arXiv subjects

E. Oset

Publications and source records attributed to E. Oset.

At least 145 records · Page 8Linked to original sources

arXiv2015

Photoproduction of the $f_2(1270)$ resonance

We have performed a calculation of the $γp \to π^+ π^- p$ reaction, where the two pions have been separated in $D$-wave producing the $f_2(1270)$ resonance. We use elements of the local hidden gauge approach that provides the interaction of vector mesons in which the $f_2(1270)$ resonance appears as a $ρ$-$ρ$ molecular state in $L=0$ and spin 2. The vector meson dominance, incorporated in the local hidden gauge approach converts a photon into a $ρ^0$ meson and the other meson connects the photon with the proton. The picture is simple and has no free parameters, since the parameters of the theory have been constrained in the previous study of the vector-vector states. In a second step we introduce new elements, not present in the local hidden gauge approach, adapting the $ρ$ propagator to Regge phenomenology and introducing the $ρNN$ tensor coupling. We find that both the differential cross section as well as the $t$ dependence of the cross section are in good agreement with the experimental results and provide support for the molecular picture of the $f_2(1270)$ in the first baryonic reaction where it has been tested.

nucl-th↗

arXiv2015

States of $ρB^* \bar{B}^*$ with $J=3$ within the Fixed Center Approximation to Faddeev equations

In this work we study the $ρB^*\bar{B}^*$ three-body system solving the Faddeev equations in the fixed center approximation. We assume the $B^*\bar{B}^*$ system forming a cluster, and in terms of the two-body $ρB^*$ unitarized scattering amplitudes in the local Hidden Gauge approach we find a new $I(J^{PC})=1(3^{--})$ state. The mass of the new state corresponds to a two particle invariant mass of the $ρB^\ast$ system close to the resonant energy of the $B^\ast_2(5747)$, indicating that the role of this $J=2$ resonance is important in the dynamical generation of the new state.

hep-ph↗

arXiv2015

The LHCb pentaquark as a $\bar{D}^Σ_c-\bar{D}^Σ_c^*$ molecular state

We perform a theoretical analysis of the $Λ_b \to J/ψK^- p$ reaction from where a recent LHCb experiment extracts a $Λ(1405)$ contribution in the $K^- p$ spectrum close to threshold and two baryon states of hidden charm in the $J/ψ\,p$ spectrum. We recall that baryon states of this type have been theoretically predicted matching the mass, width and $J^P$ of the experiment, concretely some states built up from the $J/ψ\, N$, $\bar D^* Λ_c$, $\bar D^* Σ_c$, $\bar D Σ^*_c$ and $\bar D^* Σ^*_c$ coupled channels. We assume that the observed narrow state around 4450 MeV has this nature and we are able to describe simultaneously the shapes and relative strength of the the $K^- p$ mass distribution close to threshold and the peak of the $J/ψ\,p$ distribution, with values of the $J/ψ\, p$ coupling to the resonance in line with the theoretical ones. The non trivial matching of many properties gives support to a $J^P=3/2^-$ assignment to this state and to its nature as a molecular state mostly made of $\bar D^* Σ_c$ and $\bar D^* Σ^*_c$.

hep-ph↗

arXiv2015

Two, three, many body systems involving mesons. Multimeson condensates

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.

hep-ph↗

arXiv2015

Semileptonic $Λ_c$ decay to $νl^+$ and $Λ(1405)$

We study the semileptonic decay of $Λ_c$ to $νl^+$ and $Λ(1405)$, where the $Λ(1405)$ is seen in the invariant mass distribution of $πΣ$. We perform the hadronization of the quarks produced in the reaction in order to have a meson baryon pair in the final state and then let these hadron pairs undergo final state interaction from where the $Λ(1405)$ is dynamically generated. The reaction is particularly suited to study this resonance because we show that it filters I=0. It is also free of tree level $πΣ$ production, which leads to a clean signal of the resonance with no background. This same feature has as a consequence that one populates the state of the $Λ(1405)$ with higher mass around 1420 MeV, predicted by the chiral unitary approach. We make absolute predictions for the invariant mass distributions and find them within measurable range in present facilities. The implementation of this reaction would allow us to gain insight into the existence of the predicted two $Λ(1405)$ states and their nature as molecular states.

hep-ph↗

arXiv2015

Strategies for an accurate determination of the X(3872) energy from QCD lattice simulations

We develop a method to determine accurately the binding energy of the X(3872) from lattice data for the DD* interaction. We show that, because of the small difference between the neutral and charged components of the X(3872), it is necessary to distinguish them in the energy levels of the lattice spectrum if one wishes to have a precise determination of the the binding energy of the X(3872). The analysis of the data requires the use of coupled channels. Depending on the number of levels available and the size of the box we determine the precision needed in the lattice energies to finally obtain a desired accuracy in the binding energy.

hep-ph↗

arXiv2015

$\bar{B}^0$ and $\bar{B}^0_s$ decays into $J/ψ$ and $f_0(1370),~f_0(1710),~f_2(1270),~f'_2(1525),~K^*_2(1430)$

We make predictions for the ratios of branching fractions of ${\bar B}^0$ and ${\bar B}^0_s$ decays into $J/ψ$ and the scalar mesons $f_0(1370),~f_0(1710)$ or tensor mesons $f_2(1270),~f'_2(1525),~K^*_2(1430)$. The theoretical approach is based on results of chiral unitary theory where these resonances are shown to be generated from the vector meson-vector meson interaction. Eight independent ratios can be predicted and comparison is made with the recent data on $\bar{B}^0_s$ decay into $J/ψf'_2(1525)$ versus the $\bar{B}^0_s$ decay into $J/ψf_2(1270)$.

hep-ph↗

arXiv2015

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

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 $κ(800)$. We also compare the $π^+ π^-$ production in the scalar channel with that observed in the $ρ$ 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 $κ(800)$ 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 scalar resonances are predicted with no free parameters. Comparison with experimental data is done when available.

hep-ph↗

arXiv2015

The $ρ(ω)B^*(B)$ interaction and states of $J=0,1,2$

In this work, we study systems composed of a $ρ/ω$ and $B^*$ meson pair. We find three bound states in isospin, spin-parity channels $(1/2, 0^+)$, $(1/2, 1^+)$ and $(1/2, 2^+)$. The state with $J=2$ can be a good candidate for the $B_2^*(5747)$. We also study the $ρB$ system, and a bound state with mass $5728$ MeV and width around $20$ MeV is obtained, which can be identified with the $B_1(5721)$ resonance. In the case of $I=3/2$, one obtains repulsion and thus, no exotic (molecular) mesons in this sector are generated in the approach.

hep-ph↗

arXiv2015

The $Λ_b \to J/ψ~ K ~ Ξ$ decay and the higher order chiral terms of the meson baryon interaction

We study the weak decay of the $Λ_b$ into $ J/ψ~ K ~ Ξ$ and $J/ψ~ η~ Λ$ states, and relate these processes to the $Λ_b \to J/ψ~ \bar K ~N$ decay mode. The elementary weak transition at the quark level proceeds via the creation of a $J/ψ$ meson and an excited $sud$ system with $I=0$, which upon hadronization leads to $\bar K N$ or $ηΛ$ pairs. These states undergo final state interaction in coupled channels and produce a final meson-baryon pair. The $K Ξ$ state only occurs via rescattering, hence making the $Λ_b \to J/ψ~ K ~ Ξ$ process very sensitive to the details of the meson-baryon interaction in strangeness $S=-1$ and isospin $I=0$. We show that the corresponding invariant mass distribution is dominated by the next-to-leading order terms of the chiral interaction. The $I=0$ selectivity of this decay, and its large sensitivity to the higher order terms, makes its measurement very useful and complementary to the $K^- p \to K Ξ$ cross section data. The rates of the $Λ_b \to J/ψ~ K ~ Ξ$ and $Λ_b \to J/ψ~ η~ Λ$ invariant mass distributions are sizable compared to those of the $Λ_b \to J/ψ~ \bar K ~N$ decay, which is measured experimentally, thus, we provide arguments for an experimental determination of these decay modes that will help us understand better the chiral dynamics at higher energies.

hep-ph↗

arXiv2015

Reanalysis of lattice QCD spectra leading to the $D_{s0}^(2317)$ and $D_{s1}^(2460)$

We perform a reanalysis of the energy levels obtained in a recent lattice QCD simulation, from where the existence of bound states of $KD$ and $KD^*$ are induced and identified with the narrow $D_{s0}^*(2317)$ and $D_{s1}^*(2460)$ resonances. The reanalysis is done in terms of an auxiliary potential, employing a single-channel basis $KD^{(*)}$, and a two-channel basis $KD^{(*)}, ηD_s^{(*)}$. By means of an extended Lüscher method we determine poles of the continuum $t$-matrix, bound by about 40 MeV with respect to the $KD$ and $KD^*$ thresholds, which we identify with the $D_{s0}^*(2317)$ and $D_{s1}^*(2460)$ resonances. Using a sum rule that reformulates Weinberg compositeness condition we can determine that the state $D_{s0}^*(2317)$ contains a $KD$ component in an amount of about 70%, while the state $D_{s1}^*(2460)$ contains a similar amount of $KD^*$. We argue that the present lattice simulation results do not still allow us to determine which are the missing channels in the bound state wave functions and we discuss the necessary information that can lead to answer this question.

hep-lat↗

arXiv2015

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

We investigate the decay of $\bar B^0 \to \bar K^{*0} R$ and $\bar B^0_s \to ϕR$ 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 predict the order of magnitude of the branching ratios which we find of the order of $10^{-4}$, well within the present measurable range. In order to further test the dynamical nature of these resonances we study the $\bar B^0_s \to ϕD^* \bar D^*$ and $\bar B^0_s \to ϕD_s^* \bar D_s^*$ decays close to the $D^* \bar D^*$ and $D_s^* \bar D_s^*$ thresholds and make predictions for the ratio of the mass distributions in these decays and the $\bar B^0_s \to ϕR$ decay widths. The measurement of these decays rates can help unravel the nature of these resonances.

hep-ph↗

arXiv2015

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

The s-wave interaction of $\bar{D} Λ_c, \bar{D} Σ_c, \bar{D} Λ_c, \bar{D}{}^* Σ_c$ and $\bar{D}Σ^*_c, \bar{D}{}^*Σ^*_c$, is studied within a unitary coupled channels scheme with the extended local hidden gauge approach. In addition to the Weinberg-Tomozawa term, several additional diagrams via the pion-exchange are also taken into account as box potentials. Furthermore, in order to implement the full coupled channels calculation, some of the box potentials which mix the vector-baryon and pseudoscalar-baryon sectors are extended to construct the effective transition potentials. As a result, we have observed six possible states in several angular momenta. Four of them correspond to two pairs of admixture states, two of $\bar{D}Σ_c$ - $\bar{D}{}^*Σ_c$ with $J^P = 1/2^-$, and two of $\bar{D}Σ^*_c$ - $\bar{D}{}^*Σ^*_c$ with $J^P = 3/2^-$. Moreover, we find a $\bar{D}{}^* Σ_c$ resonance which couples to the $\bar{D}Λ_c$ channel and one spin degenerated bound state of $\bar{D}{}^*Σ^*_c$ with $J^P = 1/2^-, 5/2^-$.

hep-ph↗

arXiv2015

Antineutrino induced Lambda(1405) production off the proton

We have studied the strangeness changing antineutrino induced reactions $\barν_{l} p \rightarrow l^+ ϕB $, with $ϕB = K^-p$, $\bar{K}^0n$, $π^0Λ$, $π^0Σ^0$, $ηΛ$, $ηΣ^0$, $π^+Σ^-$, $π^-Σ^+$, $K^+Ξ^-$ and $K^0Ξ^0$, using a chiral unitary approach. These ten coupled channels are allowed to interact strongly, using a kernel derived from the chiral Lagrangians. This interaction generates two $Λ(1405)$ poles, leading to a clear single peak in the $πΣ$ invariant mass distributions. At backward scattering angles in the center of mass frame, $\barν_μ p \rightarrow μ^+ π^0 Σ^0$ is dominated by the $Λ(1405)$ state at around 1420~MeV while the lighter state becomes relevant as the angle decreases, leading to an asymmetric line shape. In addition, there are substantial differences in the shape of $πΣ$ invariant mass distributions for the three charge channels. If observed, these differences would provide valuable information on a claimed isospin I=1, strangeness S=-1 baryonic state around 1400 MeV. Integrated cross sections have been obtained for the $πΣ$ and $\bar K N$ channels, investigating the impact of unitarization in the results. The number of events with $Λ(1405)$ excitation in $\barν_μp$ collisions in the recent antineutrino run at the MINERvA experiment has also been obtained. We find that this reaction channel is relevant enough to be investigated experimentally and to be taken into account in the simulation models of future experiments with antineutrino beams.

hep-ph↗

arXiv2015

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

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 find two states with nearly zero width which are associated to the $Λ_c(2595)$ and $Λ_c(2625)$. The lower state, with $J^P = 1/2^-$, couples to $D N$ and $D^* N$, and the second one, with $J^P = 3/2^-$, to $D^* N$. In addition to these two $Λ_c$ states, we find four more states with $I=0$, one of them nearly degenerate in two states of $J=1/2,\ 3/2$. Furthermore we find three states in $I=1$, two of them degenerate in $J=1/2, 3/2$.

hep-ph↗

arXiv2015

$f_1(1285)$ decays into $a_0(980)π^0$, $f_0(980)π^0$ and isospin breaking

We evaluate the decay width for the processes $f_1(1285) \to π^0 a_0(980)$ and $f_1(1285) \to π^0 f_0(980)$ taking into account that all three resonances are dynamically generated from the meson-meson interaction, the $f_1(1285)$ from $K^* \bar K -c.c$ and the $a_0(980)$, $f_0(980)$ from $πη, K \bar K$ and $ππ, K \bar K$ respectively. We use a triangular mechanism similar to that of the $η(1405) \to ππη$, which provides a decay width for $f_1(1285) \to π^0 a_0(980)$ with a branching fraction of the order of 30%, in agreement with experiment. At the same time we evaluate the decay width for the isospin forbidden $f_1(1285) \to π^0 f_0(980)$, which appears when we consider different masses for the charged and neutral kaons, and show that it is much more suppressed than in the $η(1405) \to ππη$ case, but gives rise to a narrow shape of the $π^+ π^-$ distribution similar to the one found in the $η(1405) \to ππη$ decay.

hep-ph↗

arXiv2015

Testing the molecular nature of $\bm{D_{s 0}^{\ast}(2317)}$ and $\bm{D_{0}^{\ast} (2400)}$ in semileptonic $\bm{B_s}$ and $\bm{B}$ decays

We study the semileptonic $B_s$ and $B$ decays into the $D_{s 0}^{\ast} (2317)$ and $D_{0}^{\ast} (2400)$ resonances, respectively. With the help of a chiral unitarity model in coupled channels we compute the ratio of the decay widths of both processes. Using current values of the width for the $\bar{B}^{0} \to D_{0}^{\ast} (2400)^{+} \barν_{l} l^{-}$ decay we make predictions for the rate of the $\bar{B}_{s}^{0} \to D_{s0}^{\ast} (2317)^{+} \barν_{l} l^{-}$ decay.

hep-ph↗

arXiv2015

States of $ρD^* \bar D^*$ with $J=3$ within the Fixed Center Approximation to the Faddeev equations

We study the interaction of the a $ρ$ and $D^*$, $\bar D^*$ with spins aligned using the Fixed Center Approximation to the Faddeev equations. We select a cluster of $D^* \bar D^*$, which is found to be bound in $I=0$ and can be associated to the X(3915), and let the $ρ$ meson orbit around the $D^*$ and $\bar D^*$. In this case we find an $I=1$ state with mass around 4340 MeV and narrow width of about 50 MeV. We also investigate the case with a cluster of $ρD^*$ and let the $\bar D^*$ orbit around the system of the two states. The $ρD^*$ cluster is also found to bind and leads to the $D^*_2(2460)$ state. The addition of the extra $\bar D^*$ produces further binding and we find, with admitted uncertainties, a state of $I=0$ around 4000 MeV, and a less bound narrow state with $I=1$ around 4200 MeV.

hep-ph↗