet models.

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arXiv2002

Difficulties in Obtaining Weak Phases from $b\to d$ Penguin Decays

We re-examine a recent proposal for obtaining βusing the measurements of the b -> d penguin decays B_d(t) -> K^0 \kbar and B_s(t) -> ϕK_S, along with a theoretical assumption. We show that there are in fact three assumptions one can make, so that the method can in principle be used to extract α, βor γ. We also show that it is the assumption which yields γwhich is the best. However, the theoretical error on this assumption is still 25-30%, which leads to an error on γof at least 20-25%. Given our current understanding of hadronic physics, it does not seem possible to reduce this error.

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arXiv2002

Measurement of the Width Difference of B_d Mesons

We estimate ΔGamma_d/Γ_d, including 1/m_b contributions and part of the next-to-leading order QCD corrections, and find it to be around 0.3%. We show the methods to measure ΔGamma_d/Γ_d by using at least two different final states on the untagged B_d decay. The nonzero width difference can also be used to identify new physics effects and to resolve a twofold discrete ambiguity in the B_d-\bar{B}_d mixing phase. With the high statistics and accurate time resolution of the upcoming LHC experiment, the measurement of ΔGamma_d seems to be possible. This measurement would be important for an accurate measurement of \sin2ϕ_1 at the LHC. We also derive an upper bound on the value of ΔGamma_d/Γ_d in the presence of new physics.

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arXiv2001

Measurement of the Lifetime Difference of $B_d$ Mesons: Possible and Worthwhile?

We estimate the decay width difference $ΔGamma_d / Γ_d$ in the $B_d$ system including $1/m_b$ contributions and next-to-leading order QCD corrections, and find it to be around 0.3%. We explicitly show that the time measurements of an untagged $B_d$ decaying to a single final state isotropically can only be sensitive to quadratic terms in $ΔGamma_d / Γ_d$, and hence the use of at least two different final states is desired. We discuss such pairs of candidate decay channels for the final states and explore the feasibility of a $ΔGamma_d / Γ_d$ measurement through them. The measurement of this width difference is essential for an accurate measurement of $\sin(2β)$ at the LHC. The nonzero width difference may also be used to identify new physics effects and to resolve a twofold discrete ambiguity in the $B_d$-$\bar{B}_d$ mixing phase. We also derive an upper bound on the value of $ΔGamma_d / Γ_d$ in the presence of new physics, and point out some differences in the phenomenology of width differences in the $B_s$ and $B_d$ systems.

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arXiv2001

Using Bs(t) -> phi K_s to measure Sin 2 beta

In this talk we show that, unlike other pure $b\to d$ penguin processes, the decay $\bs(t)\toϕ\ks$ is dominated by a single amplitude, that of the internal $t$-quark. Thus, the indirect CP asymmetry in this decay probes $\sin 2β$. This cancellation holds for most part of the parameter space and error on $\sin 2β$ is less than 10%. By measuring the direct CP asymmetry, one can get a better idea of the probable error on $\sin 2β$.

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arXiv2001

Study of Semileptonic Decays $B^\pm \to η^{(\prime)} l ν$

We study semileptonic decays $B^\pm \to η^{(\prime)} l ν$, which are suggested to be used to extract the hadronic form factors of $B$ meson decays to $η(η^{\prime})$ and the angle of $η-η^{\prime}$ mixing. This would be of great benefit to theoretical studies of $B$ nonleptonic decays involving $η$ and $η^{\prime}$, and could lead to a reliable and complementary determination of $V_{ub}$. The branching ratios are estimated to be ${\cal B}(B^\pm \toη^{(\prime)} l ν)=4.32 \pm 0.83 (2.10 \pm 0.40) \times 10^{-5}$, which could be extensively studied experimentally at $BaBar$ and Belle.

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arXiv2001

Hadronic B Decays to Charmless VT Final States

Charmless hadronic decays of B mesons to a vector meson (V) and a tensor meson (T) are analyzed in the frameworks of both flavor SU(3) symmetry and generalized factorization. We also make comments on B decays to two tensor mesons in the final states. Certain ways to test validity of the generalized factorization are proposed, using $B \to VT$ decays. We calculate the branching ratios and CP asymmetries using the full effective Hamiltonian including all the penguin operators and the form factors obtained in the non-relativistic quark model of Isgur, Scora, Grinstein and Wise.

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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.

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