arXiv subjects

Eulogio Oset

Publications and source records attributed to Eulogio Oset.

At least 127 records · Page 7Linked to original sources

arXiv2016

The $Λ_{b}\rightarrow J/ψK^{0}Λ$ reaction and a hidden-charm pentaquark state with strangeness

We study the $Λ_{b}\rightarrow J/ψK^{0}Λ$ reaction considering both the $K^{0}Λ$ interaction with its coupled channels and the $J/ψΛ$ interaction. The latter is described by taking into account the fact that there are predictions for a hidden-charm state with strangeness that couples to $J/ψΛ$. By using the coupling of the resonance to $J/ψΛ$ from these predictions we show that a neat peak can be observed in the $J/ψΛ$ invariant mass distribution, rather stable under changes of unknown magnitudes. In some cases, one finds a dip structure associated to that state, but a signal of the state shows up in the $J/ψ$ spectrum.

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arXiv2016

$D^\ast_{s0}(2317)$ and $DK$ scattering in $B$ decays from BaBar and LHCb data

We study the experimental $DK$ invariant mass spectra of the reactions $B^+ \to \bar{D}^0 D^0 K^+$, $B^0 \to D^- D^0 K^+$ (measured by the BaBar Collaboration) and $B_s \to π^+ \bar{D}^0 K^-$ (measured by the LHCb Collaboration), where an enhancement right above the threshold is seen. We show that this enhancement is due to the presence of $D^\ast_{s0}(2317)$, which is a $DK$ bound state in the $I(J^P) = 0(0^+)$ sector. We employ a unitarized amplitude with an interaction potential fixed by heavy meson chiral perturbation theory. We obtain a mass $M_{D^\ast_{s0}} = 2315^{+12}_{-17}\ ^{+10}_{-5}\ \text{MeV}$, and we also show, by means of the Weinberg compositeness condition, that the $DK$ component in the wave function of this state is $P_{DK} = 70^{+4}_{-6}\ ^{+4}_{-8} \%$, where the first (second) error is statistical (systematic).

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arXiv2016

Can $X(5568)$ be described as a $B_sπ$, $B\bar{K}$ resonant state?

The D0 Collaboration has recently seen a resonant-like peak in the $B_sπ$ invariant mass spectrum, claimed to be a new state called $X(5568)$. Using a $B_sπ$--$B\bar{K}$ coupled channel analysis, implementing unitarity, and with the interaction derived from Heavy Meson Chiral Perturbation Theory, we are able to reproduce the reported spectrum, with a pole that can be associated to the claimed $X(5568)$ state, and with mass and width in agreement with the ones reported in the experimental analysis. However, if the $T$-matrix regularization is performed by means of a momentum cutoff, the value for the latter needed to reproduce the spectrum is $Λ= 2.80 \pm 0.04\ \text{GeV}$, much larger than a "natural" value $Λ\simeq 1\ \text{GeV}$. In view of this, it is difficult to interpret the nature of this new state. This state would not qualify as a resonance dynamically generated by the unitarity loops. Assuming the observed peak to correspond to a physical state, we make predictions for partners in the $D$, $D^\ast$, and $B^\ast$ sectors. Their observation (or lack thereof) would shed light into this issue.

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arXiv2016

Antikaon-nucleon interaction and Lambda(1405) in chiral SU(3) dynamics

The properties of the Lambda(1405) resonance are key ingredients for determining the antikaon-nucleon interaction in strangeness nuclear physics, and the novel internal structure of the Lambda(1405) is of great interest in hadron physics, as a prototype case of a baryon that does not fit into the simple three-quark picture. We show that a quantitative description of the antikaon-nucleon interaction with the Lambda(1405) is achieved in the framework of chiral SU(3) dynamics, with the help of recent experimental progress. Further constraints on the Kbar N subthreshold interaction are provided by analyzing pi Sigma spectra in various processes, such as the K-d -> pi Sigma n reaction and the Lambda_c -> pi pi Sigma decay. The structure of the Lambda(1405) is found to be dominated by an antikaon-nucleon molecular configuration, based on its wavefunction derived from a realistic Kbar N potential and the compositeness criteria from a model-independent weak-binding relation.

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arXiv2016

Weak decays of heavy hadrons into dynamically generated resonances

In this review we give a perspective of the theoretical work done recently on the interpretation of results from $B$, $D$, $Λ_b$, $Λ_c$ weak decays into final states that contain interacting hadrons, and how it is possible to obtain additional valuable information that is increasing our understanding of hadron interactions and the nature of many hadronic resonances. The novelty of these processes is that one begins with a clean picture at the quark level which allows one to select the basic mechanisms by means of which the process proceeds. Finally, one has a final state described in terms of quarks. To make contact with the experiments, where mesons and baryons are observed, one must hadronize, creating pairs of $q \bar q$ and writing the new states in terms of mesons and baryons. This concludes the primary hadron production in these processes. After that, the interaction of these hadrons takes place, offering a rich spectrum of resonances and special features from where it is possible to learn much about the interaction of these hadrons and the nature of many resonances in terms of the components of their wave functions.

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arXiv2016

$χ_{c0}(1P)$ decay into $\barΣ~Σπ$ in search of an $I=1$, $1/2^-$ baryon state around $\bar K N$ threshold

We present the theoretical study of the process $χ_{c0}(1P)\to\barΣΣπ$ decay, by taking into account the $πΣ$ and $π\barΣ$ final state interactions of the final meson-baryon pair based on the chiral unitary approach. We show that the process filters the isospin $I=1$ in the $πΣ$ channel and offers a reaction to test the existence of an $I=1$ state with strangeness $S=-1$ and spin-parity $J^p=1/2^-$ around the $\bar KN$ threshold predicted by some theories and supported by some experiments.

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arXiv2015

$\bar K$ induced formation of the $f_0(980)$ and $a_0(980)$ resonances on proton targets

We perform a calculation of the cross section for nine reactions induced by $\bar K$ scattering on protons. The reactions studied are $K^-p \to Λπ^+ π^-$, $K^-p \to Σ^0 π^+ π^-$, $K^-p \to Λπ^0 η$, $K^-p \to Σ^0 π^0 η$, $K^-p \to Σ^+ π^- η$, $\bar K^0 p \to Λπ^+ η$, $\bar K^0 p \to Σ^0 π^+ η$, $\bar K^0 p \to Σ^+ π^+ π^-$, $\bar K^0 p \to Σ^+ π^0 η$. We find that in the reactions producing $π^+ π^-$ a clear peak for the $f_0(980)$ resonance is found, while no trace of $f_0(500)$ appears. Similarly, in the cases of $πη$ production a strong peak is found for the $a_0(980)$ resonance, with the characteristic strong cusp shape. Cross sections and invariant mass distributions are evaluated which should serve, comparing with future data, to test the dynamics of the chiral unitary approach used for the evaluations and the nature of these resonances.

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arXiv2015

Weak decay of Lambda_c^+ for the study of Lambda(1405) and Lambda(1670)

We study the Lambda_c decay process to pi^+ and the meson-baryon final state for the analysis of Lambda resonances. Considering the Cabibbo-Kobayashi-Maskawa matrix, color suppression, diquark correlation and the kinematical condition, we show that the final meson-baryon state should be in a pure I=0 combination, when the meson-baryon invariant mass is small. Because the I=1 contamination usually makes it difficult to analyze Lambda resonances directly from experiments, the Lambda_c decay is an ideal process to study Lambda resonances. Calculating the final state interaction by chiral unitary approaches, we find that the piSigma invariant mass distributions have the same peak structure in the all charge combination of the piSigma states related to the higher pole of the two poles of the Lambda(1405). Furthermore, we obtain a clear the Lambda(1670) peak structure in the KbarN and etaLambda spectra.

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arXiv2015

Investigating the nature of light scalar mesons with semileptonic decays of D mesons

We study the semileptonic decays of $D_{s}^{+}$, $D^{+}$, and $D^{0}$ mesons into the light scalar mesons [$f_{0} (500)$, $K_{0}^{\ast} (800)$, $f_{0} (980)$, and $a_{0}(980)$] and the light vector mesons [$ρ(770)$, $ω(782)$, $K^{\ast} (892)$, and $ϕ(1020)$]. With the help of a chiral unitarity approach in coupled channels, we compute the branching fractions for scalar meson processes of the semileptonic $D$ decays in a simple way. Using current known values of the branching fractions, we make predictions for the branching fractions of the semileptonic decay modes with other scalar and vector mesons. Furthermore, we calculate the $π^{+} π^{-}$, $πη$, $πK$, and $K^{+} K^{-}$ invariant mass distributions in the semileptonic decays of $D$ mesons, which will help us clarify the nature of the light scalar mesons.

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arXiv2015

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

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 $Ξ^-_b\rightarrow J/ψK^- Λ$ 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 $J/ψΛ$. 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 $P_c(4450)$, can be clearly seen. The decay rate is estimated to be of similar magnitude as the $Λ_b^0\rightarrow J/ψK^- p$ observed by the LHCb collaboration.

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arXiv2015

Photoproduction of the $f'_2(1525)$ and $K^*_2(1430)$

Assuming that the $f'_2(1525)$ and $K^*_2(1430)$ resonances are dynamically generated states from the vector meson-vector meson interactions in $S$-wave with spin $S=2$, we study the $γp \to f'_2(1525) p$ and $γp \to K^*_2(1430) Λ(Σ)$ reactions. These reactions proceed in the following way: the incoming photon first mutates into a $ρ^0$, $ω$, or $ϕ$ meson via vector meson dominance, which then interacts with the $ρ^0$, $ω$ or $K^*$ emitted by the incoming proton to form the tensor mesons $f'_2(1525)$ and $K^*_2(1430)$. The picture is simple and has no free parameters, as all the parameters of the mechanism have been fixed in previous studies. We predict the differential and total cross sections of these reactions. The results can be tested in future experiments and therefore offer new clues on the nature of these tensor states.

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arXiv2015

$S$-wave $KK^*$ interaction in a finite volume and the $f_1(1285)$

Lattice QCD simulations provide a promising way to disentangle different interpretations of hadronic resonances, which might be of particular relevance to understand the nature of the so-called $XYZ$ particles. Recent studies have shown that in addition to the well-established naive quark model picture, the axial-vector meson $f_1(1285)$ can also be understood as a dynamically generated state built upon the $KK^*$ interaction. In this work, we calculate the energy levels of the $KK^*$ system in the $f_1(1285)$ channel in finite volume using the chiral unitary approach. We propose to calculate the loop function in the dimensional regularization scheme, which is equivalent to the hybrid approach adopted in previous studies. We also study the inverse problem of extracting the bound state information from synthetic lattice QCD data and comment on the difference between our approach and the L{\" u}scher method.

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arXiv2015

Predictions for the $Λ_b \to J/ψ~ Λ(1405)$ decay

We calculate the shape of the $πΣ$ and $\bar K N$ invariant mass distributions in the $Λ_b \to J/ψ\, πΣ$ and $Λ_b \to J/ψ\,\bar K N$ decays that are dominated by the $Λ(1405)$ resonance. The weak interaction part is the same for both processes and the hadronization into the different meson-baryon channels in the final state is related by SU(3) symmetry. The most important feature is the implementation of the meson-baryon final-state interaction using two chiral unitary models from different theoretical groups. Both approaches give a good description of antikaon-nucleon scattering data, the complex energy shift in kaonic hydrogen and the line shapes of $πΣK$ in photoproduction, based on the two-pole scenario for the $Λ(1405)$. We find that this reaction reflects more the higher mass pole and we make predictions of the line shapes and relative strength of the meson-baryon distributions in the final state.

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arXiv2015

$D_{s0}^{\ast\pm}(2317)$ and $KD$ scattering from $B^0_s$ decay

We study the $\bar{B}_s^0\to D_s^-(DK)^+$ weak decay, and look at the $DK$ invariant mass distribution with the aim of obtaining relevant information on the nature of the $D_{s0}^{\ast+}(2317)$ resonance. We make a simulation of the experiment using the actual mass of the $D_{s0}^{\ast+}(2317)$ resonance and recent lattice QCD relevant parameters of the $KD$ scattering amplitude. We then solve the inverse problem of obtaining the $KD$ amplitude from these synthetic data, to which we have added a 5\% or 10\% error. We prove that one can obtain from these "data" the existence of a bound $KD$ state, the $KD$ scattering length and effective range, and most importantly, the $KD$ probability in the wave function of the bound state obtained, which was found to be largely dominant from the lattice QCD results. This means that one can obtain information on the nature of the $D_{s0}^{\ast+}(2317)$ resonance from the implementation of this experiment, in the line of finding the structure of resonances, which is one of the main aims in hadron spectroscopy.

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arXiv2014

Heavy Mesons in Nuclear Matter and Nuclei

Heavy mesons in nuclear matter and nuclei are analyzed within different frameworks, paying a special attention to unitarized coupled-channel approaches. Possible experimental signatures of the properties of these mesons in matter are addressed, in particular in connection with the future FAIR facility at GSI.

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arXiv2014

Test of the $h_1(1830)$ made of $K^{}\bar{K}^$ with the $η_c\rightarrow ϕK^{}\bar{K}^{}$ decay

We present a new reaction, complementary to the $J/ψ\rightarrow ηK^{*0}\bar{K}^{*0}$ from which an $h_1$ resonance with mass around $1830$ MeV was reported from a BESIII experiment. The new reaction is $η_c\rightarrow ϕK^*\bar{K}^*$, or $η_c(2S)\rightarrow ϕK^*\bar{K}^*$. Using the information from the analysis of $J/ψ\rightarrow ηK^{*0}\bar{K}^{*0}$, we find that the $K^*\bar{K}^*$ invariant mass distribution for those two $η_c$ decays exhibits a clear peak around $1830$ MeV perfectly distinguishable from what one obtains with pure phase space. We suggest the implementation of these reactions to assert the existence of this elusive resonance which, by its nature as a vector-vector molecule with $0^-(1^{+-})$ quantum numbers, only couples to the $K^*\bar{K}^*$ channel.

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arXiv2014

The width of the $ω$ meson in dense matter

We obtain the width of the $ω$ meson in dense nuclear matter by taking into account (i) the free decay of the $ω$ into three pions, which is dominated by $ρπ$ mode, (ii) the processes induced by a vector-baryon interaction dominated by vector meson exchange, and (iii) the $ω\to K \bar K$ mechanism in matter. The $ω$ meson develops an important width in matter, coming from the dominant $ω\to ρπ$ decay mode, with a value of $121 \pm 10$ MeV at normal nuclear matter density for an $ω$ at rest. At finite momentum, the width of the $ω$ meson increases moderately with values of 200 MeV at 600 MeV/c.

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arXiv2013

Tests on the molecular structure of $f_2(1270)$, $f'_2(1525)$ from $ψ(nS)$ and $Υ(nS)$ decays

Based on previous studies that support the vector-vector molecular structure of the $f_2(1270)$, $f'_2(1525)$, $\bar{K}^{*\,0}_2(1430)$, $f_0(1370)$ and $f_0(1710)$ resonances, we make predictions for $ψ(2S)$ decay into $ω(ϕ) f_2(1270)$, $ω(ϕ) f'_2(1525)$, $K^{*0}(892) \bar{K}^{*\,0}_2(1430)$ and radiative decay of $Υ(1S),Υ(2S), ψ(2S)$ into $γf_2(1270)$, $γf'_2(1525)$, $γf_0(1370)$, $γf_0(1710)$. Agreement with experimental data is found for three available ratios, without using free parameters, and predictions are done for other cases.

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