Neutron–Proton Dynamics and Pion Production in Heavy-ion Collisions by the AMD+JAM Approach

Initial-final state strong interaction corrections to the B¯→Dv¯ℓ (v¯ττ) decays

The Z(3985) as a threshold effect from the D¯s⁎D+D¯sD⁎ interaction

Abstract We study the e + e − → K + ( D s ⁎ − D 0 + D s − D ⁎ 0 ) reaction recently measured at BESIII, from where a new Z c s state has been reported. We study the interaction of D ¯ s D ⁎ with the coupled channels J / ψ K − , K ⁎ − η c , D s − D ⁎ 0 , D s ⁎ − D 0 by means of an extension to the charm sector of the local hidden gauge approach. We find that the D s − D ⁎ 0 + D s ⁎ − D 0 combination couples to J / ψ K − and K ⁎ − η c , but the D s − D ⁎ 0 − D s ⁎ − D 0 combination does not. The coupled channels help to build up strength in the D s − D ⁎ 0 + D s ⁎ − D 0 diagonal scattering matrix close to threshold and, although the interaction is not strong enough to produce a bound state or…

χc1 decays into a pseudoscalar meson and a vector-vector molecule

We evaluate ratios of the $\chi_{c1}$ decay rates to $\eta$ ($\eta', K^-$) and one of the $f_0(1370)$, $f_0(1710)$, $f_2(1270)$, $f_2'(1525)$, $K^{*}_2(1430)$ resonances, which in the local hidden gauge approach are dynamically generated from the vector-vector interaction. With the simple assumption that the $\chi_{c1}$ is a singlet of SU(3), and the input from the study of these resonances as vector-vector molecular states, we describe the experimental ratio $\mathcal{B}(\chi_{c1} \rightarrow \eta f_2(1270))/ \mathcal{B}(\chi_{c1} \rightarrow \eta' f_2'(1525))$ and make predictions for six more ratios that can be tested in future experiments.

Molecular picture for the Ω ( 2012 ) revisited

We conduct a study of the interaction of the K̄Ξ∗, ηω(s-wave), and K̄Ξ(d-wave) channels within a coupled channel unitary approach where the transition potential between the K̄Ξ∗ and ηω channels is obtained from chiral Lagrangians. The transition potential between K̄Ξ∗, ηω, and K̄Ξ is taken in terms of free parameters, which together with a cutoff to regularize the meson-baryon loops are fitted to the ω(2012) data. We find that all data including the recent Belle experiment on Γω∗→πK̄Ξ/Γω∗→K̄Ξ, are compatible with the molecular picture stemming from meson baryon interaction of these channels.

Semileptonic $\Lambda_c$ decay to $\nu l^+$ and $\Lambda(1405)$

We study the semileptonic decay of $\Lambda_c$ to $\nu l^+$ and $\Lambda(1405)$, where the $\Lambda(1405)$ is seen in the invariant mass distribution of $\pi \Sigma$. We perform the hadronization of the quarks produced in the reaction in order to have a meson baryon pair in the final state and then let these hadron pairs undergo final state interaction from where the $\Lambda(1405)$ is dynamically generated. The reaction is particularly suited to study this resonance because we show that it filters I=0. It is also free of tree level $\pi \Sigma$ production, which leads to a clean signal of the resonance with no background. This same feature has as a consequence that one populates the state …

Molecular states of $ D^* D^* \bar{K}^*$ nature

We study the interaction of two $ D^* $ and a $\bar{K}^{*}$ by using the Fixed Center Approximation to the Faddeev equations to search for bound states of the three body system. Since the $ D^* D^* $ interaction is attractive and gives a bound state, and so is the case of the $D^* \bar{K}^{*}$ interaction, where the $J^{P}=0^{+}$ bound state is identified with the $X_0 (2900)$, the $ D^* D^* \bar{K}^{*}$ system leads to manifestly exotic bound states with $ccs$ open quarks. We obtain bound states of isospin $I=1/2$, negative parity and total spin $J=0,1,2$. For $J=0$ we obtain one state, and for $J=1,2$ we obtain two states in each case. The binding energies range from $56$ MeV to $151$ MeV…

Production of X resonances in Bc− decays

Triangle singularity mechanism for the pp→π+d fusion reaction

We develop a model for the $pp\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}d$ reaction based on the $pp\ensuremath{\rightarrow}\mathrm{\ensuremath{\Delta}}(1232)N$ transition followed by $\mathrm{\ensuremath{\Delta}}(1232)\ensuremath{\rightarrow}\ensuremath{\pi}{N}^{\ensuremath{'}}$ decay and posterior fusion of $N{N}^{\ensuremath{'}}$ to give the deuteron. We show that the triangle diagram depicting this process develops a triangle singularity leading to a large cross section of this reaction compared to ordinary fusion reactions. The results of the calculation also show that the process is largely dominated by the $pp$ system in $L=2$ and $S=0$, which transfers $J=2$ to the final ${\ensu…

Molecular states of D*D*K¯* nature

Sequential single pion production explaining the dibaryon "d*(2380)" peak*

We study the two step sequential one pion production mechanism, $np(I=0)\to \pi^-pp$, followed by the fusion reaction $pp\to \pi^+d$, in order to describe the $np\to \pi^+\pi^-d$ reaction with $\pi^+\pi^-$ in $I=0$, where a narrow peak, so far identified with a "$d(2380)$" dibaryon, has been observed. We find that the second step $pp\to \pi^+d$ is driven by a triangle singularity that determines the position of the peak of the reaction and the large strength of the cross section. The combined cross section of these two mechanisms produce a narrow peak with the position, width and strength compatible with the experimental observation within the approximations done. This novel interpretation …

Effects of Pauli blocking on pion production in central collisions of neutron-rich nuclei

Pauli blocking is carefully investigated for the processes of $NN \rightarrow N \Delta$ and $\Delta \rightarrow N \pi$ in heavy-ion collisions, aiming at a more precise prediction of the $\pi^-/ \pi^+$ ratio which is an important observable to constrain the high-density symmetry energy. We use the AMD+JAM approach, which combines the antisymmetrized molecular dynamics for the time evolution of nucleons and the JAM model to treat processes for $\Delta$ resonances and pions. As is known in general transport-code simulations, it is difficult to treat Pauli blocking very precisely due to unphysical fluctuations and additional smearing of the phase-space distribution function, when Pauli blockin…

ϒ(nl) decay into B(⁎)B¯(⁎)

Abstract We have evaluated the decay modes of the ϒ ( 4 s ) , ϒ ( 3 d ) , ϒ ( 5 s ) , ϒ ( 6 s ) states into B B ¯ , B B ¯ ⁎ + c . c . , B ⁎ B ¯ ⁎ , B s B ¯ s , B s B ¯ s ⁎ + c . c . , B s ⁎ B ¯ s ⁎ using the P 0 3 model to hadronize the b b ¯ vector seed, fitting some parameters to the data. We observe that the ϒ ( 4 s ) state has an abnormally large amount of meson-meson components in the wave function, while the other states are largely b b ¯ . We predict branching ratios for the different decay channels which can be contrasted with experiment for the case of the ϒ ( 5 s ) state. While globally the agreement is fair, we call the attention to some disagreement that could be a warning for t…