B. Vlček

Very recently, the IceCube Collaboration reported a flux of neutrinos in the energy range $50\text{ }\text{ }\mathrm{TeV}\ensuremath{\lesssim}{E}_{\ensuremath{\nu}}\ensuremath{\lesssim}2\text{ }\text{ }\mathrm{PeV}$, which departs from expectations from atmospheric background at the $5.7\ensuremath{\sigma}$ level. This flux is in remarkable agreement with the expected diffuse flux of neutrinos from starburst galaxies, and the three highest energy events have uncertainty contours encompassing some of such systems. These events, all of which have well-measured energies above 1 PeV, exhibit shower topologies, for which the angular resolution is about 15\ifmmode^\circ\else\textdegree\fi{}. Due to this angular uncertainty and the a posteriori nature of cuts used in our study, it is not possible to assign a robust statistical significance to this association. Using muon tracks, which have angular resolution $<1\ifmmode^\circ\else\textdegree\fi{}$, we compute the number of observations required to make a statistically significant statement and show that in a few years of operation the upgraded IceCube detector should be able to confirm or refute this hypothesis. We also note that double bang topology rates constitute a possible discriminator among various astrophysical sources.

The Fermi Gamma-ray Space Telescope discovered two $\ensuremath{\gamma}$-ray emitting bubble-shaped structures that extend nearly symmetrically on either side of our Galaxy and appear morphologically connected to the Galactic center. The origin of the emission is still not entirely clear. It was recently shown that the spectral shape of the emission from the Fermi bubbles is well described by an approximately 50 GeV dark matter particle annihilating to $b\overline{b}$, with a normalization corresponding to a velocity average annihilation cross section $⟨{\ensuremath{\sigma}}_{b}v⟩\ensuremath{\approx}8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}27}\text{ }\text{ }{\mathrm{cm}}^{3}/\mathrm{s}$. We study the minimal hidden sector recently introduced by Weinberg and examine to what extent its weakly interacting massive particles are capable of accommodating both the desired effective annihilation rate into quarks and the observed dark matter density.

Motivated by recent IceCube observations we reexamine the idea that microquasars are high energy neutrino emitters. By stretching to the maximum the parameters of the Fermi engine we show that the nearby high-mass x-ray binary LS 5039 could accelerate protons up to above about 20 PeV. These highly relativistic protons could subsequently interact with the plasma producing neutrinos up to the maximum observed energies. After that we adopt the spatial density distribution of high-mass x-ray binaries obtained from the deep INTEGRAL Galactic plane survey, and we assume LS 5039 typifies the microquasar population to demonstrate that these powerful compact sources could provide a dominant contribution to the diffuse neutrino flux recently observed by IceCube.

We discuss the phenomenology and cosmology of a Standardlike Model inspired by string theory, in which the gauge fields are localized on D-branes wrapping certain compact cycles on an underlying geometry, whose intersection can give rise to chiral fermions. The energy scale associated with string physics is assumed to be near the Planck mass. To develop our program in the simplest way, we work within the construct of a minimal model with gauge-extended sector $U(3{)}_{B}\ifmmode\times\else\texttimes\fi{}Sp(1{)}_{L}\ifmmode\times\else\texttimes\fi{}U(1{)}_{{I}_{R}}\ifmmode\times\else\texttimes\fi{}U(1{)}_{L}$. The resulting $U(1)$ content gauges the baryon number $B$, the lepton number $L$, and a third additional Abelian charge ${I}_{R}$ which acts as the third isospin component of an $SU(2{)}_{R}$. All mixing angles and gauge couplings are fixed by rotation of the $U(1)$ gauge fields to a basis diagonal in hypercharge $Y$ and in an anomaly-free linear combination of ${I}_{R}$ and $B\ensuremath{-}L$. The anomalous ${Z}^{\ensuremath{'}}$ gauge boson obtains a string scale St\"uckelberg mass via a 4D version of the Green-Schwarz mechanism. To keep the realization of the Higgs mechanism minimal, we add an extra $SU(2)$ singlet complex scalar, which acquires a VEV and gives a TeV-scale mass to the nonanomalous gauge boson ${Z}^{\ensuremath{'}\ensuremath{'}}$. The model is fully predictive and can be confronted with dijet and dilepton data from LHC8 and, eventually, LHC14. We show that ${M}_{{Z}^{\ensuremath{'}\ensuremath{'}}}\ensuremath{\approx}3--4\text{ }\text{ }\mathrm{TeV}$ saturates current limits from the CMS and ATLAS Collaborations. We also show that for ${M}_{{Z}^{\ensuremath{'}\ensuremath{'}}}\ensuremath{\lesssim}5\text{ }\text{ }\mathrm{TeV}$, LHC14 will reach discovery sensitivity $\ensuremath{\gtrsim}5\ensuremath{\sigma}$. After that, we demonstrate in all generality that ${Z}^{\ensuremath{'}\ensuremath{'}}$ milliweak interactions could play an important role in observational cosmology. Finally, we examine some phenomenological aspects of the supersymmetric extension of the D-brane construct.

We discuss a number of experimental constraints on Weinberg's Higgs portal model. In this framework, the standard model (SM) particle spectrum is extended to include one complex scalar field $S$ and one Dirac fermion $\ensuremath{\psi}$. These new fields are singlets under the SM gauge group and are charged under a global $U(1)$ symmetry. Breaking of this $U(1)$ symmetry results in a massless Goldstone boson $\ensuremath{\alpha}$ and a massive $CP$-even scalar $r$ and splits the Dirac fermion into two new mass-eigenstates ${\ensuremath{\psi}}_{\ifmmode\pm\else\textpm\fi{}}$, corresponding to Majorana fermions. The interest on such a minimal SM extension is twofold. On the one hand, if the Goldstone bosons are in thermal equilibrium with SM particles until the era of muon annihilation, their contribution to the effective number of neutrino species can explain the hints from cosmological observations of extra relativistic degrees of freedom at the epoch of last scattering. On the other hand, the lightest Majorana fermion ${\ensuremath{\psi}}_{\ensuremath{-}}$ provides a plausible dark matter candidate. Mixing of $r$ with the Higgs doublet $\ensuremath{\phi}$ is characterized by the mass of hidden scalar ${m}_{h}$ and the mixing angle $\ensuremath{\theta}$. We constrain this parameter space using a variety of experimental data, including heavy meson decays with missing energy, the invisible Higgs width, and direct dark matter searches. We show that different experimental results compress the allowed parameter space in complementary ways, covering a large range of ${\ensuremath{\psi}}_{\ensuremath{-}}$ masses ($5\ensuremath{\lesssim}{m}_{\ensuremath{-}}\ensuremath{\lesssim}100\text{ }\text{ }\mathrm{GeV}$). Though current results narrow the parameter space significantly (for the mass range of interest, $\ensuremath{\theta}\ensuremath{\lesssim}{10}^{\ensuremath{-}3}$ to ${10}^{\ensuremath{-}4}$), there is still room for discovery ($\ensuremath{\alpha}$ decoupling at the muon annihilation era requires $\ensuremath{\theta}\ensuremath{\gtrsim}{10}^{\ensuremath{-}5}$ to ${10}^{\ensuremath{-}4}$). In the near future, measurements from ATLAS, CMS, LHCb, NA62, XENON1T, LUX, and CDMSlite will probe nearly the full parameter space.