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Feijoo, A., Valcarce Cadenas, V., & Magas, V. K. (2023). The Xi(1620) and Xi(1690) molecular states from S =-2 meson-baryon interaction up to next-to-leading order. Phys. Lett. B, 841, 137927–6pp.
Abstract: We have studied the meson-baryon interaction in the neutral S = -2 sector using an extended Unitarized Chiral Perturbation Theory, which takes into account not only the leading Weinberg-Tomozawa term (as all the previous studies in S = -2 sector), but also the Born terms and next-to-leading order contribution. Based on the SU(3) symmetry of the chiral Lagrangian we took most of the model parameters from the BCN model [1], where these were fitted to a large amount of experimental data in the neutral S = -1 sector. We have shown that our approach is able to generate dynamically both Xi(1620) and Xi(1690) states in very reasonable agreement with the data, and can naturally explain the puzzle with the decay branching ratios of Xi(1690). Our results clearly illustrate the reliability of chiral models implementing unitarization in coupled channels and the importance of considering Born and NLO contributions for precise calculations.
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Xiao, C. W., Nieves, J., & Oset, E. (2019). Prediction of hidden charm strange molecular baryon states with heavy quark spin symmetry. Phys. Lett. B, 799, 135051–10pp.
Abstract: We have studied the meson-baryon S-wave interaction in the isoscalar hidden-charm strange sector with the coupled-channels, eta(c)Lambda, J/psi Lambda, (D) over bar Xi(c), (D) over bar (s)Lambda(c), (D) over bar Xi(c)', (D) over bar*Lambda(c), (D) over bar*Xi(c)', (D) over bar*Xi*(c) in J(p) = 1/2(-), J/psi Lambda, (D) over bar*Xi(c), (D) over bar (s)*Lambda(c), (D) over bar*Xi(c)', (D) over bar Xi(c)*, (D) over bar*Xi(c)* in 3/2(-) and (D) over bar*Xi(c)* in 5/2(-). We impose constraints of heavy quark spin symmetry in the interaction and obtain the non vanishing matrix elements from an extension of the local hidden gauge approach to the charm sector. The ultraviolet divergences are renormalized using the same meson-baryon-loops regulator previously employed in the non-strange hidden charm sector, where a good reproduction of the properties of the newly discovered pentaquark states is obtained. We obtain five states of 1/2(-), four of 3/2(-) and one of 5/2(-), which could be compared in the near future with forthcoming LHCb experiments. The 5/2(-), three of the 3/2(-) and another three of the 1/2(-) resonances are originated from isoscalar (D) over bar (()*())Xi(c)' and (D) over bar (()*()) Xi(c)* interactions. They should be located just few MeV below the corresponding thresholds (4446, 4513, 4588 and 4655 MeV), and would be SU(3)-siblings of the isospin 1/2 (D) over bar (()*())Sigma(()(c)*()) quasi-bound states previously found, and that provided a robust theoretical description of the P-c(4440), P-c(4457) and P-c(4312) LHCb exotic states. The another two 1/2(-) and 3/2(-) states obtained in this work are result of the (D) over bar (()*())Xi(c)- D-s(()*()) Lambda(c) coupled-channels isoscalar interaction, are significantly broader than the others, with widths of the order of 15 MeV, being (D) over bar (()(s)*())Lambda(c) the dominant decay channel.
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Das, D., Dey, U. K., & Pal, P. B. (2016). S-3 symmetry and the quark mixing matrix. Phys. Lett. B, 753, 315–318.
Abstract: We impose an S-3 symmetry on the quark fields under which two of three quarks transform like a doublet and the remaining one as singlet, and use a scalar sector with the same structure of SU(2) doublets. After gauge symmetry breaking, a Z(2) subgroup of the S-3 remains unbroken. We show that this unbroken subgroup can explain the approximate block structure of the CKM matrix. By allowing soft breaking of the S-3 symmetry in the scalar sector, we show that one can generate the small elements, of quadratic or higher order in the Wolfenstein parametrization of the CKM matrix. We also predict the existence of exotic new scalars, with unconventional decay properties, which can be used to test our model experimentally.
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Casals, M., Fabbri, A., Martinez, C., & Zanelli, J. (2016). Quantum dress for a naked singularity. Phys. Lett. B, 760, 244–248.
Abstract: We investigate semiclassical backreaction on a conical naked singularity space-time with a negative cosmological constant in (2 + 1)-dimensions. In particular, we calculate the renormalized quantum stress-energy tensor for a conformally coupled scalar field on such naked singularity space-time. We then obtain the backreacted metric via the semiclassical Einstein equations. We show that, in the regime where the semiclassical approximation can be trusted, backreaction dresses the naked singularity with an event horizon, thus enforcing (weak) cosmic censorship.
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Aceti, F., Xie, J. J., & Oset, E. (2015). The K(K)over-bar pi decay of the f(1) (1285) and its nature as a K*(K)over-bar – cc molecule. Phys. Lett. B, 750, 609–614.
Abstract: We investigate the decay of f(1) (1285) > pi K (K) over bar with the assumption that the f(1) (1285) is dynamically generated from the K*(K) over bar – cc interaction. In addition to the tree level diagrams that proceed via f(1)(1285) -> K*(K) over bar – cc -> pi K (K) over bar, we take into account also the final state interactions of K (K) over bar -> K (K) over bar and pi K -> pi K. The partial decay width and mass distributions of f(1) (1285) -> pi K (K) over bar 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*(K) over bar – cc nature of the f(1) (1285) state.
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Barenboim, G., & Park, W. I. (2016). Gravitational waves from first order phase transitions as a probe of an early matter domination era and its inverse problem. Phys. Lett. B, 759, 430–438.
Abstract: We investigate the gravitational wave background from a first order phase transition in a matter-dominated universe, and show that it has a unique feature from which important information about the properties of the phase transition and thermal history of the universe can be easily extracted. Also, we discuss the inverse problem of such a gravitational wave background in view of the degeneracy among macroscopic parameters governing the signal.
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Choi, K. Y., Gong, J. O., Joh, J., Park, W. I., & Seto, O. (2023). Light cold dark matter from non-thermal decay. Phys. Lett. B, 845, 138126–8pp.
Abstract: We investigate the mass range and the corresponding free-streaming length scale of dark matter produced non-thermally from decay of heavy objects which can be either dominant or sub-dominant at the moment of decay. We show that the resulting dark matter could be very light well below keV scale with a free-streaming length satisfying the Lyman-alpha constraints. We demonstrate two explicit examples for such light cold dark matter.
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Hiller Blin, A. N., Ledwig, T., & Vicente Vacas, M. J. (2015). Chiral dynamics in the (gamma)over-right-arrowp -> p pi(0) reaction. Phys. Lett. B, 747, 217–222.
Abstract: We investigate the neutral pion photoproduction on the proton near threshold in covariant chiral perturbation theory with the explicit inclusion of A degrees of freedom. This channel is specially sensitive to chiral dynamics and the advent of very precise data from the Mainz microtron has shown the limits of the convergence of the chiral series for both the heavy baryon and the covariant approaches. We show that the inclusion of the Delta resonance substantially improves the convergence leading to a good agreement with data for a wider range of energies.
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Barenboim, G., Calatayud-Cadenillas, A. M., Gago, A. M., & Ternes, C. A. (2024). Quantum decoherence effects on precision measurements at DUNE and T2HK. Phys. Lett. B, 852, 138626–11pp.
Abstract: We investigate the potential impact of neutrino quantum decoherence on the precision measurements of standard neutrino oscillation parameters in the DUNE and T2HK experiments. We show that the measurement of delta(CP), sin(2) theta(13) and sin(2) theta(23) is stronger effected in DUNE than in T2HK. On the other hand, DUNE would have a better sensitivity than T2HK to observe decoherence effects. By performing a combined analysis of DUNE and T2HK we show that a robust measurement of standard parameters would be possible, which is not guaranteed with DUNE data alone.
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Addazi, A., Marciano, A., Morais, A. P., Pasechnik, R., Srivastava, R., & Valle, J. W. F. (2020). Gravitational footprints of massive neutrinos and lepton number breaking. Phys. Lett. B, 807, 135577–8pp.
Abstract: We investigate the production of primordial Gravitational Waves (GWs) arising from First Order Phase Transitions (FOPTs) associated to neutrino mass generation in the context of type-I and inverse seesaw schemes. We examine both “high-scale” as well as “low-scale” variants, with either explicit or spontaneously broken lepton number symmetry U(1)(L), in the neutrino sector. In the latter case, a pseudo-Goldstone majoron-like boson may provide a candidate for cosmological dark matter. We find that schemes with softly-broken U(1)(L), and with single Higgs-doublet scalar sector lead to either no FOPTs or too weak FOPTs, precluding the detestability of GWs in present or near future measurements. Nevertheless, we found that, in the majoron-like seesaw scheme with spontaneously broken U(1)(L), at finite temperatures, one can have strong FOPTs and non-trivial primordial GW spectra which can fall well within the frequency and amplitude sensitivity of upcoming experiments, including LISA, BBO and u-DECIGO. However, GWs observability clashes with invisible Higgs decay constraints from the LHC. A simple and consistent fix is to assume the majoron-like mass to lie above the Higgs-decay kinematical threshold. We also found that the majoron-like variant of the low-scale seesaw mechanism implies a different GW spectrum than the one expected in the high-scale seesaw. This feature will be testable in future experiments. Our analysis shows that GWs can provide a new and complementary portal to test the neutrino mass generation mechanism.
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