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Pavao, R., Gubler, P., Fernandez-Soler, P., Nieves, J., Oka, M., & Takahashi, T. T. (2021). The negative-parity spin-1/2 A baryon spectrum from lattice QCD and effective theory. Phys. Lett. B, 820, 136473–8pp.
Abstract: The spectrum of the negative-parity spin-1/2 Lambda baryons is studied using lattice QCD and hadronic effective theory in a unitarized coupled-channel framework. A direct comparison between the two approaches is possible by considering the hadronic effective theory in a finite volume and with hadron masses and mesonic decay constants that correspond to the situation studied on the lattice. Comparing the energy level spectrum and SU(3) flavor decompositions of the individual states, it is found that the lowest two states extracted from lattice QCD can be associated with one of the two Lambda(1405)-poles and the Lambda(1670) resonance. The quark mass dependences of these two lattice QCD levels are in good agreement with their effective theory counterparts. However, as current lattice QCD studies still rely on three-quark operators to generate the physical states, clear signals corresponding to the meson-baryon scattering states, that appear in the finite volume effective theory calculation, are not yet seen.
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Albertus, C., Hernandez, E., & Nieves, J. (2011). Exclusive c -> s, d semileptonic decays of ground-state spin-1/2 doubly charmed baryons. Phys. Lett. B, 704(5), 499–509.
Abstract: We evaluate exclusive semileptonic decays of ground-state spin-1/2 doubly heavy charmed baryons driven by a c -> s, d transition at the quark level. Our results for the form factors are consistent with heavy quark spin symmetry constraints which are valid in the limit of an infinitely massive charm quark and near zero recoil. Only a few exclusive semileptonic decay channels have been theoretically analyzed before. For those cases we find that our results are in a reasonable agreement with previous calculations.
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Nieves, J., Ruiz Simo, I., & Vicente Vacas, M. J. (2012). The nucleon axial mass and the MiniBooNE quasielastic neutrino-nucleus scattering problem. Phys. Lett. B, 707(1), 72–75.
Abstract: The charged-current double differential neutrino cross section, measured by the MiniBooNE Collaboration, has been analyzed using a microscopical model that accounts for, among other nuclear effects, long range nuclear (RPA) correlations and multinucleon scattering. We find that MiniBooNE data are fully compatible with the world average of the nucleon axial mass in contrast with several previous analyses which have suggested an anomalously large value. We also discuss the reliability of the algorithm used to estimate the neutrino energy.
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Nieves, J., Ruiz Simo, I., & Vicente Vacas, M. J. (2013). Two particle-hole excitations in charged current quasielastic antineutrino-nucleus scattering. Phys. Lett. B, 721(1-3), 90–93.
Abstract: We evaluate the quasielastic and multinucleon contributions to the antineutrino-nucleus scattering cross section and compare our results with the recent MiniBooNE data. We use a local Fermi gas model that includes RPA correlations and gets the multinucleon part from a systematic many body expansion of the W boson selfenergy in the nuclear medium. The same model had been quite successful for the neutrino cross section and contains no new parameters. We have also analyzed the relevance of 2p2h events for the antineutrino energy reconstruction.
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Hidalgo-Duque, C., Nieves, J., Ozpineci, A., & Zamiralov, V. (2013). X(3872) and its partners in the heavy quark limit of QCD. Phys. Lett. B, 727(4-5), 432–437.
Abstract: In this Letter, we propose interpolating currents for the X(3872) resonance, and show that, in the heavy quark limit of QCD, the X(3872) state should have degenerate partners, independent of its internal structure. Magnitudes of possible I = 0 and I = 1 components of the X(3872) are also discussed.
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Albertus, C., Hernandez, E., Hidalgo-Duque, C., & Nieves, J. (2014). (B)over-bar(s) -> K semileptonic decay from an Omnes improved constituent quark model. Phys. Lett. B, 738, 144–149.
Abstract: We study the f(+) form factor for the semileptonic (B) over bar (s) -> K+ l(-) (V) over bar (l) decay in a constituent quark model. The valence quark estimate is supplemented with the contribution from the (B) over bar* pole that dominates the high q(2) region. We use a multiply-subtracted Omnes dispersion relation to extend the quark model predictions from its region of applicability near q(max)(2) = (M-Bs – M-K)(2) similar to 23.75 GeV2 to all q(2) values accessible in the physical decay. To better constrain the dependence of f(+) on q(2), we fit the subtraction constants to a combined input from previous light cone sum rule by Duplancic and Melic (2008) [11] and the present quark model results. From this analysis, we obtain Gamma ( (B) over bar (s) -> K+ l(-) (V) over bar (l)) = (5.47(-0.46)(+0.54)) vertical bar Vub vertical bar(2) x 10(-9) MeV, which is about 10% and 20% higher than the predictions based on Lattice QCD and QCD light cone sum rules respectively. The former predictions, for both the form factor f(+) (q(2)) and the differential decay width, lie within the 1 sigma band of our estimated uncertainties for all q(2) values accessible in the physical decay, except for a quite small region very close to q(max)(2). Differences with the light cone sum results for the form factor f(+) are larger than 20% in the region above q(2) = 15 GeV2.
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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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Yamagata-Sekihara, J., Garcia-Recio, C., Nieves, J., Salcedo, L. L., & Tolos, L. (2016). Formation spectra of charmed meson-nucleus systems using an antiproton beam. Phys. Lett. B, 754, 26–32.
Abstract: We investigate the structure and formation of charmed meson--nucleus systems, with the aim of understanding the charmed meson-nucleon interactions and the properties of the charmed mesons in the nuclear medium. The (D) over bar mesic nuclei are of special interest, since they have tiny decay widths due to the absence of strong decays for the (D) over barN pair. Employing an effective model for the (D) over barN and DN interactions and solving the Klein-Gordon equation for (D) over bar and D in finite nuclei, we find that the D0-11B system has 1s and 2p mesic nuclear states and that the D0-11B system binds in a 1s state. In view of the forthcoming experiments by the PANDA and CBM Collaborations at the future FAIR facility and the J-PARC upgrade, we calculate the formation spectra of the [(D) over bar B--11] and [D-0-B-11] mesic nuclei for an antiproton beam on a C-12 target. Our results suggest that it is possible to observe the 2p D- mesic nuclear state with an appropriate experimental setup.
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Albaladejo, M., Nieves, J., Oset, E., Sun, Z. F., & Liu, X. (2016). Can X(5568) be described as a B-s pi, B(K)over-bar resonant state? Phys. Lett. B, 757, 515–519.
Abstract: The DO Collaboration has recently seen a resonant-like peak in the B-s pi invariant mass spectrum, claimed to be a new state called X(5568). Using a B-s pi-B (K) over bar 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 Lambda = 2.80 +/- 0.04 GeV, which is much larger than a “natural” value Lambda similar or equal to 1 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*, and B* sectors. Their observation (or lack thereof) would shed light into this issue.
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Albaladejo, M., Guo, F. K., Hidalgo-Duque, C., & Nieves, J. (2016). Z(c)(3900): What has been really seen? Phys. Lett. B, 755, 337–342.
Abstract: The Z(c)(+/-)(3900)/Z(c)(+/-)(3885) resonant structure has been experimentally observed in the Y(4260) -> J/Psi pi pi and Y(4260) -> (D) over bar* D pi decays. This structure is intriguing since it is a prominent candidate of an exotic hadron. Yet, its nature is unclear so far. In this work, we simultaneously describe the (D) over bar* D and J/Psi pi invariant mass distributions in which the Z(c) peak is seen using amplitudes with exact unitarity. Two different scenarios are statistically acceptable, where the origin of the Z(c) state is different. They correspond to using energy dependent or independent (D) over bar *D S-wave interaction. In the first one, the Z(c) peak is due to a resonance with a mass around the D (D) over bar* threshold. In the second one, the Z(c) peak is produced by a virtual state which must have a hadronic molecular nature. In both cases the two observations, Z(c)(+/-)(3900) and Z(c)(+/-)(3885), are shown to have the same common origin, and a (D) over bar *D bound state solution is not allowed. Precise measurements of the line shapes around the D (D) over bar* threshold are called for in order to understand the nature of this state.
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