Anamiati, G., Fonseca, R. M., & Hirsch, M. (2018). Quasi-Dirac neutrino oscillations. Phys. Rev. D, 97(9), 095008–16pp.
Abstract: Dirac neutrino masses require two distinct neutral Weyl spinors per generation, with a special arrangement of masses and interactions with charged leptons. Once this arrangement is perturbed, lepton number is no longer conserved and neutrinos become Majorana particles. If these lepton number violating perturbations are small compared to the Dirac mass terms, neutrinos are quasi-Dirac particles. Alternatively, this scenario can be characterized by the existence of pairs of neutrinos with almost degenerate masses, and a lepton mixing matrix which has 12 angles and 12 phases. In this work we discuss the phenomenology of quasi-Dirac neutrino oscillations and derive limits on the relevant parameter space from various experiments. In one parameter perturbations of the Dirac limit, very stringent bounds can be derived on the mass splittings between the almost degenerate pairs of neutrinos. However, we also demonstrate that with suitable changes to the lepton mixing matrix, limits on such mass splittings are much weaker, or even completely absent. Finally, we consider the possibility that the mass splittings are too small to be measured and discuss bounds on the new, nonstandard lepton mixing angles from current experiments for this case.
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Miranda, O. G., Pasquini, P., Tortola, M., & Valle, J. W. F. (2018). Exploring the potential of short-baseline physics at Fermilab. Phys. Rev. D, 97(9), 095026–9pp.
Abstract: We study the capabilities of the short-baseline neutrino program at Fermilab to probe the unitarity of the lepton mixing matrix. We find the sensitivity to be slightly better than the current one. Motivated by the future DUNE experiment, we have also analyzed the potential of an extra liquid Argon near detector in the LBNF beamline. Adding such a near detector to the DUNE setup will substantially improve the current sensitivity on nonunitarity. This would help to remove CP degeneracies due to the new complex phase present in the neutrino mixing matrix. We also study the sensitivity of our proposed setup to light sterile neutrinos for various configurations.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2018). Search for the rare decay Lambda(+)(c) -> p mu(+ )mu(-). Phys. Rev. D, 97(9), 091101–10pp.
Abstract: A search for the flavor-changing neutral-current decay Lambda(+)(c) -> p mu(+)mu(-) is reported using a data set corresponding to an integrated luminosity of 3.0 fb(-1) collected by the LHCb Collaboration. No significant signal is observed outside of the dimuon mass regions around the phi and omega resonances, and an upper limit is placed on the branching fraction of B(Lambda(+ )(c)-> p mu(+)mu(-)) < 7.7(9.6) x 10(-8) at 90%(95%) confidence level. A significant signal is observed in the omega dimuon mass region for the first time.
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Debastiani, V. R., Dias, J. M., Liang, W. H., & Oset, E. (2018). Molecular Omega(c) states generated from coupled meson-baryon channels. Phys. Rev. D, 97(9), 094035–11pp.
Abstract: We have investigated Omega(c) states that are dynamically generated from the meson-baryon interaction. We use an extension of the local hidden gauge to obtain the interaction from the exchange of vector mesons. We show that the dominant terms come from the exchange of light vectors, where the heavy quarks are spectators. This has as a consequence that heavy quark symmetry is preserved for the dominant terms in the (1/m(Q)) counting, and also that the interaction in this case can be obtained from the SU(3) chiral Lagrangians. We show that for a standard value for the cutoff regulating the loop, we obtain two states with J(P) = 1/2(-) and two more with J(P) = 3/2(-), three of them in remarkable agreement with three experimental states in mass and width. We also make predictions at higher energies for states of vector-baryon nature.
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Sun, Z. F., Xie, J. J., & Oset, E. (2018). Bottom strange molecules with isospin 0. Phys. Rev. D, 97(9), 094031–9pp.
Abstract: Using the local hidden gauge approach, we study the possibility of the existence of bottom strange molecular states with isospin 0. We find three bound states with spin parity 0(+), 1(+), and 2(+) generated by the (K) over bar *B* and omega B-s(*) interaction, among which the state with spin 2 can be identified as B(s2)(*()5840). In addition, we also study the (K) over bar *B* and omega B-s(*) interaction and find a bound state which can be associated to B-s1(5830). In addition, the (K) over barB*, eta B-s(*)(K) over barB, and eta B-s systems are studied, and two bound states are predicted. We expect that further experiments can confirm our predictions.
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