We investigate the scenario where the standard model is extended with classical scale invariance, which is broken by chiral symmetry breaking and confinement in a new strongly coupled gauge theory that resembles QCD. The standard model Higgs field emerges as a result of the mixing of a scalar meson in the new strong dynamics and a massless elementary scalar field. The mass and scalar decay constant of that scalar meson, which are generated dynamically in the new gauge theory, give rise to the Higgs field mass term, automatically possessing the correct negative sign by the bosonic seesaw mechanism. Using analogy with QCD, we evaluate the dynamical scale of the new gauge theory and further make quantitative predictions for light pseudo-Nambu-Goldstone bosons associated with the spontaneous breaking of axial symmetry along chiral symmetry breaking in the new gauge theory. A prominent consequence of the scenario is that there should be a standard model gauge singlet pseudo-Nambu-Goldstone boson with mass below 220 GeV, which couples to two electroweak gauge bosons through the Wess-Zumino-Witten term, whose strength is thus determined by the dynamical scale of the new gauge theory. Other pseudo-Nambu-Goldstone bosons, charged under the electroweak gauge groups, also appear. Concerning the theoretical aspects, it is shown that the scalar quartic coupling can vanish at the Planck scale with the top quark pole mass as large as 172.5 GeV, realizing the flatland scenario without being in tension with the current experimental data.

We present a novel extension of the Standard Model which fulfills the multiple-point principle without contradicting the Higgs particle mass measurement. In the model, the scalar potential has two minima where the scalar field has vacuum expectation values of 246 GeV and the Planck mass $\simeq 2.44\times 10^{18}\mathrm{GeV}$, the latter of which is realized by considering a classically scale invariant setup and requiring that the scalar quartic coupling and its beta function vanish at the Planck scale. The Standard Model (SM) Higgs field is a mixture of an elementary scalar and composite scalars in a new strongly coupled gauge theory, and the strong dynamics gives rise to the negative mass for the SM Higgs field, and at the same time causes separation of the SM Higgs quartic coupling and the quartic coupling for the elementary scalar, which leads to the vanishing of the latter quartic coupling and its beta function at the Planck scale. The model predicts new scalar particles with about 300 GeV mass possessing electroweak charges and Yukawa-type couplings with Standard Model fermions, and a new light gauge boson that couples to Standard Model fermions.

This article reports on the detailed study of the three-gluon vertex in four-dimensional $SU(3)$ Yang-Mills theory employing lattice simulations with large physical volumes and high statistics. A meticulous scrutiny of the so-called symmetric and asymmetric kinematical configurations is performed, and it is shown that the associated form factor changes sign at a given range of momenta. The lattice results are compared to the model-independent predictions of Schwinger-Dyson equations, and a very good agreement between the two is found.

We report a calculation of the nucleon axial form factors $G_A^q(Q^2)$ and $G_P^q(Q^2)$ for all three light quark flavors $q\in \{u,d,s\}$ in the range $0\le Q^2\lesssim 1.2{\mathrm{GeV}}^2$ using lattice QCD. This work was done using a single ensemble with pion mass 317 MeV and made use of the hierarchical probing technique to efficiently evaluate the required disconnected loops. We perform nonperturbative renormalization of the axial current, including a nonperturbative treatment of the mixing between light and strange currents due to the singlet-nonsinglet difference caused by the axial anomaly. The form factor shapes are fit using the model-independent $z$ expansion. From $G_A^q(Q^2)$, we determine the quark contributions to the nucleon spin and axial radii. By extrapolating the isovector $G_P^{u-d}(Q^2)$, we obtain the induced pseudoscalar coupling relevant for ordinary muon capture and the pion-nucleon coupling constant. We find that the disconnected contributions to $G_P$ form factors are large, and give an interpretation based on the dominant influence of the pseudoscalar poles in these form factors.

Recently, LHCb reported the discovery of five extremely narrow excited ${\mathrm{\Omega }}_c$ baryons decaying into ${\mathrm{\Xi }}_c^{+}{K}^{-}$. We interpret these baryons as bound states of a $c$ quark and a $P$-wave $ss$ diquark. For such a system, there are exactly five possible combinations of spin and orbital angular momentum. The narrowness of the states could be a signal that it is hard to pull apart the two $s$ quarks in a diquark. We predict two of spin $1/2$, two of spin $3/2$, and one of spin $5/2$, all with negative parity. Of the five states, two can decay in $S$-wave, and three can decay in $D$-wave. Some of the $D$-wave states might be narrower than the $S$-wave states. We discuss the relations among the five masses expected in the quark model and the likely spin assignments, and we compare them with the data. A similar pattern is expected for negative-parity excited ${\mathrm{\Omega }}_b$ states. An alternative interpretation is noted in which the heaviest two states are $2S$ excitations with $J^P=1/2^{+}$ and $3/2^{+}$, while the lightest three are those with $J^P=3/2^{-}$, $3/2^{-}$, $5/2^{-}$, expected to decay via $D$-waves. In this case, we expect $J^P=1/2^{-}$ ${\mathrm{\Omega }}_c$ states around 2904 and 2978 MeV.

A scale-invariant chiral effective Lagrangian is constructed for octet pions and a dilaton figuring, as Nambu-Goldstone bosons, with vector mesons incorporated as hidden gauge fields. The Lagrangian is built to the next-to-leading order in chiral-scale counting without baryon fields and then to leading order including baryons. The resulting theory is hidden scale symmetric and local symmetric. We also discuss some possible applications of the present Lagrangian.

We study the problem of a four-dimensional brane lying in the five-dimensional degenerate Schwarzschild–de Sitter (Nariai) black hole in five-dimensional $F(R)$ gravity. We show that there cannot exist the brane in the Nariai bulk space except for the case where the brane tension vanishes. We demonstrate that the five-dimensional Nariai bulk is unstable in a large region of the parameter space. In particular, the Nariai bulk can have classical (anti)evaporation instabilities. The bulk instability backreacts on the four-dimensional brane, in that case, the brane tension vanishes, and the unstable modes propagate in their world volume.

Modeling the nonlinearity of the halo bispectrum remains a major challenge in modern cosmology, in particular for ongoing and upcoming large-scale structure observations that are performed to study the inflationary physics. The “power spectrum response” offers a solution for the bispectrum in the so-called squeezed limit, in which one wave number is much smaller than the other two. As a first step, we demonstrate that the halo squeezed-limit bispectrum computed from the second-order standard perturbation theory agrees precisely with the responses of linear halo power spectrum to large-scale density and potential fluctuations. Since the halo power spectrum responses to arbitrarily small scales can straightforwardly be obtained by separate universe simulations, the response approach provides a novel and powerful technique for modeling the nonlinear halo squeezed-limit bispectrum.

What are the fundamental limitations of reconstructing the properties of dark energy, given cosmological observations in the quasilinear regime in a range of redshifts, to be as precise as required? The aim of this paper is to address this question by constructing model-independent observables, while completely ignoring practical problems of real-world observations. Non-Gaussianities already present in the initial conditions are not directly accessible from observations because of a perfect degeneracy with the non-Gaussianities arising from the (weakly) nonlinear matter evolution in generalized dark energy models. By imposing a specific set of evolution equations that should cover a range of dark energy cosmologies, we find, however, a constraint equation for the linear structure growth rate $f_1$ expressed in terms of model-independent observables. Entire classes of dark energy models which do not satisfy this constraint equation could be ruled out, and for models satisfying it, we could reconstruct e.g. the nonlocal bias parameters $b_1$ and $b_2$.

We use the most recent type Ia supernovae (SNe Ia) observations to perform a statistical comparison between the standard $\mathrm{\Lambda }\mathrm{CDM}$ model and its extensions [$w\mathrm{CDM}$ and $w(z)\mathrm{CDM}$] and some alternative cosmologies: namely, the Dvali-Gabadadze-Porrati (DGP) model, a power-law $f(R)$ scenario in the metric formalism and an example of vacuum decay [$\mathrm{\Lambda }(t)\mathrm{CDM}$] cosmology in which the dilution of pressureless matter is attenuated with respect to the usual $a^{-3}$ scaling due to the interaction of the dark matter and dark energy fields. We perform a Bayesian model selection analysis using the MultiNest algorithm. To obtain the posterior distribution for the parameters of each model, we use the joint light-curve analysis (JLA) SNe Ia compilation containing 740 events in the interval $0.01<z<1.3$ along with current measurements of baryon acoustic oscillations (BAO). The JLA data are analyzed with the SALT2 light-curve fitter and the model selection is then performed by computing the Bayesian evidence of each model and the Bayes factor of the $\mathrm{\Lambda }\mathrm{CDM}$ cosmology related to the other models. The results indicate that the JLA data alone are unable to distinguish the standard $\mathrm{\Lambda }\mathrm{CDM}$ model from some of its alternatives but its combination with current measurements of baryon acoustic oscillations shows up an ability to distinguish them. In particular, the DGP model is practically not supported by both the BAO and the joint $\mathrm{JLA}+\mathrm{BAO}$ data sets compared to the standard scenario. Finally, we provide a rank order for the models considered.

Recently, a new measurement of the auto- and cross-correlation angular power spectrum (APS) of the isotropic gamma-ray background was performed, based on 81 months of data of the Fermi Large-Area Telescope (LAT). Here, we fit, for the first time, the new APS data with a model describing the emission of unresolved blazars. These sources are expected to dominate the anisotropy signal. The model we employ in our analysis reproduces well the blazars resolved by Fermi LAT. When considering the APS obtained by masking the sources listed in the 3FGL catalog, we find that unresolved blazars underproduce the measured APS below $\sim 1\mathrm{GeV}$. Contrary to past results, this suggests the presence of a new contribution to the low-energy APS, with a significance of, at least, $5\sigma$. The excess can be ascribed to a new class of faint gamma-ray emitters. If we consider the APS obtained by masking the sources in the 2FGL catalog, there is no underproduction of the APS below 1 GeV, but the new source class is still preferred over the blazars-only scenario (with a significance larger than $10\sigma$). The properties of the new source class and the level of anisotropies induced in the isotropic gamma-ray background are the same, independent of the APS data used. In particular, the new gamma-ray emitters must have a soft energy spectrum, with a spectral index ranging, approximately, from 2.7 to 3.2. This complicates their interpretation in terms of known sources, since, normally, star-forming and radio galaxies are observed with a harder spectrum. The new source class identified here is also expected to contribute significantly to the intensity of the isotropic gamma-ray background.

We present a method to classify initial conditions of a long gamma ray bursts model sourced by a single relativistic shock. It is based on the use of artificial neural networks (ANNs) that are trained with light curves (LC) generated with radiation relativistic hydrodynamics simulations. The model we use consists in a single shock with a highly relativistic injected beam into a stratified surrounding medium with profile $1/r^2$. In the process we only consider the bremsstrahlung radiation and Thomson scattering process. The initial conditions we use to train the ANN are three: the rest mass density, Lorentz factor and radiation energy density of the beam that produces the relativistic shock, together with the LC generated during the process. The classification selects the location of a box in the 3d parameter space that better fits a given LC, and in order to decrease the uncertainty of the parameters this box is refined and the classification selects a new box of smaller size.

We write down a theory for non-Abelian superfluids with a partially broken (semisimple) Lie group. We adapt the off-shell formalism of hydrodynamics to superfluids and use it to comment on the superfluid transport compatible with the second law of thermodynamics. We find that the second law can be also used to derive the Josephson equation, which governs dynamics of the Goldstone modes. In the course of our analysis, we derive an alternate and mutually distinct parametrization of the recently proposed classification of hydrodynamic transport and generalize it to superfluids.

Recently, some singly bottom baryons have been established experimentally, but none of the doubly or triply bottom baryons have been observed. Under the Regge phenomenology, the mass of an unobserved ground-state doubly or triply bottom baryon is expressed as a function of masses of the well-established light baryons and singly bottom baryons. Then, the values of Regge slopes and Regge intercepts for baryons containing one, two, or three bottom quarks are calculated. After that, the masses of the orbitally excited singly, doubly, and triply bottom baryons are estimated. Our predictions may be useful for the discovery of these baryons and their $J^P$ assignments.

We examine the parameter space of the two-Higgs-doublet model of type II after imposing the relevant theoretical and experimental constraints from the precision electroweak data, $B$-meson decays, and the LHC run I and run II data. We find that the searches for Higgs bosons via the ${\tau }^{+}{\tau }^{-}$, $WW$, $ZZ$, $\gamma \gamma$, $hh$, $hZ$, $HZ$, and $AZ$ channels can give strong constraints on the $CP$-odd Higgs $A$ and heavy $CP$-even Higgs $H$, and the parameter space excluded by each channel is respectively carved out in detail assuming that either $m_A$ or $m_H$ are fixed to 600 or 700 GeV in the scans. The surviving samples are discussed in two different regions. (i) In the standard model–like coupling region of the 125 GeV Higgs, $m_A$ is allowed to be as low as 350 GeV, and a strong upper limit is imposed on $\tan \beta$. $m_H$ is allowed to be as low as 200 GeV for the appropriate values of $\tan \beta$, $\sin (\beta -\alpha )$, and $m_A$, but is required to be larger than 300 GeV for $m_A=700\mathrm{GeV}$. (ii) In the wrong-sign Yukawa coupling region of the 125 GeV Higgs, the $b\overline{b}\to A/H\to {\tau }^{+}{\tau }^{-}$ channel can impose the upper limits on $\tan \beta$ and $\sin (\beta -\alpha )$, and the $A\to hZ$ channel can give the lower limits on $\tan \beta$ and $\sin (\beta -\alpha )$. $m_A$ and $m_H$ are allowed to be as low as 60 and 200 GeV, respectively, but $320\mathrm{GeV}<m_A<500\mathrm{GeV}$ is excluded for $m_H=700\mathrm{GeV}$.

We use the LHC Higgs data to derive updated constraints on electroweak-scale sterile neutrinos that naturally occur in many low-scale seesaw extensions of the Standard Model to explain the neutrino masses. We also analyze the signal sensitivity for a new final state involving a single charged lepton and two jets with missing energy, which arises from the decay of sterile neutrinos produced through the Higgs and $W$, $Z$ boson mediated processes at the LHC. Future prospects of these sterile neutrino signals in precision Higgs measurements, as well as at a future 100 TeV collider, are also discussed.

We present an effective description of a spin two massive state and a pseudo-Nambu-Goldstone boson Higgs in a two site model. Using this framework, we model the spin-two state as a massive graviton and we study its phenomenology at the LHC. We find that a reduced set of parameters can describe the most important features of this scenario. We address the question of which channel is the most sensitive to detect this graviton. Instead of designing search strategies to estimate the significance in each channel, we compare the ratio of our theoretical predictions to the limits set by available experimental searches for all the decay channels and as a function of the free parameters in the model. We discuss the phenomenological details contained in the outcome of this simple procedure. The results indicate that, for the studied masses between 0.5 and 3 TeV, the channels to look for such a graviton resonance are mainly $ZZ$, $WW$, and $\gamma \gamma$. This is the case even though top and bottom quarks dominate the branching ratios, since their experimental sensitivity is not as good as the one of the electroweak gauge bosons. We find that as the graviton mass increases, the $ZZ$ and $WW$ channels become more important because of its relatively better enhancement over background, mainly due to fat jet techniques. We determine the region of the parameter space that has already been excluded and the reach for the LHC next stages. We also estimate the size of the loop-induced contributions to the production and decay of the graviton, and show in which region of the parameter space their effects are relevant for our analysis.

The observed deep inelastic nucleon spin asymmetries $A_1^{p,n}$ and the spin dependent quark distributions break SU(6) spin-flavor symmetry. In quark models two mechanisms for breaking SU(6) symmetry are well known: the hyperfine interaction and the pion cloud of the nucleon. I re-evaluate these mechanisms and show how the breaking of SU(6) in each case affects spin dependent valence quark distributions of the proton. In particular I investigate the properties of these mechanisms in the kinematic region $0.3<x<0.7$ and attempt to test these against known data. Both mechanisms are able to explain the quantitative features of the spin asymmetries.

We determine the flavor dependence of the renormalization-group-invariant running interaction through judicious use of both unquenched Dyson-Schwinger equation and lattice results for QCD’s gauge-sector two-point functions. An important step is the introduction of a physical scale setting procedure that enables a realistic expression of the effect of different numbers of active quark flavours on the interaction. Using this running interaction in concert with a well constrained class of dressed–gluon-quark vertices, we estimate the critical number of active lighter-quarks above which dynamical chiral symmetry breaking becomes impossible: $n_f^{\mathrm{cr}}\approx 9$; and hence in whose neighborhood QCD is plausibly a conformal theory.