arXiv subjects

Ju-Jun Xie

Publications and source records attributed to Ju-Jun Xie.

At least 91 records · Page 5Linked to original sources

arXiv2022

Can we understand the decay width of the $T_{cc}^+$ state?

Inspired by the recent discovery of a doubly charmed tetraquark state $T_{cc}^+$ by the LHCb Collaboration, we employ the effective Lagrangian approach to investigate the decay width of $T_{cc}^{+}\to D^{+} D^{0}π^{0}/D^{0} D^{0}π^{+}$ and $T_{cc}^{+}\to D^{0}D^{+}γ$ with the assumption that $T_{cc}^{+}$ is an isoscalar $DD^{\ast}$ molecule. We show that both the $T_{cc}\to D Dπ$ and $T_{cc}\to DDγ$ modes contribute to the decay width of $T_{cc}$, with the former being dominant. The resulting total decay width of about $Γ=63$ keV is smaller than the experimental decay width obtained from the Breit-Wigner fit of the LHCb data, $Γ=410\pm 165\pm 43^{+18}_{-38}$ keV, while close to the number obtained from the alternative unitary analysis, $Γ=48\pm 2^{+0}_{-14}$ keV, which supports the molecular nature of $T_{cc}$.

hep-ph↗

arXiv2021

Electromagnetic form factors of neutron and neutral stange hyperons in the oscillating view of point

Based on the recently precise measurements of the electron-positron annihilation reactions into a neutron and anti-neutron pair by BESIII collaboration, the effective form factor of neutron was determined in the time like region, and it was found that the effective form factor of neutron is smaller than the ones of proton. The effective form factors of neutron shows a periodic behaviour, similar to the case of proton. Here, a compared analysis for $Λ$, $Σ^0$ and $Ξ^0$ is performed. Fits of the available data on the effective form factors of $Λ$, $Σ^0$ and $Ξ^0$ with charge zero, allow to show a universal phenomenon of the oscillation behavior in their effective form factors. However, this needs to be confirmed by future precise experiments. Both theoretical and experimental investigations of this phenomenon can shed light on the reaction mechanisms of the electron-positron annihilation process.

hep-ph↗

arXiv2021

The $Ω_{cc}$ resonances with negative parity in the chiral constituent quark model

Spectrum of the low-lying $Ω_{cc}$ resonances with negative parity, which are assumed to be dominated by $sccq\bar{q}$ pentaquark components, is investigated using the chiral constituent quark model. Energies of the $Ω_{cc}$ resonances are obtained by considering the hyperfine interaction between quarks by exchanging Goldstone boson. Possible $sccq\bar{q}$ configurations with spin-parity $1/2^{-}$, $3/2^{-}$ and $5/2^{-}$ are taken into account. Numerical results show that the lowest $Ω_{cc}$ resonances with negative parity may lie at $4050 \pm 100$ MeV. In addition, the transitions of the $Ω_{cc}$ resonance to a pseudoscalar meson and a ground baryon state are also investigated within the chiral Lagrangian approach. We expect that these $Ω_{cc}$ resonances could be observed in the $\bar{D}Ξ_{c}$ channel by future experiments.

hep-ph↗

arXiv2021

Remarks on non-perturbative three--body dynamics and its application to the $KK\bar K$ system

A formalism is discussed that allows for a straightforward treatment of the relativistic three-body problem while keeping the correct analytic structure. In particular it is demonstrated that sacrificing covariance for analyticity can be justified by the hierarchy of different contributions in the spirit of an effective field theory. For definiteness the formalism is applied to the $KK\bar K$ system allowing for the emergence of the $a_0(980)$ and the $f_0(980)$ as hadronic molecules. For simplicity all inelastic channels are switched off.

hep-ph↗

arXiv2021

The axial charges of proton within an extended chiral constituent quark model

We have performed a study of the isovector, octet and singlet axial charges of the proton in an extended chiral constituent quark model, where all the possible $uudq\bar{q}$~($q=u,d,s$) five-quark Fock components in the proton wave function are taken into account. The $^3P_0$ quark-antiquark creation mechanism is assumed to account for the transition coupling between three- and five-quark components in proton, and the corresponding transition coupling strength is fixed by fitting the intrinsic sea flavor asymmetry $\bar{d}-\bar{u}$ data for proton. Accordingly, with all the parameters fixed by empirical values, the probabilities of the intrinsic five-quark Fock components in proton wave function should be $\sim30 - 50\%$, which lead to the numerical results for quark spin $Δu$, $Δd$ and $Δs$, as well the axial charges of proton consistent with the experimental data and predictions by other theoretical approaches.

hep-ph↗

arXiv2021

Electromagnetic form factors of $Σ^{+}$ and $Σ^{-}$ in the vector meson dominance model

Based on the recently measurements of the $e^{+} e^{-} \to Σ^{+} \barΣ^{-}$ and $e^{+} e^{-} \to Σ^{-} \barΣ^{+}$ processes, the electromagnetic form factors of the hyperon $Σ^+$ and $Σ^-$ in the timelike region are investigate by using the vector meson dominance model. We have included the contributions from the $ρ$, $ω$ and $ϕ$ mesons. The model parameters are determined with the BESIII experimental data on the timelike effective form factors $|G_{\rm eff}|$ of $Σ^{+}$ and $Σ^{-}$ for center-of-mass energy from 2.3864 to 3.02 GeV. Then, we analytically continue the electromagnetic form factors to spacelike region and evaluate the spacelike form factors of $Σ^+$ and $Σ^-$. The obtained electromagnetic form factors of the $Σ^+$ and $Σ^-$ baryons are comparable with other model calculations.

hep-ph↗

arXiv2021

Spin-parities of the $P_c(4440)$ and $P_c(4457)$ in the One-Boson-Exchange Model

The LHCb collaboration has recently observed three pentaquark peaks, the $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$. They are very close to a pair of heavy baryon-meson thresholds, with the $P_c(4312)$ located $8.9\,{\rm MeV}$ below the $\bar{D} Σ_c$ threshold, and the $P_c(4440)$ and $P_c(4457)$ located $21.8$ and $4.8\,{\rm MeV}$ below the $\bar{D}^* Σ_c$ one. The spin-parities of these three states have not been measured yet. In this work we assume that the $P_c(4312)$ is a $J^P = \tfrac{1}{2}^{-}$ $\bar{D} Σ_c$ bound state, while the $P_c(4440)$ and $P_c(4457)$ are $\bar{D}^* Σ_c$ bound states of unknown spin-parity, where we notice that the consistent description of the three pentaquarks in the one-boson-exchange model can indeed determine the spin and parities of the later, i.e. of the two $\bar{D}^* Σ_c$ molecular candidates. For this determination we revisit first the one-boson-exchange model, which in its original formulation contains a short-range delta-like contribution in the spin-spin component of the potential. We argue that it is better to remove these delta-like contributions because, in this way, the one-boson-exchange potential will comply with the naive expectation that the form factors should not have a significant impact in the long-range part of the potential (in particular the one-pion-exchange part). Once this is done, we find that it is possible to consistently describe the three pentaquarks, to the point that the $P_c(4440)$ and $P_c(4457)$ can be predicted from the $P_c(4312)$ within a couple of MeV with respect to their experimental location. In addition the so-constructed one-boson-exchange model predicts the preferred quantum numbers of the $P_c(4440)$ and $P_c(4457)$ molecular pentaquarks to be $\tfrac{3}{2}^-$ and $\tfrac{1}{2}^-$, respectively.

hep-ph↗

arXiv2021

Electron-Ion Collider in China

Lepton scattering is an established ideal tool for studying inner structure of small particles such as nucleons as well as nuclei. As a future high energy nuclear physics project, an Electron-ion collider in China (EicC) has been proposed. It will be constructed based on an upgraded heavy-ion accelerator, High Intensity heavy-ion Accelerator Facility (HIAF) which is currently under construction, together with a new electron ring. The proposed collider will provide highly polarized electrons (with a polarization of $\sim$80%) and protons (with a polarization of $\sim$70%) with variable center of mass energies from 15 to 20 GeV and the luminosity of (2-3) $\times$ 10$^{33}$ cm$^{-2}$ s$^{-1}$. Polarized deuterons and Helium-3, as well as unpolarized ion beams from Carbon to Uranium, will be also available at the EicC. The main foci of the EicC will be precision measurements of the structure of the nucleon in the sea quark region, including 3D tomography of nucleon; the partonic structure of nuclei and the parton interaction with the nuclear environment; the exotic states, especially those with heavy flavor quark contents. In addition, issues fundamental to understanding the origin of mass could be addressed by measurements of heavy quarkonia near-threshold production at the EicC. In order to achieve the above-mentioned physics goals, a hermetical detector system will be constructed with cutting-edge technologies. This document is the result of collective contributions and valuable inputs from experts across the globe. The EicC physics program complements the ongoing scientific programs at the Jefferson Laboratory and the future EIC project in the United States. The success of this project will also advance both nuclear and particle physics as well as accelerator and detector technology in China.

nucl-ex↗

arXiv2021

Can the nature of $a_0(980)$ be tested in the $D_s^{+}\to π^{+}π^0 η$ decay?

From the amplitude analysis of the $D^+_s \to π^+ π^0 η$ decay, the BESIII Collaboration firstly observed the $D^+_s \to a_0(980)^+π^0$ and $D^+_s \to a_0(980)^0π^+$ decay modes, which are expected to occur through the pure $W$-annihilation processes. The measured branching fraction $\mathcal{B}[D_{s}^{+}\to a_{0}(980)^{+(0)}π^{0(+)},a_{0}(980)^{+(0)}\to π^{+(0)}η]$ is, however, found to be larger than those of known $W$-annihilation decays by one order of magnitude. This apparent contradiction can be reconciled if the two decays are induced by internal $W$-conversion or external $W$-emission mechanisms instead of $W$-annihilation mechanism. In this work, we propose that the $D^+_s$ decay proceeds via both the external and internal $W$-emission instead of $W$-annihilation mechanisms. In such a scenario, we perform a study of the $D^+_s \to π^+π^0η$ decay by taking into account the contributions from the tree diagram $D^+_s \to ρ^+ η\to π^+ π^0 η$ and the intermediate $ρ^+ η$ and $K^*\bar{K}/K\bar{K}^*$ triangle diagrams. The intermediate $a_0(980)$ state can be dynamically generated from the final state interactions of coupled $K \bar{K}$ and $πη$ channels, and it is shown that the experimental data can be described fairly well, which supports the interpretation of $a_0(980)$ as a molecular state.

hep-ph↗

arXiv2021

Search for a $D \bar{D}$ bound state in the $Λ_b \rightarrow ΛD\bar{D}$ process

We have investigated the process of $Λ_b\to ΛD\bar{D}$, by taking into account the contributions from the $s$-wave $D\bar{D}$ interaction within the coupled-channel unitary approach, and the intermediate $ψ(3770)$ resonance. In addition to the peak of the $ψ(3770)$, an enhancement near the $D\bar{D}$ mass threshold is found in the $D\bar{D}$ invariant mass distributions, which should be the reflection of the $D\bar{D}$ bound state. We would like to encourage our experimental colleagues to measure the $D\bar{D}$ invariant mass distribution of the $Λ_b\to ΛD\bar{D}$ process, which is crucial to search for the $D\bar{D}$ bound state and to understand the heavy-hadron heavy-hadron interactions.

hep-ph↗

arXiv2020

Can $Z_{cs}(3985)$ be a molecular state of $\bar{D}_s^D$ and $\bar{D}_sD^$ ?

We study the $Z_{cs}(3985)$ state recently observed by the BESIII Collaboration in the one-boson-exchange model, assuming that it is a $\bar{D}_s^{(*)}D^{(*)}$ molecule, which has the quark content $c\bar{c}s\bar{q}$ with $q = u$, $d$. It is shown that the one-boson-exchange potential is too weak to generate dynamcally $\bar{D}_s D$, $\bar{D}^*_s D$, and $\bar{D}_sD^*$ states, while for the case of $\bar{D}^*_s D^*$, very loosely bound states are likely, with binding energies of the order of several MeV. We conclude that, the observed $Z_{cs}(3985)$ state, if confirmed by further experiments, cannot be a pure hadronic molecular state of $\bar{D}_s D^*$ and $\bar{D}_s^*D$ and could consist of large components of compact nature.

hep-ph↗

arXiv2020

The role of $X(4140)$ and $X(4160)$ in the reactions of $B^+ \to J/ψϕK^+$

We have studied the $J/ψϕ$ mass distribution of the process $B^+\to J/ψϕK^+$ from the threshold to about 4250 MeV, by considering the contribution of the $X(4140)$ with a narrow width, together with the $X(4160)$ state. Our results show that the cusp structure at the $D^*_s\bar{D}^*_s$ threshold is tied to the molecular nature of the $X(4160)$ state.

hep-ph↗

arXiv2020

The scalar $f_0(500)$ and $f_0(980)$ resonances and vector mesons in the single Cabibbo-suppressed decays $Λ_c \to p K^+K^-$ and $pπ^+π^-$

In the chiral unitary approach, we have studied the single Cabibbo-suppressed decays $Λ_c\to pK^+K^-$ and $Λ_c \to p π^+π^-$ by taking into account the $s$-wave meson-meson interaction as well as the contributions from the intermediate vectors $ϕ$ and $ρ^0$. Our theoretical results for the ratios of the branching fractions of $Λ_c\to p \bar{K}^{*0}$ and $Λ_c\to p ω$ with respect to the one of $Λ_c\to p ϕ$ are in agreement with the experimental data. Within the picture that the scalar resonances $f_0(500)$, $f_0(980)$, and $a_0(980)$ are dynamically generated from the pseudoscalar-pseudoscalar interactions in $s$-wave, we have calculated the $K^+K^-$ and $π^+π^-$ invariant mass distributions respectively for the decays $Λ_c\to pK^+K^-$ and $Λ_c\to pπ^+π^-$. One can find a broad bump structure for the $f_0(500)$ and a narrow peak for the $f_0(980)$ in the $π^+π^-$ invariant mass distribution of the decay $Λ_c\to pπ^+π^-$. For the $K^+K^-$ invariant mass distribution, in addition to the narrow peak for the $ϕ$ meson, there is an enhancement structure near the $K^+K^-$ threshold mainly due to the contribution from the $f_0(980)$. Both the $π^+π^-$ and $K^+K^-$ invariant mass distributions are compatible with the BESIII measurement. We encourage our experimental colleagues to measure these two decays, which would be helpful to understand the nature of the $f_0(500)$, $f_0(980)$, and $a_0(980)$.

hep-ph↗

arXiv2020

Strong decays of $\bar{D}^{}K^{}$ molecules and the newly observed $X_{0,1}$ states

Lately, the LHCb Collaboration reported the discovery of two new states in the $B^+\rightarrow D^+D^- K^+$ decay, i.e., $X_0(2866)$ and $X_1(2904)$. In the present work, we study whether these states can be understood as $D^*\bar{K}^*$ molecules from the perspective of their two-body strong decays into $D^-K^+$ via triangle diagrams and three-body decays into $D^*\bar{K}π$. The coupling of the two states to $D^*\bar{K}^*$ are determined from the Weinberg compositeness condition, while the other relevant couplings are well known. The obtained strong decay width for the $X_0(2866)$, in marginal agreement with the experimental value within the uncertainty of the model, hints at a large $D^*\bar{K}^*$ component in its wave function. On the other hand, the strong decay width for the $X_1(2904)$, much smaller than its experimental counterpart, effectively rules out its assignment as a $D^*\bar{K}^*$ molecule.

hep-ph↗

arXiv2020

$X_0(2866)$ as a $D^\bar{K}^$ molecular state

Very recently the LHCb Collaboration reported the discovery of two open charm tetraquark states, $X_{0}(2866)$ and $X_{1}(2904)$. In the present work, we study the $D^{(\ast)}$ and $\bar{K}^{(\ast)}$ interaction in the one-boson exchange model and show that the $X_{0}(2866)$ can be understood as a $D^{\ast}\bar{K}^{\ast}$ molecule with $I(J^{P})=0(0^{+})$, or at least it has a large molecular component. On the other hand, the $X_{1}(2904)$ can not be interpreted as a molecular state. Inspired by the discovery of the $X_0(2866)$ and the fact that the $D^*\bar{K}^*$ interaction is strong enough to generate a bound state, we also discuss likely existence of other open charm molecules. In the meson-meson sector, two molecules near the mass thresholds of $DD^{\ast}$ and $D^{\ast}D^{\ast}$ with $I(J^{P})=0(1^{+})$ are obtained, and using the heavy quark flavor symmetry their $\bar{B}\bar{B}^{\ast}$ and $\bar{B}^{\ast}\bar{B}^{\ast}$ counterparts are also predicted. In the meson-baryon sector, 7 open charm molecules with $I=1/2$ near the mass thresholds of $D^{(\ast)}Σ_{c}^{(\ast)}$ naturally appear, as dictated by the heavy quark spin symmetry.

hep-ph↗

arXiv2020

Triangle singularity as the origin of $X_0(2900)$ and $X_1(2900)$ observed in $B^+\to D^+ D^- K^+$

The LHCb collaboration reported the observation of a narrow peak in the $D^- K^+$ invariant mass distributions from the $B^+\to D^+ D^- K^+$ decay. The peak is parameterized in terms of two resonances $X_0(2900)$ and $X_1(2900)$ with the quark contents $\bar{c}\bar{s}ud$, and their spin-parity quantum numbers are $0^+$ and $1^-$, respectively. We investigate the rescattering processes which may contribute to the $B^+\to D^+ D^- K^+$ decays. It is shown that the $D^{*-}K^{*+}$ rescattering via the $χ_{c1}K^{*+}D^{*-}$ loop or the $\bar{D}_{1}^{0}K^{0}$ rescattering via the $D_{sJ}^{+}\bar{D}_{1}^{0}K^{0}$ loop simulate the $X_0(2900)$ and $X_1(2900)$ structures. Such phenomena are due to the analytical property of the scattering amplitudes with the triangle singularities located to the vicinity of the physical boundary.

hep-ph↗

arXiv2020

Theoretical study of the $Ω(2012)$ state in the $Ω_c^0 \to π^+ Ω(2012)^- \to π^+ (\bar{K}Ξ)^-$ and $π^+ (\bar{K}Ξπ)^-$ decays

We report on a theoretical study of the newly observed $Ω(2012)$ resonance in the nonleptonic weak decays of $Ω_c^0 \to π^+ \bar{K}Ξ^*(1530) (ηΩ) \to π^+ (\bar{K}Ξ)^-$ and $π^+ (\bar{K}Ξπ)^-$ via final-state interactions of the $\bar{K}Ξ^*(1530)$ and $ηΩ$ pairs. The weak interaction part is assumed to be dominated by the charm quark decay process: $c(ss) \to (s + u + \bar{d})(ss)$, while the hadronization part takes place between the $sss$ cluster from the weak decay and a quark-antiquark pair with the quantum numbers $J^{PC} = 0^{++}$ of the vacuum, produces a pair of $\bar{K}Ξ^*(1530)$ and $ηΩ$. Accordingly, the final $\bar{K}Ξ^*(1530)$ and $ηΩ$ states are in pure isospin $I= 0$ combinations, and the $Ω_c^0 \to π^+ \bar{K}Ξ^*(1530)(ηΩ) \to π^+ (\bar{K}Ξ)^-$ decay is an ideal process to study the $Ω(2012)$ resonance. With the final-state interaction described in the chiral unitary approach, up to an arbitrary normalization, the invariant mass distributions of the final state are calculated, assuming that the $Ω(2012)$ resonance with spin-parity $J^P = 3/2^-$ is a dynamically generated state from the coupled channels interactions of the $\bar{K}Ξ^*(1530)$ and $ηΩ$ in $s$-wave and $\bar{K}Ξ$ in $d$-wave. We also calculate the ratio, $R^{\bar{K}Ξπ}_{\bar{K}Ξ} = {\rm Br}[Ω_c^0 \to π^+ Ω(2012)^- \to π^+ (\bar{K}Ξπ)^-] / {\rm Br}[Ω_c^0 \to π^+ Ω(2012)^- \to π^+ (\bar{K}Ξ)^-$]. The proposed mechanism can provide valuable information on the nature of the $Ω(2012)$ and can in principle be tested by future experiments.

hep-ph↗

arXiv2020

Revisiting the $Ω(2012)$ as a hadronic molecule and its strong decays

Recently, the Belle collaboration measured the ratios of the branching fractions of the newly observed $Ω(2012)$ excited state. They did not observe significant signals for the $Ω(2012) \to \bar{K} Ξ^*(1530) \to \bar{K} πΞ$ decay, and reported an upper limit for the ratio of the three body decay to the two body decay mode of $Ω(2012) \to \bar{K} Ξ$. In this work, we revisit the newly observed $Ω(2012)$ from the molecular perspective where this resonance appears to be a dynamically generated state with spin-parity $3/2^-$ from the coupled channels interactions of the $\bar{K} Ξ^*(1530)$ and $ηΩ$ in $s$-wave and $\bar{K} Ξ$ in $d$-wave. With the model parameters for the $d$-wave interaction, we show that the ratio of these decay fractions reported recently by the Belle collaboration can be easily accommodated.

hep-ph↗