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Sep 17, 2013
09/13

by
Chien-Wen Hwang

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In this paper, a study of light-cone distribution amplitudes (LCDAs) for $s$-wave heavy meson are presented in both general and heavy quark frameworks. Within the light-front approach, the leading twist light-cone distribution amplitudes, $\phi_M(u)$, and their relevant decay constants of heavy pseudoscalar and vector mesons, $f_M$, have simple relations. These relations can be further simplified when the heavy quark limit is taken into consideration. After fixing the parameters that appear in...

Source: http://arxiv.org/abs/1003.0972v3

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48

Sep 18, 2013
09/13

by
Chien-Wen Hwang

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The strong decays of the heavy baryons \Sigma^{(*)}_Q \to \Lambda_Q \pi are studied by combining the chiral dynamics and the MIT bag model. In charm sector, we calculate the decay widths \Gamma(\Sigma^{(*)}_c\to \Lambda_c\pi) and compare with the experimental data and other theoretical estimations. In addition, we also predict the strong decay widths \Gamma(\Sigma^{(*)}_b\to \Lambda_b\pi).

Source: http://arxiv.org/abs/hep-ph/0611221v2

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97

Sep 17, 2013
09/13

by
Chien-Wen Hwang

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We discuss the semileptonic weak decays of $P\to P$ ($P$ denotes a pseudoscalar meson). In these timelike processes, the problem of the nonvalence contribution is solved systematically as well as the valence one. These contributions are related to the light-front quark model (LFQM), and the numerical results show the nonvalence contribution of the light-to-light transition is larger than of the heavy-to-light one. In addition, the relevant CKM matrix elements are calculated. They are consistent...

Source: http://arxiv.org/abs/hep-ph/0108251v2

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46

Sep 22, 2013
09/13

by
Chien-Wen Hwang

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We study the hyperfine mass differences of heavy hadrons in the heavy quark effect theory (HQET). The effects of one-gluon exchange interaction are considered for the heavy mesons and baryons. Base on the known experimental data, we predict the masses of some heavy baryons in a model-independent way.

Source: http://arxiv.org/abs/0805.2439v1

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57

Sep 22, 2013
09/13

by
Chien-Wen Hwang

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In this paper, the quark distribution amplitudes of 1S and 2S heavy quarkonium states are studied in terms of Gaussian-type wave functions. The transverse momenta $p_\perp$ integrals of the formulae for the decay constant are performed analytically. Then the quark distribution amplitudes are obtained. In addition, the $\xi$-moments are also calculated. After fixing the relevant parameters appearing in the quark distribution amplitude, the curves of the quark distribution amplitude for 1S and 2S...

Source: http://arxiv.org/abs/0811.0648v2

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Sep 18, 2013
09/13

by
Chien-Wen Hwang

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The charge and transition form factors of pion ($F_\pi$, $F_{\pi\gamma}$, and $F_{\pi\gamma^*}$) are studied with the light-front quark model. We find that our results for $F_\pi$ and $F_{\pi\gamma}$ agree very well with experimental data. Furthermore, the decay constants of $\eta$ and $\eta'$ are evaluated. We also calculate $F_{\eta\gamma}$ and $F_{\eta'\gamma}$ and compare with the experimental data.

Source: http://arxiv.org/abs/hep-ph/0005163v2

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Sep 22, 2013
09/13

by
Chien-Wen Hwang

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In this paper, a study of light-cone distribution amplitudes for p-wave heavy quarkonium states are presented. Within the light-front framework, the leading twist light-cone distribution amplitudes, and their relevant decay constants, have some simple relations. These relations can be further simplified when the non-relativistic limit and the wave function as a function of relative momentum |\vec\kappa| are taken into consideration. In addition, the \kappa_\perp integrations in the equations of...

Source: http://arxiv.org/abs/0906.4412v2

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Sep 19, 2013
09/13

by
Chien-Wen Hwang

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In this paper, the decay constants and mean square radii of pseudoscalar heavy mesons are studied in the SU(3) symmetry breaking. Within the light-front framework, the ratios $f_{D_s}/f_D$ and $f_{B_s}/f_B$ are individually estimated using the hyperfine splittings in the $D_{(s)}^*-D_{(s)}$ and $B_{(s)}^*-B_{(s)}$ states and the light quark masses, $m_{s,q}$ ($q=u,d$), to extract the wave function parameter $\beta$. The values $f_{D_s}/f_D= 1.29\pm0.07$ and $f_{B_s}/f_B= 1.32\pm 0.08$ are...

Source: http://arxiv.org/abs/0910.0145v4

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Sep 22, 2013
09/13

by
Chien-Wen Hwang

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The electromagnetic (EM) form fators of the pseudoscalar and vector mesons are calculated in the light-front framework. We extract these form factors from the relevant matrix elements directly, instead of choosing the Breit frame. The results show that the charge radius of the meson are related to both the first and second longitudinal momentum square derivative of the momentum distribution function. In addition, the static properties of the EM form factors and the heavy quark symmetry of the...

Source: http://arxiv.org/abs/hep-ph/0106194v1

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47

Sep 18, 2013
09/13

by
Chien-Wen Hwang

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We write down some relevant matrix elements for the scattering and decay processes of the pion by considering a quark-meson vertex function. The pion charge and transition form factors $F_\pi$, $F_{\pi\gamma}$, and $F_{\pi\gamma^*}$ are extracted from these matrix elements using a relativistic quark model on the light-front. We found that, the form factors $F_\pi$ and $F_{\pi\gamma}$ in the space-like region agree well with experiment. Furthermore, the branching ratios of all observed decay...

Source: http://arxiv.org/abs/hep-ph/0105016v1

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Sep 18, 2013
09/13

by
Chien-Wen Hwang

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In this paper, a study of light-cone distribution amplitudes for p-wave heavy mesons is presented in both general and heavy quark frameworks. Within the light-front approach, the leading twist light-cone distribution amplitudes, \phi_M(u) and their relevant decay constants of heavy scalar, axial-vector and tensor mesons, f_M, are formulated. The relations of some decay constants can be simplified when the heavy quark limit is taken into account. After fixing the parameters which appear in a...

Source: http://arxiv.org/abs/1209.4713v2

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Sep 21, 2013
09/13

by
Chien-Wen Hwang

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We study the wave functions of light and heavy mesons in both hard-wall (HW) and soft-wall (SW) holographic models which use AdS/CFT correspondence. In the case of massless constituents, the asymptotic behaviors of the electromagnetic form factor, the distribution amplitudes, and the decay constants for the two models are the same, if the relation between the dilaton scale parameter and the size of meson is an inverse proportion. On the other hand, by introducing a quark mass dependence in the...

Source: http://arxiv.org/abs/1204.1791v2

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10.0

Jun 28, 2018
06/18

by
Chi-Yee Cheung; Chien-Wen Hwang

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In this paper, we investigate three symmetry breaking effects in strong and radiative decays of strange heavy mesons. We study 1/m_Q corrections within the heavy quark effect theory, as well as SU(3) and SU(2) symmetry breakings induced by light quark mass differences and the \eta-\pi mixing vertex. These effects are studied in a covariant model. The numerical results show that the 1/m_Q corrections of the coupling constants are consistent with \alpha_s \Lambda_{QCD}/m_Q. The SU(3) symmetry...

Topic: High Energy Physics - Phenomenology

Source: http://arxiv.org/abs/1508.07686

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6.0

Jun 30, 2018
06/18

by
Chi-Yee Cheung; Chien-Wen Hwang

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In this paper, we investigate symmetry breaking effects in strong and radiative decays of heavy mesons. We study $1/m_Q$ corrections within the heavy quark effective theory. These effects are studied in a covariant model for heavy mesons. The numerical results are consistent with the experimental data and some other theoretical calculations. These provide a vote of confidence for the validity of this covariant model.

Topic: High Energy Physics - Phenomenology

Source: http://arxiv.org/abs/1401.3917

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89

Jul 20, 2013
07/13

by
Chien-Wen Hwang; Zheng-Tao Wei

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The light-front approach is a relativistic quark model and offers many insights to the internal structures of the hadronic bound states. In this study, we apply the covariant light-front approach to ground-state heavy quarkonium. The pesudoscalar and vector meson decay constants are discussed. We present a detailed study of two-photon annihilation P \to \gamma \gamma and magnetic dipole transition V \to P \gamma processes. The numerical predictions of the light-front approach are consistent...

Source: http://arxiv.org/abs/hep-ph/0609036v2

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48

Jul 20, 2013
07/13

by
Chien-Wen Hwang; Ching-Ho Chung

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In this paper, the electromagnetic mass differences of heavy hadrons are discussed, while ignoring the relevant hyperfine interactions. The effects of one-photon exchange interaction and up-down quark mass difference are parameterized. Two mass difference equations 2\Sigma_c^+ - (\Sigma_c^{++} + \Sigma_c^0) = 2\Sigma_b^0 - (\Sigma_b^+ + \Sigma_b^-) and (\Xi_{cc}^+ - \Xi_{cc}^{++}) + (\Xi_{bb}^- - \Xi_{bb}^{0}) =2(\Xi_{bc}^0 - \Xi_{bc}^{+}) for the heavy baryons are obtained. In addition, the...

Source: http://arxiv.org/abs/0804.4044v3

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53

Jul 19, 2013
07/13

by
Chien-Wen Hwang; Rurng-Sheng Guo

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In this paper, a study of two-photon and two-gluon decays in the context of p-wave heavy quarkonia is presented. Within the covariant light-front framework, the annihilation rates of scalar and tensor quarkonium states are derived. In the absence of free parameters in this case, the results for the charmonium decay widths are consistent with the experimental data. However, in comparison to other theoretical calculations, there are large discrepancies in our results regarding bottomonia.

Source: http://arxiv.org/abs/1005.2811v3

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56

Sep 22, 2013
09/13

by
Hai-Yang Cheng; Chun-Khiang Chua; Chien-Wen Hwang

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We study the decay constants and form factors of the ground-state s-wave and low-lying p-wave mesons within a covariant light-front approach. Numerical results of the form factors for transitions between a heavy pseudoscalar meson and an s-wave or p-wave meson and their momentum dependence are presented in detail. In particular, form factors for heavy-to-light and B to D** transitions, where D** denotes generically a p-wave charmed meson, are compared with other model calculations. The...

Source: http://arxiv.org/abs/hep-ph/0310359v4

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Sep 23, 2013
09/13

by
Hai-Yang Cheng; Chi-Yee Cheung; Chien-Wen Hwang

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Within the light-front framework, form factors for $P\to P$ and $P\to V$ transitions ($P$: pseudoscalar meson, $V$: vector meson) due to the valence-quark configuration are calculated directly in the entire physical range of momentum transfer. The behavior of form factors in the infinite quark mass limit are examined to see if the requirements of heavy-quark symmetry are fulfilled. We find that the Bauer-Stech-Wirbel type of light-front wave function fails to give a correct normalization for...

Source: http://arxiv.org/abs/hep-ph/9607332v1

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47

Sep 22, 2013
09/13

by
Hai-Yang Cheng; Chun-Khiang Chua; Chien-Wen Hwang

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Assuming the two diquark structure for the pentaquark state as advocated in the Jaffe-Wilczek model, there exist exotic parity-even anti-sextet and parity-odd triplet heavy pentaquark baryons. The theoretical estimate of charmed and bottom pentaquark masses is quite controversial and it is not clear whether the ground-state heavy pentaquark lies above or below the strong-decay threshold. We study the weak transitions of heavy pentaquark states using the light-front quark model. In the heavy...

Source: http://arxiv.org/abs/hep-ph/0403232v2

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Sep 19, 2013
09/13

by
Hai-Yang Cheng; Chi-Yee Cheung; Chien-Wen Hwang; Wei-Min Zhang

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In this paper we construct a covariant light-front model of heavy mesons within the framework of heavy quark effective theory (HQET). The covariant model consists of the light-front heavy meson bound states constructed in the heavy quark limit with heavy quark symmetry and heavy quark effective theory as its basis. Within this model, the Isgur-Wise function and decay constants in the infinite quark mass limit can be evaluated in a very simple and the most general way. The results are ensured to...

Source: http://arxiv.org/abs/hep-ph/9709412v2

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Sep 19, 2013
09/13

by
Tzuu-Kang Chyi; Chien-Wen Hwang; W. F. Kao; Guey-Lin Lin; Kin-Wang Ng; Jie-Jun Tseng

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The weak-field expansion of the charged fermion propagator under a uniform magnetic field is studied. Starting from Schwinger's proper-time representation, we express the charged fermion propagator as an infinite series corresponding to different Landau levels. This infinite series is then reorganized according to the powers of the external field strength $B$. For illustration, we apply this expansion to $\gamma\to \nu\bar{\nu}$ and $\nu\to \nu\gamma$ decays, which involve charged fermions in...

Source: http://arxiv.org/abs/hep-th/9912134v2

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51

Sep 21, 2013
09/13

by
Tzuu-Kang Chyi; Chien-Wen Hwang; W. F. Kao; Guey-Lin Lin; Kin-Wang Ng; Jie-Jun Tseng

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We study the neutrino-photon processes such as $\gamma\gamma\to \nu\bar{\nu}$ and $\nu\gamma\to \nu\gamma$ in a background magnetic field smaller than the critical magnetic field $B_c\equiv m_e^2/e$. Using Schwinger's proper-time method, we extract leading magnetic-field contributions to the above processes. Our result is valid throughout the kinematic regime where both neutrino and photon energies are significantly smaller than $m_W$. We briefly discuss the astrophysical implications of our...

Source: http://arxiv.org/abs/hep-ph/9907384v2