Abstract: We apply the general formalism derived by Penalva et al. [Phys. Rev. D 101, 113004 (2020)] to the semileptonic decay of pseudoscalar mesons containing a b quark. While present (B) over bar -> D-(*()) data give the strongest evidence in favor of lepton flavor universality violation, the observables that are normally considered are not able to distinguish between different new physics (NP) scenarios. In the above reference we discussed the relevant role that the various contributions to the double differential decay widths d(2)Gamma (d omega d cos theta(l)) and d(2)Gamma (d omega dE(l)) could play to this end. Here omega is the product of the two hadron fourvelocities, theta(l) is the angle made by the final lepton and final hadron three-momenta in the center of mass of the final two-lepton system, and E-l is the final charged lepton energy in the laboratory system. The formalism was applied by Penalva et al. to the analysis of the Lambda(b) -> Lambda(c) semileptonic decay, showing the new observables were able to tell apart different NP scenarios. Here we analyze the (B) over barc -> eta(c)tau(nu) over bar (tau), (B) over barc -> J/psi tau(nu) over bar (tau), (B) over bar -> D tau(nu) over bar (tau) and (B) over bar -> D*tau(nu) over bar (tau) , semileptonic decays. We find that, as a general rule, the (B) over barc -> J/psi observables, even including (tau) polarization, are less optimal for distinguishing between NP scenarios than those obtained from (B) over barc -> eta(c) decays, or those presented by Penalva et al. for the related Lambda(b) -> Lambda(c) semileptonic decay. Finally, we show that (B) over bar -> D and (B) over barc -> eta(c) , and (B) over bar -> D* and (B) over barc -> J/psi decay observables exhibit similar behaviors.

Abstract: We study the behavior of the chi(c1) (3872), also known as X(3872), in dense nuclear matter. We begin from a picture in vacuum of the X(3872) as a purely molecular (D (D) over bar*-c.c.) state, generated as a bound state from a heavy-quark symmetry leading-order interaction between the charmed mesons, and analyze the D (D) over bar* scattering T matrix (T-D (D) over bar*) inside of the medium. Next, we consider also mixed-molecular scenarios and, in all cases, we determine the corresponding X(3872) spectral function and the D (D) over bar* amplitude, with the mesons embedded in the dense environment. We find important nuclear corrections for T-D (D) over bar* and the pole position of the resonance, and discuss the dependence of these results on the D (D) over bar* molecular component in the X(3872) wave function. These predictions could be tested in the finite-density regime that can be accessed in the future CBM and PANDA experiments at the Facility for Antiproton and Ion Research (FAIR).

Abstract: We have performed a combined analysis of the BESIII data for both the Z(c)(3900) and Z(cs)(3985) structures, assuming that the latter is an SU(3) flavor partner of the former one. We have improved on the previous analysis of Albaladejo et al. [Phys. Lett. B 755, 337 (2016)] by computing the amplitude for the D-1(D) over barD* triangle diagram considering both D- and S-wave D1D*x couplings. We have also investigated effects from SU(3) light-flavor violations, which are found to be moderate and of the order of 20%. The successful reproduction of the BESIII spectra, in both the hidden-charm and hidden-charm strange sectors, strongly supports that the Z(cs)(3985) and Z(c)(3900) are SU(3) flavor partners placed in the same octet multiplet. The best results are obtained when an energy-dependent term in the diagonal D(*) (D) over bar ((s))((*)) interaction is included, leading to resonances (poles above the thresholds) to describe these exotic states. We have also made predictions for the isovector Z*c and isodoublet Z*(cs), D*(D) over bar*, and D*??D*s molecules, with J(PC) = 1(+-) and J(P) = 1(+), respectively. These states would be heavy-quark spin symmetry (HQSS) partners of the Z(c) and Z(cs). Besides the determination of the masses and widths of the Z(c)(3900) and Z(cs)(3985), we also predict those of the Z*(c) and Z*(cs) resonances.

Abstract: Recently, the LHCb Collaboration reported a near-threshold enhancement X(3960) in the D+sD-s invariant mass distribution. We show that the data can be well described by either a bound or a virtual state below the D+sD-s threshold. The mass given by the pole position is (3928 +/- 3) MeV. Using this mass and the existing information on the X(3872) and Zc(3900) resonances, a complete spectrum of the S-wave hadronic molecules formed by a pair of ground state charmed and anticharmed mesons is established. Thus, pole positions of the partners of the X(3872) , Zc(3900) , and the newly observed D+sD-s state are predicted. Calculations have been carried out at the leading order of nonrelativistic effective field theory and considering both heavy quark spin and light flavor SU(3) symmetries, though conservative errors from the breaking of these symmetries are provided.

Abstract: We discuss the modification of the properties of the tetraquark-like Tcc(3875)+ and Tc over bar c over bar (3875)- states in dense nuclear matter. We consider the Tcc+ and Tc over bar c over bar – in vacuum as purely isoscalar D*D and D*D S-wave bound states, respectively, dynamically generated from a heavy-quark effective interaction between the charmed mesons. We compute the D, D, D*, and D* spectral functions embedded in a nuclear medium and use them to determine the corresponding Tcc+ and Tc over bar c over bar – self-energies and spectral functions. We find important modifications of the D*D and D*D scattering amplitudes and of the pole position of these exotic states already for p0/2, with p0 the normal nuclear density. We also discuss the dependence of these results on the D*D (D*D) molecular component in the Tcc+ (Tc over bar c- over bar ) wave function. Owing to the different nature of the D(*)N and D(*)N interactions, we find characteristic changes of the in-medium properties of the Tcc(3875)+ and Tc over bar c over bar (3875)-, which become increasingly visible as the density increases. The experimental confirmation of the found distinctive density pattern will give support to the existence of molecular components in these tetraquark-like states, since in the case they were mostly colorless compact quark structures (cct over bar t over bar and c over bar c over bar tt, with t = u, d), the density behaviors of the Tcc(3875)+ and Tc over bar c over bar (3875)- nuclear medium spectral functions, though different, would not likely be the same as those found in this work for molecular scenarios. Finally, we perform similar analyses for the isoscalar JP = 1+ heavy-quark spin symmetry partners of the Tcc+ (T cc *+ ) and the T c over bar c- over bar (T*- c over bar c over bar ) by considering the D*0D*+ and D*0D*- scattering T matrices.