Study the $$B^{0}_{(s)}$$ decays into $$\phi $$ and a scalar or vector meson

In the present work, we investigate the decays of $$B^{0}_{(s)} \rightarrow \phi \pi ^{+}\pi ^{-}$$ B ( s ) 0 → ϕ π + π - with the final state interaction based on the chiral unitary approach. In the final state interaction of the $$\pi ^+\pi ^-$$ π + π - with its coupled channels, we study the effects of the $$\eta \eta $$ η η channel in the two-body interaction for the reproduction of the $$f_{0}(980)$$ f 0 ( 980 ) state, where its contribution to the $$f_{0}(980)$$ f 0 ( 980 ) state can be ignored. Our results for the $$\pi ^+\pi ^-$$ π + π - invariant mass distributions of the decay $$B^{0}_{s} \rightarrow \phi \pi ^{+}\pi ^{-}$$ B s 0 → ϕ π + π - describe the experimental data up to 1 GeV well, with the resonance contributions from the $$f_{0}(980)$$ f 0 ( 980 ) and $$\rho $$ ρ . For the predicted invariant mass distributions of the $$B^{0} \rightarrow \phi \pi ^{+}\pi ^{-}$$ B 0 → ϕ π + π - decay, we find that the contributions from the $$f_{0}(500)$$ f 0 ( 500 ) are significant, but not from the $$f_{0}(980)$$ f 0 ( 980 ) state. With some experimental branching ratios to determine the production vertex factors, we make predictions for the branching ratios of the other decay channels, including the vector mesons, in the $$B^0_{(s)}$$ B ( s ) 0 decays, some of which are consistent with the experimental measurements within the uncertainties.

Theoretical study of the $$D^0 \rightarrow K^- \pi ^+ \eta $$ reaction

We develop a model to study the $$D^0 \rightarrow K^- \pi ^+ \eta $$ D 0 → K - π + η weak decay, starting with the color favored external emission and Cabibbo favored mode at the quark level. A less favored internal emission decay mode is also studied as a source of small corrections. Some pairs of quarks are allowed to hadronize producing two pseudoscalar mesons, which posteriorly are allowed to interact to finally provide the $$K^- \pi ^+ \eta $$ K - π + η state. The chiral unitary approach is used to take into account the final state interaction of pairs of mesons, which has as a consequence the production of the $$\kappa $$ κ ($$K^*_0(700)$$ K 0 ∗ ( 700 ) ) and the $$a_0(980)$$ a 0 ( 980 ) resonances, well visible in the invariant mass distributions. We also introduce the $$\bar{K}^{*0} \eta $$ K ¯ ∗ 0 η production in a phenomenological way and show that the s-wave pseudoscalar interaction together with this vector excitation mode are sufficient to provide a fair reproduction of the experimental data. The model provides the relative weight of the $$a_0(980)$$ a 0 ( 980 ) to the $$\kappa $$ κ excitation, and their strength is clearly visible in the low energy part of the $$K \pi $$ K π spectrum.

Role of scalar $$a_0(980)$$ in the single Cabibbo suppressed process $$D^+ \rightarrow \pi ^{+} \pi ^{0} \eta $$

Taking into account that the scalar $$a_0(980)$$ a 0 ( 980 ) can be dynamically generated from the pseudoscalar-pseudoscalar interaction within the chiral unitary approach, we have studied the single Cabibbo suppressed process $$D^+\rightarrow \pi ^+\pi ^0\eta $$ D + → π + π 0 η . We find clear peaks of $$a_0(980)^+$$ a 0 ( 980 ) + and $$a_0(980)^0$$ a 0 ( 980 ) 0 in the $$\pi ^+\eta $$ π + η and $$\pi ^0\eta $$ π 0 η invariant mass distributions, respectively. The predicted Dalitz plots of $$D^+\rightarrow \pi ^+\pi ^0\eta $$ D + → π + π 0 η also manifest the significant signals for $$a_0(980)^+$$ a 0 ( 980 ) + and $$a_0(980)^0$$ a 0 ( 980 ) 0 states. The uncertainties of the results due to the free parameters are also discussed. Our study shows that the process $$D^+\rightarrow \pi ^+\pi ^0\eta $$ D + → π + π 0 η can be used to explore the nature of the scalar $$a_0(980)$$ a 0 ( 980 ) , thus we encourage the experimental physicists to measure this reaction with more precision.

Tau decay into $$\nu _\tau $$ and $$a_1(1260)$$, $$b_1(1235)$$, and two $$K_1(1270)$$

We study the $$\tau \rightarrow \nu _\tau A$$τ→ντA decay, with A an axial-vector meson. We produce the $$a_1(1260)$$a1(1260) and $$b_1(1235)$$b1(1235) resonances in the Cabibbo favored mode and two $$K_1(1270)$$K1(1270) states in the Cabibbo suppressed mode. We take advantage of previous chiral unitary approach results where these resonances appear dynamically from the vector and pseudoscalar meson interaction in s-wave. Actually two different poles were obtained associated to the $$K_1(1270)$$K1(1270) quantum numbers. We find that the unmeasured rates for $$b_1(1235)$$b1(1235) production are similar to those of the $$a_1(1260)$$a1(1260) and for the two $$K_1$$K1 states we suggest to separate the present information on the $$\bar{K} \pi \pi $$K¯ππ invariant masses into $$\bar{K}^* \pi $$K¯∗π and $$\rho K$$ρK modes, the channels to which these two resonances couple most strongly, predicting that these modes peak at different energies and have different widths. These measurements should shed light on the existence of these two $$K_1$$K1 states. In addition, we have gone one step further making a comparison with experimental results of three meson decay channels, letting the vector mesons of our approach decay into pseudoscalars, and we find an overall good agreement with experiment.

Role of N*(1535) in the Λ+c → K0ηp decay and the possible фp state in the Λ+c → π0фp decay

The nonleptonic weak decays of Λ+c → K0ηp and Λ+c → π0фp are investigated from the viewpoint of probing the N*(1535) resonance and the possible фp state. For the Λ+c → K0ηp decay, we study the invariant mass distribution of ηp with both the chiral unitary approach and an effective Lagrangian model. Within the chiral unitary approach, the N*(1535) resonance is dynamically generated from the final state interaction of mesons and baryons in coupled channels. While for the effective Lagrangian model, we take a Breit-Wigner formula for the N*(1535) resonance. We found that the behavior of the N*(1535) resonance in the Λ+c → K0N*(1535) → K0ηp decay within the two approaches is different. For the Λ+c → π0фp decay, we consider a triangle singularity mechanism, where the Λ+c decays into the K*Σ*(1385), the Σ*(1385) decays into the π0Σ/Λ, and then the K*Σ/Λ merge to produce the фp in the final state. This mechanism produces a peak structure around 2020 MeV. In addition, the possibility that there is a hidden-strange pentaquark-like state is also considered by taking into account the final state interactions of K*Λ, K*Σ, and фp. We conclude that it is difficult to search for the hidden-strange state in this decay. However, we do expect nontrivial behavior in the фp invariant mass distribution. The proposed Λ+c decay mechanism here can provide valuable information on the properties of these nuclear resonances and can in principle be tested by experiments such as BESIII, LHCb and Belle-II.

KN scattering amplitude revisited in a chiral unitary approach and a possible broad resonance in S = +1 channel

We revisit the $KN$ scattering amplitude in order to investigate the possibility of the existence of a broad resonance in the $I=0$$KN$ channel around the energy of 1617 MeV with 305 MeV width. We use the chiral unitary model to describe the $KN$ scattering amplitudes and determine the model parameters so as to reproduce the differential cross sections of the $K^{+}N$ scatterings and the $I=0$ and 1 total cross sections up to $p_{\rm lab} = 800$ MeV/c, from which inelastic contributions start to be significant. Performing analytic continuation of the determined amplitude to the complex energy plane, we find a pole for a broad resonance state. We point out that the rapid increase appearing in the $I=0$ total cross section around $p_{\rm lab}=500$ MeV/c is a hint of the possible broad resonance of strangeness $S=+1$.

Weak decays of heavy hadrons into dynamically generated resonances

In this paper, we present a review of recent works on weak decay of heavy mesons and baryons with two mesons, or a meson and a baryon, interacting strongly in the final state. The aim is to learn about the interaction of hadrons and how some particular resonances are produced in the reactions. It is shown that these reactions have peculiar features and act as filters for some quantum numbers which allow to identify easily some resonances and learn about their nature. The combination of basic elements of the weak interaction with the framework of the chiral unitary approach allow for an interpretation of results of many reactions and add a novel information to different aspects of the hadron interaction and the properties of dynamically generated resonances.