|
|
NA48/2 Collaboration(Batley, J. R. et al), & Fiorini, L. (2019). First observation and study of the K-+/- -> pi(+/-)pi(0)e(+)e(-) decay. Phys. Lett. B, 788, 552–561.
Abstract: The NA48/2 experiment at CERN reports the first observation of the K-+/- -> pi(+/-)pi(0)e(+)e(-) decay from an exposure of 1.7 x 10(11) charged kaon decays recorded in 2003-2004. A sample of 4919 candidates with 4.9% background contamination allows the determination of the branching ratio in the full kinematic region, BR(K-+/- -> pi(+/-)pi(0)e(+)e(-)) = (4.24 +/- 0.14) x 10(-6). The study of the kinematic space shows evidence for a structure dependent contribution in agreement with predictions based on chiral perturbation theory. Several P- and CP-violating asymmetries are also evaluated.
|
|
|
|
ANTARES, I. C., LIGO and Virgo Collaborations(Albert, A. et al), Barrios-Marti, J., Coleiro, A., Colomer, M., Hernandez-Rey, J. J., Illuminati, G., et al. (2019). Search for Multimessenger Sources of Gravitational Waves and High-energy Neutrinos with Advanced LIGO during Its First Observing Run, ANTARES, and IceCube. Astrophys. J., 870(2), 134–16pp.
Abstract: Astrophysical sources of gravitational waves, such as binary neutron star and black hole mergers or core-collapse supernovae, can drive relativistic outflows, giving rise to non-thermal high-energy emission. High-energy neutrinos are signatures of such outflows. The detection of gravitational waves and high-energy neutrinos from common sources could help establish the connection between the dynamics of the progenitor and the properties of the outflow. We searched for associated emission of gravitational waves and high-energy neutrinos from astrophysical transients with minimal assumptions using data from Advanced LIGO from its first observing run O1, and data from the ANTARES and IceCube neutrino observatories from the same time period. We focused on candidate events whose astrophysical origins could not be determined from a single messenger. We found no significant coincident candidate, which we used to constrain the rate density of astrophysical sources dependent on their gravitational-wave and neutrino emission processes.
|
|
|
|
Bordes, J., Hong-Mo, C., & Tsun, T. S. (2018). Generation patterns, modified gamma – Z mixing, and hidden sector with dark matter candidates as framed standard model results. Int. J. Mod. Phys. A, 33(36), 1830034–23pp.
Abstract: A descriptive summary is given of the results to-date from the framed standard model (FSM) which: Assigns geometric meaning to the Higgs field and to fermion generations, hence offering an explanation for the observed mass and mixing patterns of quarks and leptons, reproducing near-quantitatively 17 of SM parameters with only 7. Predicts a new vector boson G which mixes with gamma and Z, leading to deviations from the SM mixing scheme. For m(G) > 1 TeV, these deviations are within present experimental errors but should soon be detectable at LHC when experimental accuracy is further improved. Suggests the existence of a hidden sector of particles as yet unknown to experiment which interact but little with the known particles. The lowest members of the hidden sector of mass around 17 MeV, being electrically neutral and stable, may figure as dark matter constituents. The idea is to retrace the steps leading to the above results unencumbered by details already worked out and reported elsewhere. This has helped to clarify the logic, tighten some arguments and dispense with one major assumption previously thought necessary, thus strengthening earlier results in opening up possibly a new and exciting vista for further exploration.
|
|
|
|
Lopez-Honorez, L., Mena, O., & Villanueva-Domingo, P. (2019). Dark matter microphysics and 21 cm observations. Phys. Rev. D, 99(2), 023522–12pp.
Abstract: Dark matter interactions with massless or very light standard model particles, as photons or neutrinos, may lead to a suppression of the matter power spectrum at small scales and of the number of low mass haloes. Bounds on the dark matter scattering cross section with light degrees of freedom in such interacting dark matter (IDM) scenarios have been obtained from e.g., early time cosmic microwave background physics and large scale structure observations. Here we scrutinize dark matter microphysics in light of the claimed 21 cm EDGES 78 MHz absorption signal. IDM is expected to delay the 21 cm absorption features due to collisional damping effects. We identify the astrophysical conditions under which the existing constraints on the dark matter scattering cross section could be largely improved due to the IDM imprint on the 21 cm signal, providing also an explicit comparison to the WDM scenario.
|
|
|
|
Husek, T., Goudzovski, E., & Icampf, K. (2019). Precise Determination of the Branching Ratio of the Neutral-Pion Dalitz Decay. Phys. Rev. Lett., 122(2), 022003–6pp.
Abstract: We provide a new value for the ratio R = Gamma(pi(0) -> e(+)e(-)gamma(gamma))/Gamma(pi(0) -> gamma gamma) = 11.978(6) x 10(-3), which is by 2 orders of magnitude more precise than the current Particle Data Group average. It is obtained using the complete set of the next-to-leading-order radiative corrections in the QED sector, and incorporates up-to-date values of the pi(0)-transition-form-factor slope. The ratio R translates into the branching ratios of the two main pi(0) decay modes: B(pi(0) -> gamma gamma) = 98.8131(6)% and B(pi(0) -> e(+)e(-)gamma(gamma)) = 1.1836(6)%.
|
|
