Searcharxiv⌕ Search

arXiv subjects

Yuan-Ben Dai

Publications and source records attributed to Yuan-Ben Dai.

At least 19 recordsLinked to original sources
arXiv2008

Contribution of $DK$ Continuum in the QCD Sum Rule for $D_{sJ}(2317)$

Using the soft-pion theorem and the assumption on the final-state interactions, we include the contribution of $DK$ continuum into the QCD sum rules for $D_{sJ}(2317)$ meson. We find that this contribution can significantly lower the mass and the decay constant of $D_s(0^+)$ state. For the value of the current quark mass $m_c(m_c)=1.286 {\rm GeV}$, we obtain the mass of $D_s(0^+)$ $M=2.33 \pm 0.02 {\rm GeV}$ in the interval $s_0=7.5-8.0 {\rm GeV}^2$, being in agreement with the experimental data, and the vector current decay constant of $D_s(0^+)$ $f_0=0.128 \pm 0.013 {\rm GeV}$, much lower than those obtained in previous literature.

hep-ph↗
arXiv2006

New QCD Sum Rule for $D(0^+)$

We derive a new QCD sum rule for $D(0^+)$ which has only the $Dπ$ continuum with a resonance in the hadron side, using the assumption similar to that has been successfully used in our previous work to the mass of $D_s(0^+)(2317)$. For the value of the pole mass $M_c=1.38 $ GeV as used in the $D_s(0^+)$ case we find that the mass of $D(0^+)$ derived from this sum rule is significantly lower than that derived from the sum rule with the pole approximation. Our result is in agreement with the experimental dada from Belle.

hep-ph↗
arXiv2004

Exclusive Semileptonic Rare Decays $B \to K^{(*)} l^+ l^-$ in a SUSY SO(10) GUT

In the SUSY SO(10) GUT context, we study the exclusive processes $B \to K^{(*)} l^+l^-(l=μ,τ)$. Using the Wilson coefficients of relevant operators including the new operators $Q_{1,2}^{(\prime)}$ which are induced by neutral Higgs boson (NHB) penguins, we evaluate some possible observables associated with these processes like, the invariant mass spectrum (IMS), lepton pair forward backward asymmetry (FBA), lepton polarization asymmetries etc. In this model the contributions from Wilson coefficients $C_{Q_{1,2}}^\prime$, among new contributions, are dominant. Our results show that the NHB effects are sensitive to the FBA, $dL/d\hat{s}$, and $dT/d\hat{s}$ of $B \to K^{(*)} τ^+ τ^-$ decay, which are expected to be measured in B factories, and the average of the normal polarization $dN/d\hat{s}$ can reach several percent for $B \to K μ^+ μ^-$ and it is 0.05 or so for $B\to K τ^+τ^-$, which could be measured in the future super B factories and provide a useful information to probe new physics and discriminate different models.

hep-ph↗
arXiv2004

Possible Interpretations of $D_{sJ}^+(2632)$ If It Really Exists

We analyze various possible interpretations of the narrow state $D_{sJ}^+(2632)$ observed by SELEX Collaboration recently, which lies above threshold and has abnormal decay pattern. These interpretations include: (1) several versions of tetraquarks; (2) conventional $c\bar s$ meson such as the first radial excitation of $D_s(2112)$ with abnormally large SU(3) symmetry breaking; (3) conventional $c\bar s$ meson with abnormally large $η_1$ coupling; (4) heavy hybrid meson. We discuss the physical implications of each interpretation. For example, if the existence of $D_{sJ}^+(2632)$ is confirmed as the first radial excitation of $D_s(2112)$ by other experiments, it will be helpful to look for (1) its SU(3) flavor partners $D_{J}^{0,+}(2530)$; (2) its B-meson analogues $B_{J}^{0,+}(5840), B_{sJ}^+(5940)$; (3) S-wave two pion decay modes.

hep-ph↗
arXiv2004

CP asymmetry in B \to phi K_S in a SUSY SO(10) GUT

We study the $B\to ϕK_S$ decay in a SUSY SO(10) GUT. We calculate the mass spectrum of sparticles for a given set of parameters at the GUT scale. We complete the calculations of the Wilson coefficients of operators including the new operators which are induced by NHB penguins at LO using the MIA with double insertions. It is shown that the recent experimental results on the time-dependent CP asymmetry $S_{ϕK}$ in $B\to ϕK_S$, which is negative and can not be explained in SM, can be explained in the model where there are flavor non-diagonal right-handed down squark mass matrix elements of 2nd and 3rd generations whose size satisfies all relevant constraints from known experiments ($τ\to μγ$, $B\to X_Sγ, B_s\to μ^+μ^-, B\to X_s μ^+μ^-, B\to X_s g, ΔM_s$, etc.). At the same time, the branching ratio for the decay can also be in agreement with experimental measurements.

hep-ph↗
arXiv2004

Dynamically Spontaneous Symmetry Breaking and Masses of Lightest Nonet Scalar Mesons as Composite Higgs Bosons

Based on the (approximate) chiral symmetry of QCD Lagrangian and the bound state assumption of effective meson fields, a nonlinearly realized effective chiral Lagrangian for meson fields is obtained from integrating out the quark fields by using the new finite regularization method. As the new method preserves the symmetry principles of the original theory and meanwhile keeps the finite quadratic term given by a physically meaningful characteristic energy scale $M_c$, it then leads to a dynamically spontaneous symmetry breaking in the effective chiral field theory. The gap equations are obtained as the conditions of minimal effective potential in the effective theory. The instanton effects are included via the induced interactions discovered by 't Hooft and found to play an important role in obtaining the physical solutions for the gap equations. The lightest nonet scalar mesons($σ$, $f_0$, $a_0$ and $κ$) appearing as the chiral partners of the nonet pseudoscalar mesons are found to be composite Higgs bosons with masses below the chiral symmetry breaking scale $Λ_χ \sim 1.2$ GeV. In particular, the mass of the singlet scalar (or the $σ$) is found to be $m_σ \simeq 677$ MeV.

hep-ph↗
arXiv2004

D_s(2317) and D_s(2457) from HQET Sum Rules

Within the framework of the heavy quark effective theory, QCD sum rules are used to calculate the masses of p-wave (c-bar s) states. The results for 0^+ and 1^+ states with the angular momentum of the light component j_l=1/2 are consistent with the experimental values for D_s(2317) and D_s(2457), respectively.

hep-ph↗
arXiv2003

Understanding the $D^+_{sJ}(2317)$ and $D^+_{sJ}(2460)$ with Sum Rules in HQET

In the framework of heavy quark effective theory we use QCD sum rules to calculate the masses of the $\bar c s$ $(0^+, 1^+)$ and $(1^+, 2^+)$ excited states. The results are consistent with that the states $D_{sJ}(2317)$ and $D_{sJ}(2460)$ observed by BABAR and CLEO are the $0^+$ and $1^+$ states in the $j_l={1\over 2}^+$ doublet.

hep-ph↗
arXiv2003

CP violation in $B_{d,s} \to l^+l^-$ in the model III 2HDM

We have calculated the Wilson coefficients $C_{10}, C_{Q_i}$ (i=1,2) in the $\bar{MS}$ renormalization scheme in the model III 2HDM. Using the obtained Wilson coefficients, we have analyzed the CP violation in decays $B^0_q\to l^+l^-$ (q=d,s) in the model. The CP asymmetry, $A_{CP}$, depends on the parameters of models and $A_{CP}$ in $B_d\to l^+l^-$ can be as large as 40% and 35% for $l=τ$ and $l=μ$ respectively. It can reach 4% for $B^0_s$ decays. Because in SM CP violation is smaller than or equal to O($10^{-3}$) which is unobservably small, an observation of CP asymmetry in the decays $B^0_q \to l^+l^- (q=d,s)$ would unambiguously signal the existence of new physics.

hep-ph↗
arXiv2002

LMA Solution to the Solar Neutrino Problem and a Phenomenological Charged Lepton Mass Matrix

We propose a phenomenological form of the charged lepton mass matrix, which extends the idea of ``lopsided'' mass matrix in the literature. The features of the form are that both the 2-3 and 1-3 elements of the charged lepton mass matrix are of order 1 and that the small elements have a new structure . This form leads to an interesting result that both large atmospheric and solar neutrino mixing can be accounted for by the matrix. Another interesting result of this mass matrix is that it leads to very small 1-3 mixing in the lepton sector and can suppress the branching ratio of $μ\to eγ$ under the present experimental limit in the supersymmetric see-saw case.

hep-ph↗
arXiv2002

Lepton Flavor Violation in the SUSY-GUT Models with Lopsided Mass Matrix

The tiny neutrino masses measured in the neutrino oscillation experiments can be naturally explained by the supersymmetric see-saw mechanism. If the supersymmetry breaking is mediated by gravity, the see-saw models may predict observable lepton flavor violating effects. In this work, we investigate the lepton flavor violating process $μ\to eγ$ in the kind of neutrino mass models based on the idea of the ``lopsided'' form of the charged lepton mass matrix. The constraints set by the muon anomalous magnetic moment are taken into account. We find the present models generally predict a much larger branching ratio of $μ\to eγ$ than the experimental limit. Conversely, this process may give strong constraint on the lepton flavor structure. Following this constraint we then find a new kind of the charged lepton mass matrix. The feature of the structure is that both the elements between the 2-3 and 1-3 generations are ``lopsided''. This structure produces a very small 1-3 mixing and a large 1-2 mixing in the charged lepton sector, which naturally leads to small $Br(μ\to eγ)$ and the LMA solution for the solar neutrino problem.

hep-ph↗
arXiv2001

g-2 in composite models of leptons

Based on the bound state description of the muon and general relativistic covariant quantum field theory, we illustrate with a simple composite model that the observed deviation of (g-2)_μcan be a demonstration of the substructure of the muon and give the constraints on the radius of the muon in different cases of light constituents and heavy constituents.

hep-ph↗
arXiv2000

Large Yukawa coupling corrections to scalar quark pair production in $e^+e^-$ annihilation

We calculate the large Yukawa coupling corrections to the top and bottom scalar quark pair production in $\ee$ annihilation within the Minimal Supersymmetric Standard Model. We include the vertex corrections and the corrections to the gauge boson propagator enhanced by large masses. We find the total corrections are quite significant. In some regions of the parameter space the corrections are larger than 10%.

hep-ph↗
arXiv2000

Lepton Flavor Violation in Supersymmetric SO(10) Grand Unified Models

The study for lepton flavor violation combined with the neutrino oscillation may provide more information about the lepton flavor structure of the grand unified theory. In this paper, we study two lepton flavor violation processes, $τ\to μγ$ and $Z\to τμ$, in the context of supersymmetric SO(10) grand unified models. We find the two processes are both of phenomenological interest. In particular the latter may be important in some supersymmetric parameter space where the former is suppressed. Thus, Z-dacay may offer another chance for looking for lepton flavor violation.

hep-ph↗
arXiv1999

QCD and SUSY-QCD corrections to the Three-Body Decay of the Charged Higgs Boson

The ${\cal O}(α_s)$ QCD corrections to the three-body decay width of the charged Higgs $Γ$($H^+\to W^+b\bar{b}$) are discussed in the MSSM model. Our calculations indicate that the standard QCD corrections to the three-body decay mode raise the width by about 12% and the supersymmetric QCD corrections(due to $\tilde{g}, \tilde{t}, \tilde{b}$ exchanges) can be comparable to or even larger than the standard QCD corrctions in some regions of the supersymmetric parameter space. This is mainly due to the effect of large left-right mixing of stop($\tilde{t}$). It could significantly affect the phenomenology of the $H^+$ search.

hep-ph↗
arXiv1999

CP violation in semi-leptonic decays of the top quark within MSSM

We calculate the CP-violating effects in the top quark semi-leptonic three body decays induced by the supersymmetric CP-odd phase of the top squark trilinear soft breaking term $\arg(A_t)$. The light top squark mass is assumed to be close to the top quark mass $m_{\tilde{t}}\sim m_t$. The CP-conserving phase is provided by the $χ^+$ and $χ^0$ cut. We find that the partial rate asymmetry is in the 0.1% level. In the most favorable parameter region the decay rate asymmetr can reach up to 0.55%.

hep-ph↗