Lobo, F. S. N., Olmo, G. J., Orazi, E., Rubiera-Garcia, D., & Rustam, A. (2020). Structure and stability of traversable thin-shell wormholes in Palatini f(R) gravity. Phys. Rev. D, 102(10), 104012–11pp.
Abstract: We study the structure and stability of traversable wormholes built as (spherically symmetric) thin shells in the context of Palatini f(R) gravity. Using a suitable junction formalism for these theories we find that the effective number of degrees of freedom on the shell is reduced to a single one, which fixes the equation of state to be that of massless stress-energy fields, contrary to the general relativistic and metric f(R) cases. Another major difference is that the surface energy density threading the thin shell, needed in order to sustain the wormhole, can take any sign and may even vanish, depending on the desired features of the corresponding solutions. We illustrate our results by constructing thin-shell wormholes by surgically grafting Schwarzschild space-times and show that these configurations are always linearly unstable. However, surgically joined Reissner-Nordstrom space-times allow for linearly stable, traversable thin-shell wormholes supported by a positive energy density provided that the (squared) mass-to-charge ratio, given by y = Q(2)/M-2, satisfies the constraint 1 < y < 9/8 (corresponding to overcharged Reissner-Nordstrom configurations having a photon sphere) and lies in a region bounded by specific curves defined in terms of the (dimensionless) radius of the shell x(0) = R/M.
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Vijande, J., Valcarce, A., Richard, J. M., & Sorba, P. (2016). Search for doubly-heavy dibaryons in a quark model. Phys. Rev. D, 94(3), 034038–6pp.
Abstract: We study the stability of hexaquark systems containing two heavy quarks and four light quarks within a simple quark model. No bound or metastable state is found. The reason stems from a delicate interplay between chromoelectric and chromomagnetic effects. Our calculation also provides information about anticharmed pentaquarks that are seemingly unbound in simple quark models.
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Sekihara, T., & Oset, E. (2015). Investigating the nature of light scalar mesons with semileptonic decays of D mesons. Phys. Rev. D, 92(5), 054038–17pp.
Abstract: We study the semileptonic decays of D-s(+), D+, and D-0 mesons into the light scalar mesons [f(0)(500), K-0(*)(800), f(0)(980), and a(0)(980)] and the light vector mesons [rho(770), omega(782), K-*(892), and phi(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 pi(+)pi(-), pi eta, pi K, 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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Ikeno, N., & Oset, E. (2016). Semileptonic Lambda(c) decay to nu l(+) and Lambda(1405). Phys. Rev. D, 93(1), 014021–7pp.
Abstract: We study the semileptonic decay of Lambda(c) to nu l(+) and Lambda(1405), where the Lambda(1405) is seen in the invariant mass distribution of pi Sigma. 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 Lambda(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 pi Sigma 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 Lambda(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 the measurable range in present facilities. The implementation of this reaction would allow us to gain insight into the existence of the predicted two Lambda(1405) states and their nature as molecular states.
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Navarra, F. S., Nielsen, M., Oset, E., & Sekihara, T. (2015). Testing the molecular nature of D-s0*(2317) and D-0*(2400) in semileptonic B-s and B decays. Phys. Rev. D, 92(1), 014031–14pp.
Abstract: We study the semileptonic B-s and B decays into the D-s0*(2317) and D-0*(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 (B) over bar (0) -> D-0*(2400)(+)(v) over bar (l)l(-) we make predictions for the rate of the (B) over bar (0)(s) -> D-s0*(2317)(+)(v) over bar (l)l(-) decay and for the DK invariant mass distribution in the (B) over bar (0)(s) -> DK (v) over bar (l)l(-) decay.
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