arXiv subjects

E. Oset

Publications and source records attributed to E. Oset.

At least 55 records · Page 3Linked to original sources

arXiv2022

Exotic states with triple charm

In this work we investigate the possibility of the formation of states from the dynamics involved in the $D^*D^*D^*$ system by considering that two $D^*$'s generate a $J^P=1^+$ bound state, with isospin 0, which has been predicted in an earlier theoretical work. We solve the Faddeev equations for this system within the fixed center approximation and find the existence of $J^P=0^-$, $1^-$ and $2^-$ states with charm $3$, isospin $1/2$, masses $\sim 6000$ MeV, which are manifestly exotic hadrons, i.e., with a multiquark inner structure.

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arXiv2022

The $T_{c\bar{s}}(2900)$ as a threshold effect from the interaction of the $D^K^$, $D^*_sρ$ channels

We look at the mass distribution of the $D_s^+ π^-$ in the $B^0 \to \bar{D}^0 D_s^+ π^-$ decay, where a peak has been observed in the region of the $D^*_s ρ$, $D^* K^*$ thresholds. By creating these two channels together with a $\bar{D}^0$ in $B^0$ decay and letting them interact as coupled channels, we obtain a structure around their thresholds, short of producing a bound state, which leads to a peak in the $D_s^+ π^-$ mass distribution in the $B^0 \to \bar{D}^0 D_s^+ π^-$ decay. We conclude that the interaction between the $D^*K^*$ and $D^*_sρ$ is essential to produce the cusp structure that we associate to the recently seen $T_{c\bar{s}}(2900)$, and that its experimental width is mainly due to the decay width of the $ρ$ meson. The peak obtained together with a smooth background reproduces fairly well the experimental mass distribution observed in the $B_0 \to \bar{D}^0 D_s^+ π^-$ decay.

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arXiv2022

Method to observe the $J^{P}=2^{+}$ partner of the $X_{0}(2866)$ in the $B^+ \to D^{+} D^{-} K^{+} $ reaction

We propose a method based on the moments of the $D^{-} K^{+}$ mass distribution in the $B^+ \to D^{+} D^{-} K^{+} $ decay to disentangle the contribution of the $ 2^{+} $ state, partner of $X_{0}(2900)$ in the $ \bar D^{*} K^{*}$ picture for this resonance. Some of these moments show the interference patterns of the $X_{1}(2900)$ and $X_{0}(2900)$ with the $ 2^{+} $ state, which provide a clearer signal of the $ 2^{+} $ resonance than the $ 2^{+} $ signal alone. The construction of these magnitudes from present data is easy to implement, and based on these data we show that clear signals for that resonance should be seen even with the present statistics.

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arXiv2022

The $X(3960)$ seen in $D_{s}^{+} D_{s}^{-}$ as the $X(3930)$ state seen in $ D^{+} D^{-} $

We perform a calculation of the interaction of the $ D \bar{D} $, $ D_{s} \bar{D}_{s} $ coupled channels and find two bound states, one coupling to $ D \bar{D} $ and another one at higher energies coupling mostly to $D_{s}^{+} D_{s}^{-}$. We identify this latter state with the $X_{0}(3930)$ seen in the $D^{+} D^{-}$ mass distribution in the $B^+ \to D^{+} D^{-} K^{+} $ decay, and also show that it produces an enhancement of the $D_{s}^{+} D_{s}^{-}$ mass distribution close to threshold which is compatible with the LHCb recent observation in the $B^+ \to D_{s}^{+} D_{s}^{-} K^{+} $ decay which has been identified as a new state, $X_{0}(3960)$.

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arXiv2022

Exotic molecular meson states of $B^{()} K^{()}$ nature

We evaluate theoretically the interaction of the open bottom and strange systems $\bar B\bar K$, $\bar B^* \bar K$, $\bar B\bar K^*$ and $\bar B^*\bar K^*$ to look for possible bound states which could correspond to exotic non--quark-antiquark mesons since they would contain at least one $b$ and one $s$ quarks. The s-wave scattering matrix is evaluated implementing unitarity by means of the Bethe-Salpeter equation, with the potential kernels obtained from contact and vector meson exchange mechanisms. The vertices needed are supplied from Lagrangians derived from suitable extensions of the hidden gauge symmetry approach to the bottom sector. We find poles below the respective thresholds for isospin 0 interaction and evaluate the widths of the different obtained states by including the main sources of imaginary part, which are the $B^*\to Bγ$ decay in the $\bar B^* \bar K$ channels, the $K^*\to K π$ in the channels involving a $K^*$, plus the box diagrams with $\bar B\bar K$ and $\bar B^*\bar K$ intermediate states for the $\bar B^*\bar K^*$ channels.

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arXiv2022

How much is the compositeness of a bound state constrained by $a$ and $r_0$? The role of the interaction range

We present an approach that allows one to obtain information on the compositeness of molecular states from combined information of the scattering length of the hadronic components, the effective range, and the binding energy. We consider explicitly the range of the interaction in the formalism and show it to be extremely important to improve on the formula of Weinberg obtained in the limit of very small binding and zero range interaction. The method allows obtaining good information also in cases where the binding is not small. We explicitly apply it to the case of the deuteron and the $D^{*}_{s0}(2317)$ and $D^{*}_{s1}(2460)$ states and determine simultaneously the value of the compositeness within a certain range, as well as get qualitative information on the range of the interaction.

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arXiv2022

The role of meson interactions in the $D_s^{+}\rightarrow π^{+}π^{+}π^{-}η$ decay

We perform a theoretical study of the $D_s^{+}\to π^{+}π^{+}π^{-}η$ decay. We look first at the basic $D_s^{+}$ decay at the quark level from external and internal emission. Then hadronize a pair or two pairs of $q\bar{q}$ states to have mesons at the end. Posteriorly the pairs of mesons are allowed to undergo final state interaction, by means of which the $a_0(980)$, $f_0(980)$, $a_1(1260)$, and $b_1(1235)$ resonances are dynamically generated. The $G$-parity is used as a filter of the possible channels, and from those with negative $G$-parity only the ones that can lead to $π^{+}π^{+}π^{-}η$ at the final state are kept. Using transition amplitudes from the chiral unitary approach that generates these resonances, and a few free parameters, we obtain a fair reproduction of the six mass distributions reported in BESIII experiment.

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arXiv2022

The $\bar{B}^0 \to D^{+} \bar{D}^{0} K^- $ reaction to detect the $I=0, J^P=1^+$ partner of the $X_0(2866)$

We have chosen the $\bar{B}^0 \to D^{*+} \bar{D}^{*0} K^-$ reaction in order to observe the $I=0, J^P=1^+$ ($R_1$) partner state of the $X_0(2866)$ stemming from the $D^*\bar{K}^*$ molecular picture. The reaction proceeds via external emission in the most favored Cabibbo decay mode and one observes the $R_1$ state as a very strong peak versus the background in the $D^{*+} K^-$ spectrum. The branching ratio for $R_1$ production in this reaction is estimated of the order of $4\times 10^{-3}$. The method used, applied to the $B^+ \to D^- D^+ K^+$ reaction, produces a ratio of signal to background in the $D^- K^+$ spectrum in very good agreement with the LHCb experiment that observed the $X_0(2866)$.

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arXiv2022

Looking for the exotic $X_0(2866)$ and its $J^P=1^+$ partner in the $\bar{B}^0 \to D^{()+} K^- K^{()0} $ reactions

We propose two reactions, $\bar{B}^0 \to K^0 D^{+} K^-$ and $\bar{B}^0 \to K^{*0} D^{*+} K^-$, already measured at Belle, to look into the $J^P=0^+$, $X_0(2866)$ state and a $1^+$ partner of molecular $D^*\bar{K}^*$ nature, by looking at the $D^+ K^-$ and $D^{*+} K^-$ invariant mass distributions, respectively. Very clear peaks over the background are predicted and the branching ratios for the production of these states are evaluated to facilitate the task of determining the needed statistics for their observation. The fact that the $K^{*0} K^-$ mass distribution from accumulation of events of different reactions is already available, indicates that one is not far away from having the needed statistics to see peaks in the $D^{(*)+} K^-$ mass distributions, so far not yet analyzed.

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arXiv2022

Masses and widths of the exotic molecular $B_{(s)}^{()} B_{(s)}^{()}$ states

We study the interaction of the doubly bottom systems $BB$, $B^* B$, $B_s B$, $B_s^* B$, $B^* B^*$, $B^* B_s$, $B^*B_s^*$, $B_s B_s$, $B_s B_s^*$, $B_s^* B_s^*$ by means of vector meson exchange with Lagrangians from an extension of the local hidden gauge approach. The full s-wave scattering matrix is obtained implementing unitarity in coupled channels by means of the Bethe-Salpeter equation. We find poles below the channel thresholds for the attractively interacting channels $B^* B$ in $I=0$, $B^*_s B-B^*B_s$ in $I=\frac{1}{2}$, $B^* B^*$ in $I=0$, and $B^*_s B^*$ in $I=\frac{1}{2}$, all of them with $J^P=1^+$. For these cases the widths are evaluated identifyng the dominant source of imaginary part. We find binding energies of the order of $10-20$ MeV, and the widths vary much from one system to the other: of the order of 10-100 eV for the $B^* B$ system and $B^*_s B-B^*B_s$, about $6$ MeV for the $B^* B^*$ system and of the order of $0.5$ MeV for the $B^*_s B^*$ system.

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arXiv2021

The $D_s^+ \to π^+ K_s^0 K_s^0 $ reaction \\and the $I=1$ partner of the $f_0(1710)$ state

We have identified the decay modes of the $D_s^+ \to π^+ K^+ K^- , π^+ K_s^0 K_s^0$ reactions producing two vector mesons and one pseudoscalar. The posterior vector-vector interaction generates two resonances that we associate to the $f_0(1710)$ and the $a_0(1710)$ recently claimed. We find two acceptable scenarios that give results for the ratio of the branching ratios of these two reactions in agreement with experiment. With these two scenarios we make predictions for the branching ratios of the $D_s^+ \to π^0 K^+ K_s^0$ reaction, finding values within the range of $(2.0 \pm 0.7)\times 10^{-3}$. Comparison of these predictions with coming experimental results on that latter reaction will be very most useful to deepen our understanding on the nature of these two resonances.

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arXiv2021

The $D_s^+ \to a_0(980) e^+ ν_e$ reaction and the $a_0(980)-f_0(980)$ mixing

We perform a study of the $D_s^+ \to a_0(980)(f_0(980)) e^+ ν_e$ reactions investigating the different sources of isospin violation which make the production of the $a_0(980)$ possible. We find that loops involving kaons in the production mechanism provide a source of isospin violation since they do not cancel due to the different mass of charged and neutral kaons, but we also find that the main source comes from the breaking of isospin in the meson-meson transition $T$ matrices, which contain information on the nature of the low lying scalar mesons. The reaction is thus very sensitive to the nature of the $a_0(980)$ and $f_0(980)$ resonances. Our results are consistent with the present upper bound for $a_0(980)$ production and only a factor three smaller, indicating that future runs with more statistics should find actual numbers for this reaction from where we can learn more about the origin of the scalar resonances and their nature.

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arXiv2021

Prediction of new $T_{cc}$ states of $D^{} D^{}$ and $D^{}_s D^{}$ molecular nature

We extend the theoretical framework used of describe the $T_{cc}$ state as a molecular state of $D^* D$ and make predictions for the $D^*D^*$ and $D^*_s D^*$ systems, finding that they lead to bound states only in the $J^P=1^+$ channel. Using input needed to describe the $T_{cc}$ state, basically one parameter to regularize the loops of the Bethe-Salpeter equation, we find bound states with bindings of the order of the MeV and similar widths for $D^*D^*$ system, while the $D^{*}_s D^{*}$ system develops a strong cusp around threshold.

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arXiv2021

$D^0 D^0 π^+$ mass distribution in the production of the $T_{cc}$ exotic state

We perform a unitary coupled channel study of the interaction of the $D^{*+} D^0, D^{*0} D^+$ channels and find a state barely bound, very close to isospin $I=0$. We take the experimental mass as input and obtain the width of the state and the $D^0 D^0 π^+$ mass distribution. When the mass of the $T_{cc}$ state quoted in the experimental paper from raw data is used, the width obtained is of the order of the $80 \;{\rm keV}$, small compared to the value given in that work. Yet, when the mass obtained in an analysis of the data considering the experimental resolution is taken, the width obtained is about $43 \;{\rm keV}$ and both the width and the $D^0 D^0 π^+$ mass distribution are in remarkable agreement with the results obtained in that latter analysis.

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arXiv2021

Unveiling the $K_1(1270)$ double-pole structure in the $\bar{B}\to J/ψρ\bar{K}$ and $\bar{B}\to J/ψ\bar{K}^*π$ decays

By looking at the pseudoscalar-vector meson spectra in the $\bar{B}\to J/ψρ\bar{K}$ and $\bar{B}\to J/ψ\bar{K}^*π$ weak decays, we theoretically investigate the double-pole structure of the $K_1(1270)$ resonance by using the Chiral Unitary approach to account for the final state interactions between the pseudoscalar and vector mesons. The $K_1(1270)$ resonance appears as dynamically generated through these interactions in coupled channels and influence the shape of the invariant mass distributions under consideration. We show how those shapes are affected by the $K_1(1270)$ double-pole structure to confront the results from our model with future experiments that might investigate the $PV$ spectra in these decays.

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arXiv2021

The $πf_0(500)$ decay of the $a_1(1260)$

We evaluate the $a_1(1260) \to πσ(f_0(500))$ decay width from the perspective that the $a_1(1260)$ resonance is dynamically generated from the pseudoscalar-vector interaction and the $σ$ arises from the pseudoscalar-pseudoscalar interaction. A triangle mechanism with $a_1(1260) \to ρπ$ followed by $ρ\to ππ$ and a fusion of two pions within the loop to produce the $σ$ provides the mechanism for this decay under these assumptions for the nature of the two resonances. We obtain widths of the order of $13-22$ MeV. Present experimental results differ substantially from each other, suggesting that extra efforts should be devoted to the precise extraction of this important partial decay width, which should provide valuable information on the nature of the axial vector and scalar meson resonances and help clarify the role of the $πσ$ channel in recent lattice QCD calculations of the $a_1$.

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arXiv2021

Inconsistency of the data on the $K_1(1270) \to πK^*_0(1430)$ decay width

We show, using the same Lagrangian for the $K_1(1270) \to πK^*_0(1430)$ and $K^*_0(1430) \to K_1(1270) π$ decays, that the present PDG data on the partial decay width of $K_1(1270) \to πK^*_0(1430)$ implies a width for $K^*_0(1430) \to K_1(1270) π$ decay which is about ten times larger than the total $K^*_0(1430)$ width. A discussion on this inconsistency is done, stressing its relationship to the existence of two $K_1(1270)$ states obtained with the chiral unitary theory, which are not considered in the experimental analyses of $Kππ$ data.

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arXiv2020

Scalar resonances in the $D^+\to K^-K^+K^+$ decay

We study theoretically the resonant structure of the double Cabibbo suppressed $D^+\to K^- K^+K^+$ decay. We start from an elementary production diagram, considered subleading in previous approaches, which cannot produce a final $K^- K^+$ pair at the tree level but which we show to be able to provide the strength of the decay through final meson-meson state interaction. The different meson-meson elementary productions are related through SU(3) and the final rescattering is implemented from a suitable implementation of unitary extensions of ChPT which generate dynamically the scalar resonances $f_0(980)$ and $a_0(980)$. We obtain a good agreement with recent experimental data from the LHCb collaboration with a minimal freedom in the fit and show the dominance of the $a_0(980)$ contribution close to the threshold of the $K^- K^+$ spectrum.

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