arXiv subjects

E. Oset

Publications and source records attributed to E. Oset.

At least 127 records · Page 7Linked to original sources

arXiv2017

Predictions for $Ξ_b^- \rightarrow π^- \left(D_s^- \right) \ Ξ_c^0 (2790) \left(Ξ_c^0 (2815) \right)$ and $Ξ_b^- \rightarrow \barν_l l \ Ξ_c^0 (2790) \left(Ξ_c^0 (2815) \right)$

We have performed the calculations for the nonleptonic $Ξ_b^- \rightarrow π^- \ Ξ_c^0 (2790) \left(J=\frac{1}{2}\right)$ and $Ξ_b^- \rightarrow π^- \ Ξ_c^0 (2815) \left(J=\frac{3}{2}\right)$ and the same reactions replacing the $π^-$ by a $D_s^-$. At the same time we evaluate the semileptonic rates for $Ξ_b^- \rightarrow \barν_l l \ Ξ_c^0 (2790)$ and $Ξ_b^- \rightarrow \barν_l l \ Ξ_c^0 (2815)$. We look at the reactions from the perspective that the $Ξ_c^0 (2790)$ and $Ξ_c^0 (2815)$ resonances are dynamically generated from the pseudoscalar-baryon and vector-baryon interactions. We evaluate ratios of the rates of these reactions and make predictions that can be tested in future experiments. We also find that the results are rather sensitive to the coupling of the $Ξ_c^*$ resonances to the $D^* Σ$ and $D^* Λ$ components.

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arXiv2017

Role of a triangle singularity in the $πN(1535)$ contribution to $γp \to p π^0 η$

We have studied the $γp \to p π^0 η$ reaction paying attention to the two main mechanisms at low energies, the $γp \to Δ(1700) \to ηΔ(1232)$ and the $γp \to Δ(1700) \to πN(1535)$. Both of them are driven by the photoexcitation of the $Δ(1700)$ and the second one involves a mechanism that leads to a triangle singularity. We are able to evaluate quantitatively the cross section for this process and show that it agrees with the experimental determination. Yet, there are some differences with the standard partial wave analysis which does not include explicitly the triangle singularity. The exercise also shows the convenience to explore possible triangle singularities in other reactions and how a standard partial analysis can be extended to accommodate them.

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arXiv2017

Role of a triangle singularity in the $πΔ$ decay of the $N(1700)(3/2^-)$

We show the important role played by the $πΔ(1232)$ channel in the build up of the $N(1700)(3/2^-)$ resonance due to the non-trivial enhancement produced by a singularity of a triangular loop. The $N(1700)$ is one of the dynamically generated resonances produced by the coupled channel vector-baryon interaction. The $πΔ$ channel was neglected in previous works but we show that it has to be incorporated into the coupled channel formalism due to an enhancement produced by a singularity in the triangular loop with $ρ$, nucleon and $π$ as internal loop lines and $π$ and $Δ$ as external ones. The enhancement is of non-resonant origin but it contributes to the dynamical generation of the $N(1700)$ resonance due to the non-linear dynamics involved in the coupled channel mechanisms. We obtain an important increase of the total width of the $N(1700)$ resonance when the $πΔ$ channel is included and provide predictions for the partial widths of the $N(1700)$ decays into $VB$ and $πΔ$.

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arXiv2016

Predictions for $η_c \to ηπ^+ π^-$ producing $f_0(500)$, $f_0(980)$ and $a_0(980)$

We perform calculations for the $η_c \to ηπ^+ π^-$ 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 $ηπ^+ π^-$, 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 $χ_{c1} \to ηπ^+ π^-$, 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 the low mass scalar mesons.

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arXiv2016

Revising the $f_1(1420)$ resonance

We have studied the production and decay of the $f_1(1285)$ into $πa_0(980)$ and $K^* \bar K$ as a function of the mass of the resonance and find a shoulder around 1400 MeV, tied to a triangle singularity, for the $πa_0(980)$ mode, and a peak around 1420 MeV with about 60 MeV width for the $K^* \bar K$ mode. Both these features agree with the experimental information on which the $f_1(1420)$ resonance is based. In addition, we find that if the $f_1(1420)$ is a genuine resonance, coupling mostly to $K^* \bar K$ as seen experimentally, one finds unavoidably about a 20\% fraction for $πa_0(980)$ decay of this resonance, in drastic contradiction with all experiments. Altogether, we conclude that the $f_1(1420)$ is not a genuine resonance, but the manifestation of the $πa_0(980)$ and $K^* \bar K$ decay modes of the $f_1(1285)$ at higher energies than the nominal one.

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arXiv2016

$f_0(980)$ production in $D_s^+ \rightarrow π^+ \, π^+ \, π^-$ and $D_s^+ \rightarrow π^+ \, K^+ \, K^-$ decays

We study the $D_s^+ \rightarrow π^+ \, π^+ \, π^-$ and $D_s^+ \rightarrow π^+ \, K^+ \, K^-$ decays adopting a mechanism in which the $D_s^+$ meson decays weakly into a $π^+$ and a $q\bar{q}$ component, which hadronizes into two pseudoscalar mesons. The final state interaction between these two pseudoscalar mesons is taken into account by using the Chiral Unitary approach in coupled channels, which gives rise to the $f_0(980)$ resonance. Hence, we obtain the invariant mass distributions of the pairs $π^+ π^-$ and $K^+ K^-$ after the decay of that resonance and compare our theoretical amplitudes with those available from the experimental data. Our results are in a fair agreement with these data, and a $f_0(980)$ signal is seen in both the $π^+π^-$ and $K^+K^-$ distributions.

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arXiv2016

$f_0(500)$, $f_0(980)$ and $a_0(980)$ production in the $χ_{c1} \to ηπ^+π^-$ reaction

We study the $χ_{c1} \to ηπ^+ π^-$ decay, paying attention to the production of $f_0(500)$, $f_0(980)$ and $a_0(980)$ from the final state interaction of pairs of mesons that can lead to these three mesons in the final state, which is implemented using the chiral unitary approach. Very clean and strong signals are obtained for the $a_0(980)$ excitation in the $ηπ$ invariant mass distribution and for the $f_0(500)$ in the $π^+ π^-$ mass distribution. A smaller, but also clear signal for the $f_0(980)$ excitation is obtained. The results are contrasted with experimental data and the agreement found is good, providing yet one more test in support of the picture where these resonances are dynamically generated from the meson-meson interaction.

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arXiv2016

On the hidden charm pentaquark-s in $Λ_b \to J/ψK^- p$ decay

In a previous work we presented a theoretical analysis of the $Λ_b \to J/ψK^- p$ reaction from where a recent experiment by the LHCb collaboration at CERN claimed the existence of two hidden charm pentaquarks, $P_c(4380)^+$ and $P_c(4450)^+$. In that work we focused only on the $Λ(1405)$ and $P_c(4450)^+$ signals and discussed the possible explanation of this pentaquark state within the picture of a dynamical meson-baryon molecule made up mostly from $\bar D^* Σ_c$ and $\bar D^* Σ^*_c$ components. In the present work we improve upon the previous one by considering the total $K^- p$ and $J/ψp$ data including all the relevant resonances contributing to the spectra, and discuss the possible nature of both $P_c(4380)^+$ and $P_c(4450)^+$. We also discuss several important topics, like the effect of the contact term in the reaction, the viability of reproducing the data without the $P_c(4380)^+$ and the possible quantum numbers assignment to these pentaquarks.

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arXiv2016

The "$a_1(1420)$" peak as the $πf_0(980)$ decay mode of the $a_1(1260)$

We study the decay mode of the $a_1(1260)$ into a $π^+$ in p-wave and the $f_0(980)$ that decays into $π^+ π^-$ in s-wave. The mechanisms proceeds via a triangular mechanism where the $a_1(1260)$ decays into $K^* \bar K$, the $K^*$ decays to an external $π^+$ and an internal $K$ that fuses with the $\bar K$ to produce the $f_0(980)$ resonance. The mechanism develops a singularity at a mass of the $a_1(1260)$ around 1420 MeV, producing a peak in the cross section of the $πp$ reaction, used to generate the mesonic final state, which provides a natural explanation of all the features observed in the COMPASS experiment, where a peak observed at this energy is tentatively associated to a new resonance called $a_1(1420)$. On the other hand, the triangular singularity studied here gives rise to a remarkable feature, where a peak is seen for a certain decay channel of a resonance at an energy about 200 MeV higher than its nominal mass.

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arXiv2016

A hidden-charm $S=-1$ pentaquark from the decay of $Λ_b$ into $J/ψηΛ$

The hidden charm pentaquark state $P_c(4450)$ observed recently by the LHCb collaboration may be of molecular nature, as advocated by some unitary approaches that also predict pentaquark partners in the strangeness $S=-1$ sector. In this work we argue that a hidden-charm strange pentaquark could be seen from the decay of the $Λ_b$, just as in the case of the non-strange $P_c(4450)$, but looking into the $J/ψηΛ$ decay mode and forming the invariant mass spectrum of $J/ψΛ$ pairs. In the model presented here, which assumes a standard weak decay topology and incorporates the hadronization process and final state interaction effects, we find the $J/ψηΛ$ final states to be populated with similar strength as the $J/ψK^- p$ states employed for the observation of the non-strange pentaquark. This makes the $Λ_ b \to J/ψηΛ$ decay to be an interesting process to observe a possible strange partner of the $P_c(4450)$ . We study the dependence of the $J/ψΛ$ mass spectra on various model ingredients and on the unknown properties of the strange pentaquark.

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arXiv2016

$D_{s0}^{*}(2317)^+$ in the decay of $B_c$ into $J/ψDK$

In this paper we study the relationship between the $D_{s0}^{*}(2317)^+$ resonance and the decay of the $B_c$ meson into $J/ψDK$. In this process, the $B_c$ meson decays first into $J/ψ$ and the quark pair $c\bar{s}$, and then the quark pair hadronizes into $DK$ or $D_sη$ components, which undergo final state interaction. This final state interaction, generating the $D_{s0}^{*}(2317)^+$ resonance, is described by the chiral unitary approach. With the parameters which allow us to match the pole position of the $D_{s0}^{*}(2317)^+$, we obtain the $DK$ invariant mass distribution of the decay $B_c\to J/ψDK$, and also the rate for $B_c\to J/ψD_{s0}^{*}(2317)$. The ratio of these two magnitude is then predicted.

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arXiv2016

Determination of the compositeness of resonances from decays: the case of the $B^0_s\to J/ψf_1(1285)$

We develop a method to measure the amount of compositeness of a resonance, mostly made as a bound state of two hadrons, by simultaneously measuring the rate of production of the resonance and the mass distribution of the two hadrons close to threshold. By using different methods of analysis we conclude that the method allows one to extract the value of 1-Z with about $0.1$ of uncertainty. The method is applied to the case of the $\bar B^0_s \to J/ψf_1(1285)$ decay, by looking at the resonance production and the mass distribution of $K \bar K^*$.

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arXiv2016

Workshop on Physics with Neutral Kaon Beam at JLab (KL2016) Mini-Proceedings

The KL2016 Workshop is following the Letter of Intent LoI12-15-001 "Physics Opportunities with Secondary KL beam at JLab" submitted to PAC43 with the main focus on the physics of excited hyperons produced by the Kaon beam on unpolarized and polarized targets with GlueX setup in Hall D. Such studies will broaden a physics program of hadron spectroscopy extending it to the strange sector. The Workshop was organized to get a feedback from the community to strengthen physics motivation of the LoI and prepare a full proposal. Further details about the Workshop can be found on the web page of the conference: http://www.jlab.org/conferences/kl2016/index.html .

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arXiv2016

$\bar B^0$, $B^-$ and $\bar B^0_s$ decays into $J/ψ$ and $K \bar K$ or $πη$

We study the $\bar B^0_s \to J/ψK^+ K^-$, $\bar B^0 \to J/ψK^+ K^-$, $B^- \to J/ψK^0 K^-$, $\bar B^0 \to J/ψπ^0 η$ and $B^- \to J/ψπ^- η$ decays and compare their mass distributions with those obtained for the $\bar B^0_s \to J/ψπ^+ π^-$ and $\bar B^0 \to J/ψπ^+ π^-$. 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 parameters. Comparison is made with the limited experimental information available. Further comparison of these results with coming LHCb measurements will be very valuable to make progress in our understanding of the meson-meson interaction and the nature of the low lying scalar meson resonances, $f_0(500), f_0(980)$ and $a_0(980)$.

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arXiv2016

Role of the $f_1(1285)$ state in the $J/ψ\to ϕ\bar{K} K^*$ and $J/ψ\to ϕf_1(1285)$ decays

We study the role of the $f_1(1285)$ resonance in the decays of $J/ψ\to ϕ\bar{K} K^*$ and $J/ψ\to ϕf_1(1285)$. The theoretical approach is based on the results of chiral unitary theory where the $f_1(1285)$ resonance is dynamically generated from the $K^* \bar{K} - c.c.$ interaction. In order to further test the dynamical nature of the $f_1(1285)$ state, we investigate the $J/ψ\to ϕ\bar{K} K^*$ decay close to the $\bar{K} K^*$ threshold and make predictions for the ratio of the invariant mass distributions of the $J/ψ\to ϕ\bar{K} K^*$ decay and the $J/ψ\to ϕf_1(1285)$ partial decay width with all the parameters of the mechanism fixed in previous studies. The results can be tested in future experiments and therefore offer new clues on the nature of the $f_1(1285)$ state.

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arXiv2015

$B^0 \to D^0 \bar D^0 K^0$, $B^+ \to D^0 \bar D^0 K^+$ and the scalar $D \bar D$ bound state

We study the $B^0$ decay to $D^0 \bar D^0 K^0$ based on the chiral unitary model that generates the X(3720) resonance, and make predictions for the $D^0 \bar D^0$ invariant mass distribution. From the shape of the distribution, the existence of the resonance below threshold could be induced. We also predict the rate of production of the X(3720) resonance to the $D^0 \bar D^0$ mass distribution with no free parameters.

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arXiv2015

The $K \bar K π$ decay of the $f_1(1285)$ and its nature as a $K^* \bar K -cc$ molecule

We investigate the decay of $f_1(1285) \to πK \bar K$ with the assumption that the $f_1(1285)$ is dynamically generated from the $K^* \bar{K} - cc$ interaction. In addition to the tree level diagrams that proceed via $f_1(1285) \to K^* \bar{K} - cc \to πK \bar K$, we take into account also the final state interactions of $K \bar K \to K \bar K$ and $πK \to πK$. The partial decay width and mass distributions of $f_1(1285) \to πK \bar K$ are evaluated. We get a value for the partial decay width which, within errors, is in fair agreement with the experimental result. The contribution from the tree level diagrams is dominant, but the final state interactions have effects in the mass distributions. The predicted mass distributions are significantly different from phase space and tied to the $K^* \bar{K} - cc$ nature of the $f_1(1285)$ state.

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arXiv2015

Study of the $f_2(1270)$, $f'_2(1525)$, $\bar{K}^*_{2}(1430)$, $f_0(1370)$ and $f_0(1710)$ production from $ψ(nS)$ and $Υ(nS)$ decays

Based on previous studies that support the important role of the $f_2(1270)$, $f'_2(1525)$, and $\bar{K}^{*}_{2}(1430)$ resonances in the $J/ψ[ψ(2S)] \to ϕ(ω) VV$ decays, we make an analysis of the analogous decays of $Υ(1S)$ and $Υ(2S)$, taking into account recent experimental data. In addition, we study the $J/ψ$ and $ψ(2S)$ radiative decays and we also made predictions for the radiative decay of $Υ(1S)$ and $Υ(2S)$ into $γf_2(1270)$, $γf'_2(1525)$, $γf_0(1370)$ and $γf_0(1710)$, comparing with the recent results of a CLEO experiment. We can compare our results for ratios of decay rates with eight experimental ratios and find agreement in all but one case, where experimental problems are discussed.

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