arXiv subjects

Ju-Jun Xie

Publications and source records attributed to Ju-Jun Xie.

At least 55 records · Page 3Linked to original sources

arXiv2024

Review of the low-lying excited baryons $Σ^*(1/2^-)$

Strong empirical and phenomenological indications exist for large sea-quark admixtures in the low-lying excited baryons. Investigating the low-lying excited baryon $Σ^*(1/2^-)$ is important to determine the nature of the low-lying excited baryons. We review the experimental and theoretical progress on the studies of the $Σ^*(1/2^-)$. Although several candidates have received intensive discussions, such as $Σ(1620)$ and $Σ(1480)$, their existence needs further confirmation. Following the prediction of the unquenched quark models for the $Σ^*(1/2^-)$, many theoretical works suggested the existence of these states in various processes. Future experimental measurements could shed light on the existence of the low-lying excited $Σ^*(1/2^-)$ state.

hep-ph↗

arXiv2024

Theoretical study of $N(1535)$ and $Σ^*(1/2^-)$ in the Cabibbo-favored process $Λ_c^+ \to p \bar{K}^0η$

Motivated by the recent experimental measurements, we have investigated the Cabibbo-favored process $Λ_c^+ \to p \bar{K}^0η$, where the $N(1535)$ resonance is dynamically generated from the $S$-wave pseudoscalar meson-octet baryon interactions within the chiral unitary approach. The contributions from the intermediate $N(1650)$ and the predicted low-lying baryon $Σ^*(1/2^-)$ are also considered. In addition, a Breit-Wigner amplitude for the $N(1535)$ resonance is checked. By comparing with the measured $ηp$, $\bar{K}^0 η$, and $p \bar{K}^0$ invariant mass squared distributions, our results support the interpretation of $N(1535)$ as a dynamically generated state. Furthermore, we demonstrate that, with the contribution from $Σ^*(1/2^-)$ taken into account, the calculated invariant mass spectrum agrees with the Belle measurements. Future precise measurements of the $Λ_c^+\to p \bar{K}^0η$ process can further elucidate the existence of the low-lying baryon $Σ^*(1/2^-)$.

hep-ph↗

arXiv2024

Theoretical study on low-lying hidden-bottom and double-bottom tetraquark states

We perform a theoretical study on the spectrum of the low-lying hidden-bottom ($q\bar{q}b\bar{b}$ with $q=$ $u$, $d$ and $s$) and double-bottom ($q\bar{q}bb$) tetraquark states within a nonrelativistic quark model, in which the instanton-induced interaction is taken as the residual spin-dependent hyperfine interaction between quarks. All the model parameters are fixed by fitting the spectrum of the ground hadron states. The numerical results indicate that masses of several $X_{q\bar{q}}$, $Z_{b}$, and $Z_{bs}$ tetraquark states are below and near thresholds of corresponding meson-meson channels, thus these states may form components of exotic meson states with reasonable probabilities. Especially, in present model, masses of several obtained states with quantum number $I^G(J^P)=1^+(1^{+})$ are close to $Z_b^\pm(10610)$, so one may expect these states to be non-negligible components of the experimentally observed $Z_{b}$ states. Concerning to the double-bottom tetraquark states, the present results are in general consistent with other previous works. Two possible stable $T_{bb}$ states with quark content $bb\bar{n}\bar{n}$ ($n=u$ or $d$ quark) lying at energies $10558$ MeV and $10650$ MeV are found, and one possible stable $bb\bar{n}\bar{s}$ state is found, whose energy is $\sim10687$ MeV.

hep-ph↗

arXiv2024

Evidence of the low-lying baryon $Σ^*(1/2^-)$ in the process $Λ_c^+\to ηπ^+Λ$

Motivated by the Belle measurements of the process $Λ_c^+\to ηπ^+Λ$, we investigate this process by considering the contributions from the $Λ(1670)$, $a_0(980)$, and $Σ(1385)$. In addition, we also consider the predicted low-lying baryon $Σ^*(1/2^-)$. Our results involving the $Σ^*(1/2^-)$ are favored by fitting to the Belle data of the $ηΛ$ and $π^+Λ$ invariant mass distributions. Furthermore, we predict the $ηπ^+$ invariant mass distribution and the angular distribution $dΓ/d{\rm cos}θ$, which are significantly different depending on whether or not the contribution from the $Σ^*(1/2^-)$ is considered. Finally, we show that, with the contribution from the $Σ^*(1/2^-)$, the calculated Dalizt plot agrees with the Belle measurements. Future precise measurements of the process $Λ_c^+\to ηπ^+Λ$ could shed further light on the existence of the low-lying $Σ^*(1/2^-)$.

hep-ph↗

arXiv2024

Pionic transitions of the spin-2 partner of $X(3872)$ to $χ_{cJ}$

We investigated the pionic transitions between the $X_2$ [spin-2 partner of the $X(3872)$] and $χ_{c1,2}$ using a nonrelativistic effective field theory. The $X_2$ is assumed to be a bound state of the $D^{*}$ and $\bar{D}^*$ mesons and to decay through several kinds of loops, including the bubble, triangle and box loops. Within the present model, the widths for the single-pion decays $X_2\toπ^0χ_{cJ}$ are predicted to be about $3$--$30$ keV. For the dipion decays, the widths are a few keVs. These widths yield a branching fraction of $10^{-3}$--$10^{-2}$. The ratio $R_{\mathrm{c}0}=Γ(X_2\toπ^+π^-χ_{cJ})/Γ(X_2\toπ^0π^0χ_{cJ}) \simeq 1.6$, which is a bit smaller than the expected value of $2$, and $R_{21}=Γ(X_2\toππχ_{c2})/Γ(X_2\toππχ_{c1}) \simeq 0.85$. These ratios are nearly independent of the $X_2$ mass and the coupling constants, which might be a good quantity for the experiments. Moreover, the invariant mass spectra of the $π^0χ_{cJ}$ final state for the dipion processes are presented, showing a cusp structure at the $D {\bar D}^*$ threshold enhanced and narrowed by the nearby triangle singularity.

hep-ph↗

arXiv2024

Unveiling the $a_0(1710)$ nature in the process $J/ψ\to {\bar{K}}^0K^+ρ^- $

We have investigated the process $J/ψ\to {\bar{K}}^0K^+ρ^-$ by taking into account the $S$-wave ${K^*\bar{K}^*}$, $ρω$, and $ρϕ$ final-state interactions, where the scalar meson $a_0(1710)$ is generated. In addition, we also take into account the contributions from the scalar $a_0(980)(\to \bar{K}^0K^+)$ and the intermediate resonances $K_1(1270)^{-}(\to {\bar{K}}^0ρ^-) $ and $K_1(1270)^{0}(\to K^+ρ^-)$. Our results show that, in the ${\bar{K}^0K^+}$ invariant mass distribution, a clear peak structure around 1.8~GeV appears, which could be associated with the scalar $a_0(1710)$, however, no significant structure of the $a_0(980)$ is observed. On the other hand, one can find clear peaks of the $K_1(1270)$ in the ${\bar{K}}^0ρ^-$ and $K^+ρ^-$ invariant mass distributions. The future precise measurement of this process by the BESIII and Belle II Collaborations and the planned Super Tau-Charm Facility (STCF) in the future could shed light on the nature of $a_0(1710)$.

hep-ph↗

arXiv2024

Identifying the two-pole structure of the $Λ(1405)$ using an SU(3) flavor filter

We propose a novel method to identify the two-pole structure of the $Λ(1405)$. The two poles owe their origin to different quark flavor irreducible representations in the meson-baryon coupled-channel interactions, thus they should be individually manifested in reactions that provide good flavor eigenstate sources. Hadronic decays of charmonia into $\barΛΣπ$ and $\barΛ(1520)Σπ$ are such reactions, and the flavor octet and singlet poles can be approximately singled out in these two decay modes. This SU(3) flavor filter works even considering the flavor symmetry breaking. With the huge charmonium data sets collected, it is therefore promising to solve the long-standing $Λ(1405)$ puzzle employing the proposed flavor filter.

hep-ph↗

arXiv2024

Charmless decays of the spin-2 partner of $X(3872)$

The Belle collaboration recently reported a promising candidate for the spin-2 $D^*\bar{D}^*$ partner of the $X(3872)$, called the $X_2$ for short, having a mass of $(4014.3 \pm 4.0 \pm 1.5)~\mathrm{MeV}$ and a width of $(4 \pm 11 \pm 6)~\mathrm{MeV} $. In present work, we assume the $X_2$ as a pure molecule of the $D^*\bar{D}^*$ under three cases, i.e., pure neutral components ($θ= 0$), isospin singlet ($θ= π/4$) and neutral components dominant ($θ= π/6$), where $θ$ is a phase angle describing the proportion of neutral and charged constituents. Using an effective Lagrangian approach, we calculated the partial widths of $X_2\to VV$ and $X_2 \to PP$ ($V$ and $P$ stand for light vector and pseudoscalar mesons, respectively). The predicted decay widths of $X_2 \to VV$ can reach a few hundreds of $\mathrm{keV}$, while the decay widths of $X_2 \to PP$ are about several tens of $\mathrm{keV}$. In addition, the effects from the proportion of neutral and charged constituent on the decay widths of $X_2\to VV$ and $PP$ are also investigated. We hope that the present calculations will be checked experimentally in the future.

hep-ph↗

arXiv2024

The $Ω(2012)$ as a hadronic molecule

Recently, a new excited baryon state, $Ω(2012)$, was observed in the invariant mass spectra of $K^-Ξ^0$ and $K^0_S Ξ^-$ by the Belle Collaboration. This state has a narrow width ($\sim 6$ MeV) compared to other baryon states with a similar mass. In this paper, we provide a mini-review on the $Ω(2012)$ state from the molecular perspective, where it 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. Additionally, alternative explanations for the $Ω(2012)$ resonance are also discussed.

hep-ph↗

arXiv2024

Production of $X_b$ via radiative transition of $Υ(10753)$

We studied the radiative transitions between the $Υ(10753)$, the $S$-$D$ mixed state of the $Υ(4S)$ and $Υ_1(3\,{}^3D_1)$, and the $X_b$, the heavy quark flavor symmetry counterpart of the $X(3782)$ in the bottomonium sector. The radiative transition was assumed to occur through the intermediate bottom mesons, including $P$-wave $B_1^{(\prime)}$ mesons as well as the $S$-wave $B^{(*)}$ ones. The consideration of the $B_1^{(\prime)}$ mesons leads to the couplings to be in $S$-wave, and hence enhances the contributions of the intermediate meson loops. The radiative decay width for the $Υ(10753)\toγX_b$ is predicted to be order of $10~\mathrm{keV}$, corresponding to a branching fraction of $10^{-4}$. Based on the theoretical results, we strongly suggest to search for the $X_b$ in the $e^+e^-\toγX_b$ with $X_b\toππχ_{b1}$ near $\sqrt{s}=10.754~\mathrm{GeV}$, and it is hoped that the calculations here could be tested by the future Belle II experiments.

hep-ph↗

arXiv2024

Analysis of $B_s^0 \to X(3872) [ψ(2S)] π^+π^- (K^+ K^-)$ decays

We have phenomenologically investigated the decays $B_s^0 \to X(3872) π^+π^- (K^+ K^-)$ and $B_s^0 \to ψ(2S) π^+ π^- (K^+K^-)$. In our analysis, the scalar meson $f_0(980)$ is formed through the final state interactions of coupled channels $ππ$ and $K\bar{K}$. Our findings indicate that the $π^+π^-$ invariant mass distribution of the $B_s^0 \to ψ(2S)π^+π^-$ decay can be accurately reproduced. Furthermore, we have explored the $π^+π^- (K^+ K^-)$ invariant mass distribution of the $B_s^0 \to X(3872) π^+π^- (K^+ K^-)$ decay, accounting for the different production mechanisms between $X(3872)$ and $ψ(2S)$, up to a global factor. It is found that the production rates for $X(3872)$ and $ψ(2S)$ are much different, which indicates that the structure of $X(3872)$ is more complicated than the $ψ(2S)$, which is a conventional $c\bar{c}$ state. Additionally, we have considered the contributions from $f_0(1500)$ to $π^+π^-$ and the $ϕ$ meson to $K^+ K^-$ in our analysis. Utilizing the model parameters, we have calculated the branching fraction of $B_s^0 \to X(3872) K^+ K^-$, and anticipate that the findings of our study can be experimentally tested in the future.

hep-ph↗

arXiv2024

Understanding oscillating features of the timelike nucleon electromagnetic form factors within the extending vector meson dominance model

We investigate the nonmonotonic behavior observed in the time-like nucleon electromagnetic form factors. Using a phenomenological extending vector meson dominance model, where the ground states $ρ$ and $ω$ and their excited states $ρ(2D)$, $ω(3D)$, and $ω(5S)$ are taken into account, we have successfully reproduced the cross sections of $e^+ e^- \to p \bar{p}$ and $e^+ e^- \to n \bar{n}$ reactions. Furthermore, we have derived the nucleon electromagnetic form factors in the time-like region, and it is found that the so-called periodic behaviour of the nucleon effective form factors is not confirmed. However, there are indeed nonmonotonic structures in the line shape of nucleon effective form factors, which can be naturally reproduced by considering the contributions from the low-lying excited vector states.

nucl-th↗

arXiv2024

$e^+ e^- \to Λ^+_c \barΛ^-_c$ cross sections and the $Λ_c^+$ electromagnetic form factors within the extended vector meson dominance model

Within the extended vector meson dominance model, we investigate the $e^+ e^- \to Λ^+_c \barΛ^-_c$ reaction and the electromagnetic form factors of the charmed baryon $Λ_c^+$. The model parameters are determined by fitting them to the cross sections of the process $e^+e^-\rightarrow Λ_c^+ \barΛ_c^-$ and the magnetic form factor $|G_M|$ of $Λ^+_c$. By considering four charmoniumlike states, called $ψ(4500)$, $ψ(4660)$, $ψ(4790)$, and $ψ(4900)$, we can well describe the current data on the $e^+ e^- \to Λ^+_c \barΛ^-_c$ reaction from the reaction threshold up to $4.96 \ \mathrm{GeV}$. In addition to the total cross sections and $|G_M|$, the ratio $|G_E/G_M|$ and effective form factor $|G_{\mathrm{eff}}|$ for $Λ^+_c$ are also calculated, and found that these calculations are consistent with the experimental data. Within the fitted model parameters, we have also estimated the charge radius of the charmed $Λ_c^+$ baryon.

hep-ph↗

arXiv2024

Dynamically generated states from the $ηK^\bar{K}^$, $πK^\bar{K}^$, and $K K^\bar{K}^$ systems within the fixed-center approximation

The three-body systems $ηK^* \bar{K}^*$, $πK^* \bar{K}^*$, and $K K^* \bar{K}^*$ are further investigated within the framework of fixed-center approximation, where $K^* \bar{K}^*$ is treated as the fixed-center, corresponding to the possible scalar meson $a_0(1780)$ or the tensor meson $f_2'(1525)$. The interactions between $η$, $π$, $K$, and $K^*$ are taken from the chiral unitary approach. The resonance structures appear in the modulus squared of the three-body scattering amplitude and suggest that $η/ π/ K$-$(K^*\bar{K}^*)_{a_0(1780)/f'_2(1525)}$ hadron state can be formed. By scattering the $η$ meson on the fixed-center $(K^* \bar{K}^*)_{a_0(1780)}$, it is found that there is a distinct peak around 2100 MeV, as shown in the modulus squared of the three-body scattering amplitude, which can be associated with the meson $π(2070)$. For the scattering of the $η$ meson on the $(K^* \bar{K}^*)_{f_2'(1525)}$, a resonance structure around 1890 MeV is found and it can be associated with the $η_2(1870)$ meson. Other resonance structures are also found and can be associated with $π_2(1880)$ and $η(2010)$.

hep-ph↗

arXiv2023

Theoretical study of scalar meson $a_0(1710)$ in the $η_c \to {\bar{K}}^0K^+π^- $ reaction

We investigate the process $η_c \to {\bar{K}}^0K^+π^-$ by taking into account the $S$-wave ${K^*\bar{K}^*}$ and $ρω$ interactions within the unitary coupled-channel approach, where the scalar meson $a_0(1710)$ is dynamically generated. In addition, the contributions from the intermediate resonances $K_0^*(1430)^{-}\to {\bar{K}}^0π^- $ and $K_0^*(1430)^{0}\to K^+π^-$ are also considered. We find a significant dip structure around 1.8~GeV, associated to the $a_0(1710)$, in the ${\bar{K}^0K^+}$ invariant mass distribution, and the clear peaks of the $K_0^*(1430)$ in the ${\bar{K}}^0π^-$ and $K^+π^-$ invariant mass distributions, consistent with the {\it BABAR} measurements. We further estimate the branching fractions $\mathcal{B}(η_c \to \bar{K}^{*0}K^{\ast+}π^-)= 5.5\times10^{-3}$ and $\mathcal{B}(η_c \to ωρ^+π^-)= 7.9\times10^{-3}$. Our predictions can be tested by the BESIII and BelleII experiments in the future.

hep-ph↗

arXiv2023

Theoretical study on $Λ_c^+ \to ΛK^+\bar{K}^0$ decay and $Ξ^*(1690)$ resonance

We present a theoretical study of $Ξ^*(1690)$ resonance in the $Λ_c^+ \to ΛK^+ \bar{K}^0$ decay, where the weak interaction part proceeds through the Cabibbo-favored process $c \to s + u\bar{d}$. Next, the intermediate two mesons and one baryon state can be constructed with a pair of $q\bar{q}$ with the vacuum quantum numbers. Finally, the $Ξ^*(1690)$ is mainly produced from the final state interactions of $\bar{K}Λ$ in coupled channels, and it is shown in the $\bar{K}Λ$ invariant mass distribution. Besides, the scalar meson $a_0(980)$ and nucleon excited state $N^*(1535)$ are also taken into account in the decaying channels $K^+\bar{K}^0$ and $K^+Λ$, respectively. Within model parameters, the $K^+ \bar{K}^0$, $\bar{K}^0 Λ$ and $K^+ Λ$ invariant mass distributions are calculated, and it is found that our theoretical results can reproduce well the experimental measurements, especially for the clear peak around $1690$ MeV in the $\bar{K}Λ$ spectrum. The proposed weak decay process $Λ_c^+ \to ΛK^+ \bar{K}^0$ and the interaction mechanism can provide valuable information on the nature of the $Ξ^*(1690)$ resonance.

hep-ph↗

arXiv2023

Photo-production of lowest $Σ^*_{1/2^-}$ state within the Regge-effective Lagrangian approach

Since the lowest $Σ^{*}$ state, with quantum numbers spin-parity $J^{P} =1/2^{-}$, is far from established experimentally and theoretically, we have performed a theoretical study on the $Σ^*_{1/2^-}$ photo-production within the Regge-effective Lagrangian approach. Taking into account that the $Σ^*_{1/2^-}$ couples to the $\bar{K}N$ channel, we have considered the contributions from the $t$-channel $K$ exchange diagram. Moreover, these contributions from $t$-channel $K^*$ exchange, $s$-channel nucleon pole, $u$-channel $Σ$ exchange, and the contact term, are considered. The differential and total cross sections of the process $γn \to K^{+}Σ^{*-}_{1/2^-}$ are predicted with our model parameters. The results should be helpful to search for the $Σ^*_{1/2^-}$ state experimentally in future.

hep-ph↗

arXiv2023

Production of $X_b$ via $Υ(5S, 6S)$ radiative decays

We investigate the production of $X_b$ in the process $Υ(5S,6S)\to γX_b$, where $X_b$ is assumed to be a $B {\bar B}^*$ molecular state. Two kinds of meson loops of $B^{(*)}{\bar B}^{(*)}$ and $B_1^{\prime}{\bar B}^{(*)}$ were considered. To explore the rescattering mechanism, we calculated the relevant branching ratios using the effective Lagrangian based on the heavy quark symmetry. The branching ratios for the $Υ(5S\,,6S) \to γX_b$ were found to be at the orders of $10^{-7} \sim 10^{-6}$. Such sizeable branching ratios might be accessible at BelleII, which would provide important clues to the inner structures of the exotic state $X_b$.

hep-ph↗