arXiv subjects

E. Oset

Publications and source records attributed to E. Oset.

At least 109 records · Page 6Linked to original sources

arXiv2018

Triangle singularity enhancing isospin violation in $\bar B_s^0 \to J/ψπ^0 f_0(980)$

We perform calculations for the $\bar B_s^0 \to J/ψπ^0 f_0(980)$ and $\bar B_s^0 \to J/ψπ^0 a_0(980)$ reactions, showing that the first one is isospin-suppressed while the second one is isospin-allowed. The reaction proceeds via a triangle mechanism, with $\bar B_s^0 \to J/ψK^* \bar K +c.c.$, followed by the decay $K^* \to Kπ$ and a further fusion of $K\bar K$ into the $f_0(980)$ or $a_0(980)$. We show that the mechanism develops a singularity around the $π^0 f_0(980)$ or $π^0 a_0(980)$ invariant mass of 1420 MeV where the $π^0 f_0$ and $π^0 a_0$ decay modes are magnified and also the ratio of $π^0 f_0$ to $π^0 a_0$ production. Using experimental information for the $\bar B_s^0 \to J/ψK^* \bar K +c.c.$ 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 contrasted with actual experiments should be very valuable to obtain information on the nature of the low lying scalar mesons.

hep-ph↗

arXiv2018

Production of $N^(1535)$ and $N^(1650)$ in $Λ_c\rightarrow\bar{K}^0ηp$ $(πN)$ decay

In order to study the properties of the $N^*$(1535) and $N^*$(1650) we calculate the mass distributions of $M B$ in the $Λ_c \rightarrow \bar{K}^0 M B$ decay, with $MB=πN(I=1/2),ηp$ and $KΣ(I=1/2)$. We do this by calculating the tree-level and loop contributions, mixing pseudoscalar-baryon and vector-baryon channels using the local hidden gauge formalism. The loop contributions for each channel are calculated using the chiral unitary approach. We observe that for the $ηN$ mass distribution only the $N^*$(1535) is seen, with the $N^*$(1650) contributing to the width of the curve, but for the $πN$ mass distribution both resonances are clearly visible. In the case of $MB=KΣ$, we found that the strength of the $KΣ$ mass distribution is smaller than that of the mass distributions of the $πN$ and $ηp$ in the $Λ_c^+\rightarrow\bar{K}^0πN$ and $Λ_c^+\rightarrow\bar{K}^0ηp$ processes, in spite of this channel having a large coupling to the $N^*(1650)$. This is because the $KΣ$ pair production is suppressed in the primary production from the $Λ_c$ decay.

nucl-th↗

arXiv2018

Triangle singularities in $B^-\rightarrow K^-π^-D_{s0}^+$ and $B^-\rightarrow K^-π^-D_{s1}^+$

We study the appearance of structures in the decay of the $B^-$ into $K^- π^- D_{s0}^+(2317)$ and $K^- π^- D_{s1}^+(2460)$ final states by forming invariant mass distributions of $π^- D_{s0}^+$ and $π^- D_{s1}^+$ pairs, respectively. The structure in the distribution is associated to the kinematical triangle singularity that appears when the $B^- \to K^- K^{*\,0} D^0$ ($B^- \to K^- K^{*\,0} D^{*\,0}$) decay process is followed by the decay of the $K^{*\,0}$ into $π^- K^+$ and the subsequent rescattering of the $K^+ D^0$ ($K^+ D^{*\,0}$) pair forming the $D_{s0}^+(2317)$ ($D_{s1}^+(2460)$) resonance. We find this type of non-resonant peaks at 2850 MeV in the invariant mass of $π^- D_{s0}$ pairs from $B^- \to K^- π^- D_{s0}^+(2317)$ decays and around 3000 MeV in the invariant mass of $π^- D_{s1}^+$ pairs from $B^- \to K^- π^- D_{s1}^+(2460)$ decays. By employing the measured branching ratios of the $B^- \to K^- K^{*\,0} D^0$ and $B^- \to K^- K^{*\,0} D^{*\,0}$ decays, we predict the branching ratios for the processes $B^-$ into $K^- π^-D_{s0}^+(2317)$ and $K^- π^- D_{s1}^+(2460)$, in the vicinity of the triangle singularity peak, to be about $8\times10^{-6}$ and $1\times 10^{-6}$, respectively. The observation of this reaction would also give extra support to the molecular picture of the $D_{s0}^+(2317)$ and $D_{s1}^+(2460)$.

hep-ph↗

arXiv2018

Disclosing $D^\bar{D}^$ molecular states in the $B_c^- \to π^- J/ψω$ decay

We study the $B_c^- \to π^- J/ψω$ and $B_c^- \to π^- D^* \bar{D}^*$ reactions and show that they are related by the presence of two resonances, the $X(3940)$ and $X(3930)$, that are of molecular nature and couple most strongly to $D^* \bar{D}^*$, but also to $J/ψω$. Because of that, in the $J/ψω$ mass distribution we find a cusp with large strength at the $D^* \bar{D}^*$ threshold and predict the ratio of strengths between the peak of the cusp and the maximum of the $D^* \bar{D}^*$ distribution close to $D^* \bar{D}^*$ threshold, which are distinct features of the molecular nature of these two resonances.

hep-ph↗

arXiv2018

Molecular $Ω_c$ states generated from coupled meson-baryon channels

We have investigated $Ω_c$ 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 $J^{P}={3/2}^{-}$, three of them in remarkable agreement with three experimental states in mass and width. We also make predictions at higher energies for states of vector-baryon nature.

hep-ph↗

arXiv2018

Production and mixing of scalar mesons in $η_c$ and $χ_{c1}$ decays

We briefly discuss how the chiral unitary approach in coupled channels and $SU(3)$ symmetry can be used to describe the production of $f_0(500)$, $f_0(980)$ and $a_0(980)$ in the $χ_{c1} \to ηπ^+ π^-$ reaction, recently measured by the BESIII collaboration. In this reaction a very strong peak for the $a_0(980)$ can be seen in the $ηπ$ invariant mass, while clear signals for the $f_0(500)$ and $f_0(980)$ appear in the one of $π^+π^-$. Next, we show the predictions made with the same model for the analogous decay $η_c \to ηπ^+ π^-$, which could also be measured experimentally. We discuss the differences of these two reactions which are interesting to test the picture where these scalar mesons are dynamically generated from the interaction of pairs of pseudoscalars. Furthermore, we comment on a new recent work where the same model was used to study the $a_0(980) - f_0(980)$ mixing in the $χ_{c1} \to π^0 π^0 η$ and $χ_{c1} \to π^0 π^+ π^-$ reactions, showing that quantitative agreement with the experimental measurement of this mixing, also performed by BESIII, can be obtained, revealing interesting aspects of the dynamics of this process and the importance of coupled channels.

hep-ph↗

arXiv2018

Study of the $DK K$ and $DK \bar{K}$ systems

Using the Fixed Center Approximation to Faddeev equations we have investigated the $DKK$ and $DK\bar{K}$ three-body systems, considering that the $D^*_{s0}(2317)$ acts as the heavy cluster in both cases, generated from the $DK$ interaction in isospin 0. For the $DK\bar{K}$ system we have found evidence of a state with $I(J^P)=1/2(0^-)$ and mass about $2833 - 2858$ MeV, above the threshold of $D^*_{s0}(2317)\bar{K}$. Our results indicate that this state is dominated by a $Df_0(980)$ component, then it could be searched for in the $ππD$ invariant mass. On the other hand, no clear evidence related to a state from the $DKK$ interaction is found.

hep-ph↗

arXiv2018

The bottomed strange molecules with isospin 0

Using the local hidden gauge approach, we study the possibility of the existence of bottomed strange molecular states with isospin 0. We find three bound states with spin-parity $0^+$, $1^+$ and $2^+$ generated by the $\bar{K}^*B^*$ and $ωB_s^*$ interaction, among which the state with spin 2 can be identified as $B_{s2}^*(5840)$. In addition, we also study the $\bar{K}^*B$ and $ωB_s$ interaction and find a bound state which can be associated to $B_{s1}(5830)$. Besides, the $\bar{K}B^*$ and $ηB_s^*$ and $\bar{K}B$ and $ηB_s$ systems are studied, and two bound states are predicted. We expect that further experiments can confirm our predictions.

hep-ph↗

arXiv2017

An analysis of the Lattice QCD spectra for $D^_{s0}(2317)$ and $D^_{s1}(2460)$

In this talk I present the results obtained using effective field theories in a finite volume from a reanalysis of lattice data on the $KD^{(*)}$ systems, where bound states of $KD$ and $KD^*$ are found and associated with the states $D^*_{s0}(2317)$ and $D^*_{s1}(2460)$, respectively. We confirm the presence of such states on the lattice data and determine the weight of the $KD$ channel in the wave function of $D^*_{s0}(2317)$ and that of $KD^*$ in the wave function of $D^*_{s1}(2460)$. Our results indicate a large meson-meson component in both cases.

hep-lat↗

arXiv2017

Calculation of the ratios and absolute rates of the $Ξ_b^- \to π^- (D_s^- ) \ Ξ_c^0 (2790) \left(Ξ_c^0 (2815) \right)$ and $Ξ_b^- \to \barν_l l \ Ξ_c^0 (2790) \left(Ξ_c^0 (2815) \right)$ decays

In this work we calculate the ratios of rates of the $Ξ_b$ nonleptonic and semileptonic decays into the $Ξ_c$(2790) and $Ξ_c$(2815) ($Ξ_c^*$) resonances. These resonances are dynamically generated from the pseudoscalar-baryon and vector-baryon interactions, whose mixing is done using the chiral Weinberg-Tomozawa (WT) meson-baryon interaction extended to four flavors. The first part of the decay is a weak decay that we analyze through their quark constituents where it is noted that only the heavy quarks ($b$ and $c$) participate in the interaction, leaving the light pair ($ds$) as spectators. This first decay then produces a meson-baryon pair that creates the $Ξ_c^*$ through the WT interaction. We then proceed to calculate the decay rates to $Ξ_c$(2790) and $Ξ_c$(2815) for both the nonleptonic and semileptonic cases and then calculate the ratios between them. We do this calculation nonrelativistically and fully relativistically and notice that, even though both approaches yield somewhat different results in the rates, the ratios are very similar (difference on the order of 1\%) in both cases. The absolute values of the decay rates are also successfully calculated by obtaining the rates between our decays and $Λ_b \to π(D_s ) \ Λ_c (2595) \left(Λ_c (2625) \right)$ and $Λ_b \to \barν_l l \ Λ_c (2595) \left(Λ_c (2625) \right)$ for which there are experimental results, since the momentum transfer is similar such we can cancel out the influence of the quark wave functions in the ratios.

hep-ph↗

arXiv2017

The radiative decay $D^0 \to \bar{K}^{*0} γ$ with vector meson dominance

Motivated by the experimental measurements of $D^0$ radiative decay modes we have proposed a model to study the $D^0\to \bar{K}^{*0}γ$ decay, by establishing a link with $D^0\to \bar{K}^{*0}V$ $(V=ρ^0,\, ω)$ decays through the vector meson dominance hypothesis. In order to do this properly, we have used the Lagrangians from the local hidden gauge symmetry approach to account for $Vγ$ conversion. As a result, we have found the branching ratio $\mathcal{B}[D^0\to \bar{K}^{*0}γ] =(1.55 - 3.44)\times 10^{-4}$, which is in fair agreement with the experimental values reported by Belle and Babar collaborations.

hep-ph↗

arXiv2017

The role of the triangle singularity in $Λ(1405)$ production in the $π^-p\rightarrow K^0πΣ$ and $pp\rightarrow pK^+πΣ$ processes

We have investigated the cross section for the $π^-p\rightarrow K^0πΣ$ and $pp\rightarrow pK^+πΣ$ reactions paying attention to a mechanism that develops a triangle singularity. The triangle diagram is realized by the decay of a $N^*$ to $K^*Σ$ and the $K^*$ decay into $πK$, and the $πΣ$ finally merges into $Λ(1405)$. The mechanism is expected to produce a peak around $2140$ MeV in the $KΛ(1405)$ invariant mass. We found that a clear peak appears around $2100$ MeV in the $KΛ(1405)$ invariant mass which is about $40$ MeV lower than the expectation, and that is due to the resonance peak of a $N^*$ resonance which plays a crucial role in the $K^*Σ$ production. The mechanism studied produces the peak of the $Λ(1405)$ around or below 1400 MeV, as is seen in the $pp\rightarrow pK^+πΣ$ HADES experiment.

hep-ph↗

arXiv2017

On the binding of the $BD\bar{D}$ and $BDD$ systems

We study theoretically the $BD\bar{D}$ and $BDD$ systems to see if they allow for possible bound or resonant states. The three-body interaction is evaluated implementing the Fixed Center Approximation to the Faddeev equations which considers the interaction of a $D$ or $\bar{D}$ particle with the components of a $BD$ cluster, previously proved to form a bound state. We find an $I(J^P)=1/2(0^-)$ bound state for the $BD\bar{D}$ system at an energy around $8925-8985$ MeV within uncertainties, which would correspond to a bottom--hidden-charm meson. In contrast, the $BDD$ system, which would be bottom--double-charm and hence manifestly exotic, we have found hints of a bound state in the energy region $8935-8985$ MeV, but the results are not stable under the uncertainties of the model, and we cannot assure, neither rule out, the possibility of a $BDD$ three-body state.

hep-ph↗

arXiv2017

Production of $f_0(500)$, $f_0(980)$ and $a_0(980)$ in the $χ_{c1} \to ηπ^+ π^-$ and $η_c \to ηπ^+ π^-$ decays

Using the chiral unitary approach in coupled channels and $SU(3)$ symmetry we describe the production of $f_0(500)$, $f_0(980)$ and $a_0(980)$ in the $χ_{c1} \to ηπ^+ π^-$ reaction, recently performed by the BESIII collaboration. A very strong peak for the $a_0(980)$ can be seen in the $ηπ$ invariant mass, while clear signals for the $f_0(500)$ and $f_0(980)$ appear in the one of $π^+π^-$. Next, we make predictions for the analogous decay $η_c \to ηπ^+ π^-$, which could also be measured experimentally. We discuss the differences of these reactions which are interesting to test the picture where these scalar mesons are dynamically generated from the interaction of pairs of pseudoscalars.

hep-ph↗

arXiv2017

Charm-beauty meson bound states from $B(B^)D(D^)$ and $B(B^)\bar D(\bar D^)$ interaction

We evaluate the s-wave interaction of pseudoscalar and vector mesons with both charm and beauty to investigate the possible existence of molecular $BD$, $B^*D$, $BD^*$, $B^*D^*$, $B\bar D$, $B^*\bar D$, $B\bar D^*$ or $B^* \bar D^*$ meson states. The scattering amplitude is obtained implementing unitarity starting from a tree level potential accounting for the dominant vector meson exchange. The diagrams are evaluated using suitable extensions to the heavy flavor sector of the hidden gauge symmetry Lagrangians involving vector and pseudoscalar mesons{, respecting heavy quark spin symmetry}. We obtain bound states at energies above 7 GeV for $BD$ ($J^P=0^+$), $B^*D$ ($1^+$), $BD^*$ ($1^+$) and $B^*D^*$ ($0^+$, $1^+$, $2^+$), all in isospin 0. For $B\bar D$ ($0^+$), $B^*\bar D$ ($1^+$), $B\bar D^*$ ($1^+$) and $B^*\bar D^*$ ($0^+$, $1^+$, $2^+$) we also find similar bound states in $I=0$, but much less bound, which would correspond to exotic meson states with $\bar b$ and $\bar c$ quarks, and for the $I=1$ we find a repulsive interaction. We also evaluate the scattering lengths in all cases, which can be tested in current investigations of lattice QCD.

hep-ph↗

arXiv2017

Abnormal isospin violation and $a_0 -f_0$ mixing in the $D_s^+ \to π^+ π^0 a_0(980) (f_0(980))$ reactions

We have chosen the reactions $D_s^+ \to π^+ π^0 a_0(980) (f_0(980))$ investigating the isospin violating channel $D_s^+ \to π^+ π^0 f_0(980)$. The reaction was chosen because by varying the $π^0 a_0(980) (f_0(980))$ invariant mass one goes through the peak of a triangle singularity emerging from $D_s^+ \to π^+\bar K^* K$, followed by $\bar K^* \to \bar K π^0$ and the further merging of $K \bar K$ to produce the $a_0(980)$ or $f_0(980)$. We found that the amount of isospin violation had its peak precisely at the value of the $π^0 a_0(980) (f_0(980))$ invariant mass where the singularity has its maximum, stressing the role of the triangle singularities as a factor to enhance the mixing of the $f_0(980)$ and $a_0(980)$ resonances. We calculate absolute rates for the reactions and show that they are within present measurable range. 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 energy scalar mesons.

hep-ph↗

arXiv2017

Triangle singularities in $B^-\rightarrow D^{0}π^-π^0η$ and $B^-\rightarrow D^{0}π^-π^+π^-$

The possible role of the triangle mechanism in the $B^-$ decay into $D^{*0}π^-π^0η$ and $D^{*0}π^-π^+π^-$ is investigated. In this process, the triangle singularity appears from the decay of $B^-$ into $D^{*0}K^-K^{*0}$ followed by the decay of $K^{*0}$ into $π^-K^+$ and the fusion of the $K^+K^-$ which forms the $a_0(980)$ or $f_0(980)$ which finally decay into $π^0η$ or $π^+π^-$ respectively. The triangle mechanism from the $\bar{K}^*K\bar{K}$ loop generates a peak around 1420 MeV in the invariant mass of $π^-a_0$ or $π^-f_0$, and gives sizable branching fractions $Br(B^-\rightarrow D^{*0}π^- a_0;a_0 \rightarrow π^0η)= 1.66 \times 10^{-6}$ and $Br(B^-\rightarrow D^{*0}π^- f_0 ; f_0 \rightarrow π^+π^-)= 2.82 \times 10^{-6}$.

hep-ph↗

arXiv2017

Study of the $DKK$ and $DK\bar{K}$ systems

Using the Fixed Center Approximation to Faddeev equations we have investigated the $DKK$ and $DK\bar{K}$ three-body systems, considering that the $DK$ dynamically generates, through its $I=0$ component, the $D^*_{s0}(2317)$ molecule. According to our findings, for $DK\bar{K}$ interaction we have found an evidence of a state $I(J^P)=1/2(0^-)$ just above the $D^*_{s0}(2317)\bar{K}$ threshold and around the $Df_0(980)$ thresholds, with mass about $2833 - 2858$ MeV, made mostly of $Df_0(980)$. On the other hand, no evidence related to a state from the $DKK$ interaction is found. The state found could be seen in the $ππD$ invariant mass.

hep-ph↗