Zhang, X. Y., Shi, P. P., & Guo, F. K. (2025). Production of 1-+ exotic charmonium-like states in electron-positron collisions. Phys. Lett. B, 867, 139603–8pp.
Abstract: The absence of observed charmonium-like states with the exotic quantum numbers J=1+ has prompted us to investigate the production rates of the 1 DD, (2420) and D D, (2420) hadronic molecules, which we refer to as n and, respectively, in electron-positron collisions. Assuming a hadronic molecular nature for the vector charmonium-like states (4360) and yr(4415), we evaluate the radiative decay widths of (4360)-> 77 and (4415) yn. Using these decay widths, we estimate the cross sections for producing, and, in electron-positron annihilations, as well as the event numbers at the planned Super r-Charm Facility. Our results suggest that the ideal energy region for observing these states is around 4.44 and 4.50 GeV, just above the D D (2420) and D D (2460) thresholds, respectively.
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Shi, P. P., Albaladejo, M., Du, M. L., Guo, F. K., & Nieves, J. (2025). P-wave charmonium contribution to hidden-charm states from a reanalysis of lattice QCD data. Phys. Rev. D, 111(7), 074043–26pp.
Abstract: We reanalyze, considering the contribution of P-wave charmonia, lattice data for the DD<overline>-DSD<overline>S coupled-channel of Prelovsek et al. [J. High Energy Phys. 06 (2021) 035.] and DD<overline>* systems of Prelovsek et al. [Phys. Rev. Lett. 111, 192001 (2013).] with m pi <^> 280 and 266 MeV, and L = 24a/32a (a <^> 0.09 fm) and L = 16a (a <^> 0.1239(13) fm), respectively. The hidden-charm states with JPC = 0++, 1++, and 2++ quantum numbers are then searched for. For 0++, the analysis reveals three poles in the DD<overline>-DSD<overline>S coupled-channel amplitude, corresponding to three states. Two of these poles, located near the DD<overline> and DSD<overline>S thresholds, can be interpreted as mostly molecular states. A third pole above the DSD<overline>S threshold is originated from the P-wave chi c0(2P) charmonium state. The number of poles found in the DD<overline>-DSD<overline>S system is the same as that found in the original lattice analysis though the position of the third pole changes sizeably. In the 1++ sector, we find two poles in the complex energy plane. The first one is related to the molecular X(3872) state, with a compositeness exceeding 90%, while the second one, stemming from the chi c1(2P) charmonium, appears above the DD<overline>* threshold and it likely corresponds to the recently discovered chi c1(4010) state. In the 2++ sector, we also report two poles and find that the dressed chi c2(2P) is lighter than the D*D<overline>* molecular state, with the dynamics of the latter closely related to that of the heavy-quark spin-symmetry partner of the X(3872). Our exploratory study of the 1++ and 2++ sectors offers valuable insights into their dynamics, but given that the fits that we carry out are underconstrained, more lattice data are required to draw robust conclusions.
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Du, M. L., Filin, A., Baru, V., Dong, X. K., Epelbaum, E., Guo, F. K., et al. (2023). Role of Left-Hand Cut Contributions on Pole Extractions from Lattice Data: Case Study for Tcc(3875)+. Phys. Rev. Lett., 131(13), 131903–7pp.
Abstract: We discuss recent lattice data for the T-cc(3875)(+) state to stress, for the first time, a potentially strong impact of left-hand cuts from the one-pion exchange on the pole extraction for near-threshold exotic states. In particular, if the left-hand cut is located close to the two-particle threshold, which happens naturally in the DD* system for the pion mass exceeding its physical value, the effective-range expansion is valid only in a very limited energy range up to the cut and as such is of little use to reliably extract the poles. Then, an accurate extraction of the pole locations requires the one-pion exchange to be implemented explicitly into the scattering amplitudes. Our findings are general and potentially relevant for a wide class of hadronic near-threshold states.
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Shi, P. P., Baru, V., Guo, F. K., Hanhart, C., & Nefediev, A. (2024). Production of the X(4014) as the Spin-2 Partner of X(3872) in e + e – Collisions. Chin. Phys. Lett., 41(3), 031301–7pp.
Abstract: In 2021, the Belle collaboration reported the first observation of a new structure in the psi(2S)gamma final state produced in the two-photon fusion process. In the hadronic molecule picture, this new structure can be associated with the shallow isoscalar D*D* bound state and as such is an excellent candidate for the spin-2 partner of the X(3872) with the quantum numbers J(PC) = 2(++) conventionally named X-2. In this work we evaluate the electronic width of this new state and argue that its nature is sensitive to its total width, the experimental measurement currently available being unable to distinguish between different options. Our estimates demonstrate that the planned Super tau-Charm Facility offers a promising opportunity to search for and study this new state in the invariant mass distributions for the final states J/psi gamma and psi(2S)gamma.
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Ji, T., Dong, X. K., Albaladejo, M., Du, M. L., Guo, F. K., Nieves, J., et al. (2023). Understanding the 0(++) and 2(++) charmonium(-like) states near 3.9 GeV. Sci. Bull., 68(7), 688–697.
Abstract: We propose that the X(3915) observed in the J/psi x channel is the same state as the chi(c2)(3930), and the X(3960), observed in the Ds+Ds- channel, is an S-wave Ds+Ds- hadronic molecule. In addition, the J(PC) = 0(++) component in the B+ -> D+D-K+ assigned to the X(3915) in the current Review of Particle Physics has the same origin as the X(3960), which has a mass around 3.94 GeV. To check the proposal, the available data in the D (D) over bar and Ds+Ds- channels from both B decays and gamma gamma fusion reaction are analyzed considering both the D (D) over bar -D-s(D) over bar (s)-D*(D) over bar*-D-s*(D) over bar (s)* coupled channels with 0(++) and a 2(++) state introduced additionally. It is found that all the data in different processes can be simultaneously well reproduced, and the coupled-channel dynamics produce four hidden-charm scalar molecular states with masses around 3.73, 3.94, 3.99 and 4.23 GeV, respectively. The results may deepen our understanding of the spectrum of charmonia as well as of the interactions between charmed hadrons.
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