arXiv subjects

Hong-Wei Ke

Publications and source records attributed to Hong-Wei Ke.

At least 73 records · Page 4Linked to original sources

arXiv2012

Is $Z_b(10610)$ a Molecular State?

Whether molecular states indeed exist in nature has been disputed for a long time. Several new resonances have been observed in the recent experiments and they seem to be of exotic structures and some of them have been proposed to be molecular states. The very recent observation of $Z_b(10610)[(10608.4\pm 2.0)$ MeV] and $Z_b(10650)[(10653.2\pm 1.5)$ MeV] encourages the interpretation of multi-quark states. In the Beter-Salpeter (BS) approach, we study the possibility if two heavy mesons can form a molecular state by exchanging light mesons. Our results indicate that two heavy mesons can form an isospin singlet (I=0) bound state but cannot form an isospin triplet (I=1) when the contribution of $σ-$ exchange is reasonably small, i.e. as the coupling of $σ$ with mesons $g_σ$ takes the value given in previous literatures. Thus we conclude that the newly observed $Z_b(10610)$ should not be a molecular state, but a tetraquark state instead, at most, the fraction of the molecular state in the physical resonance $Z_b(10610)$ is tiny.

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arXiv2011

What do the radiative decays of X(3872) tell us

Since the discovery of X(3872), its structure has been in ceaseless dispute. The data of $X(3872)\rightarrow π^+π^-π^0 J/ψ$ suggest that X(3872) may be a high-spin charmonium-like of $2^{-+}$. In terms of the light front quark model (LFQM) we calculate the rates of the radiative decays $X(3872)\rightarrow J/ψ(ψ')γ$ supposing X(3872) to be a $2^{-+}$ charmonium. Within this framework, our theoretical prediction on $\mathcal{BR}(X(3872)\rightarrowψ(1S)γ)$ is at order of $10^{-3}$ which is slightly lower than the Babar's data but close to the Belle's. Our prediction on $\mathcal{BR}(X(3872)\rightarrowψ'γ)$ is at order of $10^{-5}$ if $ψ'$ is a pure 2S state or $10^{-4}$ if $ψ'$ is a $2S-1D$ mixture, which does not conflict with the upper bound set by the Belle collaboration, but is much lower than the Babar's data. Thus if the future measurement decides the branching ratio of $\mathcal{BR}(X(3872)\rightarrowψ'γ)$ to be much larger than $10^{-4}$, the $2^{-+}$ assignment for X(3872) should be ruled out.

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arXiv2011

Vertex functions for d-wave mesons in the light-front approach

While the light-front quark model (LFQM) is employed to calculate hadronic transition matrix elements, the vertex functions must be pre-determined. In this work we derive the vertex functions for all d-wave states in this model. Especially, since both of $^3D_1$ and $^3S_1$ are $1^{--}$ mesons, the Lorentz structures of their vertex functions are the same. Thus when one needs to study the processes where $^3D_1$ is involved, all the corresponding formulas for $^3S_1$ states can be directly applied, only the coefficient of the vertex function should be replaced by that for $^3D_1$. The results would be useful for studying the newly observed resonances which are supposed to be d-wave mesons and furthermore the possible 2S-1D mixing in $ψ'$ with the LFQM.

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arXiv2011

Fraction of the gluonium component in $η'$ and $η$

It is interesting to determine the fraction of the gluonium component in $η$ and $η'$ which has been under serious discussion for many years. Measurements on different decay and/or production modes were employed in literatures, thus larger uncertainties were unavoidable. In this paper we suggest to determine the mixing angles of $η-η'-G$ using the data of semileptonic decays of $D$ and $D_s$. We extract the mixing angles $ϕ'$, $ϕ_G$ and the model parameters simultaneously. Thanks to the new measurements carried out by CLEO Collaboration and there are sufficient decay modes to determine both the model parameters and mixing angles. The mixing angles from data are $ϕ'=(41.5\pm2.0)^\circ$ and $\sinϕ_G=0.00\pm0.36$. Even though the central value of $\sinϕ_G$ is still zero, an upper bound is set. Moreover, as suggested in literature, $η(1405)$ is a glueball candidate whereas in our picture, $η(1405)$ may be identified as $G$ with glueonium being its main content. Using all the model-parameters obtained above, we estimate the branching ratios of $D_s^+(D^+)\rightarrow Ge^+ν_e$ where G is identified as $η(1405)$.

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arXiv2010

Re-study on the contribution of scalar potential and spectra of $c\bar c$, $b\bar b$ and $b\bar c(\bar b c)$ families

We indicated in our previous work that for QED the role of the scalar potential which appears at the loop level is much smaller than that of the vector potential and in fact negligible. But the situation is different for QCD, one reason is that the loop effects are more significant because $α_s$ is much larger than $α$, and secondly the non-perturbative QCD effects may induce a sizable scalar potential. In this work, we phenomenologically study the contribution of the scalar potential to the spectra of charmonia, bottomonia and $b\bar c(\bar b c)$ family. Taking into account both vector and scalar potentials, by fitting the well measured charmonia and bottomonia spectra, we re-fix the relevant parameters and test them by calculating other states of not only the charmonia, bottomonia, but also further the $b\bar c$ family. We also consider the Lamb shift of the spectra.

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arXiv2010

Phenomenological study on the significance of the scalar potential and Lamb shift

We indicated in our previous work that for QED the contributions of the scalar potential which appears at the loop level is much smaller than that of the vector potential and in fact negligible. But the situation may be different for QCD, one reason is that the loop effects are more significant because $α_s$ is much larger than $α$, and secondly the non-perturbative QCD effects may induce the scalar potential. In this work, we phenomenologically study the contribution of the scalar potential to the spectra of charmonia. Taking into account both vector and scalar potentials, by fitting the well measured charmonia spectra, we re-fix the relevant parameters and test them by calculating other states of the charmonia family. We also consider the role of the Lamb shift and present the numerical results with and without involving the Lamb shift.

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arXiv2010

$B^{()}\bar B^{()}$ intermediate state contribution to $Υ(4S,5S)\to η_b+γ$ radiative decay

In this work, we investigate the re-scattering effects in the radiative decay $Υ(5S)\toη_b+γ$, which were suggested to be crucially important for understanding the anomalous largeness of the branching ratios $B(Υ(5S)\to Υ(1S)+ππ)$ and $B(Υ(5S)\to Υ(1S)+η)$. Our calculations show that the re-scattering effects may enhance $Γ(Υ(10860)\to η_b+γ)$ by four orders, but the tetraquark structure does not. Recently the BaBar and CLEO collaborations have measured the mass of ${η_b}$ and the branching ratios $\mathcal{B}(Υ(2S)\rightarrowη_b+γ)$, $\mathcal{B}(Υ(3S)\rightarrowη_b+γ)$. We hope that very soon, $Υ(10860)\to η_b+γ$ will be measured and it would be an ideal opportunity for testing whether the re-scattering or the tetraquark structure is responsible for the anomaly of $\mathcal{B}\big(Υ(5S)\rightarrowΥ(nS)π^+π^- (n=1,2,3)\big)$, $i.e.$, the future measurements on the radiative decays of $Υ(5S)$ might be a touchstone of the two mechanisms.

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arXiv2010

Re-Study on the wave functions of $Υ(nS)$ states in LFQM and the radiative decays of $Υ(nS)\to η_b+γ$

The Light-front quark model (LFQM) has been applied to calculate the transition matrix elements of heavy hadron decays. However, it is noted that using the traditional wave functions of the LFQM given in literature, the theoretically determined decay constants of the $Υ(nS)$ obviously contradict to the data. It implies that the wave functions must be modified. Keeping the orthogonality among the $nS$ states and fitting their decay constants we obtain a series of the wave functions for $Υ(nS)$. Based on these wave functions and by analogy to the hydrogen atom, we suggest a modified analytical form for the $Υ(nS)$ wave functions. By use of the modified wave functions, the obtained decay constants are close to the experimental data. Then we calculate the rates of radiative decays of $Υ(nS)\to η_b+γ$. Our predictions are consistent with the experimental data on decays $Υ(3S)\to η_b+γ$ within the theoretical and experimental errors.

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arXiv2010

Determining the $η-η'$ mixing by the newly measured $BR(D(D_s)\toη(η')+\bar l+ν_l$

The mixing of $η-η'$ or $η-η'-G$ is of a great theoretical interest, because it concerns many aspects of the underlying dynamics and hadronic structure of pseudoscalar mesons and glueball. Determining the mixing parameters by fitting data is by no means trivial. In order to extract the mixing parameters from the available processes where hadrons are involved, theoretical evaluation of hadronic matrix elements is necessary. Therefore model-dependence is somehow unavoidable. In fact, it is impossible to extract the mixing angle from a unique experiment because the model parameters must be obtained by fitting other experiments. Recently $BR(D\toη+\bar l+ν_l)$ and $BR(D_s\toη(η')+\bar l+ν_l)$ have been measured, thus we are able to determine the $η-η'$ mixing solely from the semileptonic decays of D-mesons where contamination from the final state interactions is absent. Thus we hope that the model-dependence of the extraction can be somehow alleviated. Once $BR(D\toη'+\bar l+ν_l)$ is measured, we can further determine all the mixing parameters for $η-η'-G$. As more data are accumulated, the determination will be more accurate. In this work, we obtain the transition matrix elements of $D_{(s)}\to η^{(\prime)}$ using the light-front quark model whose feasibility and reasonability for such processes have been tested.

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arXiv2010

Study on the radiative decays of $Υ(nS)\to η_b+γ$

In this work, we investigate the characteristics of the spin-singlet state $η_b$ of the bottomonia family via the radiative decays of $Υ(nS)\to η_b+γ$. The theoretical estimation of the decay widths is carried out in terms of the light-front quark model (LFQM). Recently CLEO and BaBar collaborations have measured $\mathcal{B}(Υ(3S)\toγη_b)$ and the mass of ${η_b}$. In terms of the data we fix the concerned input parameters in our calculations of $Υ(nS)\to η_b+γ$. A special attention is paid on the transition of $Υ(5S)\to η_b+γ$. The BELLE data showed that the width of $Υ(5S)\to Υ(2S,1S)+ππ$ is two orders larger than that of $Υ(4S)\to Υ(2S,1S)+ππ$, thus some theoretical explanations have been proposed. Among them, it is suggested the inelastic final state interaction (IFSI) $Υ(5S)\to B\bar B\to Υ(1S)+ππ$ may be a natural one. If so, a similar mechanism also applies to $Υ(5S)\to B^{(*)}\bar B^{(*)}\to η_b+γ$, the precise measurement would serve as a good test whether $Υ(5S)$ possess exotic components. Our calculation in the LFQM indicates that the rate of the direct process $Υ(5S)\toη_b+γ$ is not anomalous compared to $Υ(mS)\toη_b+γ(m=1,2,3,4)$, thus if the IFSI does apply, the rate of $Υ(5S)\toη_b+γ$ should be larger than the others by orders.

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arXiv2010

The magnetic dipole transitions in the $(c\bar{b})$ binding system

The magnetic dipole transitions between the vector mesons $B_c^*$ and their relevant pseudoscalar mesons $B_c$ ($B_c$, $B_c^*$, $B_c(2S)$, $B_c^*(2S)$, $B_c(3S)$ and $B_c^*(3S)$ etc, the binding states of $(c\bar{b})$ system) of the $B_c$ family are interesting. To see the `hyperfine' splitting due to spin-spin interaction is an important topic for understanding the spin-spin interaction and the spectrum of the the $(c\bar{b})$ binding system. The knowledge about the magnetic dipole transitions is also very useful for identifying the vector boson $B_c^*$ mesons experimentally, whose masses are just slightly above the masses of their relevant pseudoscalar mesons $B_c$ accordingly. Considering the possibility to observe the vector mesons via the transitions at $Z^0$ factory and the potentially usages of the theoretical estimate on the transitions, we fucus our efforts on calculating the magnetic dipole transitions, i.e. precisely to calculate the rates for the transitions such as decays $B_c^*\to B_cγ$ and $B_c^*\to B_c e^+e^-$, and particularly work in the Behte-Salpeter framework. In the estimate, as a typical example, we carefully investigate the dependance of the rate $Γ(B_c^*\to B_cγ)$ on the mass difference $ΔM=M_{B_c^*}-M_{B_c}$ as well.

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arXiv2010

Search for $B_c(ns)$ via the $B_c(ns)\to B_c(ms)π^+π^-$ transition at LHCb and $Z_0$ factory

It is interesting to study the characteristics of the whole family of $B_c$ which contains two different heavy flavors. LHC and the proposed $Z^0$ factory provide an opportunity because a large database on the $B_c$ family will be achieved. $B_c$ and its excited states can be identified via their decay modes. As suggested by experimentalists, $B_c^*(ns)\to B_c+γ$ is not easy to be clearly measured, instead, the trajectories of $π^+$ and $π^-$ occurring in the decay of $B_c(ns)\to B_c(ms)+π^+π^-$ ($n>m$) can be unambiguously identified, thus the measurement seems easier and more reliable, therefore this mode is more favorable at early running stage of LHCb and the proposed $Z^0$ factory. In this work, we calculate the rate of $B_c(ns)\to B_c(ms)+π^+π^-$ in terms of the QCD multipole-expansion and the numerical results indicate that the experimental measurements with the luminosity of LHC and $Z^0$ factory are feasible.

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arXiv2009

Evaluating decay Rates and Asymmetries of $Λ_b$ into Light Baryons in LFQM

In this work we calculate the branching ratios of semi-leptonic and non-leptonic decays of $Λ_b$ into light baryons ($p$ and $Λ$), as well as the measurable asymmetries which appear in the processes, in the light front quark model (LFQM). In the calculation, we adopt the diquark picture and discuss the justifiability of applying the picture in our case. Our result on the branching ratio of $Λ_b\toΛ+J/ψ$ is in good agreement with data. More predictions are made in the same model and the results will be tested in the future experiments which will be conducted at LHCb and even ILC.

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arXiv2009

Symmetry of Dirac Equation and Corresponding Phenomenology

It has been suggested that the high symmetries in the Schrödinger equation with the Coulomb or harmonic oscillator potentials may remain in the corresponding relativistic Dirac equation. If the principle is correct, in the Dirac equation the potential should have a form as ${(1+β)\over 2}V(r)$ where $V(r)$ is ${-e^2\over r}$ for hydrogen atom and $κr^2$ for harmonic oscillator. However, in the case of hydrogen atom, by this combination the spin-orbit coupling term would not exist and it is inconsistent with the observational spectra of hydrogen atom, so that the symmetry of SO(4) must reduce into SU(2). The governing mechanisms QED and QCD which induce potential are vector-like theories, so at the leading order only vector potential exists. However, the higher order effects may cause a scalar fraction. In this work, we show that for QED, the symmetry restoration is very small and some discussions on the symmetry breaking are made. At the end, we briefly discuss the QCD case and indicate that the situation for QCD is much more complicated and interesting.

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arXiv2009

Whether new data on $D_s\to f_0(980) e^+ ν_e$ can be understood if $f_0(980)$ consists of only the conventional $q\bar{q}$ structure

Only two isospin-singlet scalar mesons $f_0(600)$ ($σ$) and $f_0(980)$ exist below 1 GeV, so that it is natural to suppose that they are two energy eigenstates which are mixtures of ${1\over\sqrt 2}(u\bar u+d\bar d)$ and $s\bar s$. Is this picture right? Generally, it is considered that $f_0(600)$ mainly consists of ${1\over\sqrt 2}(u\bar u+d\bar d)$, if so, the dominant component of $f_0(980)$ should be $s\bar s$. The recent measurement of the CLEO collaboration on the branching ratio of $D_s\to f_0(980) e^+ ν_e$ provides an excellent opportunity to testify the structure of $f_0(980)$, namely whether the data can be understood as long as it consists of mainly the conventional $q\bar q$ structure. We calculate the form factors of $D_s\to f_0(980)$ in the light-front quark model (LFQM) and the corresponding branching ratio of the semileptonic decay. By fitting the data, we obtain the mixing angle $ϕ$. The obtained mixing angle shows that the $s\bar s$ component in $f_0(980)$ may not be dominant.

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arXiv2009

Interpretation of the "$f_{D_s}$ puzzle" in SM and beyond

The recent measurement on the decay constant of $D_s$ shows a discrepancy between theory and experiment. We study the leptonic and semileptonic decays of $D$ and $D_s$ simultaneously within the standard model by employing a lightfront quark model. There is space by tuning phenomenological parameters which can explain the "$f_{D_s}$ puzzle" and do not contradict other experiments on the semileptonic decays. We also investigate the leptonic decays of D and $D_{s}$ with a new physics scenario, unparticle physics. The unparticle effects induce a constructive interference with the standard model contribution. The nontrivial phase in unparticle physics could produce direct CP violation which may distinguish it from other new physics scenarios.

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arXiv2009

The line shape of the radiative open-charm decay of Y(4140) and Y(3930)

In this work, we study the radiative open-charm decays $Y(4140)\to {D}_s^{\ast+} D_s^- γ$ and $Y(3930)\to{D}^{\ast+} D^-γ$ under the assignments of $D_{s}^*\bar{D}_s^*$ and $D^*\bar{D}^*$ as molecular states for Y(4140) and Y(3930) respectively. Based on our numerical result, we propose the experimental measurement of the photon spectrum of $Y(4140)\to {D}_s^{\ast+} D_s^- γ, D_{s}^+D_{s}^{*-}γ$ and $Y(3930)\to D^{*0}\bar{D}^0γ, D^{0}\bar{D}^{*0}γ, D^{*+}D^-γ, D^+D^{*-}γ$ can further test the molecular assignment for Y(4140) and Y(3930).

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arXiv2009

Testing the Bell Inequality at Experiments of High Energy Physics

Besides using the laser beam, it is very tempting to directly testify the Bell inequality at high energy experiments where the spin correlation is exactly what the original Bell inequality investigates. In this work, we follow the proposal raised in literature and use the successive decays $J/ψ\toγη_c\to Λ\barΛ\to pπ^-\bar pπ^+$ to testify the Bell inequality. Our goal is twofold, namely, we first make a Monte-Carlo simulation of the processes based on the quantum field theory (QFT). Since the underlying theory is QFT, it implies that we pre-admit the validity of quantum picture. Even though the QFT is true, we need to find how big the database should be, so that we can clearly show deviations of the correlation from the Bell inequality determined by the local hidden variable theory. There have been some critiques on the proposed method, so in the second part, we suggest some improvements which may help to remedy the ambiguities indicated by the critiques. It may be realized at an updated facility of high energy physics, such as BES III.

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