Search

We study from the theoretical point of view the $\Lambda_c^+\to \pi^+ \eta \Lambda$ reaction, recently measured by the Belle and BESIII Collaborations, where clear signals are observed for $a_0(980)$, $\Lambda(1670)$, and $\Sigma(1385)$ excitation. By considering the $a_0(980)$ and $\Lambda(1670)$ as dynamically generated resonances from the meson meson and meson baryon interaction, respectively, we are able to determine their relative production strength in the reaction, which is also tied to the strength of the $\pi^+ \eta \Lambda$ tree level contribution. We observe that this latter strength is very big and there are large destructive interferences between the tree level and the rescattering terms where the $a_0(980)$ and $\Lambda(1670)$ are generated. The $\Sigma(1385)$ contribution is included by means of a free parameter, the only one of the theory, up to a global normalization, when one considers only external emission, and we observe that the spin flip part of this term, usually ignored in theoretical and experimental works, plays an important role determining the shape of the mass distributions. Internal emission is also considered and it is found to play a minor role.

We study the \proc reaction, showing that a peak in the \dk mass distribution around 2834 MeV reported by LHCb could be associated with a theoretical exotic state with that mass, a width of 19 MeV and $J^P=2^+$, stemming from the interaction of the $D^{*+}K^{*+}$ and $D^{*+}_s \rho^+$ channels, which is a partner of the $0^+$ $T_{c\bar{s}}(2900)$. We show that the data is compatible with this assumption, but also see that the mass distribution itself cannot discriminate between the spins $J=0$, $1$, $2$ of the state. Then we evaluate the momenta of the angular mass distribution and show that they are very different for each of the spin assumptions, and that the momenta coming from interference terms have larger strength at the resonant energy than the peaks seen in the angular integrated mass distribution. We make a call for the experimental determination of these magnitudes, which has already been used by the LHCb in related decay reactions.

Recently, the LHCb Collaboration has measured two decay processes $B^0\to\bar{D}^0D_s^+\pi^-$ and $B^+\to D^-D_s^+\pi^+$ related to isospin symmetry, where two new open-flavor tetraquark states $T_{c\bar{s}}(2900)^0$ and $T_{c\bar{s}}(2900)^{++}$ that belong to an isospin triplet were observed in the $D_s^+\pi^-$ and $D_s^+\pi^+$ invariant mass distributions. In this work, we have investigated the validity of the process $\bar{B}_s^0\to K^0D^0\pi^0$ as the promising process to confirm the existence of $T_{c\bar{s}}(2900)^0$ resonance. Taking into account the tetraquark state $T_{c\bar{s}}(2900)$, as well as intermediate resonances $K^*(892)$, $K_0^*(1430)$, and $K_2^*(1430)$, it has been shown that a clear peak of the open-flavor tetraquark $T_{c\bar{s}}(2900)$ appears in the $K^0D^0$ invariant mass distribution of the process $\bar{B}_s^0\to K^0D^0\pi^0$, which could be tested by future experiments., Comment: 10 pages, 10 figures, comments are welcome!

We use the Belle data on the $K^- p$ mass distribution of the $\Lambda_c^+ \to p K^- \pi^+$ reaction near the $\eta \Lambda$ threshold to determine the $\eta \Lambda $ scattering length and effective range. We show that from these data alone we can determine the value of $a$ with better precision than so far determined, and the value of $r_0$ for the first time. The addition of the $K^- p \to \eta \Lambda$ data allows us to improve the precision of these magnitudes, with errors smaller than $15\%$. We also determine with high precision the pole position of the $\Lambda(1670)$.

We investigate the meson-baryon interaction in coupled channels with the quantum numbers of the pentaquarks $P_{bss}$ and $P_{bsss}$. The interaction is derived from an extension of the local hidden gauge approach to the heavy quark sector, which has demonstrated accurate results compared to experiments involving $\Omega_{b}$, $\Xi_{b}$ states, and pentaquarks $P_{c}$ and $P_{cs}$. In our study, we identify several molecular states with small decay widths within the chosen set of coupled channels. The spin-parity ($J^P$) of these states is as follows: $J^P={\frac{1}{2}}^-$ for pseudoscalar-baryon (${\frac{1}{2}}^+$) coupled channels, $J^P={\frac{3}{2}}^-$ for pseudoscalar-baryon (${\frac{3}{2}}^+$) coupled channels, $J^P={\frac{1}{2}}^-$ and ${\frac{3}{2}}^-$ for vector-baryon (${\frac{1}{2}}^+$) coupled channels, and $J^P={\frac{1}{2}}^-$, ${\frac{3}{2}}^-$, ${\frac{5}{2}}^-$ for vector-baryon (${\frac{3}{2}}^+$) coupled channels. We search for the poles of these states and evaluate their couplings to the different channels., Comment: 8 pages, 1 figures

Recently, the Belle and LHCb Collaborations have measured the $\Lambda^+_c \to p K^- \pi^+$ decay and reported the $p K^-$ invariant mass distribution, which shows a clear cusp structure around the $\eta \Lambda$ threshold. In this work, we have analyzed this process by considering the triangle mechanism and the $S$-wave pseudoscalar meson-octet baryon interactions within the chiral unitary approach, which dynamically generate the $\Lambda(1670)$. Our results are in good agreement with the Belle measurements, which implies that the cusp structure around $\eta\Lambda$ threshold could be associated with the $\Lambda(1670)$ with the molecular nature.

We propose the reaction $\psi(3686) \to \bar{\Xi}^+ \bar{K}^0 \Sigma^{*-}$, with the $\Sigma^{*-}$ decaying to $\pi^- \Lambda$ in order to show evidence for the existence of two $\Xi(1820)$ states, one around $1824$ MeV and narrow, and another one around $1875$ MeV and wide. The phase space for $\bar{K}^0 \Sigma^{*-}$ production reduces the effect of the lower mass resonance, magnifying the effect of the higher mass resonance that shows clearly over the phase space. The estimated rate of the production is bigger than the one of the $\psi(3686) \to \bar{\Xi}^+ K^- \Lambda$ reaction, where a clear peak for $\Xi(1820)$ was observed by the BESIII collaboration, what makes the Beijing facility ideal to carry out the reaction proposed., Comment: 4 pages, 2 figures, 1 table

Recently, the LHCb Collaboration has measured the processes $B^0\to\bar{D}^0D_s^+\pi^-$ and $B^+\to\bar{D}^0D_s^+\pi^+$, where the $D_s^+\pi^-$ and $D_s^+\pi^+$ invariant mass distributions show the significant signals of two new open-flavor tetraquark states $T_{c\bar{s}}(2900)^0$ and $T_{c\bar{s}}(2900)^{++}$, as the two of the isospin triplet. In this work, we have investigated the process $\Lambda_b\to K^0D^0\Lambda$ by taking into account the intermediate nucleon resonance $N^*(1535)$ and the tetraquark state $T_{c\bar{s}}(2900)^0$, which could be dynamically generated by the interactions of the $D^*K^*/D^*_s\rho$ and the pseoduscalar mesons-octet baryons, respectively. Our results show that a clear peak of the open-flavor tetraquark $T_{c\bar{s}}(2900)$ may appear in the $K^0D^0$ invariant mass distribution of the process $\Lambda_b\to K^0D^0\Lambda$, which could be tested by future experiments., Comment: 9 pages, 11 figures, 1 table

Motivated by the recent observation of $T_{c\bar{s}0}(2900)^0$ and $T_{c\bar{s}0}(2900)^{++}$ in the $D_s \pi$ invariant mass distributions, we investigate $D^{\ast}K^{\ast}$ interactions in a coupled-channel approach. We show that the relativistic corrections could be significant for the energy far away from the threshold. Within the hidden local symmetry formalism, a sizable attraction interaction is found in the $J=0$ isospin triplet sector that can form a bound or a virtual state, which is consistent with the experimentally observed $T_{c\bar{s}0}(2900)$. By reproducing a $D_s^*\rho$-$D^*K^*$ bound/virtual state with the pole mass equal to that of the $T_{c\bar{s}0}(2900)$ measured by LHCb in the sector $(I,J)=(1,0)$, we determine the unknown parameter in the loop function, and then search for possible poles in the sectors of $I=1$, $J=1,$ 2 and $I=0$, $J=0$, 1, 2. The predicted resonances provide a useful reference for the future experimental studies of the $(C,S)=(1,1)$ systems and can be also helpful to unravel the nature of the $T_{c\bar{s}0}(2900)$.10, Comment: 10 pages, 6 figures, 3 tables

Motivated by the recent LHCb observations of $T_{c\bar{s}0}(2900)^0$ and $T_{c\bar{s}0}(2900)^{++}$ in the processes $B^0\to\bar{D}^0D_s^+\pi^-$ and $B^+\to D^-D_s^+\pi^+$, we have investigated the decay $B^-\to D_s^+K^-\pi^-$ by taking into account the contributions from the $S$-wave vector-vector interactions, and the $S$-wave $D^+_s K^-$ interactions. Our results show that the $D_s^+K^-$ invariant mass distribution has an enhancement structure near the threshold, associated with the $D^*_0(2300)$, which is in good agreement with the Belle measurements. We have also predicted the $D^+_s\pi^-$ invariant mass distribution and the Dalitz plot, which show the significant signal of the $T_{c\bar{s}0}(2900)$. With the same formalism, the $D^-_sK^0_s$ invariant mass distribution of the process $B^0 \to D^-_sK^0_s\pi^+$ measured by Belle could be well reproduced, and the peak of $T_{c\bar{s}0}(2900)$ is expected to be observed around 2900~MeV in the $D^-_s\pi^+$ invariant mass distribution. Our results could be tested by the Belle II and LHCb experiments in the future., Comment: 11 pages, 13 figures

Inspired by recent observations of $T_{c\bar{s}0}(2900)^0$ in the $D_s^+ \pi^-$ invariant mass distribution of $B^0 \to \bar{D}^0 D_s^+ \pi^-$ decay and $T_{c\bar{s}0}(2900)^{++}$ in the $D_s^+ \pi^+$ invariant mass distribution of $B^+ \to D^- D_s^+ \pi^+$ decay, we investigate the $T_{c\bar{s}0}(2900)^{++}$ contribution to the $B^+ \to K^+ D^+ D^-$ decay in a molecular scenario, where we consider $T_{c\bar{s}0}(2900)r^{++}$ as a $D^{\ast +} K^{\ast+}$ molecular state. Our estimations indicate that the fit fraction of $T_{c\bar{s}0}(2900)^{++}$ in the $B^+ \to K^+ D^+ D^-$ is about $12.5\%$, and its signal is visible in the $D^+ K^+$ invariant mass distribution. With the involvement of $T_{c\bar{s}0}(2900)^{++}$, the fit fractions of $\chi_{c0}(3915)$ and $\chi_{c2}(3930)$ may be much different with the ones obtained by the present amplitude analysis [Phys. Rev. D \textbf{102}, 112003 (2020)], which may shed light on the long standing puzzle of $\chi_{c0}(3915)$ as the conventional charmonium., Comment: 7 pages, 3 figures. Comments are welcome

Inspired by the recent observation of a new structure, $X(4014)$, in the process $\gamma\gamma\to \gamma\psi(2S)$, we evaluate the possibility of assigning $X(4014)$ as a $D^\ast \bar{D}^\ast$ molecular state with $I(J^{PC})=0(0^{++})$ by investigating the hidden charm decays of $X(4014)$. The partial widths of $J/\psi\omega$, $ \eta_{c}\eta$ and $\eta_{c}\eta^{\prime}$ channels are evaluated to be about $(0.41\sim 5.00)$, $(2.05\sim7.49)$ and $(0.11\sim0.51)\ \mathrm{MeV}$, respectively. Considering the experimental observation and the present estimations, we proposed to search $X(4014)$ in the $\gamma \gamma \to J/\psi \omega$ process in Belle II., Comment: 7 pages, 5 figures, accepted for publication in Phys. Rev. D

Within the framework of the local hidden gauge approach, we have studied the near-threshold interaction of the $D^* \bar{D}^*$ channel with quantum numbers $I(J^{PC}) = 0(0^{++})$, $0(2^{++})$, $1(0^{++})$, and $1(2^{++})$, respectively. The contact interaction is taken into account alone, since it is expected to give the dominant contribution near the threshold. One pole, which is found in the case of the quantum numbers $I(J^{PC}) = 0(0^{++})$, could be associated to the $X(4014)$ recently observed by the Belle Collaboration. Thus, we suggest that the $X(4014)$ may be an $D^* \bar{D}^*$ molecular state with $I(J^{PC}) = 0(0^{++})$, and more precise information about $X(4014)$, such as resonance parameters and decay properties, could be useful to shed light on its structure., Comment: 6 pages, 5 figures

Within the framework of the local hidden gauge formalism, we have reanalyzed the hidden-charm vector-vector meson $D^*\bar{D}^*$, $K^*\bar{K}^*$, and $\rho\rho$ interactions with the quantum numbers $I(J^P)=1(1^+)$. The estimation indicates that $D^*\bar{D}^*$ system could form a bound state around 4010 MeV. By comparing our theoretical estimation with the BESIII measurements of the $e^+e^- \to (D^*\bar{D}^*)^{\pm}\pi^{\mp}$ and $e^+e^- \to (D^*\bar{D}^*) ^{0}\pi^{0}$ reactions at $\sqrt{s}=4.26$ GeV , we find that the enhancement structure of the $Z_c(4025)$ in the $D^*\bar{D}^*$ invariant mass distribution observed by BESIII could be interpreted by a shallow $D^*\bar{D}^*$ bound state., Comment: 8 pages, 4 figures

In this work, we have investigated the process $D_s^+\to K^+ K^- \pi^+$, taking into account the contributions from the $S$-wave pseudoscalar-pseudoscalar interaction within the chiral unitary approach, and also the intermediate $\phi$ resonance. By analyzing the BESIII and {\it BABAR} measurements, we conclude that the $f_0(980)$ state, dynamically generated from the $S$-wave pseudoscalar-pseudoscalar interaction, gives the dominant contribution close to the $K^+K^-$ threshold in the $K^+K^-$ invariant mass distribution of the decay $D_s^+\to K^+ K^- \pi^+$ in $S$-wave. On the other hand, our results imply that the lineshape adopted by BESIII and {\it BABAR} for the resonances $a_0(980)$ and $f_0(980)$ is not advisable in the fit to the data close to the $K^+K^-$ threshold., Comment: 9 pages, 9 figures, 1 table, Published in Phys.Lett.B 821(2021)136617

In this work, we have investigated the Cabibbo-suppressed process $\Lambda_c \to \pi^0\eta p$, by taking into account the intermediate scalar state $a_0(980)$, which could be dynamically generated from the $S$-wave pseudoscalar-pseudoscalar interaction within the chiral unitary approach. We have calculated the $\pi^0\eta$ invariant mass distribution, and found that there is a significant structure associated to the $a_0(980)$. We have also roughly estimated the branching fraction $\mathcal{B}(\Lambda_c \to \pi^0\eta p) \sim 10^{-4}$. We encourage our experimental colleagues to measure the process $\Lambda_c \to \pi^0\eta p$ for searching for the state $a_0(980)$ in this reaction., Comment: 7 pages, 5 figures

Taking into account that the scalar $a_0(980)$ can be dynamically generated from the pseudoscalar-pseudoscalar interaction within the chiral unitary approach, we have studied the single Cabibbo-suppressed process $D^+\to \pi^+\pi^0\eta$. We find clear peaks of $a_0(980)^+$ and $a_0(980)^0$ in the $\pi^+\eta$ and $\pi^0\eta$ invariant mass distributions, respectively. The predicted Dalitz plots of $D^+\to \pi^+\pi^0\eta$ also manifest the significant signals for $a_0(980)^+$ and $a_0(980)^0$ states. The uncertainties of the results due to the free parameters are also discussed. Our study shows that the process $D^+\to \pi^+\pi^0\eta$ can be used to explore the nature of the scalar $a_0(980)$, thus we encourage the experimental physicists to measure this reaction with more precision., Comment: 7 pages, 6 figures, comments are welcome

We have analyzed the reaction $\chi_{c0}\to \bar{p} K^+\Lambda$ reported by the BESIII Collaboration, taking into account the contributions from the intermediate $K(1830)$, $N(2300)$, and $\Lambda(1520)$ resonances. Our results are in good agreement with the BESIII measurements, and it is found that the anomalous enhancement near the $\bar{p}\Lambda$ threshold is mainly due to the contribution of the $K(1830)$ resonance. We also show that the interference of the high-mass $N^*$ and $\Lambda^*$ can not produce the anomalous enhancement near the $\bar{p}\Lambda$ threshold., Comment: 9 pages, 7 figures, the version to be presented in PRD