Open-charm Channels Research Articles

Branching ratios and decay widths of the main, hidden and open charm channels of tetraquark state

Branching ratios and decay widths of the main, hidden and open charm channels of tetraquark state

D-wave excited tetraquark states with and * *Supported by the National Natural Science Foundation of China (12175318), the National Key R & D Program of China (2020YFA0406400), the Natural Science Foundation of Guangdong Province of China (2022A1515011922), and the Fundamental Research Funds for the Central Universities

We study the mass spectra of D-wave excited tetraquark states with and in both symmetric and antisymmetric color configurations using the QCD sum rule method. We construct the D-wave diquark-antidiquark type of tetraquark interpolating currents in various excitation structures with . Our results support the interpretation of the recently observed resonance as a D-wave tetraquark state with in the or excitation mode, although some other possible excitation structures cannot be excluded exhaustively within theoretical errors. Moreover, our results provide the mass relations and for the positive and negative -parity D-wave tetraquarks, respectively. We suggest searching for these possible D-wave tetraquarks in both the hidden-charm channels and , as well as open-charm channels such as and .

P c resonances in the compact pentaquark picture

P c resonances are studied in the approach of quark model and group theory. It is found that there are totally 17 possible pentaquark states with the quark contents (q are u and d quarks; Q is c quark) in the compact pentaquark picture, where the hidden charm pentaquark states may take the color singlet–singlet and color octet–octet configurations. The theoretical results of partial decay widths of the pentaquark states show that open charm channels are the dominant decay modes for almost all hidden charm pentaquark states, but there are four pentaquark states which decay through the pJ/ψ channel with sizable partial decay widths.

Exploration of the hidden charm decays of Zcs(3985)

In the present work, we investigate the decays of $Z^-_{cs}(3985)$ in the $D_s^{-} D^{\ast0} + D_s^{\ast -}D^0$ molecular frame. By using an effective Lagrangian approach, the branching ratios of $Z^-_{cs}\rightarrow J/\psi K^-$ and $Z^-_{cs}\rightarrow \eta_c K^{\ast-}$ are estimated. It is found that the dominating decay mode of $Z^-_{cs}(3985)$ is open charm channel, while, the branching ratio of the hidden charm decay channels is about $20\%$. In particular, the branching ratios of $Z^-_{cs}\rightarrow J/\psi K^-$ and $Z^-_{cs}\rightarrow \eta_c K^{\ast-}$ are predicted to be of order of $10\%$. Moreover, our estimation indicates that the fraction of the quasi-two-body cascade decay via $Z_{cs}(3985)$ and the total cross section of $e^+ e^- \to K^+ K^- J/\psi$ around 4.68 GeV is $\left(6.8^{+10.5}_{-6.2} \right)\%$. All the predicted branching ratios in the present work could be tested by further measurements in BESIII and Belle II.

Exotic molecular states and tetraquark states with JP =0+, 1+, 2+ * *Supported in part by National Key R&D Program of China under Contracts No. 2020YFA0406400, the National Natural Science Foundation of China (11722540, 12075019), the Fundamental Research Funds for the Central Universities

We have calculated the mass spectra for the molecular states and tetraquark states with . The masses of the axial-vector , molecular states and , tetraquark states are predicted to be approximately 3.98 GeV, in good agreement with the mass of from BESIII. In both the molecular and diquark-antidiquark scenarios, our results suggest that there may exist two almost degenerate states, as the strange partners of and . We propose to carefully examine in future experiments to verify this. One may also search for more hidden-charm four-quark states with strangeness in not only the open-charm channels but also the hidden-charm channels , .

Pc(4457)+ , Pc(4440)+ , and Pc(4312)+ : Molecules or compact pentaquarks?

In a chromomagnetic model, we analyse the properties of the newly observed $P_c(4457)^+$, $P_c(4440)^+$, and $P_c(4312)^+$ states. We estimate the masses of the $(uud)_{8_c}(c\bar{c})_{8_c}$ and $(uds)_{8_c}(c\bar{c})_{8_c}$ pentaquark states by considering the isospin breaking effects. Their values are determined by calculating mass distances from the $\Sigma_c^{++}D^-$ and $\Xi_c^{\prime+}D^-$ thresholds, respectively. It is found that the isospin breaking effects on the spectrum are small. From the uncertainty consideration and the rearrangement decay properties in a simple model, we find that it is possible to assign the $P_c(4457)^+$, $P_c(4440)^+$, and $P_c(4312)^+$ as $J^P=3/2^-$, $1/2^-$, and $3/2^-$ pentaquark states, respectively. The assignment in the molecule picture can be different, in particular for the $P_c(4312)^+$. The information from open-charm channels, e.g. ${\cal B}[P_c\to\Sigma_c^{++}D^-]/{\cal B}[P_c\to J/\psi p]$, will play an important role in distinguishing the inner structures of the $P_c$ states. Discussions and predictions based on the calculations are also given.

Rescattering effects in antiproton-induced exclusive J/$ \psi$ and $ \psi^{{\prime}}_{}$ production on the deuteron

On the basis of the generalized eikonal approximation we study the exclusive reactions $\bar p d \to J/\psi\, n$ and $\bar p d \to \psi^\prime\, n$ in vicinity of the thresholds for charmonium production on a free proton target. It is shown that the rescattering of the incoming antiproton and outgoing charmonium on the spectator neutron leads to a depletion of the charmonium production at low- and to an enhancement at high transverse momenta. This is in qualitative agreement with previous studies of hard proton knockout in proton-deuteron collisions. We analyze different physical sources of uncertainty which may influence the extraction of the total charmonium-neutron cross section. The color transparency effect for the incoming $\bar p$ largely compensates the influence of charmonium rescattering both at low and high transverse momenta. Different choices of the deuteron wave function lead to significant uncertainties at high transverse momenta. As an outcome of the calculations of charmonium production, we also provide predictions on the production of open charm hadrons due to the dissociation of the charmonium on the neutron. It is shown that the open charm production cross section is proportional to the total charmonium-nucleon cross section and quite stable with respect to the variation of other parameters of the model. We thus suggest that open charm channels are most suited for future studies of charmonium-nucleon interactions at PANDA with a deuteron target.

Hidden-charm pentaquarks and Pc states

Recently, the LHCb Collaboration reported three $P_c$ states in the ${J/\psi}p$ channel. We systematically study the mass spectrum of the hidden charm pentaquark in the framework of an extended chromomagnetic model. For the $nnnc\bar{c}$ pentaquark with $I=1/2$, we find that (i) the lowest state is $P_{c}(4327.0,1/2,1/2^{-})$ [We use $P_{c}(m,I,J^{P})$ to denote the $nnnc\bar{c}$ pentaquark], which corresponds to the $P_{c}(4312)$. Its dominant decay mode is $\Lambda_{c}\bar{D}^{*}$. (ii) We find two states in the vicinity of $P_{c}(4380)$. The first one is $P_{c}(4367.4,1/2,3/2^{-})$ and decays dominantly to $N{J/\psi}$ and $\Lambda_{c}\bar{D}^{*}$. The other one is $P_{c}(4372.4,1/2,1/2^{-})$. Its dominant decay mode is $\Lambda_{c}\bar{D}$, and its partial decay width of $N\eta_{c}$ channel is comparable to that of $N{J/\psi}$. (iii) In higher mass region, we find $P_{c}(4476.3,1/2,3/2^{-})$ and $P_{c}(4480.9,1/2,1/2^{-})$, which correspond to $P_{c}(4440)$ and $P_{c}(4457)$. In the open charm channels, both of them decay dominantly to the $\Lambda_{c}\bar{D}^{*}$. (iv) We predict two states above $4.5~\text{GeV}$, namely $P_{c}(4524.5,1/2,3/2^{-})$ and $P_{c}(4546.0,1/2,5/2^{-})$. The masses of the $nnnc\bar{c}$ state with $I=3/2$ are all over $4.6~\text{GeV}$. Moreover, we use the model to explore the $nnsc\bar{c}$, $ssnc\bar{c}$ and $sssc\bar{c}$ pentaquark states.

Constructing J/ψ family with updated data of charmoniumlike Y states

Based on the updated data of charmoniumlike state $Y(4220)$ reported in the hidden-charm %and open-charm channels of the $e^+e^-$ annihilation, we propose a $4S$-$3D$ mixing scheme to categorize $Y(4220)$ into the $J/\psi$ family. We find that the present experimental data can support this charmonium assignment to $Y(4220)$. Thus, $Y(4220)$ plays a role of a scaling point in constructing higher charmonia above 4 GeV. To further test this scenario, we provide more abundant information on the decay properties of $Y(4220)$, and predict its charmonium partner $\psi(4380)$, whose evidence is found by analyzing the $e^+e^-\to \psi(3686)\pi^+\pi^-$ data from BESIII. If $Y(4220)$ is indeed a charmonium, we must face how to settle the established charmonium $\psi(4415)$ in the $J/\psi$ family. In this work, we may introduce a $5S$-$4D$ mixing scheme, and obtain the information of the resonance parameters and partial open-charm decay widths of $\psi(4415)$, which do not contradict the present experimental data. Additionally, we predict a charmonium partner $\psi(4500)$ of $\psi(4415)$, which can be accessible at future experiments, especially, BESIII and BelleII. The studies presented in this work provide new insights to establish the higher charmonium spectrum.

Exclusive open-charm near-threshold cross sections in a coupled-channel approach

Data on 7 open-charm channels collected by the Belle Collaboration are analyzed simultaneously using a unitary approach based on a coupled channel model in a wide energy range $ \sqrt s $ = 3.7 − 4.7 GeV. The resulting fit provides a remarkably good overall description of the line shapes in all studied channels. Parameters of 5 vector charmonium resonances are extracted from the fit. It is demonstrated, that this approach could be used account for all exclusive channels and thus solve the long-term problem of the charmonium spectra near threshold.

Disentangling the role of the Y(4260) in [formula omitted] and [formula omitted] via line shape studies

Whether the Y(4260) can couple to open charm channels has been a crucial issue for understanding its nature. The available experimental data suggest that the cross section line shapes of exclusive processes in e+e− annihilations have nontrivial structures around the mass region of the Y(4260). As part of a series of studies of the Y(4260) as mainly a D¯D1(2420)+c.c. molecular state, we show that the partial widths of the Y(4260) to the two-body open charm channels of e+e−→D⁎D¯⁎ and Ds⁎D¯s⁎ are much smaller than that to D¯D⁎π+c.c.. The line shapes measured by the Belle Collaboration for these two channels can be well described by the vector charmonium states ψ(4040), ψ(4160) and ψ(4415) together with the Y(4260). It turns out that the interference of the Y(4260) with the other charmonia produces a dip around 4.22 GeV in the e+e−→D⁎D¯⁎ cross section line shape. The data also show an evidence for the strong coupling of the Y(4260) to the DD¯1(2420), in line with the expectation in the hadronic molecular scenario for the Y(4260).

Interference effect as resonance killer of newly observed charmoniumlike states Y(4320) and Y(4390)

In this letter, we decode the newly observed charmoniumlike states, Y(4320) and Y(4390), by introducing interference effect between psi (4160) and psi (4415), which plays a role of resonance killer for Y(4320) and Y(4390). It means that two newly reported charmoniumlike states are not genuine resonances, according to which we can naturally explain why two well-established charmonia psi (4160) and psi (4415) are missing in the cross sections of e^+e^- rightarrow pi ^+ pi ^- J/psi and pi ^+ pi ^- h_c simultaneously. To well describe the detailed data of these cross sections around sqrt{s}=4.2 GeV, our study further illustrates that a charmoniumlike structure Y(4220) must be introduced. As a charmonium, Y(4220) should dominantly decay into its open-charm channel e^+e^- rightarrow D^0 pi ^+ D^{*-}, which provides an extra support to psi (4S) assignment to Y(4220). In fact, this interference effect introduced to explain Y(4320) and Y(4390) gives a typical example of non-resonant explanations to the observed XYZ states, which should be paid more attention especially before identifying the observed XYZ states as genuine resonances.

Exclusive open-charm near-threshold cross sections in a coupled-channel approach

Data on open-charm channels collected by the Belle Collaboration are analysed simultaneously using a unitary approach based on a coupled-channel model in a wide energy range $\sqrt{s}=3.7\div 4.7$ GeV. The resulting fit provides a remarkably good overall description of the line shapes in all studied channels. Parameters of 5 vector charmonium resonances are extracted from the fit.

Radially excited states of $$\eta _c$$ η c

In the framework of chiral quark model, the mass spectrum of $\eta_c(ns) (n=1,...,6)$ is studied with Gaussian expansion method. With the wave functions obtained in the study of mass spectrum, the open flavor two-body strong decay widths are calculated by using $^3P_0$ model. The results show that the masses of $\eta_c(1S)$ and $\eta_c(2S)$ are consistent with the experimental data. The explanation of X(3940) as $\eta_c(3S)$ is disfavored for X(3940) is a narrow state, $\Gamma=37^{+26}_{-15} \pm 8 $ MeV, while the open flavor two-body strong decay width of $\eta_c(3S)$ is about 200 MeV in our calculation. Although the mass of X(4160) is about 100 MeV less than that of $\eta_c(4S)$, the assignment of X(4160) as $\eta_c(4S)$ can not be excluded because the open flavor two-body strong decay width of $\eta_c(4S)$ is consistent with the experimental value of X(4160) and the branching ratios of $\eta_c(4S)$ are compatible with that of X(4160), and the mass of $\eta_c(4S)$ can be shifted downwards by taking into account the coupling effect of the open charm channels. There are still no good candidates to $\eta_c(5S)$ and $\eta_c(6S)$.

The Lost Tribes of Charmonium

To illustrate the campaign to extend our knowledge of the charmonium spectrum, I focus on a puzzling new state, $X(3872) \to \pi^+\pi^- J/\psi$. Studying the influence of open-charm channels on charmonium properties leads us to propose a new charmonium spectroscopy: additional discrete charmonium levels that can be discovered as narrow resonances of charmed and anticharmed mesons. I call attention to open issues for theory and experiment.

Charmonium levels near threshold and the narrow stateX(3872)→π+π−J/ψ

We explore the influence of open-charm channels on charmonium properties and profile the ${1}^{3}{D}_{2},$ ${1}^{3}{D}_{3},$ and ${2}^{1}{P}_{1}$ charmonium candidates for $X(3872).$ The favored candidates, the ${1}^{3}{D}_{2}$ and ${1}^{3}{D}_{3}$ levels, both have prominent radiative decays. The ${1}^{3}{D}_{2}$ might be visible in the ${D}^{0}{D}^{*0}$ channel, while the dominant decay of the ${1}^{3}{D}_{3}$ state should be into $D\overline{D}.$ We propose that additional discrete charmonium levels can be discovered as narrow resonances of charmed and anticharmed mesons.