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Dombos, A. C., Spyrou, A., Naqvi, F., Quinn, S. J., Liddick, S. N., Algora, A., et al. (2019). beta-decay half-lives of neutron-rich nuclides in the A=100-110 mass region. Phys. Rev. C, 99(1), 015802–8pp.
Abstract: beta-decay half-lives of neutron-rich nuclides in the A = 100-110 mass region have been measured using an implantation station installed inside of the Summing NaI(T1) (SuN) detector at the National Superconducting Cyclotron Laboratory. Accurate half-lives for these nuclides are important for nuclear astrophysics, nuclear structure, and nuclear technology. The half-lives from the present work are compared with previous measurements, showing overall good agreement.
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Dong, P. V., Huong, D. T., Camargo, D. A., Queiroz, F. S., & Valle, J. W. F. (2019). Asymmetric dark matter, inflation, and leptogenesis from B-L symmetry breaking. Phys. Rev. D, 99(5), 055040–17pp.
Abstract: We propose a unified setup for dark matter, inflation, and baryon asymmetry generation through the neutrino mass seesaw mechanism. Our scenario emerges naturally from an extended gauge group containing B-L as a noncommutative symmetry, broken by a singlet scalar that also drives inflation. Its decays reheat the universe, producing the lightest right-handed neutrino. Automatic matter parity conservation leads to the stability of an asymmetric dark matter candidate, directly linked to the matter-antimatter asymmetry in the Universe.
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Donini, A., Palomares-Ruiz, S., & Salvado, J. (2019). Neutrino tomography of Earth. Nat. Phys., 15(1), 37–40.
Abstract: Cosmic-ray interactions with the atmosphere produce a flux of neutrinos in all directions with energies extending above the TeV scale(1). The Earth is not a fully transparent medium for neutrinos with energies above a few TeV, as the neutrinonucleon cross-section is large enough to make the absorption probability non-negligible(2). Since absorption depends on energy and distance travelled, studying the distribution of the TeV atmospheric neutrinos passing through the Earth offers an opportunity to infer its density profiles(3-7). This has never been done, however, due to the lack of relevant data. Here we perform a neutrino-based tomography of the Earth using actual data-one-year of through-going muon atmospheric neutrino data collected by the IceCube telescope(8). Using only weak interactions, in a way that is completely independent of gravitational measurements, we are able to determine the mass of the Earth and its core, its moment of inertia, and to establish that the core is denser than the mantle. Our results demonstrate the feasibility of this approach to study the Earth's internal structure, which is complementary to traditional geophysics methods. Neutrino tomography could become more competitive as soon as more statistics is available, provided that the sources of systematic uncertainties are fully under control.
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Driencourt-Mangin, F., Rodrigo, G., Sborlini, G. F. R., & Torres Bobadilla, W. J. (2019). Universal four-dimensional representation of H -> gamma gamma at two loops through the Loop-Tree Duality. J. High Energy Phys., 02(2), 143–39pp.
Abstract: We extend useful properties of the H unintegrated dual amplitudes from one- to two-loop level, using the Loop-Tree Duality formalism. In particular, we show that the universality of the functional form regardless of the nature of the internal particle still holds at this order. We also present an algorithmic way to renormalise two-loop amplitudes, by locally cancelling the ultraviolet singularities at integrand level, thus allowing a full four-dimensional numerical implementation of the method. Our results are compared with analytic expressions already available in the literature, finding a perfect numerical agreement. The success of this computation plays a crucial role for the development of a fully local four-dimensional framework to compute physical observables at Next-to-Next-to Leading order and beyond.
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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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Durieux, G., Irles, A., Miralles, V., Peñuelas, A., Perello, M., Poschl, R., et al. (2019). The electro-weak couplings of the top and bottom quarks – Global fit and future prospects. J. High Energy Phys., 12(12), 098–44pp.
Abstract: We evaluate the implications of LHC and LEP/SLC measurements for the electro-weak couplings of the top and bottom quarks. We derive global bounds on the Wilson coefficients of ten two-fermion operators in an effective field theory description. The combination of hadron collider data with Z -pole measurements is found to yield tight limits on the operator coefficients that modify the left-handed couplings of the bottom and top quark to the Z boson. We also present projections for the high-luminosity phase of the LHC and for future electron-positron colliders. The bounds on the operator coefficients are expected to improve substantially during the remaining LHC programme, by factors of 1 to 5 if systematic uncertainties are scaled as statistical ones. The operation of an e(+)e(-) collider at a center-of-mass energy above the top-quark pair production threshold is expected to further improve the bounds by one to two orders of magnitude. The combination of measurements in pp and e(+)e(-) collisions allows for a percent-level determination of the top-quark Yukawa coupling, that is robust in a global fit.
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Ellis, J., Konoplich, R., Mavromatos, N. E., Nguyen, L., Sakharov, A. S., & Sarkisyan-Grinbaum, E. K. (2019). Robust constraint on Lorentz violation using Fermi-LAT gamma-ray burst data. Phys. Rev. D, 99(8), 083009–22pp.
Abstract: Models of quantum gravity suggest that the vacuum should be regarded as a medium with quantum structure that may have nontrivial effects on photon propagation, including the violation of Lorentz invariance. Fermi Large Area Telescope (LAT) observations of gamma-ray bursts (GRBs) are sensitive probes of Lorentz invariance, via studies of energy-dependent timing shifts in their rapidly varying photon emissions. We analyze the Fermi-LAT measurements of high-energy gamma rays from GRBs with known redshifts, allowing for the possibility of energy-dependent variations in emission times at the sources as well as a possible nontrivial refractive index in vacuo for photons. We use statistical estimators based on the irregularity, kurtosis, and skewness of bursts that are relatively bright in the 100 MeV to multi-GeV energy band to constrain possible dispersion effects during propagation. We find that the energy scale characterizing a linear energy dependence of the refractive index should exceed a few x10(17) GeV, and we estimate the sensitivity attainable with additional future sources to be detected by Fermi-LAT.
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Ellis, J., Mavromatos, N. E., Sakharov, A. S., & Sarkisyan-Grinbaum, E. K. (2019). Limits on neutrino Lorentz violation from multimessenger observations of TXS 0506+056. Phys. Lett. B, 789, 352–355.
Abstract: The observation by the IceCube Collaboration of a high-energy (E greater than or similar to 200 TeV) neutrino from the direction of the blazar TXS 0506+056 and the coincident observations of enhanced gamma-ray emissions from the same object by MAGIC and other experiments can be used to set stringent constraints on Lorentz violation in the propagation of neutrinos that is linear in the neutrino energy: Delta v = -E/M-1, where Delta v is the deviation from the velocity of light, and M-1 is an unknown high energy scale to be constrained by experiment. Allowing for a difference in neutrino and photon propagation times of similar to 10 days, we find that M-1 greater than or similar to 3 x 10(16) GeV. This improves on previous limits on linear Lorentz violation in neutrino propagation by many orders of magnitude, and the same is true for quadratic Lorentz violation.
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Elor, G., Escudero, M., & Nelson, A. E. (2019). Baryogenesis and dark matter from B mesons. Phys. Rev. D, 99(3), 035031–18pp.
Abstract: We present a new mechanism of baryogenesis and dark matter production in which both the dark matter relic abundance and the baryon asymmetry arise from neutral B meson oscillations and subsequent decays. This setup is testable at hadron colliders and B factories. In the early universe, decays of a long lived particle produce B mesons and antimesons out of thermal equilibrium. These mesons/antimesons then undergo CP violating oscillations before quickly decaying into visible and dark sector particles. Dark matter will be charged under the baryon number so that the visible sector baryon asymmetry is produced without violating the total baryon number of the Universe. The produced baryon asymmetry will be directly related to the leptonic charge asymmetry in neutral B decays: an experimental observable. Dark matter is stabilized by an unbroken discrete symmetry, and proton decay is simply evaded by kinematics. We will illustrate this mechanism with a model that is unconstrained by dinucleon decay, does not require a high reheat temperature, and would have unique experimental signals-a positive leptonic asymmetry in B meson decays, a new decay of B mesons into a baryon and missing energy, and a new decay of b-flavored baryons into mesons and missing energy. These three observables are testable at current and upcoming collider experiments, allowing for a distinct probe of this mechanism.
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Escudero, M., Hooper, D., Krnjaic, G., & Pierre, M. (2019). Cosmology with a very light Lmu – Ltau gauge boson. J. High Energy Phys., 03(3), 071–29pp.
Abstract: In this paper, we explore in detail the cosmological implications of an abelian L – L gauge extension of the Standard Model featuring a light and weakly coupled Z. Such a scenario is motivated by the longstanding approximate to 4 sigma discrepancy between the measured and predicted values of the muon's anomalous magnetic moment, (g – 2), as well as the tension between late and early time determinations of the Hubble constant. If sufficiently light, the Z population will decay to neutrinos, increasing the overall energy density of radiation and altering the expansion history of the early universe. We identify two distinct regions of parameter space in this model in which the Hubble tension can be significantly relaxed. The first of these is the previously identified region in which a approximate to 10 – 20 MeV Z reaches equilibrium in the early universe and then decays, heating the neutrino population and delaying the process of neutrino decoupling. For a coupling of g (-) similar or equal to (3 – 8) x 10(-4), such a particle can also explain the observed (g – 2) anomaly. In the second region, the Z is very light (mZ approximate to 1eV to MeV) and very weakly coupled (g (-) approximate to 10(-13) to 10(-9)). In this case, the Z population is produced through freeze-in, and decays to neutrinos after neutrino decoupling. Across large regions of parameter space, we predict a contribution to the energy density of radiation that can appreciably relax the reported Hubble tension, N-eff similar or equal to 0.2.
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