We present the results from an all-sky search for short-duration gravitational waves in the data of the first run of the Advanced LIGO detectors between September 2015 and January 2016. The search algorithms use minimal assumptions on the signal morphology, so they are sensitive to a wide range of sources emitting gravitational waves. The analyses target transient signals with duration ranging from milliseconds to seconds over the frequency band of 32 to 4096 Hz. The first observed gravitational-wave event, GW150914, has been detected with high confidence in this search; the other known gravitational-wave event, GW151226, falls below the search’s sensitivity. Besides GW150914, all of the search results are consistent with the expected rate of accidental noise coincidences. Finally, we estimate rate-density limits for a broad range of non-binary-black-hole transient gravitational-wave sources as a function of their gravitational radiation emission energy and their characteristic frequency. These rate-density upper limits are stricter than those previously published by an order of magnitude.

In this work, we present an analysis of the nonleptonic charmonium modes $B_s^0\to J/\psi f_2^{\prime }(1525)$ and $B_s^0\to J/\psi K^{+}{K}^{-}$. Within the framework of the factorization approach and using the perturbative QCD for the evaluation of the relevant form factors, we find a branching fraction for the two-body channel of $\mathrm{BR}(B_s^0\to J/\psi f_2^{\prime }(1525))=({1.6}_{-0.7}^{+0.9})\times {10}^{-4}$ which is in agreement with the experimental values reported by the LHCb and Belle Collaborations. The associated polarization fractions to this vector-tensor mode are also presented. On the other hand, nonresonant and resonant contributions to the three-body decay $B_s^0\to J/\psi K^{+}{K}^{-}$ are carefully investigated. The dominant contributions of the resonances $\varphi (1020)$ and $f_2^{\prime }(1525)$ are properly taken into account. A detailed analysis of the $K^{+}{K}^{-}$ invariant mass distributions and Dalitz plot are also performed. The overall result $\mathrm{BR}(B_s^0\to J/\psi K^{+}{K}^{-})=({9.3}_{-1.1}^{+1.3})\times {10}^{-4}$ is also in satisfactory agreement with the experimental information reported by LHCb and Belle.

We compare four- and five-flavor scheme predictions for $b$-associated production of $Z$ and Higgs bosons. The results are obtained with Sherpa ’s Mc@Nlo implementation for the four-flavor scheme, treating the $b$’s as massive, and with multijet merging at leading and next-to-leading order for the five-flavor schemes. Comparison with data for $Z+b(\overline{b})$ production at the 7 TeV LHC exhibits strengths and weaknesses of the different approaches and is used to validate predictions for $b$-associated Higgs-boson production at the 13 TeV Run II.

We study confining gauge theories with fermions vectorial under the Standard Model (SM) that produce a Higgs doublet as a Nambu-Goldstone boson. The vacuum misalignment required to break the electroweak symmetry is induced by an elementary Higgs doublet with Yukawa couplings to the new fermions. The physical Higgs is a linear combination of elementary and composite Higgses while the SM fermions remain elementary. The full theory is renormalizable and the SM Yukawa couplings are generated from the ones of the elementary Higgs allowing to eliminate all flavor problems but with interesting effects for electric dipole moments of SM particles. We also discuss how ideas on the relaxation of the electroweak scale could be realized within this framework.

We revisit the possibility of a Dirac fermion dark matter candidate in the light of current $b\to s{\ell }^{+}{\ell }^{-}$ anomalies by investigating a minimal extension of the Standard Model with a horizontal ${\mathrm{U}(1)}^{\prime }$ local symmetry. Dark matter stability is protected by a remnant ${\mathcal{Z}}_2$ symmetry arising after spontaneous symmetry breaking of ${\mathrm{U}(1)}^{\prime }$. The associated $Z^{\prime }$ gauge boson can accommodate current hints of new physics in $b\to s{\ell }^{+}{\ell }^{-}$ decays, and acts as a vector portal between dark matter and the visible sector. We find that the model is severely constrained by a combination of precision measurements at flavor factories, LHC searches for dilepton resonances, as well as direct and indirect dark matter searches. Despite this, viable regions of the parameter space accommodating the observed dark matter relic abundance and the $b\to s{\ell }^{+}{\ell }^{-}$ anomalies still persist for dark matter and $Z^{\prime }$ masses in the TeV range.

The $6.8\sigma$ anomaly in excited ${}^8\mathrm{Be}$ nuclear decays via internal pair creation is fit well by a new particle interpretation. In a previous analysis, we showed that a 17 MeV protophobic gauge boson provides a particle physics explanation of the anomaly consistent with all existing constraints. Here we begin with a review of the physics of internal pair creation in ${}^8\mathrm{Be}$ decays and the characteristics of the observed anomaly. To develop its particle interpretation, we provide an effective operator analysis for excited ${}^8\mathrm{Be}$ decays to particles with a variety of spins and parities and show that these considerations exclude simple models with scalar particles. We discuss the required couplings for a gauge boson to give the observed signal, highlighting the significant dependence on the precise mass of the boson and isospin mixing and breaking effects. We present anomaly-free extensions of the Standard Model that contain protophobic gauge bosons with the desired couplings to explain the ${}^8\mathrm{Be}$ anomaly. In the first model, the new force carrier is a ${\mathrm{U}(1)}_B$ gauge boson that kinetically mixes with the photon; in the second model, it is a $\mathrm{U}(1{)}_{B-L}$ gauge boson with a similar kinetic mixing. In both cases, the models predict relatively large charged lepton couplings $\sim 0.001$ that can resolve the discrepancy in the muon anomalous magnetic moment and are amenable to many experimental probes. The models also contain vectorlike leptons at the weak scale that may be accessible to near future LHC searches.

We revisit the possibility of generating a nonzero reactor mixing angle in a scenario where there is a sterile neutrino at the eV scale apart from the usual three sub-eV scale active neutrinos. We show that the $3\times 3$ active neutrino mass matrix can possess a $\mu -\tau$ symmetry and can still be consistent with the nonzero value of the reactor mixing angle ${\theta }_{13}$ if this $\mu -\tau$ symmetry is broken in the sterile neutrino sector. We first propose a simple model based on the discrete flavor symmetry $A_4\times Z_3\times Z_3^{\prime }$ to realize such a scenario and then numerically evaluate the complete $3+1$ neutrino parameter space that allows such a possibility. We show that the possibility of generating a nonzero ${\theta }_{13}$ can, in general, remain valid even if the present $3+1$ neutrino global fit data get ruled out by future experiments. We also discuss the possible implications at neutrinoless double beta decay $(0\nu \beta \beta )$ experiments in view of the latest results from the KamLAND-Zen experiment.

In this work we explore the applicability of a special gluon mass generating mechanism in the context of the linear covariant gauges. In particular, the implementation of the Schwinger mechanism in pure Yang-Mills theories hinges crucially on the inclusion of massless bound-state excitations in the fundamental nonperturbative vertices of the theory. The dynamical formation of such excitations is controlled by a homogeneous linear Bethe-Salpeter equation, whose nontrivial solutions have been studied only in the Landau gauge. Here, the form of this integral equation is derived for general values of the gauge-fixing parameter, under a number of simplifying assumptions that reduce the degree of technical complexity. The kernel of this equation consists of fully dressed gluon propagators, for which recent lattice data are used as input, and of three-gluon vertices dressed by a single form factor, which is modeled by means of certain physically motivated Ansätze. The gauge-dependent terms contributing to this kernel impose considerable restrictions on the infrared behavior of the vertex form factor; specifically, only infrared finite Ansätze are compatible with the existence of nontrivial solutions. When such Ansätze are employed, the numerical study of the integral equation reveals a continuity in the type of solutions as one varies the gauge-fixing parameter, indicating a smooth departure from the Landau gauge. Instead, the logarithmically divergent form factor displaying the characteristic “zero crossing,” while perfectly consistent in the Landau gauge, has to undergo a dramatic qualitative transformation away from it, in order to yield acceptable solutions. The possible implications of these results are briefly discussed.

Non-unitary neutrino mixing implies an extra $CP$ violating phase that can fake the leptonic Dirac $CP$ phase ${\delta }_{CP}$ of the simplest three-neutrino mixing benchmark scheme. This would hinder the possibility of probing for $CP$ violation in accelerator-type experiments. We take T2K and T2HK as examples to demonstrate the degeneracy between the “standard” (or “unitary”) and “nonunitary” $CP$ phases. We find, under the assumption of nonunitary mixing, that their $CP$ sensitivities severely deteriorate. Fortunately, the TNT2K proposal of supplementing T2(H)K with a $\mu \mathrm{DAR}$ source for better measurement of ${\delta }_{CP}$ can partially break the $CP$ degeneracy by probing both $\cos {\delta }_{CP}$ and $\sin {\delta }_{CP}$ dependences in the wide spectrum of the $\mu \mathrm{DAR}$ flux. We also show that the further addition of a near detector to the $\mu \mathrm{DAR}$ setup can eliminate the degeneracy completely.

The COMPASS collaboration has collected the currently largest data set on diffractively produced ${\pi }^{-}{\pi }^{-}{\pi }^{+}$ final states using a negative pion beam of $190\mathrm{GeV}/c$ momentum impinging on a stationary proton target. This data set allows for a systematic partial-wave analysis in 100 bins of three-pion mass, $0.5<m_{3\pi }<2.5\mathrm{GeV}/c^2$, and in 11 bins of the reduced four-momentum transfer squared, $0.1<t^{\prime }<1.0(\mathrm{GeV}/c{)}^2$. This two-dimensional analysis offers sensitivity to genuine one-step resonance production, i.e. the production of a state followed by its decay, as well as to more complex dynamical effects in nonresonant $3\pi$ production. In this paper, we present detailed studies on selected $3\pi$ partial waves with $J^{PC}=0^{-+}$, $1^{++}$, $2^{-+}$, $2^{++}$, and $4^{++}$. In these waves, we observe the well-known ground-state mesons as well as a new narrow axial-vector meson $a_1(1420)$ decaying into $f_0(980)\pi$. In addition, we present the results of a novel method to extract the amplitude of the ${\pi }^{-}{\pi }^{+}$ subsystem with $I^G{J}^{PC}=0^{+}{0}^{++}$ in various partial waves from the ${\pi }^{-}{\pi }^{-}{\pi }^{+}$ data. Evidence is found for correlation of the $f_0(980)$ and $f_0(1500)$ appearing as intermediate ${\pi }^{-}{\pi }^{+}$ isobars in the decay of the known $\pi (1800)$ and ${\pi }_2(1880)$.

We study the evolution of holographic screens, both generally and in explicit examples, including cosmology and gravitational collapse. A screen $H$ consists of a one-parameter sequence of maximal surfaces called leaves. Its causal structure is nonrelativistic. Each leaf can store all of the quantum information on a corresponding null slice holographically at no more than one bit per Planck area. Therefore, we expect the screen geometry to reflect certain coarse-grained quantities in the quantum gravity theory. In a given spacetime, there are many different screens, which are naturally associated with different observers. We find that this ambiguity corresponds precisely to the free choice of a single function on $H$. We also consider the background-free construction of $H$, where the spacetime is not given. The evolution equations then constrain aspects of the full spacetime and the screen’s embedding in it.

We construct gravitational modifications that go beyond Horndeski, namely theories with extended nonminimal derivative couplings, in which the coefficient functions depend not only on the scalar field but also on its kinetic energy. Such theories prove to be ghost-free in a cosmological background. We investigate the early-time cosmology and show that a de Sitter inflationary phase can be realized as a pure result of the novel gravitational couplings. Additionally, we study the late-time evolution, where we obtain an effective dark energy sector which arises from the scalar field and its extended couplings to gravity. We extract various cosmological observables and analyze their behavior at small redshifts for three choices of potentials, namely for the exponential, the power-law, and the Higgs potentials. We show that the Universe passes from deceleration to acceleration in the recent cosmological past, while the effective dark energy equation-of-state parameter tends to the cosmological-constant value at present. Finally, the effective dark energy can be phantomlike, although the scalar field is canonical, which is an advantage of the model.

Twisted geometries are understood to be the discrete classical limit of loop quantum gravity. In this paper, SU(2) flat connections on a (decorated) 2D Riemann surface are shown to be equivalent to the generalized twisted geometries in 3D space with cosmological constant. Various flat connection quantities on a Riemann surface are mapped to the geometrical quantities in discrete 3D space. We propose that the moduli space of SU(2) flat connections on a Riemann surface generalizes the phase space of twisted geometry or loop quantum gravity to include a cosmological constant.

Continuing work initiated in an earlier publication [A. Ishihara, Y. Suzuki, T. Ono, T. Kitamura, and H. Asada, Phys. Rev. D 94, 084015 (2016).], we discuss a method of calculating the bending angle of light in a static, spherically symmetric, and asymptotically flat spacetime, especially by taking into account the finite distance from a lens object to a light source and a receiver. For this purpose, we use the Gauss-Bonnet theorem to define the bending angle of light, such that the definition can be valid also in the strong deflection limit. Finally, this method is applied to Schwarzschild spacetime in order to discuss also possible observational implications. The proposed corrections for Sgr ${\mathrm{A}}^{*}$ for instance are able to amount to $\sim {10}^{-5}\mathrm{arcseconds}$ for some parameter range, which may be within the capability of near-future astronomy, while also the correction for the Sun in the weak-field limit is $\sim {10}^{-5}\mathrm{arcseconds}$.

Ultralight degrees of freedom coupled to matter lead to resonances, which can be excited when the Compton wavelength of the field equals a dynamical scale in the problem. For binaries composed of a star orbiting a supermassive black hole, these resonances lead to a smoking-gun effect: a periastron distance which stalls, even in the presence of gravitational-wave dissipation. This effect, also called a floating orbit, occurs for generic equatorial but eccentric orbits, and we argue that finite-size effects are not enough to suppress it.

We study the impact of assumptions about neutrino properties on the estimation of inflationary parameters from cosmological data, with a specific focus on the allowed contours in the $n_s/r$ plane, where $n_s$ is the scalar spectral index and $r$ is the tensor-to-scalar ratio. We study the following neutrino properties: (i) the total neutrino mass $M_{\nu }=\sum _i{m}_i$ (where the index $i=1$, 2, 3 runs over the three neutrino mass eigenstates); (ii) the number of relativistic degrees of freedom $N_{\mathrm{eff}}$ at the time of recombination; and (iii) the neutrino hierarchy. Whereas previous literature assumed three degenerate neutrino masses or two massless neutrino species (approximations that clearly do not match neutrino oscillation data), we study the cases of normal and inverted hierarchy. Our basic result is that these three neutrino properties induce $<1\sigma$ shift of the probability contours in the $n_s/r$ plane with both current or upcoming data. We find that the choice of neutrino hierarchy (normal, inverted, or degenerate) has a negligible impact. However, the minimal cutoff on the total neutrino mass $M_{\nu ,\min }=0$ that accompanies previous works using the degenerate hierarchy does introduce biases in the $n_s/r$ plane and should be replaced by $M_{\nu ,\min }=0.059\mathrm{eV}$ as required by oscillation data. Using current cosmic microwave background (CMB) data from Planck and Bicep/Keck, marginalizing over the total neutrino mass $M_{\nu }$ and over $r$ can lead to a shift in the mean value of $n_s$ of $\sim 0.3\sigma$ toward lower values. However, once baryon acoustic oscillation measurements are included, the standard contours in the $n_s/r$ plane are basically reproduced. Larger shifts of the contours in the $n_s/r$ plane (up to $0.8\sigma$) arise for nonstandard values of $N_{\mathrm{eff}}$. We also provide forecasts for the future CMB experiments Cosmic Origins Explorer (COrE, satellite) and Stage-IV (ground-based) and show that the incomplete knowledge of neutrino properties, taken into account by a marginalization over $M_{\nu }$, could induce a shift of $\sim 0.4\sigma$ toward lower values in the determination of $n_s$ (or a $\sim 0.8\sigma$ shift if one marginalizes over $N_{\mathrm{eff}}$). Comparison to specific inflationary models is shown. Imperfect knowledge of neutrino properties must be taken into account properly, given the desired precision in determining whether or not inflationary models match the future data.

Primordial black hole (PBH) mergers have been proposed as an explanation for the gravitational wave events detected by the LIGO collaboration. Such PBHs may be formed in the early Universe as a result of the collapse of extremely rare high-sigma peaks of primordial fluctuations on small scales, as long as the amplitude of primordial perturbations on small scales is enhanced significantly relative to the amplitude of perturbations observed on large scales. One consequence of these small-scale perturbations is generation of stochastic gravitational waves that arise at second order in scalar perturbations, mostly before the formation of the PBHs. These induced gravitational waves have been shown, assuming Gaussian initial conditions, to be comparable to the current limits from the European Pulsar Timing Array, severely restricting this scenario. We show, however, that models with enhanced fluctuation amplitudes typically involve non-Gaussian initial conditions. With such initial conditions, the current limits from pulsar timing can be evaded. The amplitude of the induced gravitational-wave background can be larger or smaller than the stochastic gravitational-wave background from supermassive black hole binaries.

The Casimir effect is one of the most remarkable consequences of the nonzero vacuum energy predicted by quantum field theory. In this paper we use a local approach to study the Lorentz violation effects of the minimal standard model extension on the Casimir force between two parallel conducting plates in the vacuum. Using a perturbative method similar to that used for obtaining the Born series for the scattering amplitudes in quantum mechanics, we compute, at leading order in the Lorentz-violating coefficients, the relevant Green’s function which satisfies given boundary conditions. The standard point-splitting technique allow us to express the vacuum expectation value of the stress-energy tensor in terms of the Green’s function. We discuss its structure in the region between the plates. We compute the renormalized vacuum stress, which is obtained as the difference between the vacuum stress in the presence of the plates and that of the vacuum. The Casimir force is evaluated in an analytical fashion by two methods: by differentiating the renormalized global energy density and by computing the normal-normal component of the renormalized vacuum stress. We compute the local Casimir energy, which is found to diverge as approaching the plates, and we demonstrate that it does not contribute to the observable force.

We propose a model-independent method to test $CP$ violation in the scalar sector through measuring the inclusive cross sections of $e^{+}{e}^{-}\to Z{h}_1,Z{h}_2,h_1{h}_2$ processes with the recoil mass technique, where $h_1$, $h_2$ stand for the 125 GeV standard model-like Higgs boson and a new lighter scalar, respectively. This method effectively measures a quantity $K$ proportional to the product of the three couplings of $h_{1}ZZ,h_{2}ZZ,h_1{h}_{2}Z$ vertices. The value of $K$ encodes a part of information about $CP$ violation in the scalar sector. We simulate the signal and backgrounds for the processes mentioned above with $m_2=40\mathrm{GeV}$ at the Circular Electron-Positron Collider (CEPC) with the integrated luminosity $5{\mathrm{ab}}^{-1}$. We find that the discovery of both $Z{h}_2$ and $h_1{h}_2$ processes at $5\sigma$ level indicates an $\mathcal{O}({10}^{-2})$ $K$ value that can be measured to 16% precision. The method is applied to the weakly coupled Lee model in which $CP$ violation can be tested either before or after utilizing a “$p_T$ balance” cut (see Sec. II B for the definition). Lastly we point out that $K\ne 0$ is a sufficient but not a necessary condition for the existence of $CP$ violation in the scalar sector, namely, $K=0$ does not imply $CP$ conservation in the scalar sector.