Triangle singularity in the J/ψ → K+K− f0(980) decay

2020

Theoretical interpretation of the Ds+→π+π0η decay and the nature of a0(980)

2020

Abstract In a recent paper [1] , the BESIII Collaboration reported the so-called first observation of pure W-annihilation decays D s + → a 0 + ( 980 ) π 0 and D s + → a 0 0 ( 980 ) π + . The measured absolute branching fractions are, however, puzzlingly larger than those of other measured pure W-annihilation decays by at least one order of magnitude. In addition, the relative phase between the two decay modes is found to be about 180 degrees. In this letter, we show that all these can be easily understood if the a 0 ( 980 ) is a dynamically generated state from K ¯ K and πη interactions in coupled channels. In such a scenario, the D s + decay proceeds via internal W emission instead of W-an…

B0andBs0decays intoJ/ψf0(980)andJ/ψf0(500)and the nature of the scalar resonances

2014

Abstract We describe the B 0 and B s 0 decays into J / ψ f 0 ( 500 ) and J / ψ f 0 ( 980 ) by taking into account the dominant process for the weak decay of B 0 and B s 0 into J / ψ and a q q ¯ component. After hadronization of this q q ¯ component into pairs of pseudoscalar mesons we obtain certain weights for the meson–meson components and allow them to interact among themselves. The final state interaction of the meson–meson components, described in terms of chiral unitary theory, gives rise to the f 0 ( 980 ) and f 0 ( 500 ) resonances and we can obtain the π + π − invariant mass distributions after the decay of the resonances, which allows us to compare directly to the experiments. We …

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

2019

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.

Predictions for η→ηπ+π− producing f0(500), f0(980) and a0(980)

2017

Abstract We perform calculations for the η c → η π + π − decay using elements of SU(3) symmetry to see the weight of different trios of pseudoscalars produced in this decay, prior to the final state interaction of the mesons. After that, the interaction of pairs of mesons, leading finally to η π + π − , is done using the chiral unitary approach. We evaluate the π + π − and πη mass distributions and find large and clear signals for f 0 ( 500 ) , f 0 ( 980 ) and a 0 ( 980 ) excitation. The reaction is similar to the χ c 1 → η π + π − , which has been recently measured at BESIII and its implementation and comparison with these predictions will be very valuable to shed light on the nature of th…

Molecular Ω states

2018

Motivated by the recent finding of five Ωc states by the LHCb collaboration, and the successful reproduction of three of them in a recent approach searching for molecular states of meson–baryon with the quantum numbers of Ωc, we extend these ideas and make predictions for the interaction of meson–baryon in the beauty sector, searching for poles in the scattering matrix that correspond to physical states. We find several Ωb states: two states with masses 6405 MeV and 6465 MeV for JP=12−; two more states with masses 6427 MeV and 6665 MeV for 32−; and three states between 6500 and 6820 MeV, degenerate with JP=12−,32−, stemming from the interaction of vector–baryon in the beauty sector.

Testing the nature of h1(1380) resonance in χcJ→ϕK*K¯, ϕh1 (1380)

2020

Isospin breaking andf0(980)-a0(980) mixing in theη(1405) →π0f0(980) reaction

2014

We make a theoretical study of the η (1405) → π 0 f 0 (980) and η (1405) → π 0 a 0 (980) reactions to determine the isospin violation and the mixing of the f 0 (980) and a 0 (980) resonances. We make use of the chiral unitary approach where these two resonances appear as dynamically generated by the meson-meson interaction provided by chiral Lagrangians. We obtain a very narrow shape for the f 0 (980) production in agreement with a BES experiment. As to the amount of isospin violation, assuming constant vertices for the primary η (1405) → π 0 K K and η (1405) → π 0 π 0 η production, we find results which are much smaller than found in the experimental BES paper. The problem is solved by usi…

Abnormal isospin violation and a0−f0 mixing in the Ds+→π+π0a0(980)(f0(980)) reactions

2017

We have chosen the reactions ${D}_{s}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{0}{a}_{0}(980)({f}_{0}(980))$ investigating the isospin violating channel ${D}_{s}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{0}{f}_{0}(980)$. The reaction was chosen because by varying the ${\ensuremath{\pi}}^{0}{a}_{0}(980)({f}_{0}(980))$ invariant mass one goes through the peak of a triangle singularity emerging from ${D}_{s}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\overline{K}}^{*}K$, followed by ${\overline{K}}^{*}\ensuremath{\rightarrow}\overline{K}{\ensuremath{\pi}}^{0}$ and the further merging of $K\overline{K}$ to produce the ${a}_{0}(980)$ …

Triangle singularity enhancing isospin violation in ${\bar{{\rm{B}}}}_{{\rm{s}}}^{0}\to {\rm{J}}/{\rm{\psi }}{\pi }^{0}{{\rm{f}}}_{0}(980)$

2018

We perform calculations for the and reactions, showing that the first is isospin-suppressed while the second is isospin-allowed. The reaction proceeds via a triangle mechanism, with , followed by the decay K* → Kπ and a further fusion of into the or a0(980). We show that the mechanism develops a singularity around the π0 f0(980) or π0 a0(980) invariant mass of 1420 MeV, where the π0 f0 and π0 a0 decay modes are magnified and also the ratio of π0 f0 to π0 a0 production. Using experimental information for the decay, we are able to obtain absolute values for the reactions studied which fall into the experimentally accessible range. The reactions proposed and the observables evaluated, when con…

Two-, Three-, Many-body Systems Involving Mesons. Multimeson Condensates

2015

In this talk we review results from studies with unconventional many hadron systems containing mesons: systems with two mesons and one baryon, three mesons, some novel systems with two baryons and one meson, and finally systems with many vector mesons, up to six, with their spins aligned forming states of increasing spin. We show that in many cases one has experimental counterparts for the states found, while in some other cases they remain as predictions, which we suggest to be searched in BESIII, Belle, LHCb, FAIR and other facilities.

Semileptonic Λb→ν¯llΛc(2595) and Λb→ν¯llΛc(2625) decays in the molecular picture of Λc(2595) and Λc(2625)

2017

We evaluate the partial decay widths for the semileptonic ${\mathrm{\ensuremath{\Lambda}}}_{b}\ensuremath{\rightarrow}{\overline{\ensuremath{\nu}}}_{l}l{\mathrm{\ensuremath{\Lambda}}}_{c}(2595)$ and ${\mathrm{\ensuremath{\Lambda}}}_{b}\ensuremath{\rightarrow}{\overline{\ensuremath{\nu}}}_{l}l{\mathrm{\ensuremath{\Lambda}}}_{c}(2625)$ decays from the perspective that these two ${\mathrm{\ensuremath{\Lambda}}}_{c}^{*}$ resonances are dynamically generated from the $DN$ and ${D}^{*}N$ interaction with coupled channels. We find that the ratio of the rates obtained for these two reactions is compatible with present experimental data and is very sensitive to the ${D}^{*}N$ coupling, which becomes…

Determination of the ηHe3 threshold structure from the low energy pd→ηHe3 reaction

2017

We analyze the data on cross sections and asymmetries for the $pd\ensuremath{\rightarrow}\ensuremath{\eta}\phantom{\rule{0.16em}{0ex}}^{3}\mathrm{He}$ reaction close to threshold and look for bound states of the $\ensuremath{\eta}\phantom{\rule{0.16em}{0ex}}^{3}\mathrm{He}$ system. Rather than parameterizing the scattering matrix, as is usually done, we develop a framework in which the $\ensuremath{\eta}{\phantom{\rule{0.16em}{0ex}}}^{3}\mathrm{He}$ optical potential is the key ingredient, and its strength, together with some production parameters, are fitted to the available experimental data. The relationship of the scattering matrix to the optical potential is established using the Bethe…

Isospin breaking andf0(980)-a0(980)mixing in theη(1405)→π0f0(980)reaction

2012

We make a theoretical study of the eta(1405) -> pi(0)f(0)(980) and eta(1405) -> pi(0)a(0)(980) reactions with an aim to determine the isospin violation and the mixing of the f(0)(980) and a(0)(980) resonances. We make use of the chiral unitary approach where these two resonances appear as composite states of two mesons, dynamically generated by the meson-meson interaction provided by chiral Lagrangians. We obtain a very narrow shape for the f(0)(980) production in agreement with a BES experiment. As to the amount of isospin violation, or f(0)(980) and a(0)(980) mixing, assuming constant vertices for the primary eta(1405) -> pi K-0 (K) over bar and eta(1405) -> pi(0)pi(0)eta production, we f…

Hidden charm pentaquark and Λ(1405) in the Λb0→ηcK−p(πΣ) reaction

2018

Abstract We have performed a study of the Λ b 0 → η c K − p and Λ b 0 → η c π Σ reactions based on the dominant Cabibbo favored weak decay mechanism. We show that the K − p produced only couples to Λ ⁎ states, not Σ ⁎ and that the πΣ state is only generated from final state interaction of K ¯ N and ηΛ channels which are produced in a primary stage. This guarantees that the πΣ state is generated in isospin I = 0 and we see that the invariant mass produces a clean signal for the Λ ( 1405 ) of higher mass at 1420 MeV. We also study the η c p final state interaction, which is driven by the excitation of a hidden charm resonance predicted before. We relate the strength of the different invariant…

Triangle mechanisms in the build up and decay of the N*(1875)

2017

We have studied the $N^*(1875) (3/2^-)$ resonance with a multichannel unitary scheme, considering the $\Delta \pi$ and $\Sigma^* K$, with their interaction extracted from chiral Lagrangians, and then have added two more channels, the $N^*(1535) \pi$ and $N \sigma$, which proceed via triangle diagrams involving the $\Sigma^* K$ and $\Delta \pi$ respectively in the intermediate states. The triangle diagram in the $N^*(1535) \pi$ case develops a singularity at the same energy as the resonance mass. We determine the couplings of the resonance to the different channels and the partial decay widths. We find a very large decay width to $\Sigma^* K$, and also see that, due to interference with othe…

Molecular $\Omega_c$ states generated from coupled meson-baryon channels

2018

We have investigated $\Omega_c$ states that are dynamically generated from the meson-baryon interaction. We use an extension of the local hidden gauge to obtain the interaction from the exchange of vector mesons. We show that the dominant terms come from the exchange of light vectors, where the heavy quarks are spectators. This has as a consequence that heavy quark symmetry is preserved for the dominant terms in the $(1/m_Q)$ counting, and also that the interaction in this case can be obtained from the $\textrm{SU(3)}$ chiral Lagrangians. We show that for a standard value for the cutoff regulating the loop, we obtain two states with $J^{P}={1/2}^{-}$ and two more with $J^{P}={3/2}^{-}$, thr…

Triangle singularity enhancing isospin violation in $D_s^ + \to {\pi ^ + }{\pi ^0}{f_0}(980)$ and $\overline B _s^0 \to J/\psi {\pi ^0}{f_0}(980)$ de…

2019

We investigate isospin violation in the and reactions, which proceed via a triangle mechanism. We show that the mechanism develops a singularity around the π 0 f 0 (980) or π 0 a0 (980) invariant mass of 1420 MeV where the π 0 f 0 and π 0 a0 decay modes are magnified and also the ratio of π 0 f0 to π 0 a0 production, stressing the role of the triangle singularities as a factor to enhance isospin violation. The measurement of these reactions would bring further information into the role of triangle singularities in isospin violation and the a 0 – f 0 mixing in particular and shed further light into the nature of the low lying scalar mesons.

B¯0decay intoD0andf0(500),f0(980),a0(980),ρandB¯s0decay intoD0andκ(800),K*0

2015

We make predictions for ratios of branching fractions of ${\overline{B}}^{0}$ decays into ${D}^{0}$ and the scalar mesons ${f}_{0}(500)$, ${f}_{0}(980)$, ${a}_{0}(980)$, plus ${\overline{B}}_{s}^{0}$ decay into ${D}^{0}$ and $\ensuremath{\kappa}(800)$. We also compare the ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ production in the scalar channel with that observed in the $\ensuremath{\rho}$ channel and make predictions for the ${\overline{B}}_{s}^{0}$ decay into ${D}^{0}$ and ${K}^{*}(892)$, comparing the strength of this channel with that of $\ensuremath{\kappa}(800)$ production. The work is based on results of the chiral unitary approach where the scalar resonances are g…

K¯-induced formation of thef0(980)anda0(980)resonances on proton targets

2016

We perform a calculation of the cross section for nine reactions induced by $\overline{K}$ scattering on protons. The reactions studied are ${K}^{\ensuremath{-}}p\ensuremath{\rightarrow}\mathrm{\ensuremath{\Lambda}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$, ${K}^{\ensuremath{-}}p\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Sigma}}}^{0}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$, ${K}^{\ensuremath{-}}p\ensuremath{\rightarrow}\mathrm{\ensuremath{\Lambda}}{\ensuremath{\pi}}^{0}\ensuremath{\eta}$, ${K}^{\ensuremath{-}}p\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Sigma}}}^{0}{\ensuremath{\pi}}^{0}\ensuremath{\eta}$, ${K}^{\ensuremath{-}}p\ensuremath{\rightarrow…

Baryon states with open charm in the extended local hidden gauge approach

2014

In this paper we examine the interaction of $D N$ and $D^* N$ states, together with their coupled channels, by using an extension of the local hidden gauge formalism from the light meson sector, which is based on heavy quark spin symmetry. The scheme is based on the use of the impulse approximation at the quark level, with the heavy quarks acting as spectators, which occurs for the dominant terms where there is the exchange of a light meson. The pion exchange and the Weinberg-Tomozawa interactions are generalized and with this dynamics we look for states generated from the interaction, with a unitary coupled channels approach that mixes the pseudoscalar-baryon and vector-baryon states. We f…

Interpretation of the Ωc→π+Ω(2012)→π+(K¯Ξ) relative to Ωc→π+K¯Ξ from the Ω(2012) molecular perspective

2022

Predictions for pentaquark states of hidden charm molecular nature and comparison with experiment

2016

Predictions for hidden charm molecules, with and without strangeness, were made prior to the LHCb experiment. We discuss these issues and how these states can be observed in the reactions, Λ b → J / ψK − p , Λ b → J / ψη Λ, Λ b → J / ψπ − p , Λ b → J / ψK 0 Λ and Ξ − b → J / ψK − Λ by looking at the invariant mass distributions for J / ψp or J / ψ Λ.

Ωb−→(Ξc+K−)π− decay and the Ωc states

2018

We study the weak decay ${\mathrm{\ensuremath{\Omega}}}_{b}^{\ensuremath{-}}\ensuremath{\rightarrow}({\mathrm{\ensuremath{\Xi}}}_{c}^{+}{K}^{\ensuremath{-}}){\ensuremath{\pi}}^{\ensuremath{-}}$, in view of the narrow ${\mathrm{\ensuremath{\Omega}}}_{c}$ states recently measured by the LHCb Collaboration and later confirmed by the Belle Collaboration. The ${\mathrm{\ensuremath{\Omega}}}_{c}(3050)$ and ${\mathrm{\ensuremath{\Omega}}}_{c}(3090)$ are described as meson-baryon molecular states, using an extension of the local hidden gauge approach in coupled channels. We investigate the $\mathrm{\ensuremath{\Xi}}D$, ${\mathrm{\ensuremath{\Xi}}}_{c}\overline{K}$, and ${\mathrm{\ensuremath{\Xi}}}_…

Study of reactions disclosing hidden charm pentaquarks with or without strangeness

2016

We present results for five reactions, Lambda(b) -> J/psi K(-)p, Lambda(b) -> J/psi eta Lambda, Lambda(b) -> J/psi pi(-)p, Lambda(b) -> J/psi K-0 Lambda and Xi(-)(b) -> J/psi K-Lambda, where combining information from the meson baryon interaction, using the chiral unitary approach, and predictions made for molecular states of hidden charm, with or without strangeness, we can evaluate invariant mass distributions for the light meson baryon states, and for those of J/psi p or J/psi Lambda. We show that with the present available information, in all of these reactions one finds peaks where the pentaquark states show up. In the Lambda(b) -> J/psi K(-)p, and Lambda(b) -> J/psi pi(-)p reactions w…

Analysis of the γγ→DD¯ reaction and the DD¯ bound state

2021

In this work, we investigate the reaction of $\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\rightarrow}D\overline{D}$, taking into account the $S$-wave $D\overline{D}$ final state interaction. By fitting to the $D\overline{D}$ invariant mass distributions measured by the Belle and BABAR Collaborations, we obtain a good reproduction of the data by means of a $D\overline{D}$ amplitude that produces a bound $D\overline{D}$ state with isospin $I=0$ close to threshold. The error bands of the fits indicate, however, that more precise data on this reaction are needed to be more assertive about the position and width of such a state.

$${\bar{B}}^0$$ B ¯ 0 , $$B^{-}$$ B - and $${\bar{B}}^0_s$$ B ¯ s 0 decays into $$J/\psi $$ J / ψ and $$K {\bar{K}}$$ K K ¯ or $$\pi \eta $$ π η

2015

We study the $\bar B^0_s \to J/\psi K^+ K^-$, $\bar B^0 \to J/\psi K^+ K^-$, $B^- \to J/\psi K^0 K^-$, $\bar B^0 \to J/\psi \pi^0 \eta$ and $B^- \to J/\psi \pi^- \eta$ decays and compare their mass distributions with those obtained for the $\bar B^0_s \to J/\psi \pi^+ \pi^-$ and $\bar B^0 \to J/\psi \pi^+ \pi^-$. The approach followed consist in a factorization of the weak part and the hadronization part into a factor which is common to all the processes. Then what makes the reactions different are some trivial Cabibbo-Kobayashi-Maskawa matrix elements and the weight by which the different pairs of mesons appear in a primary step plus their final state interaction. These elements are part o…

Tetra and pentaquarks from the molecular perspective

2019

We present results for the analysis of the B+ → J/ψϕK+ which shows the contribution of two resonances, the X(4140) and X(4160) and a cusp at the $D_s^*\bar D_s^*$ threshold tied to the molecular character of the X(4160) resonance. In the second part we present the results for the theoretical approach to the new Ωcstates from the molecular perspective. In both cases we compare with results of the LHCb collaboration.

ϒ(nl) decay into B(⁎)B¯(⁎)

2020

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…

Determination of the $\boldsymbol{��^3{\rm He}}$ threshold structure from the low energy $\boldsymbol{pd \to ��^3{\rm He}}$ reaction

2016

We analyze the data on cross sections and asymmetries for the $pd (dp) \to ��^3{\rm He}$ reaction close to threshold and look for bound states of the $��^3 {\rm He}$ system. Rather than parameterizing the scattering matrix, as is usually done, we develop a framework in which the $��^3 {\rm He}$ optical potential is the key ingredient, and its strength, together with some production parameters, are fitted to the available experimental data. The relationship of the scattering matrix to the optical potential is established using the Bethe-Salpeter equation and the $��^3 {\rm He}$ loop function incorporates the range of the interaction given by the empirical $^3 {\rm He}$ density. We find a loc…

$\bar B^0$, $B^-$ and $\bar B^0_s$ decays into $J/\psi$ and $K \bar K$ or $\pi \eta$

2015

We study the $\bar B^0_s \to J/\psi K^+ K^-$, $\bar B^0 \to J/\psi K^+ K^-$, $B^- \to J/\psi K^0 K^-$, $\bar B^0 \to J/\psi \pi^0 \eta$ and $B^- \to J/\psi \pi^- \eta$ decays and compare their mass distributions with those obtained for the $\bar B^0_s \to J/\psi \pi^+ \pi^-$ and $\bar B^0 \to J/\psi \pi^+ \pi^-$. The approach followed consist in a factorization of the weak part and the hadronization part into a factor which is common to all the processes. Then what makes the reactions different are some trivial Cabibbo-Kobayashi-Maskawa matrix elements and the weight by which the different pairs of mesons appear in a primary step plus their final state interaction. These elements are part o…

Looking for a hidden-charm pentaquark state with strangeness $S=-1$ from $\Xi^-_b$ decay into $J/\psi K^- \Lambda$

2015

Assuming that the recently observed hidden-charm pentaquark state, $P_c(4450)$, is of molecular nature as predicted in the unitary approach, we propose to study the decay of $\Xi^-_b\rightarrow J/\psi K^- \Lambda$ to search for the strangeness counterpart of the $P_c(4450)$. There are three ingredients in the decay mechanism: the weak decay mechanism, the hadronization mechanism, and the finite state interactions in the meson-baryon system of strangeness $S=-2$ and isospin $I=1/2$ and of the $J/\psi\Lambda$. All these have been tested extensively. As a result, we provide a genuine prediction of the differential cross section where a strangeness hidden-charm pentaquark state, the counterpart…

Testing the origin of the “$$f_1(1420)$$ f1(1420) ” with the $${\bar{K}} p \rightarrow \Lambda (\Sigma ) K{\bar{K}} \pi $$ K¯p→Λ(Σ)KK¯π reaction

2020

We study the $${\bar{K}} p \rightarrow Y K{\bar{K}} \pi $$ K¯p→YKK¯π reactions with $${\bar{K}} = {\bar{K}}^0, K^-$$ K¯=K¯0,K- and $$Y=\Sigma ^0, \Sigma ^+, \Lambda $$ Y=Σ0,Σ+,Λ , in the region of $$K{\bar{K}} \pi $$ KK¯π invariant masses of $$1200-1550$$ 1200-1550 MeV. The strong coupling of the $$f_1(1285)$$ f1(1285) resonance to $$K^* {\bar{K}}$$ K∗K¯ makes the mechanism based on $$K^*$$ K∗ exchange very efficient to produce this resonance observed in the $$K{\bar{K}} \pi $$ KK¯π invariant mass distribution. In addition, in all these reactions one observes an associated peak at 1420 MeV which comes from the $$K^* {\bar{K}}$$ K∗K¯ decay mode of the $$f_1(1285)$$ f1(1285) when the $$K^*$$ …

Signatures of the two $$K_1(1270)$$ K1(1270) poles in $$D^+\rightarrow \nu e^+ V P$$ D+→νe+VP decay

2020

We analyze theoretically the $$D^+\rightarrow \nu e^+ \rho \bar{K}$$ D+→νe+ρK¯ and $$D^+\rightarrow \nu e^+ \bar{K}^* \pi $$ D+→νe+K¯∗π decays to see the feasibility to check the double pole nature of the axial-vector resonance $$K_1(1270)$$ K1(1270) predicted by the unitary extensions of chiral perturbation theory (UChPT). Indeed, within UChPT the $$K_1(1270)$$ K1(1270) is dynamically generated from the interaction of a vector and a pseudoscalar meson, and two poles are obtained for the quantum numbers of this resonance. The lower mass pole couples dominantly to $$K^*\pi $$ K∗π and the higher mass pole to $$\rho K$$ ρK , therefore we can expect that different reactions weighing differently…

Predictions for the $\bar B^0 \to \bar K^{*0} X (YZ)$ and $\bar B^0_s \to \phi X (YZ)$ with $X(4160), Y(3940), Z(3930)$

2015

We investigate the decay of $\bar B^0 \to \bar K^{*0} R$ and $\bar B^0_s \to \phi R$ with $R$ being the $X(4160)$, $Y(3940)$, $Z(3930)$ resonances. Under the assumption that these states are dynamically generated from the vector-vector interaction, as has been concluded from several theoretical studies, we use a reaction mechanism of quark production at the elementary level, followed by hadronization of one final $q \bar q$ pair into two vectors and posterior final state interaction of this pair of vector mesons to produce the resonances. With this procedure we are able to predict five ratios for these decays, which are closely linked to the dynamical nature of these states, and also predic…

Determination of the $\boldsymbol{\eta ^3{\rm He}}$ threshold structure from the low energy $\boldsymbol{pd \to \eta ^3{\rm He}}$ reaction

2016

We analyze the data on cross sections and asymmetries for the $pd (dp) \to \eta ^3{\rm He}$ reaction close to threshold and look for bound states of the $\eta ^3 {\rm He}$ system. Rather than parameterizing the scattering matrix, as is usually done, we develop a framework in which the $\eta ^3 {\rm He}$ optical potential is the key ingredient, and its strength, together with some production parameters, are fitted to the available experimental data. The relationship of the scattering matrix to the optical potential is established using the Bethe-Salpeter equation and the $\eta ^3 {\rm He}$ loop function incorporates the range of the interaction given by the empirical $^3 {\rm He}$ density. W…

Looking for a hidden-charm pentaquark state with strangeness $S=-1$ from $��^-_b$ decay into $J/��K^- ��$

2015

Assuming that the recently observed hidden-charm pentaquark state, $P_c(4450)$, is of molecular nature as predicted in the unitary approach, we propose to study the decay of $��^-_b\rightarrow J/��K^- ��$ to search for the strangeness counterpart of the $P_c(4450)$. There are three ingredients in the decay mechanism: the weak decay mechanism, the hadronization mechanism, and the finite state interactions in the meson-baryon system of strangeness $S=-2$ and isospin $I=1/2$ and of the $J/����$. All these have been tested extensively. As a result, we provide a genuine prediction of the differential cross section where a strangeness hidden-charm pentaquark state, the counterpart of the $P_c(445…

$\bar B^0$ decay into $D^0$ and $f_0(500)$, $f_0(980)$, $a_0(980)$, $\rho$ and $\bar B^0_s$ decay into $D^0$ and $\kappa(800)$, $K^{*0}$

2014

We make predictions for ratios of branching fractions of $\bar B^0$ decays into $D^0$ and the scalar mesons $f_0(500)$, $f_0(980)$, $a_0(980)$, plus $\bar B^0_s$ decay into $D^0$ and $\kappa(800)$. We also compare the $\pi^+ \pi^-$ production in the scalar channel with that observed in the $\rho$ channel and make predictions for the $\bar B^0_s$ decay into $D^0$ and $K^*(892)$, comparing the strength of this channel with that of $\kappa(800)$ production. The work is based on results of the chiral unitary approach where the scalar resonances are generated from the pseudoscalar-pseudoscalar interaction. Up to an arbitrary normalization, the mass distributions and rates for decays into the sca…

Hidden charm pentaquark and $\Lambda(1405)$ in the $\Lambda^0_b \to \eta_c K^- p (\pi \Sigma)$ reaction

2017

We have performed a study of the $\Lambda^0_b \to \eta_c K^- p$ and $\Lambda^0_b \to \eta_c \pi \Sigma$ reactions based on the dominant Cabibbo favored weak decay mechanism. We show that the $K^- p$ produced only couples to $\Lambda^*$ states, not $\Sigma^*$ and that the $\pi \Sigma$ state is only generated from final state interaction of $\bar{K}N$ and $\eta \Lambda$ channels which are produced in a primary stage. This guarantees that the $\pi \Sigma$ state is generated in isospin $I=0$ and we see that the invariant mass produces a clean signal for the $\Lambda(1405)$ of higher mass at $1420$ MeV. We also study the $\eta_c p$ final state interaction, which is driven by the excitation of a …

B¯0 , B- and B¯s0 decays into J/ψ and KK¯ or πη

2015

We study the B¯s0→J/ψK+K- , B¯0→J/ψK+K- , B-→J/ψK0K- , B¯0→J/ψπ0η and B-→J/ψπ-η decays and compare their mass distributions with those obtained for the B¯s0→J/ψπ+π- and B¯0→J/ψπ+π- . The approach followed consist in a factorization of the weak part and the hadronization part into a factor which is common to all the processes. Then what makes the reactions different are some trivial Cabibbo–Kobayashi–Maskawa matrix elements and the weight by which the different pairs of mesons appear in a primary step plus their final state interaction. These elements are part of the theory and thus, up to a global normalization factor, all the invariant mass distributions are predicted with no free paramete…