Production of the X(4014)as the Spin-2 Partner of X(3872)in e^(+)e^(-)Collisions

In 2021,the Belle collaboration reported the first observation of a new structure in theψ(2S)γfinal state produced in the two-photon fusion process.In the hadronic molecule picture,this new structure can be associatedwith 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).

Isospin-conserving hadronic decay of the D_(s1)(2460) into D_(s)π^(+)π^(-)

The internal structure of the charm-strange mesons D_(s0)^(*)(2317)and D_(s1)(2460)are the subject of intensive studies.Their widths are small because they decay dominantly through isospinbreaking hadronic channels D_(s0)^(*)(2317)^(+)→D_(s)^(+)π^(0) and D _(s1)(2460)^(+)→D_(s)^(*+)π^(0).The D_(s1)(2460)can also decay into the hadronic final states D_(s)^(+)ππ,conserving isospin.In that case there is,however,a strong suppression from phase space.We study the transition D_(s1)(2460)^(+)→D_(s)^(+)π^(+)π^(-)in the scenario that the D_(s1)(2460)is a D^(*)K hadronic molecule.The ππ final state interaction is taken into account through dispersion relations.We find that the ratio of the partial widths of the Γ(D_(s1)(2460)^(+)→D_(s)^(+)π^(+)π^(-)) / Γ(D_(s1)(2460)^(+)→D_(s)^(*+)π^(0))obtained in the molecular picture is consistent with the existing experimental measurement.More interestingly,we demonstrate that theπ+π−invariant mass distribution shows a double bump structure,which can be used to disentangle the hadronic molecular picture from the compact state picture for the D_(s1)(2460)^(+).Predictions on the B_(s1)^(0)→B_(s)^(0)π^(+)π^(-)are also made.

Is the existence of a J/ψJ/ψbound state plausible?

In a recent measurement LHCb reported pronounced structures in the J/ψJ/ψspectrum.One of the various possible explanations of those is that they emerge from non-perturbative interactions of vector charmonia.It is thus important to understand whether it is possible to form a bound state of two charmonia interacting through the exchange of gluons,which hadronise into two pions at the longest distance.In this paper,we demonstrate that,given our current understanding of hadron-hadron interactions,the exchange of correlated light mesons(pions and kaons)is able to provide sizeable attraction to the di-J/ψsystem,and it is possible for two J/ψmesons to form a bound state.As a side result we find from an analysis of the data for theψ/(2 S)J/ψππtransition including bothππand KK final state interactions an improved value for theψ(2 S)→J/ψtransition chromo-electric polarisability:|αψ(2 S)J/ψ|=(1.8±0.1)GeV-3,where the uncertainty also includes the one induced by the final state interactions.

Note on X(3872) production at hadron colliders and its molecular structure

The production of the X（3872） as a hadronic molecule in hadron colliders is clarified. We show that the conclusion of Bignamini et al., Phys. Rev. Lett. 103（2009） 162001, that the production of the X（3872） at high pT implies a non-molecular structure, does not hold. In particular, using the well understood properties of the deuteron wave function as an example, we identify the relevant scales in the production process.