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.

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.

Abstract: Since 2003 many new hadrons, including the lowest-lying positive-parity charm-strange mesons D*(s0) (2317) and D-s1 (2460), have been observed that do not conform with quark-model expectations. It was recently demonstrated that various puzzles in the charm-meson spectrum find a natural resolution if the SU(3) multiplets for the lightest scalar and axial-vector states, among them the D*(s0) (2317) and the D-s1 (2460), owe their existence to the nonperturbative dynamics of Goldstone-boson scattering off D-(s) and D*((s)) mesons. Most importantly the ordering of the lightest strange and nonstrange scalars becomes natural. We demonstrate for the first time that this mechanism is strongly supported by the recent high quality data on the B- -> D+ pi(-)pi(-) provided by the LHCb experiment. This implies that the lowest quark-model positive-parity charm mesons, together with their bottom counterparts, if realized in nature, do not form the ground-state multiplet. This is similar to the pattern that has been established for the scalar mesons made from light up, down, and strange quarks, where the lowest multiplet is considered to be made of states not described by the quark model. In a broader view, the hadron spectrum must be viewed as more than a collection of quark-model states.

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.

Abstract: Quantum chromodynamics presents a series of exact and approximate symmetries which can be exploited to predict new hadrons from previously known ones. The Z(c)(3900) and Z(c)(4020), which have been theorized to be isovector D*(D) over bar and D*(D) over bar* molecules [I-G(J(PC)) = 1(-)(1)(+-))], are no exception. Here we argue that from SU(3)-flavor symmetry, we should expect the existence of strange partners of the Z(c)'s with hadronic molecular configurations D*(D) over bar (s) – D (D) over bar*(s) and D*(D) over bar*(s) (or, equivalently, quark content c (c) over bars (q) over bar, with q = u, d). The quantum numbers of these Z(cs) and Z(cs)* structures would be I(J(P)) = 1/2 (1(+)). The predicted masses of these partners depend on the details of the theoretical scheme used, but they should be around the D*(D) over bar (s) – D (D) over bar*(s) and D*(D) over bar*(s) thresholds, respectively. Moreover, any of these states could be either a virtual pole or a resonance. We show that, together with a possible triangle singularity contribution, such a picture nicely agrees with the very recent BESIII data of the e(+)e(-) -> K+((Ds-D*0) + D*D--(s)0).