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Wang, E., Alvarez-Ruso, L., & Nieves, J. (2015). Single photon events from neutral current interactions at MiniBooNE. Phys. Lett. B, 740, 16–22.
Abstract: The MiniBooNE experiment has reported results from the analysis of v(e) and (v) over bar (e) appearance searches, which show an excess of signal-like events at low reconstructed neutrino energies, with respect to the expected background. A significant component of this background comes from photon emission induced by (anti) neutrino neutral current interactions with nucleons and nuclei. With an improved microscopic model for these reactions, we predict the number and distributions of photon events at the MiniBooNE detector. Our results are compared to the MiniBooNE in situ estimate and to other theoretical approaches. We find that, according to our model, neutral current photon emission from single-nucleon currents is insufficient to explain the events excess observed by MiniBooNE in both neutrino and antineutrino modes.
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Roca, L., Nieves, J., & Oset, E. (2015). LHCb pentaquark as a (D)over-bar*Sigma(c) – (D)over-bar*Sigma(c)* molecular state. Phys. Rev. D, 92(9), 094003–6pp.
Abstract: We perform a theoretical analysis of the Lambda(b) -> J/psi K(-)p reaction from where a recent LHCb experiment extracts a Lambda(1405) contribution in the K(-)p spectrum close to threshold and two baryon states of hidden charm in the J/psi 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/psi N, (D) over bar*Lambda(c), (D) over bar*Sigma(c), (D) over bar Sigma(c)* and (D) over bar*Sigma(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/psi p distribution, with values of the J/psi p coupling to the resonance in line with the theoretical ones. The nontrivial 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 (D) over bar*Sigma(c) and (D) over bar*Sigma(c)*.
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Alvarez-Ruso, L., Hernandez, E., Nieves, J., & Vicente Vacas, M. J. (2016). Watson's theorem and the N Delta(1232) axial transition. Phys. Rev. D, 93(1), 014016–16pp.
Abstract: We present a new determination of the N Delta axial form factors from neutrino induced pion production data. For this purpose, the model of Hernandez et al. [Phys. Rev. D 76, 033005 (2007)] is improved by partially restoring unitarity. This is accomplished by imposing Watson's theorem on the dominant vector and axial multipoles. As a consequence, a larger C-5(A) (0), in good agreement with the prediction from the off-diagonal Goldberger-Treiman relation, is now obtained.
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Fernandez-Soler, P., Sun, Z. F., Nieves, J., & Oset, E. (2016). The rho(omega) B*(B) interaction and states of J=0, 1, 2. Eur. Phys. J. C, 76(2), 82–12pp.
Abstract: In this work, we study systems composed of a rho/omega 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 rho B 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.
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Albaladejo, M., Fernandez-Soler, P., & Nieves, J. (2016). Z(c)(3900): confronting theory and lattice simulations. Eur. Phys. J. C, 76(10), 573–9pp.
Abstract: We consider a recent T -matrix analysis by Albaladejo et al. (Phys Lett B 755: 337, 2016), which accounts for the J/psi pi and D*(D) over bar coupled-channels dynamics, and which successfully describes the experimental information concerning the recently discovered Z(c)(3900)(+/-). Within such scheme, the data can be similarly well described in two different scenarios, where Z(c)(3900) is either a resonance or a virtual state. To shed light into the nature of this state, we apply this formalism in a finite box with the aim of comparing with recent Lattice QCD (LQCD) simulations. We see that the energy levels obtained for both scenarios agree well with those obtained in the single-volume LQCD simulation reported in Prelovsek et al. (Phys Rev D 91: 014504, 2015), thus making it difficult to disentangle the two possibilities. We also study the volume dependence of the energy levels obtained with our formalism and suggest that LQCD simulations performed at several volumes could help in discerning the actual nature of the intriguing Z(c)(3900) state.
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