arXiv subjects

C. S. Kim

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

At least 199 records · Page 11Linked to original sources

arXiv2001

Determination of the CP violating weak phase $γ$ from the Decays $B \to D π$

We propose a new method to extract the CP violating weak phase $γ$ (the phase of $V_{ub}^*$) in the CKM paradigm of the Standard Model, using $B^- \rightarrow D^0 π^- \rightarrow f π^-$ and $B^- \rightarrow \bar D^0 π^- \rightarrow f π^-$ decays, where $f$ are final states such as $K^+ π^-$, $K^+ ρ^-$, $K ππ$, {\it etc.} We also study the experimental feasibility of our new method. With possibility of new phases in the CKM matrix, we re-examine some of the previously proposed methods to determine $γ$, and find that it would be in principle possible to identify $γ$ and a new phase angle $θ$ separately.

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arXiv2001

Muon Anomalous Magnetic Moment (g-2)_mu and the Randall-Sundrum Model

We study the effects of the Kaluza-Klein gravitons in the Randall-Sundrum model on the recent BNL measurements of the muon (g-2) deviation from the standard model prediction. By examining the J-partial wave unitarity bounds of the elastic process gamma+gamma->gamma+gamma, the cut-off on the number of massive KK gravitons, n_c, has been introduced. We found that the recently measured (Delta a_mu) can be accommodated in the RS model, within the natural parameter space allowed by the perturbative unitarity. For example, dozens (hundreds) of the n_c for Lambda_pi=1-2 TeV (3 TeV) can explain the reported Delta a_mu.

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arXiv2001

Measuring sin 2βin Bs(t) -> phi K_s

We show that, unlike other pure b -> d penguin processes, the decay Bs(t) -> phi K_s is dominated by a single amplitude, that of the internal t-quark. The contributions of the u- and c-quark operators each vanish due to a cancellation between the (V-A) \otimes (V-A) and (V-A) \otimes (V+A) matrix elements. Thus, the indirect CP asymmetry in this decay probes sin 2β. Although this cancellation is complete only for certain values of the s- and b-quark masses, the theoretical uncertainty on sin 2βis still less than 10% over most (~80%) of the parameter space. By measuring the direct CP asymmetry, one can get a better idea of the probable error on sin 2β.

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arXiv2001

Determination of the CP Phase $γ$ with Possibility of New Physics

We propose a new method to extract the CP violating weak phase $γ$ in the CKM paradigm of the Standard Model, using $B^- \to D^0 π^- \to f π^-$ and $B^- \to \bar D^0 π^- \to f π^-$ decays, where $f$ are final states such as $K^+ π^-$, $K^+ ρ^-$, $K ππ$, {\it etc.} We also study the experimental feasibility of our new method. With possibility of new phases in the CKM matrix, we re-examine some of the previously proposed methods to determine $γ$, and find that it would be in principle possible to identify $γ$ and a new phase angle $θ$ separately.

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arXiv2001

Possible Supersymmetric Effects on Angular Distributions in $B \to K^* (\to K π) \ell^+ \ell^- $ Decays

We investigate the angular distributions of the rare B decay, $B \to K^* (\to K π) \ell^+ \ell^-$, in general supersymmetric extensions of the standard model. We consider the new physics contributions from the operators $O_{7,8,9,10}$ in small invariant mass region of lepton pair. We show that the azimuthal angle distribution of the decay can tell us the new physics effects clearly from the behavior of the distribution, even if new physics does not change the decay rate substantially from the standard model prediction.

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arXiv2001

New Physics Working Group Summary of LCWS2000 at FNAL

Here I summarize P5-WG (New/Alternative Physics Working Group) of LCWS2000@FNAL, held on Oct 24-28, 2000. There were 13 talks altogether, 7 talks on collider signals from new particles/interactions and 6 talks on extra dimensional physics. We had very active and hot discussions among participants for those new/alternative physics/ideas.

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arXiv2001

Charmless Hadronic Decays of B Mesons to a Pseudoscalar and a Tensor Meson

We study two-body charmless hadronic decays of $B$ mesons to a pseudoscalar meson ($P$) and a tensor meson ($T$) in the frameworks of both flavor SU(3) symmetry and generalized factorization. Certain ways to test validity of the generalized factorization are proposed, based on the flavor SU(3) analysis. We present a set of relations between a flavor SU(3) amplitude and a corresponding amplitude in the generalized factorization which bridge both approaches in $B \to PT$ decays. The branching ratios and CP asymmetries are calculated using the \emph{full} effective Hamiltonian including all the \emph{penguin} operators and the form factors obtained in the non-relativistic quark model of Isgur, Scora, Grinstein and Wise. We identify the decay modes in which the branching ratios and CP asymmetries are expected to be relatively large.

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arXiv2001

Enhancement of the Higgs pair production at LHC; the MSSM and extra dimension effects

The neutral Higgs pair production at the LHC is studied in the MSSM, the large extra dimensional (ADD) model and the Randall-Sundrum (RS) model, where the total cross section can be significantly enhanced compared to that in the SM. The $p_{_T}$, invariant mass and rapidity distributions of each model have been shown to be distinctive: The ADD model raises the $p_T$ and invariant mass distributions at high scales of $p_T$ and invariant mass; in the RS model resonant peaks appear after the SM contribution dies away; the SM and the MSSM distributions drop rapidly at those high scales; in the ADD and the RS models the rapidity distributions congregate more around the center. It is concluded that various distributions of the Higgs pair production at the LHC with restrictive kinematic cuts would provide one of the most robust signals for the extra dimensional effects.

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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.

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arXiv2000

The Effects of Non-Local Interactions in Rare B Decays, B -> X_s l^+l^-

The effects of non-local interactions in rare B decays, $\Bsll$, are investigated. We show the correlation between the branching ratio and the forward-backward asymmetry via two coefficients of the non-local interactions. This will certainly help us find any deviations from the standard model through the non-local interactions.

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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.

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arXiv2000

The CKM phase $α$ through $B \to a_0 π$

We propose the decay modes $B \to a_0 (\to ηπ) π$ to determine the CKM phase $α$. One can analyze these modes through (i) the $B \to a_0 π$ isospin pentagon, (ii) the time dependent Dalitz plot of $B^0(t) \to a_0^{\pm} π^{\mp} \to ηπ^+ π^-$, and (iii) the time dependence of $B^0(t) \to a_0^0 (\to ηπ^0) π^0$. We show that the $a_0 π$ modes have certain advantages as compared to the $ρπ$ modes, and strongly recommend the time dependent Dalitz plot analysis in the $a_0 π$ channel.

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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.

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arXiv2000

Hadronic Invariant Mass Spectrum in B -> X_u l nu Decay with Lepton Energy Cut

We discuss the implications of charged lepton energy cut to the hadronic invariant mass spectrum in charmless semileptonic B decays. Charged-lepton energy cut is inevitable in order to remove secondary leptonic events such as b -> c, tau -> l, and to identify the chaged leptons at detectors experimentally. We consider three possible lepton energy cuts, E_l^{cuts} = 0.6,1.5,2.3 GeV, and found that with the most probable cuts E_l^{cut} = 1.5 GeV and M_X^{max} = 1.5~(1.86) GeV, 45 ~ 60 % ~(58 ~ 67 %) of decay events survive. Therefore, B -> X_u l nu decay events can be efficiently distinguished from B -> X_c l nu decay events. We also discuss the possible model dependence on the results.

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arXiv2000

No CPT Violation from Tilted Brane in Neutral Meson--Antimeson Systems

Tilted brane in theories with large compact extra dimensions leads to spontaneous symmetry breaking of the Lorentz and rotational invariance in four dimensions, as shown by Dvali and Shifman. In this brief report, we point out that the mentioned Lorentz symmetry breaking, although leading to the CPT--violating interaction terms, cannot lead to the CPT violation in the experimentally interesting $K$--${\bar K}$ and analogous systems.

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arXiv2000

Is Cabibbo-Kobayasi-Maskawa Matrix Unitary?

First, we give summary of the present values of CKM matrix elements. Then, we discuss whether CKM matrix is unitary or not, and how we can find out if it is not unitary.

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arXiv2000

Heavy Majorana neutrino production at electron-muon colliders

Possibilities for detecting heavy Majorana neutrinos ($N$'s) at future $eμ$ colliders are investigated. In contrast to the $e^-e^+$ colliders (LEP200 and NLC), the center-of-mass (CMS) energies achieved at $eμ$ colliders can be much higher and the $Z$-mediated $s$ channel is excluded automatically. This opens the attractive possibility of having high production cross sections for $N$'s and at the same time probing only the strength of charged current couplings of $N$'s ($NWe$ and $NWμ$). The production cross sections and the expected numbers of events for the reaction $e^{\mp} μ^{\pm} \to NN \to W^{\pm} {\ell}^{\mp} W^{\pm} {\ell}^{\prime \mp}$ are calculated for various masses $M$ of the Majorana neutrinos and for the CMS energies $\sqrt{s} = 0.5-6.0$ TeV. The values of the charged current coupling parameters are set equal to their present upper bounds. We obtain reasonably high production cross sections. Further, the effects of the off-shell intermediate $N$'s turn out to be significant only at $\sqrt{s} \stackrel{>}{\approx} 2$ TeV.

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arXiv2000

Azimuthal Angle Distribution in $B \to K^* (\to K π) \ell^+ \ell^- $ at low invariant $m_{\ell^+ \ell^-}$ Region

We present the angular distribution of the rare B decay, $B \to K^* (\to K π) \ell^+ \ell^-$. By studying the azimuthal angle distribution in the low invariant mass region of dileptons, we can probe new physics effects efficiently. In particular, this distribution is found to be quite sensitive to the ratio of the contributions from two independent magnetic moment operators, which also contribute to $B \to K^* γ$. Therefore, our method can be very useful when new physics is introduced without changing the total decay rate of the $b \to s γ$. The angular distributions are compared with the predictions of the standard model, and are shown for the cases when the afore-mentioned ratio is different from the standard model prediction.

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