Yong-Yeon Keum
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Research Subjects
Research Interests
Yong-Yeon Keum has a total of 7 co-authors. Here are the top co-authors by number of shared publications:
- Hsiang-Nan Li
Department of Physics, National Cheng-Kung University, Tainan, Taiwan 701, Republic of China
7 shared publications - A. I. Sanda
Department of Physics, Nagoya University, Chikusa-ku Furo-cho, Nagoya 464-8602, Japan
3 shared publications - A. G. Akeroyd
KEK Theory Group 1-1 Oho Tsukuba 305-0801 Japan
2 shared publications - Chuan-Hung Chen
Department of Physics National Cheng-Kung University 701 Tainan Taiwan Republic of China
2 shared publications - Otto C. W. Kong
Institute of Physics Academia Sinica 11529 Nankang Taipei Taiwan
2 shared publications - S. Recksiegel
Theory Group KEK 305-0801 Tsukuba Ibaraki JAPAN
2 shared publications
Latest Publications
- 5 November 2001
- Published by American Physical Society (APS) in Physical Review D
- Vol. 64 (11) , 112002
Perturbative QCD analysis ofdecays and power countingWe investigate the exclusive nonleptonic B meson decays in the perturbative QCD formalism. It is shown that the end-point (logarithmic and linear) singularities in the decay amplitudes do not exist, after and threshold resummations are included. Power counting for emission and annihilation topologies of diagrams, including both factorizable and nonfactorizable ones, is discussed with Sudakov effects taken into account. Our predictions for the branching ratios are larger than those from the factorization approach because of dynamical enhancement of penguin contributions. Whether this enhancement is essential for penguin-dominated modes can be justified by experimental data.- 5 November 2001
- Published by American Physical Society (APS) in Physical Review D
- Vol. 64 (11) , 112002
Perturbative QCD analysis ofdecays and power countingWe investigate the exclusive nonleptonic B meson decays in the perturbative QCD formalism. It is shown that the end-point (logarithmic and linear) singularities in the decay amplitudes do not exist, after and threshold resummations are included. Power counting for emission and annihilation topologies of diagrams, including both factorizable and nonfactorizable ones, is discussed with Sudakov effects taken into account. Our predictions for the branching ratios are larger than those from the factorization approach because of dynamical enhancement of penguin contributions. Whether this enhancement is essential for penguin-dominated modes can be justified by experimental data.- Open AccessPerturbative QCD analysis of $B \to φK$ decays and Power countingWe 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 exist, after $k_T$ and threshold resummations are included. Power counting for emission and annihilation topologies of diagrams, including both factorizable and nonfactorizable ones, is discussed with Sudakov effects taken into account. Our predictions for the branching ratios $B(B\to\phi K)\sim 10 \times 10^{-6}$ are larger than those ($\sim 4 \times 10^{-6}$) from the factorization approach because of dynamical enhancement of penguin contributions. Whether this enhancement is essential for penguin-dominated modes can be justified by experimental data.Open AccessPerturbative QCD analysis of $B \to φK$ decays and Power countingWe 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 exist, after $k_T$ and threshold resummations are included. Power counting for emission and annihilation topologies of diagrams, including both factorizable and nonfactorizable ones, is discussed with Sudakov effects taken into account. Our predictions for the branching ratios $B(B\to\phi K)\sim 10 \times 10^{-6}$ are larger than those ($\sim 4 \times 10^{-6}$) from the factorization approach because of dynamical enhancement of penguin contributions. Whether this enhancement is essential for penguin-dominated modes can be justified by experimental data.
- 3 May 2001
- Published by American Physical Society (APS) in Physical Review D
- Vol. 63 (11)
One-loop neutron electric dipole moment from supersymmetry withoutRparity
We present a detailed analysis together with exact numerical calculations on one-loop contributions to neutron electric dipole moment from supersymmetry without R-parity, focusing on the gluino, chargino, and neutralino contributions. Apart from the neglected family mixing among quarks, complete formulae are given for the various contributions, through the quark dipole operators, to which the present study is restricted. We discuss the structure and main features of the R-parity violating contributions and the interplay between the R-parity conserving and violating parameters. In particular, the parameter combination $\mu_i^*\lambda^{\prime}_{i11}$, under the optimal parametrization adopted, is shown to be solely responsible for the R-parity violating contributions in the supersymmetric loop diagrams. While $\mu_i^*\lambda^{\prime}_{i11}$ could bear a complex phase, the latter is not necessary to have a R-parity violating contribution.Comment: 43 pages Revtex with 15 eps- and 4 ps- figure files incoporated; proofread version to be published in Phys. Rev.- 3 May 2001
- Published by American Physical Society (APS) in Physical Review D
- Vol. 63 (11)
One-loop neutron electric dipole moment from supersymmetry withoutRparity
We present a detailed analysis together with exact numerical calculations on one-loop contributions to neutron electric dipole moment from supersymmetry without R-parity, focusing on the gluino, chargino, and neutralino contributions. Apart from the neglected family mixing among quarks, complete formulae are given for the various contributions, through the quark dipole operators, to which the present study is restricted. We discuss the structure and main features of the R-parity violating contributions and the interplay between the R-parity conserving and violating parameters. In particular, the parameter combination $\mu_i^*\lambda^{\prime}_{i11}$, under the optimal parametrization adopted, is shown to be solely responsible for the R-parity violating contributions in the supersymmetric loop diagrams. While $\mu_i^*\lambda^{\prime}_{i11}$ could bear a complex phase, the latter is not necessary to have a R-parity violating contribution.Comment: 43 pages Revtex with 15 eps- and 4 ps- figure files incoporated; proofread version to be published in Phys. Rev.- Open Access
One-loop Neutron Electric Dipole Moment from Supersymmetry without R-parity
We present a detailed analysis together with exact numerical calculations on one-loop contributions to neutron electric dipole moment from supersymmetry without R-parity, focusing on the gluino, chargino, and neutralino contributions. Apart from the neglected family mixing among quarks, complete formulae are given for the various contributions, through the quark dipole operators, to which the present study is restricted. We discuss the structure and main features of the R-parity violating contributions and the interplay between the R-parity conserving and violating parameters. In particular, the parameter combination $\mu_i^*\lambda^{\prime}_{i11}$, under the optimal parametrization adopted, is shown to be solely responsible for the R-parity violating contributions in the supersymmetric loop diagrams. While $\mu_i^*\lambda^{\prime}_{i11}$ could bear a complex phase, the latter is not necessary to have a R-parity violating contribution.Open AccessOne-loop Neutron Electric Dipole Moment from Supersymmetry without R-parity
We present a detailed analysis together with exact numerical calculations on one-loop contributions to neutron electric dipole moment from supersymmetry without R-parity, focusing on the gluino, chargino, and neutralino contributions. Apart from the neglected family mixing among quarks, complete formulae are given for the various contributions, through the quark dipole operators, to which the present study is restricted. We discuss the structure and main features of the R-parity violating contributions and the interplay between the R-parity conserving and violating parameters. In particular, the parameter combination $\mu_i^*\lambda^{\prime}_{i11}$, under the optimal parametrization adopted, is shown to be solely responsible for the R-parity violating contributions in the supersymmetric loop diagrams. While $\mu_i^*\lambda^{\prime}_{i11}$ could bear a complex phase, the latter is not necessary to have a R-parity violating contribution. - Open Access
Direct CP Asymmetry of B -> X_d γin the effective SUSY model
We investigate the effect of supersymmetric CP violating phases on the inclusive decay B\to X_d\gamma. Although such a decay contains a large background from B\to X_s\gamma, if isolated it may exhibit sizeable CP violation, both in the Standard Model (SM) and in the context of models beyond the SM. With unconstrained supersymmetric CP violating phases we show that the direct CP asymmetry (A_CP) lies in the region -40% \le A_CP \le 40%, where a positive asymmetry would constitute a clear signal of physics beyond the SM. Even if a direct measurement of B\to X_d\gamma proves too dif ficult experimentally, its asymmetry contributes non-negligibly to the measurements of A_CP for B\to X_s\gamma, and thus should be included in future analyses. We show t hat there may be both constructive and destructive interference between A^d\gamma_CP and A^s\gamma_CP.
Open AccessDirect CP Asymmetry of B -> X_d γin the effective SUSY model
We investigate the effect of supersymmetric CP violating phases on the inclusive decay B\to X_d\gamma. Although such a decay contains a large background from B\to X_s\gamma, if isolated it may exhibit sizeable CP violation, both in the Standard Model (SM) and in the context of models beyond the SM. With unconstrained supersymmetric CP violating phases we show that the direct CP asymmetry (A_CP) lies in the region -40% \le A_CP \le 40%, where a positive asymmetry would constitute a clear signal of physics beyond the SM. Even if a direct measurement of B\to X_d\gamma proves too dif ficult experimentally, its asymmetry contributes non-negligibly to the measurements of A_CP for B\to X_s\gamma, and thus should be included in future analyses. We show t hat there may be both constructive and destructive interference between A^d\gamma_CP and A^s\gamma_CP.
- 5 March 2001
- Published by American Physical Society (APS) in Physical Review D
- Vol. 63 (7) , 074006
Nonleptonic charmlessBdecays: Factorization versus perturbative QCD
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 factorizable, nonfactorizable, and annihilation contributions, infrared-cutoff and scale dependences, and strong phases. It is proposed that measurement of asymmetries in two-body B meson decays provides an appropriate test of these approaches.- 5 March 2001
- Published by American Physical Society (APS) in Physical Review D
- Vol. 63 (7) , 074006
Nonleptonic charmlessBdecays: Factorization versus perturbative QCD
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 factorizable, nonfactorizable, and annihilation contributions, infrared-cutoff and scale dependences, and strong phases. It is proposed that measurement of asymmetries in two-body B meson decays provides an appropriate test of these approaches.- Open Access
Effect of Supersymmetric phases on the Direct CP Asymmetry of B -> X_d γ
We investigate the effect of supersymmetric CP violating phases on the inclusive decay B\to X_d\gamma. Although such a decay contains a large background from B\to X_s\gamma, if isolated it may exhibit sizeable CP violation, both in the Standard Model (SM) and in the context of models beyond the SM. With unconstrained supersymmetric CP violating phases we show that the direct CP asymmetry (A_CP) lies in the region -40% \le A_CP \le 40%, where a positive asymmetry would constitute a clear signal of physics beyond the SM. Even if a direct measurement of B\to X_d\gamma proves too dif ficult experimentally, its asymmetry contributes non-negligibly to the measurements of A_CP for B\to X_s\gamma, and thus should be included in future analyses. We show t hat there may be both constructive and destructive interference between A^d\gamma_CP and A^s\gamma_CP.
Open AccessEffect of Supersymmetric phases on the Direct CP Asymmetry of B -> X_d γ
We investigate the effect of supersymmetric CP violating phases on the inclusive decay B\to X_d\gamma. Although such a decay contains a large background from B\to X_s\gamma, if isolated it may exhibit sizeable CP violation, both in the Standard Model (SM) and in the context of models beyond the SM. With unconstrained supersymmetric CP violating phases we show that the direct CP asymmetry (A_CP) lies in the region -40% \le A_CP \le 40%, where a positive asymmetry would constitute a clear signal of physics beyond the SM. Even if a direct measurement of B\to X_d\gamma proves too dif ficult experimentally, its asymmetry contributes non-negligibly to the measurements of A_CP for B\to X_s\gamma, and thus should be included in future analyses. We show t hat there may be both constructive and destructive interference between A^d\gamma_CP and A^s\gamma_CP.
- Top Cited Papers
- 2 February 2001
- Published by American Physical Society (APS) in Physical Review D
- Vol. 63 (5) , 054008
Penguin enhancement anddecays in perturbative QCDWe compute the branching ratios of decays in the framework of the perturbative QCD factorization theorem. Decay amplitudes are classified into the topologies of tree, penguin, and annihilation amplitudes, all of which contain both factorizable and nonfactorizable contributions. These contributions are expressed as the convolutions of hard quark decay amplitudes with universal meson wave functions. It is shown that (1) matrix elements of penguin operators are dynamically enhanced compared to those employed in the factorization assumption, (2) annihilation diagrams are not negligible, contrary to common belief, (3) annihilation diagrams contribute large strong phases, and (4) the uncertainty of the current data of the ratio and of asymmetries is too large to give a constraint of the unitarity angle Assuming which is extracted from the best fit to the data of predictions for the branching ratios of the four modes are consistent with data.- 2 February 2001
- Published by American Physical Society (APS) in Physical Review D
- Vol. 63 (5) , 054008
Top Cited PapersPenguin enhancement anddecays in perturbative QCDWe compute the branching ratios of decays in the framework of the perturbative QCD factorization theorem. Decay amplitudes are classified into the topologies of tree, penguin, and annihilation amplitudes, all of which contain both factorizable and nonfactorizable contributions. These contributions are expressed as the convolutions of hard quark decay amplitudes with universal meson wave functions. It is shown that (1) matrix elements of penguin operators are dynamically enhanced compared to those employed in the factorization assumption, (2) annihilation diagrams are not negligible, contrary to common belief, (3) annihilation diagrams contribute large strong phases, and (4) the uncertainty of the current data of the ratio and of asymmetries is too large to give a constraint of the unitarity angle Assuming which is extracted from the best fit to the data of predictions for the branching ratios of the four modes are consistent with data. - Open Access
Fat penguins and imaginary penguins in perturbative QCD
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 approximation. It is also shown that annihilation diagrams are not negligible, and give large strong phases. Our results for branching ratios of $B\to K\pi$ decays for a representative parameter set are consistent with data. 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 approximation. It is also shown that annihilation diagrams are not negligible, and give large strong phases. Our results for branching ratios of $B\to K\pi$ decays for a representative parameter set are consistent with data.Open AccessFat penguins and imaginary penguins in perturbative QCD
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 approximation. It is also shown that annihilation diagrams are not negligible, and give large strong phases. Our results for branching ratios of $B\to K\pi$ decays for a representative parameter set are consistent with data. 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 approximation. It is also shown that annihilation diagrams are not negligible, and give large strong phases. Our results for branching ratios of $B\to K\pi$ decays for a representative parameter set are consistent with data. - Open Access
R-parity Violating Contribution to Neutron EDM at One-loop Order
We present the full result for the down squark mass-squared matrix in the complete theory of supersymmetry without R-parity where all kind of R-parity violating terms are admitted without bias. An optimal parametrization, the single-VEV parametrization, is used. The major result is a new contribution to $LR$ squark mixing, involving both bilinear and trilinear R-parity violating couplings. Among other things, the latter leads to neutron electric dipole moment at one-loop level. Similiar mechanism leading to electron electric dipole moment at the same level. We present here a short report on major features of neutron electric dipole moment from supersymmetry without R-parity and give the interesting constraints obtained.Open AccessR-parity Violating Contribution to Neutron EDM at One-loop Order
We present the full result for the down squark mass-squared matrix in the complete theory of supersymmetry without R-parity where all kind of R-parity violating terms are admitted without bias. An optimal parametrization, the single-VEV parametrization, is used. The major result is a new contribution to $LR$ squark mixing, involving both bilinear and trilinear R-parity violating couplings. Among other things, the latter leads to neutron electric dipole moment at one-loop level. Similiar mechanism leading to electron electric dipole moment at the same level. We present here a short report on major features of neutron electric dipole moment from supersymmetry without R-parity and give the interesting constraints obtained.