Isospin breaking, coupled-channel effects, and X(3872)

We re-investigate the possibility of X(3872) as a $D\bar{D}^*$ molecule with $J^{PC}=1^{++}$ within the framework of both the one-pion-exchange (OPE) model and the one-boson-exchange (OBE) model. After careful treatment of the S-D wave mixing, the mass difference between the neutral and charged $D(D^*)$ mesons and the coupling of the $D(D^*)$ pair to $D^*\bar{D}^*$, a loosely bound molecular state X(3872) emerges quite naturally with large isospin violation in its flavor wave function. For example, the isovector component is 26.24% if the binding energy is 0.30 MeV, where the isospin breaking effect is amplified by the tiny binding energy. After taking into account the phase space difference and assuming the $3\pi$ and $2\pi$ come from a virtual omega and rho meson respectively, we obtain the ratio of these two hidden-charm decay modes: $\mathcal{B}(X(3872)\rightarrow \pi^+\pi^-\pi^0 J/\psi)/\mathcal{B}(X(3872)\rightarrow \pi^+\pi^- J/\psi)=0.42$ for the binding energy being 0.3 MeV, which is consistent with the experimental value.Comment: published in Phys. Rev.

Deuteron-like states composed of two doubly charmed baryons

We present a systematic investigation of the possible molecular states composed of a pair of doubly charmed baryons ($\Xi_{cc}\Xi_{cc}$) or one doubly charmed baryon and one doubly charmed antibaryon $(\Xi_{cc}\bar{\Xi}_{cc})$ within the framework of the one-boson-exchange-potential model. For the spin-triplet systems, we take into account the mixing between the ${}^3S_1$ and ${}^3D_1$ channels. For the baryon-baryon system $\Xi_{cc}\Xi_{cc}$ with $(R,I) = (\bar{3}, 1/2)$ and $(\bar{3}, 0)$, where $R$ and $I$ represent the group representation and the isospin of the system, respectively, there exist loosely bound molecular states. For the baryon-antibaryon system $\Xi_{cc}\bar{\Xi}_{cc}$ with $(R,I) = (8, 1)$, $(8, 1/2)$ and $(8,0)$, there also exist deuteron-like molecules. The $B_{cc}\bar{B}_{cc}$ molecular states may be produced at LHC. The proximity of their masses to the threshold of two doubly charmed baryons provides a clean clue to identify them.Comment: 18 pages, 8 figure

Possible hadronic molecules composed of the doubly charmed baryon and nucleon

We perform a systematical investigation of the possible deuteron-like bound states with configuration $\Xi_{cc}N (\bar{N})$, where $N(\bar{N})$ denotes the nucleon (anti-nucleon), in the framework of the one-boson-exchange-potential model. In the spin-triplet sector we take into account both the ${}^3S_1$ and ${}^3D_1$ channels due to non-vanishing tensor force. There exist several candidates of the loosely bound molecular states for the $\Xi_{cc}N$ and $\Xi_{cc}\bar{N}$ systems, which lie below the threshold of $\Lambda_c\Lambda_c$ or $\Lambda_c{\bar\Lambda}_c$. We also investigate the possible loosely bound states with configurations $\Lambda_cN(\bar{N})$ and $\Sigma_cN(\bar{N})$. These molecular candidates may be searched for at Belle II and LHC in the near future.Comment: 14 pages, 5 figure

Possible Deuteron-like Molecular States Composed of Heavy Baryons

We perform a systematic study of the possible loosely bound states composed of two charmed baryons or a charmed baryon and an anti-charmed baryon within the framework of the one boson exchange (OBE) model. We consider not only the $\pi$ exchange but also the $\eta$, $\rho$, $\omega$, $\phi$ and $\sigma$ exchanges. The $S-D$ mixing effects for the spin-triplets are also taken into account. With the derived effective potentials, we calculate the binding energies and root-mean-square (RMS) radii for the systems $\Lambda_c\Lambda_c(\bar{\Lambda}_c)$, $\Xi_c\Xi_c(\bar{\Xi}_c)$, $\Sigma_c\Sigma_c(\bar{\Sigma}_c)$, $\Xi_c^\prime\Xi_c^\prime(\bar{\Xi}_c^\prime)$ and $\Omega_c\Omega_c(\bar{\Omega}_c)$. Our numerical results indicate that: (1) the H-dibaryon-like state $\Lambda_c\Lambda_c$ does not exist; (2) there may exist four loosely bound deuteron-like states $\Xi_c\Xi_c$ and $\Xi_c^\prime\Xi_c^\prime$ with small binding energies and large RMS radii.Comment: 17 pages, 32 figure

Nucleus-nucleus potential from identical-particle interference

Based on the quantum interference between two-identical-nucleus scattering at energies around the Coulomb barrier, the barrier positions for $^{58}$Ni+$^{58}$Ni and $^{16}$O+$^{16}$O are extracted from Mott oscillations in the angular distributions around 90$^{\circ}$ for the first time. The angle separation of pairs of Mott scattering valleys around 90$^{\circ}$ has a direct relationship with the closest distance between two nuclei in elastic scattering. Together with the barrier height from fusion excitation function, the extracted barrier position provides a sensitive probe to constrain the model predictions for the nucleus-nucleus potential barrier.Comment: 4 figures, accepted for publication in Phys. Lett.