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Fileviez Perez, P., Golias, E., Li, R. H., Murgui, C., & Plascencia, A. D. (2019). Anomaly-free dark matter models. Phys. Rev. D, 100(1), 015017–15pp.
Abstract: We investigate the predictions of anomaly-free dark matter models for direct and indirect detection experiments. We focus on gauge theories where the existence of a fermionic dark matter candidate is predicted by anomaly cancellation, its mass is defined by the new symmetry breaking scale, and its stability is guaranteed by a remnant symmetry after the breaking of the gauge symmetry. We find an upper bound on the symmetry breaking scale by applying the relic density and perturbative constraints. The anomaly-free property of the theories allows us to perform a full study of the gamma lines from dark matter annihilation. We investigate the correlation between predictions for final-state radiation processes and gamma lines. Furthermore, we demonstrate that the latter can be distinguished from the continuum gamma-ray spectrum.
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Dudouet, J. et al, Gadea, A., & Perez-Vidal, R. M. (2019). Excitations of the magic N=50 neutron-core revealed in Ga-81. Phys. Rev. C, 100(1), 011301–6pp.
Abstract: The high-spin states of the neutron-rich Ga-81, with three valence protons outside a Ni-78 core, were measured. The measurement involved prompt gamma-ray spectroscopy of fission fragments isotopically identified using the combination of the variable mode spectrometer (VAMOS++) and the advanced gamma tracking array (AGATA). The new gamma-ray transitions, observed in coincidence with Ga-81 ions, and the corresponding level scheme do not confirm the high-spin levels reported earlier. The newly observed high-spin states in Ga-81 are interpreted using the results of state-of-the-art large-scale shell model (LSSM) calculations. The lower excitation energy levels are understood as resulting from the recoupling of three valence protons to the closed doubly magic core, while the highest excitation energy levels correspond to excitations of the magic N = 50 neutron core. These results support the doubly magic character of Ni-78 and the persistence of the N = 50 shell closure but also highlight the presence of strong proton-neutron correlations associated with the promotion of neutrons across the magic N = 50 shell gap, only few nucleons away from Ni-78.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Aparisi Pozo, J. A., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., et al. (2019). Search for chargino and neutralino production in final states with a Higgs boson and missing transverse momentum at root s=13 TeV with the ATLAS detector. Phys. Rev. D, 100(1), 012006–37pp.
Abstract: A search is conducted for the electroweak pair production of a chargino and a neutralino pp -> (chi) over tilde (+/-)(1)(chi) over tilde (0)(2), where the chargino decays into the lightest neutralino and a W boson, (chi) over tilde (+/-)(1) -> (chi) over tilde W-0(1)+/- while the neutralino decays into the lightest neutralino and a Standard Model-like 125 GeV Higgs boson,(chi) over tilde (0)(2) -> (chi) over tilde (0)(1)h. Fully hadronic, semileptonic, diphoton, and multilepton (electrons, muons) final. states with missing transverse momentum are considered in this search. Higgs bosons in the final state are identified by either two jets originating from bottom quarks (h -> b (b) over bar), two photons (h -> gamma gamma), or leptons from the decay modes h -> WW, h -> ZZ or h -> tau tau. The analysis is based on 36.1 fb(-1) of s root s = 13 TeV proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider. Observations are consistent with the Standard Model expectations, and 95% confidence-level limits of up to 680 GeV in (chi) over tilde (+/-)(1)/(chi) over tilde (0)(2) mass are set in the context of a simplified supersymmetric model.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2019). Precision measurement of the Lambda(+)(c), Xi(+)(c), and Xi(0)(c) baryon lifetimes. Phys. Rev. D, 100(3), 032001–12pp.
Abstract: We report measurements of the lifetimes of the Lambda(+)(c), Xi(+)(c) and Xi(0)(c) charm baryons using proton- proton collision data at center- of- mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0 fb(-1), collected by the LHCb experiment. The charm baryons are reconstructed through the decays Lambda(+)(c) -> pK(-)pi(+),. Xi(+)(c) -> pK(-) pi(+) and Xi(0)(c) -> pK(-) K- pi(+), and originate from semimuonic decays of beauty baryons. The lifetimes are measured relative to that of the D+ meson, and are determined to be tau Lambda(+)(c) = 203.5 +/- 1.0 +/- 1.3 +/- 1.4 fs; tau Xi(+)(c) = 456.8 +/- 3.5 +/- 2.9 +/- 3.1 fs; tau Xi(0)(c) = 154.5 +/- 1.7 +/- 1.6 +/- 1.0 fs; where the uncertainties are statistical, systematic, and due to the uncertainty in the D+ lifetime. The measurements are approximately 3- 4 times more precise than the current world average values. The. +c and Xi(+)(c) lifetimes are in agreement with previous measurements; however, the Xi(0)(c) baryon lifetime is approximately 3.3 standard deviations larger than the world average value.
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Rafi Alam, M., & Ruiz Simo, I. (2019). Weak production of strange Xi baryons off the nucleon. Phys. Rev. D, 100(3), 033001–10pp.
Abstract: The charged current Cabibbo-suppressed associated K Xi production off the nucleon induced by antineutrinos is studied at low and intermediate energies. The nonresonant terms are obtained using a microscopical model based on the SU( 3) chiral Lagrangian. The basic parameters of the model are f(pi), the pion decay constant, Cabibbo's angle, the proton and neutron magnetic moments, and the axial vector coupling constants for the baryons octet, D and F, that are obtained from the analysis of the semileptonic decays of neutron and hyperons. In addition, we also consider Sigma(*)(1385) resonance, which can decay in K Xi final state when this channel is open. The studied mechanism is the prime source of Xi production at antineutrino energies around 2 GeV and the calculated cross sections at these energies can be measured at the current and future neutrino experiments.
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