arXiv subjects

Hong-Wei Ke

Publications and source records attributed to Hong-Wei Ke.

At least 55 records · Page 3Linked to original sources

arXiv2015

Study of the rare decay $J/ψ\rightarrow e^+e^- ϕ$

We study the decay process of $J/ψ\rightarrow e^+e^- ϕ$ where the relatively clean electromagnetic (EM) transitions appear at leading order at tree level while the hadronic contributions only emerge via hadronic loop transitions. We include the low-lying scalar $f_0(980)$ and pseudoscalar $η/η'$ as the dominant contributions in the evaluation of the hadronic loop contributions. It is found that the hadronic effects are negligible comparing with the EM contributions. The decay width of $J/ψ\rightarrow e^+e^- ϕ$ is determined to be about $2.12\times 10^{-6}$ keV if there is no any other leading mechanism contributing, and this result will be tested by the BESIII experiment with a large data sample of $J/ψ$.

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arXiv2015

Study on direct pion emission in decay $D^{*+} \to D^+ π$

The QCD multipole expansion (QCDME) is based on the quantum field theory, so should be more reliable. However, on another aspect, it refers to the non-perturbative QCD , so that has a certain application range. Even though it successfully explains the data of transition among members of the $Υ$ ($ψ$) family, as Eichten indicates, beyond the production threshold of mediate states it fails to meet data by several orders. In this work, by studying a simple decay mode $D^*\to D+π^0$, where a pion may be emitted before $D^*$ transiting into $D$, we analyze the contribution of QCD multipole expansion. Whereas as the $Dπ$ portal is open, the dominant contribution is an OZI allowed process where a light quark-pair is excited out from vacuum and its contribution can be evaluated by the $^3P_0$ model. Since the direct pion emission is a process which is OZI suppressed and violates the isospin conservation, its contribution must be much smaller than the dominant one. By a careful calculation, we may quantitatively estimate how small the QCDME contribution should be and offer a quantitative interpretation for Eichten's statement.

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arXiv2015

Implications of equalities among the elements of CKM and PMNS matrices

Investigating the CKM matrix in different parametrization schemes, it is noticed that those schemes can be divided into a few groups where the sine values of the CP phase for each group are approximately equal. Using those relations, several approximate equalities among the elements of CKM matrix are established. Assuming them to be exact, there are infinite numbers of solutions and by choosing special values for the free parameters in those solutions, several textures presented in literature are obtained. The case can also be generalized to the PMNS matrix for the lepton sector. In parallel, several mixing textures are also derived by using presumed symmetries, amazingly, some of their forms are the same as what we obtained, but not all. It hints existence of a hidden symmetry which is broken in the practical world. The nature makes its own selection on the underlying symmetry and the way to break it, while we just guess what it is.

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arXiv2015

An underlying symmetry determines all elements of CKM and PMNS up to a universal constant?

Observing the CKM matrix elements written in different parametrization schemes, one can notice obvious relations among the sine-values of the CP phases in those schemes. Using the relations, we establish a few parametrization-independent equations, by which the matrix elements of the CKM matrix can be completely fixed up to a universal parameter. If it is true, we expect that there should exist a hidden symmetry in the nature which determines the relations. Moreover, it requires a universal parameter, naturally it would be the famous Jarlskog invariant which is also parametrization independent. Thus the four parameters (three mixing angles and one CP phase) of the CKM matrix are not free, but determined by the symmetry and the universal parameter. As we generalize the rules to the PMNS matrix for neutrino mixing, the CP phase of the lepton sector is predicted to be within a range of $0\sim 59^\circ$ centered at $39^\circ$ (in the P$_a$ parametrization) which will be tested in the future experiments.

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arXiv2015

The hidden symmetries in the PMNS matrix and the light sterile neutrino(s)

The approximately symmetric form of the PMNS matrix suggests that there could exist a hidden symmetry which makes the PMNS matrix different from the CKM matrix for quarks. In literature, all the proposed fully symmetric textures exhibit an explicit $μ-τ$ symmetry in addition to other symmetries which may be different for various textures. Observing obvious deviations of the practical PMNS matrix elements from those in the symmetric textures, there must be a mechanism to distort the symmetry. It might be due to existence of light sterile neutrinos. In this work, we study the case of the Tribimaximal texture and propose that its apparent symmetry disappears due to existence of a sterile neutrino. We observe that introducing just one sterile neutrino is still not sufficient to recover the data, thus a slight $μ-τ$ symmetry breaking is also needed. By considering those factors, we obtain the PMNS matrix elements which are consistent with data within the experimental tolerance.

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arXiv2015

Study on the structure of the four-quark states in terms of the Born-Oppenheimer approximation

In this work, we use the Born-Oppenheimer approximation where the potential between atoms can be approximated as a function of distance between the two nuclei to study the four-quark bound states. By the approximation, Heitler and London calculated the spectrum of hydrogen molecule which includes two protons (heavy) and two electrons (light). Generally, the observed exotic mesons $Z_b(10610)$, $Z_b(10650)$, $Z_c(3900)$ and $Z_c(4020)$($Z_c(4025)$) may be molecular states made of two physical mesons and/or in diquark-anti-diquark structures. In analog to the Heitler-London method for calculating the mass of hydrogen molecule, we investigate whether there exist energy minima for these two structures. By contrary to the hydrogen molecule case where only the spin-triplet possesses an energy minimum, there exist minima for both of them. It implies that both molecule and tetraquark states can be stable objects. But since they have the same quantum numbers, the two states may mix to result in the physical states. A consequence would be that partner exotic states co-existing with $Z_b(10610)$, $Z_b(10650)$, $Z_c(3900)$ and $Z_c(4020)$($Z_c(4025)$) are predicted and should be experimentally observed.

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arXiv2014

Numerical analysis of the production of $D^{(*)}(3000)$, $D_{sJ}(3040)$ and their partners through the semileptonic decays of $B_{(s)}$ mesons in terms of the light-front quark model

Inspired by the newly observed $D^{(*)}(3000)$, and $D_{sJ}(3040)$ states, in this work we study the production of $D^{(*)}(3000)$, $D_{sJ}(3040)$ and their partners through the semileptonic decays of $B_{(s)}$ mesons, where the light-front Quark model is applied to the whole calculation. Our numerical results indicate that the $B_{(s)}$ semileptonic decays into the $2P$ states of the charmed or charmed-strange meson family have considerable branching ratios, which shows that these semileptonic decays can be accessible at future experiments, especially LHCb and the forthcoming Belle II.

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arXiv2014

Study on radiative decays of $D^_{sJ}(2860)$ and $D^_{s1}(2710)$ into $D_s$ by means of LFQM

The observed resonance peak around 2.86 GeV has been carefully reexamined by the LHCb collaboration and it is found that under the peak there reside two states $D^*_{s1}(2860)$ and $D^*_{s3}(2860)$ which are considered as $1^3D_1(c\bar s)$ and $1^3D_3(c\bar s)$ with slightly different masses and total widths. Thus, the earlier assumption that the resonance $D^*_{s1}(2710)$ was a $1D$ state should not be right. We suggest to measure the partial widths of radiative decays of $D^*_{sJ}(2860)$ and $D^*_{s1}(2710)$ to confirm their quantum numbers. We would consider $D^*_{s1}(2710)$ as $2^3S_1$ or a pure $1^3D_1$ state, or their mixture and respectively calculate the corresponding branching ratios as well as those of $D^*_{sJ}(2860)$. The future precise measurement would provide us information to help identifying the structures of those resonances .

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arXiv2014

Searching for New Physics in $D^0\rightarrow μ^+μ^-,\; e^+e^-, \;μ^{\pm}e^{\mp}$ at BES and/or Super Charm-Tau Factory

In contrast with $B^0-\bar B^0$, $B_s-\bar B_s$ mixing where the standard model (SM) contributions overwhelm that of new physics beyond standard model (BSM), a measured relatively large $D^0-\bar D^0$ mixing where the SM contribution is negligible, definitely implies the existence of new physics BSM. It is natural to consider that the rare decays of D meson might be more sensitive to new physics, and the rare decay $D^0\to μ^+μ^-$ could be an ideal area to search for new physics because it is a flavor changing process. In this work we look for a trace of new physics BSM in the leptonic decays of $D^0$, concretely we discuss the contributions of unparticle or an extra gauge boson $Z'$ while imposing the constraints set by fitting the $D^0-\bar D^0$ mixing data. We find that the long-distance SM effects for $D^0\to l\bar l$ still exceed those contributions of the BSM under consideration, but for a double-flavor changing process such as $D^0\to μ^{\pm}e^{\mp}$, the new physics contribution would be significant.

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arXiv2014

Determination of the mixing between active neutrinos and sterile neutrino through the quark-lepton complementarity and self-complementarity

It is suggested that there is an underlying symmetry which relates the quark and lepton sectors. Namely, among the mixing matrix elements of CKM for quarks and PMNS for leptons there exist complementarity relations at a high energy scale (such as the see-saw or even the GUT scales). Assuming that the relations would remain during the matrix elements running down to the EW scale. Observable breaking of the rational relation is attributed to existence of sterile neutrinos which mix with the active neutrino to result in the observable PMNS matrix. We show that involvement of a sterile in the (3+1) model, induces that $|U_{e4}|^2= 0.040$, $|U_{\mu4}|^2= 0.009$ and $\sin^2 2α=0.067$. We also find a new self-complementarity $\vartheta_{12}+\vartheta_{23}+\vartheta_{13}+α\approx90^\circ$. The numbers are generally consistent with those obtained by fitting recent measurements, especially in this scenario, the existence of a sterile neutrino does not upset the LEP data i.e. the number of neutrino types is very close to 3.

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arXiv2014

Constraining parameter space of the Little Higgs model by data of tera-Z factory and ILC

The Standard Model prediction on the forward-backward asymmetry for $b\bar b$ production ($A^b_{FB}$) is well consistent with the data of LEP I at the Z-pole, but deviates from the data at $\sqrt s=89\; 93$ GeV which are slightly away from the pole. This deviation implies that there still is room for new physics. We calculate the $A^b_{FB}$ at vicinity of Z-pole in the Little Higgs Model as well as other measurable parameters such as $R_b$ and $R_c$, by which we may constrain the parameter space of the Little Higgs Model. This can be tested in the newly proposed tera-Z factory. With the fitted parameters we further make predictions on $A^b_{FB}$ and $A^t_{FB}$ for $t\bar t$ production at the ILC energy.

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arXiv2013

The decay rate of $ψ(2S)$ to $Λ_c+\bar{Σ^+}$ in SM and beyond

With rapid growth of the database of the BES III and the proposed super flavor factory, measurement on the rare $ψ(2S)$ decays may be feasible, especially the weak decays into baryon final states. In this work we study the decay rate of $ψ(2S)$ to $Λ_c+\overline{Σ^+}$ in the SM and physics beyond the SM (here we use the unparticle model as an example). The QPC model is employed to describe the creation of a pair of $q\bar q$ from vacuum. We find that the rate of $ψ(2S)\rightarrow Λ_c+\overline{Σ^+}$ is at order of $10^{-10}$ in the SM, whereas the contribution of the unparticle is too small to be substantial. Therefore if a large branching ratio is observed, it must be due to new physics beyond SM, but by no means the unparticle.

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arXiv2013

Transitions of $B_c\rightarrow ψ(1S,2S)$ and the modified harmonic oscillator wave function in LFQM

The LHC$_b$ collaboration has systematically measured the rates of $B_c\to J/ψK$, $B_c\to J/ψD_s$, $B_c\to J/ψD_s^*$ and $B_c\to ψ(2S) π$. The new data enable us to study relevant theoretical models and further determine the model parameters. In this work, We calculate the form factors for the transitions $B_c\to J/ψ$ and $B_c\to ψ(2S)$ numerically, then determine the partial widths of the semi-leptonic and non-leptonic decays. The theoretical predictions on the ratios of $Γ(B_c\to J/ψK)/Γ(B_c\to J/ψπ)$, $Γ(B_c\to J/ψD_s)/Γ(B_c\to J/ψπ)$ and $Γ(B_c\to J/ψD_s^*)/Γ(B_c\to J/ψπ)$ are consistent with data within only 1$σ$. Especially, for calculating $Γ(B_c\to ψ(2S)X)$ the modified harmonic oscillator wave function (HOWF) which we developed in early works is employed and the results indicate that the modified harmonic oscillator wave function works better than the traditional HOWF.

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arXiv2013

Is $Z_c(3900)$ a molecular state

Assuming the newly observed $Z_c(3900)$ to be a molecular state of $D\bar D^*(D^{*} \bar D)$, we calculate the partial widths of $Z_c(3900)\to J/ψ+π;\; ψ'+π;\; η_c+ρ$ and $D\bar D^*$ within the light front model (LFM). $Z_c(3900)\to J/ψ+π$ is the channel by which $Z_c(3900)$ was observed, our calculation indicates that it is indeed one of the dominant modes whose width can be in the range of a few MeV depending on the model parameters. Similar to $Z_b$ and $Z_b'$, Voloshin suggested that there should be a resonance $Z_c'$ at 4030 MeV which can be a molecular state of $D^*\bar D^*$. Then we go on calculating its decay rates to all the aforementioned final states and as well the $D^*\bar D^*$. It is found that if $Z_c(3900)$ is a molecular state of ${1\over\sqrt 2}(D\bar D^*+D^*\bar D)$, the partial width of $Z_c(3900)\to D\bar D^*$ is rather small, but the rate of $Z_c(3900)\toψ(2s)π$ is even larger than $Z_c(3900)\to J/ψπ$. The implications are discussed and it is indicated that with the luminosity of BES and BELLE, the experiments may finally determine if $Z_c(3900)$ is a molecular state or a tetraquark.

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arXiv2013

The radiative decays of $0^{++}$ and $1^{+-}$ heavy mesons

The radiative decay is believed to be an ideal lab to study hadronic structure of newly observed resonances because the reactions are governed by only the electromagnetic interaction (tree level). However, to obtain correct theoretical values, one has to properly deal with the non-perturbative QCD effects in the wavefunction and hadronization. In this work we derive the formulas for the radiative decays of $0^{++}$ and $1^{-+}$ heavy mesons in the light front quark model (LFQM). Because $\mathcal{B}(χ_{c0}\rightarrow J/ψγ)$ is well measured, the theoretical evaluation of the transition rate can be used to test our approach. Within this theoretical framework, the width of $χ_{b0}\rightarrow Υ(1S)γ$ is evaluated. The formulas can be applied to identify the inner structures of new resonances, for example the isospin of $h_{c(b)}$ and the structure of $D_s(2317)$, via processes $h_c\rightarrow η_cγ$, $h_b\rightarrow η_bγ$ and $D_s(2317)\rightarrow D_s^*+γ$.

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arXiv2013

The FSI contribution to the observed $B_s$ decays into $K^+K^-$ and $π^+K^-$

Because at the tree level $B_s\rightarrow K^+K^-$ is Cabibbo-triple suppressed, so its branching ratio should be smaller than that of $B_s\to π^+ K^-$. The measurements present a reversed ratio as $R=\mathcal B(B_s\rightarrow π^+K^-)/\mathcal B(B_s\rightarrow K^+ K^-)\sim{4.9/33}$. Therefore, It has been suggested that the transition $B_s\to K^+K^-$ is dominated by the penguin mechanism, which is proportional to $V_{cb}V^*_{cs}$. In this work, we show that an extra contribution from the final state interaction (FSI) to $B_s\to K^+K^-$ via sequential processes $B_s\to D^{(*)}_{(s)} \bar D_s^{(*)}\to K^+K^-$ is also substantial and should be superposed on the penguin contribution. Indeed, taking into account of the FSI effects, the theoretical prediction on $R$ is well consistent with the data.

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arXiv2012

Study on the effects of the light CP-odd Higgs via the leptonic decays of pseudoscalar mesons

To explain the anomalously large decay rate of $Σ^+\to p+μ^+μ^-$, it was proposed that a new mechanism where a light CP-odd pseudoscalar boson of $m_{A_1^0}=214.3$ MeV makes a crucial contribution. Later, some authors have studied the transition $π^0\to e^+e^-$ and $Υ\to γA_1^0$ in terms of the same mechanism and their result indicates that with the suggested mass one cannot fit the data. This discrepancy might be caused by experimental error of $Σ^+\to p+μ^+μ^-$ because there were only a few events. Whether the mechanism is a reasonable one motivates us to investigate the transitions $π^0\to e^+e^-; η(η^\prime)\to μ^+μ^-; η_c\to μ^+μ^-; η_b\toτ^+τ^-$ within the same framework. It is noted that for $π^0\to e^+e^-$, the standard model (SM) prediction is smaller than the data, whereas the experimental central value of $η\to μ^+μ^-$ is also above the SM prediction. It means that there should be extra contributions from other mechanisms and the contribution of $A_1^0$ may be a possible one. Theoretically calculating the branching ratios of the concerned modes, we would check if we can obtain a universal mass for $A_1^0$ which reconcile the theoretical predictions and data for all the modes. Unfortunately, we find that it is impossible to have such a mass with the same coupling $|g_\ell|$. Therefore we conclude that the phenomenology does not favor such a light $A_1^0$, even though a small window is still open.

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arXiv2012

$Σ_{b}\toΣ_c$ and $Ω_b\toΩ_c$ weak decays in the light-front quark model

The successful operation of LHC provides a great opportunity to study the processes where heavy baryons are involved. {In this work we mainly study} the weak transitions of $Σ_b\to Σ_c$. Assuming the reasonable quark-diquark structure where the two light quarks constitute an axial vector, we calculate the widths of semi-leptonic decay $Σ_{b}\toΣ_c eν_e$ and non-leptonic decay modes $Σ_{b}\toΣ_c +M$ (light mesons) in terms of the light front quark model. We first construct the vertex function for the concerned baryons and then deduce the form factors which are related to two Isgur-Wise functions for the $Σ_{b}\toΣ_c$ transition under the heavy quark limit. Our numerical results indicate that $Γ(Σ_{b}\toΣ_c eν_e)$ is about $1.38\times10^{10}{\rm s}^{-1}$ and $Γ(Σ_{b}\toΣ_c +M)$ is slightly below $1\times10^{10}{\rm s}^{-1}$ which may be accessed at the LHCb detector. By the flavor SU(3) symmetry we estimate the rates of $Ω_b\toΩ_c$. We suggest to measure weak decays of $Ω_b\toΩ_c$, because $Ω_b$ does not decay via strong interaction, the advantage is obvious.

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