Relic gravitational waves (RGWs) generated in the early universe form a stochastic GW background, which can be directly probed by measuring the timing residuals of millisecond pulsars. In this paper, we investigate the constraints on the RGWs and on the inflationary parameters by the observations of current and potential future pulsar timing arrays. In particular, we focus on effects of various cosmic phase transitions (e.g., $e^{+}{e}^{-}$ annihilation, QCD transition, and supersymmetry breaking) and relativistic free-streaming gases (neutrinos and dark fluids) in the general scenario of the early universe, which have been neglected in the previous works. We find that the phase transitions can significantly damp the RGWs in the sensitive frequency range of pulsar timing arrays, and the upper limits of the tensor-to-scalar ratio $r$ increase by a factor $\sim 2$ for both current and future observations. However, the effects of free-steaming neutrinos and dark fluids are all too small to be detected. Meanwhile, we find that, if the effective equation of state $w$ in the early universe is larger than $1/3$, i.e., deviating from the standard hot big bang scenario, the detection of RGWs by pulsar timing arrays becomes much more promising.

We propose a new detection strategy for gravitational waves (GWs) below a few hertz based on a correlated array of atom interferometers (AIs). Our proposal allows us to reduce the Newtonian noise (NN), which limits all ground based GW detectors below a few hertz, including previous atom interferometry-based concepts. Using an array of long baseline AI gradiometers yields several estimations of the NN, whose effect can thus be reduced via statistical averaging. Considering the km baseline of current optical detectors, a NN rejection of a factor of 2 could be achieved and tested with existing AI array geometries. Exploiting the correlation properties of the gravity acceleration noise, we show that a tenfold or more NN rejection is possible with a dedicated configuration. Considering a conservative NN model and the current developments in cold atom technology, we show that strain sensitivities below $1\times {10}^{-19}/\sqrt{\mathrm{Hz}}$ in the $0.3-3\mathrm{Hz}$ frequency band can be within reach, with a peak sensitivity of $3\times {10}^{-23}/\sqrt{\mathrm{Hz}}$ at $2\mathrm{Hz}$. Our proposed configuration could extend the observation window of current detectors by a decade and fill the gap between ground-based and space-based instruments.

We present a new determination of the $N\mathrm{\Delta }$ axial form factors from neutrino induced pion production data. For this purpose, the model of Hernandez et al. [Phys. Rev. D 76, 033005 (2007)] is improved by partially restoring unitarity. This is accomplished by imposing Watson’s theorem on the dominant vector and axial multipoles. As a consequence, a larger $C_5^A(0)$, in good agreement with the prediction from the off-diagonal Goldberger-Treiman relation, is now obtained.

We discuss prospects for probing $Z$-prime and nonstandard neutrino interactions using neutrino-nucleus coherent scattering with ultralow energy ($\sim 10\mathrm{eV}$) threshold Si and Ge detectors. The analysis is performed in the context of a specific and contemporary reactor-based experimental proposal, developed in cooperation with the Nuclear Science Center at Texas A&M University, and referencing available technology based upon economical and scalable detector arrays. For expected exposures, we show that sensitivity to the $Z$-prime mass is on the order of several TeV and is complementary to the LHC search with low-mass detectors in the near term. This technology is also shown to provide sensitivity to the neutrino magnetic moment, at a level that surpasses terrestrial limits, and is competitive with more stringent astrophysical bounds. We demonstrate the benefits of combining silicon and germanium detectors for distinguishing between classes of models of new physics and for suppressing correlated systematic uncertainties.

Cosmic-ray-muon spallation-induced radioactive isotopes with $\beta$ decays are one of the major backgrounds for solar, reactor, and supernova relic neutrino experiments. Unlike in scintillator, production yields for cosmogenic backgrounds in water have not been exclusively measured before, yet they are becoming more and more important in next generation neutrino experiments designed to search for rare signals. We have analyzed the low-energy trigger data collected at Super-Kamiokande IV in order to determine the production rates of ${}^{12}\mathrm{B}$, ${}^{12}\mathrm{N}$, ${}^{16}\mathrm{N}$, ${}^{11}\mathrm{Be}$, ${}^9\mathrm{Li}$, ${}^8\mathrm{He}$, ${}^9\mathrm{C}$, ${}^8\mathrm{Li}$, ${}^8\mathrm{B}$, and ${}^{15}\mathrm{C}$. These rates were extracted from fits to time differences between parent muons and subsequent daughter $\beta$’s by fixing the known isotope lifetimes. Since ${}^9\mathrm{Li}$ can fake an inverse-beta-decay reaction chain via a $\beta +n$ cascade decay, producing an irreducible background with detected energy up to a dozen MeV, a dedicated study is needed for evaluating its impact on future measurements; the application of a neutron tagging technique using correlated triggers was found to improve this ${}^9\mathrm{Li}$ measurement. The measured yields were generally found to be comparable with theoretical calculations, except the cases of the isotopes ${}^8\mathrm{Li}/{}^8\mathrm{B}$ and ${}^9\mathrm{Li}$.

We derive a complete pure de Sitter supergravity action with nonlinearly realized supersymmetry and its rigid limit, the Volkov-Akulov action, from the corresponding models with linear supersymmetry, by computing the path integral in the limit of infinite sgoldstino mass. In this, we use a non-Gaussian functional integration formula that was recently discovered in a derivation of de Sitter (dS) supergravity from the superconformal theory. We also present explicit examples of pure dS supergravity and the case with one matter multiplet. These two simple examples serve as a test and a demo of the universal action formula valid for de Sitter supergravities with general matter coupling.

We study two-fluid systems with nonzero fluid velocities and compute their sound modes, which indicate various instabilities. For the case of two zero-temperature superfluids we employ a microscopic field-theoretical model of two coupled bosonic fields, including an entrainment coupling and a nonentrainment coupling. We analyze the onset of the various instabilities systematically and point out that the dynamical two-stream instability can occur only beyond Landau’s critical velocity, i.e., in an already energetically unstable regime. A qualitative difference is found for the case of two normal fluids, where certain transverse modes suffer a two-stream instability in an energetically stable regime if there is entrainment between the fluids. Since we work in a fully relativistic setup, our results are very general and are of potential relevance for (super)fluids in neutron stars and, in the nonrelativistic limit of our results, in the laboratory.

We study the expectation value of the energy momentum tensor during thin shell collapse for a massive, real, scalar field theory. At tree level, we find thermal, Hawking-type, behavior for the energy flux. Using the Schwinger-Keldysh technique, we calculate two-loop corrections to the tree-level correlation functions and show that they exhibit secular growth, suggesting the breakdown of the perturbation theory.

We investigate the absorption of a massive and charged scalar field in a Reissner-Nordström background. We compare our numerical results for the absorption cross section, obtained for arbitrary frequencies, with the low- and high-frequency limits. We find, in particular, that the total absorption cross section can be negative, showing that planar scalar waves can be superradiantly amplified by black holes.

Black holes are a paradigm in physics nowadays and are expected to be hosted at the centers of galaxies. Supermassive galactic black holes are not isolated, and their surroundings play crucial roles in many observational features. The absorption and scattering of fields by isolated black holes have been vastly studied, allowing the understanding of many phenomenological features. However, as far as we are aware, a study of the influence of the presence of matter surrounding black holes in their planar wave scattering and absorption spectrum is still lacking in the literature. This may be important in the analysis of, for instance, the accretion of dark matter by black holes. We consider planar massless scalar waves incident upon a Schwarzschild black hole surrounded by a thin spherical shell. We use the partial-wave method to determine the absorption cross section and present a selection of numerical results. In the low-frequency regime, we show that the absorption cross section is equal to the horizon area. At the high-frequency regime, we show that the absorption cross section approaches the geodesic capture cross section.

The possibility that a classical space-time and quantum matter cohabit at the deepest level, i.e., the possibility of having a fundamental and not phenomenological semiclassical gravity, is often disregarded for lack of a good candidate theory. The standard semiclassical theory suffers from fundamental inconsistencies (e.g., Schrödinger cat sources, faster-than-light communication and violation of the Born rule) which can only be ignored in simple typical situations. We harness the power of spontaneous localization models, historically constructed to solve the measurement problem in quantum mechanics, to build a consistent theory of (stochastic) semiclassical gravity in the Newtonian limit. Our model makes quantitative and potentially testable predictions: we recover the Newtonian pair potential up to a short distance cutoff (hence, we predict no one-particle self-interaction) and uncover an additional gravitational decoherence term which depends on the specifics of the underlying spontaneous localization model considered. We hint at a possible program to go past the Newtonian limit, towards a consistent general relativistic semiclassical gravity.

Within the next few years, Advanced LIGO and Virgo should detect gravitational waves from binary neutron star and neutron star-black hole mergers. These sources are also predicted to power a broad array of electromagnetic transients. Because the electromagnetic signatures can be faint and fade rapidly, observing them hinges on rapidly inferring the sky location from the gravitational-wave observations. Markov chain Monte Carlo methods for gravitational-wave parameter estimation can take hours or more. We introduce BAYESTAR, a rapid, Bayesian, non-Markov chain Monte Carlo sky localization algorithm that takes just seconds to produce probability sky maps that are comparable in accuracy to the full analysis. Prompt localizations from BAYESTAR will make it possible to search electromagnetic counterparts of compact binary mergers.

We present a study of cosmological implications of generic dark matter decays. We consider two-body and many-body decaying scenarios. In the two-body case the massive particle has a possibly relativistic kick velocity and thus possesses a dynamical equation of state. This has implications to the expansion history of the Universe. We use recent observational data from the cosmic microwave background, baryon acoustic oscillations and supernovae type Ia to obtain constraints on the lifetime of the dark matter particle. We find that for an energy splitting where more than 40% of the dark matter particle energy is transferred to massless, relativistic particles in the two-body case, or more than 50% in the many-body case, lifetimes less than the age of the Universe are excluded at more than 95% confidence. When the energy splitting falls to 10% the lifetime is constrained to be more than roughly half the age.

We investigate the phase structure of two-color QCD at both real and imaginary chemical potentials ($\mu$), performing lattice simulations and analyzing the data with the Polyakov-loop extended Nambu–Jona-Lasinio (PNJL) model. Lattice QCD simulations are done on an $8^3\times 4$ lattice with the clover-improved two-flavor Wilson fermion action and the renormalization-group-improved Iwasaki gauge action. We test the analytic continuation of physical quantities from imaginary $\mu$ to real $\mu$ by comparing lattice QCD results calculated at real $\mu$ with the results of an analytic function, the coefficients of which are determined from lattice QCD results at imaginary $\mu$. We also test the validity of the PNJL model by comparing model results with lattice QCD ones. The PNJL model is good in the deconfinement region, but less accurate in the transition and confinement regions. This problem is cured by introducing the baryon degree of freedom to the model. It is also found that the vector-type four-quark interaction is necessary to explain lattice data on the quark number density.

We obtain predictions for a number of radiative decays $B_{(s)}\to V\gamma$, $V$ the vector meson, which proceed through the weak-annihilation mechanism. Within the factorization approximation, we take into account the photon emission from the $B$-meson loop and from the vector-meson loop; the latter subprocesses were not considered in the previous analyses but are found to have a sizeable impact on the $B_{(s)}\to V\gamma$ decay rate. The highest branching ratios for the weak-annihilation reactions reported here are $\mathcal{B}({\overline{B}}_s^0\to J/\psi \gamma )=1.5\times {10}^{-7}$ and $\mathcal{B}(B^{-}\to {\overline{D}}_s^{*-}\gamma )=1.7\times {10}^{-7}$, the estimated accuracy of these predictions being at the level of 20%.

We present a new technique for tagging heavy-flavor jets with $p_T>500\mathrm{GeV}$ called “${\mu }_x$ tagging.” Current track-based methods of $b$-jet tagging lose efficiency and experience a large rise in fake rate in the boosted regime. Using muons from $B$ hadron decay, we combine angular information and jet substructure to tag $b$ jets, $c$ jets, light jets, and “light-heavy” jets (those containing $B$ hadrons from gluon splitting). We find tagging efficiencies of ${\epsilon }_b=14\%$, ${\epsilon }_c=6.5\%$, ${\epsilon }_{\text{light-light}}=0.14\%$, and ${\epsilon }_{\text{light-heavy}}=0.5\%$, respectively, that are nearly independent of transverse momentum at high energy. We demonstrate the usefulness of this new scheme by examining the discovery potential for multi-TeV leptophobic $Z^{\prime }$ bosons in the boosted-$b$-tagged dijet channel at the Large Hadron Collider.

Characteristic patterns of cosmic neutrino spectrum reported by the IceCube Collaboration and long-standing inconsistency between theory and experiment in muon anomalous magnetic moment are simultaneously explained by an extra leptonic force mediated by a gauge field with a mass of the MeV scale. With different assumptions for redshift distribution of cosmic neutrino sources, diffuse neutrino flux is calculated with the scattering between cosmic neutrino and cosmic neutrino background through the new leptonic force. Our analysis sheds light on a relation among lepton physics at the three different scales, PeV, MeV, and eV, and provides possible clues to the distribution of sources of cosmic neutrino and also to neutrino mass spectrum.

The three major unknown neutrino oscillation parameters at the present juncture are the mass hierarchy, the octant of the mixing angle ${\theta }_{23}$ and the $CP$ phase ${\delta }_{CP}$. It is well known that the presence of hierarchy-${\delta }_{CP}$ and octant degeneracies affects the unambiguous determination of these parameters. In this paper, we show that a comprehensive way to study the remaining parameter degeneracies is in the form of a generalized hierarchy-${\theta }_{23}\text{−}{\delta }_{CP}$ degeneracy. This is best depicted as contours in the test (${\theta }_{23}-{\delta }_{CP}$) plane for different representative true values of parameters. We show that the wrong-hierarchy and/or wrong-octant solutions can be further classified into eight different solutions depending on whether they occur with the wrong or right value of ${\delta }_{CP}$. These eight solutions are different from the original eightfold degenerate solutions and can exist, in principle, even if ${\theta }_{13}$ is known. These multiple solutions, apart from affecting the determination of the true hierarchy and octant, also affect the accurate estimation of ${\delta }_{CP}$. We identify which of these eight different degenerate solutions can occur in the test (${\theta }_{23}-{\delta }_{CP}$) parameter space, taking the long-baseline experiment $\mathrm{NO}\nu \mathrm{A}$ running in the neutrino mode as an example. The inclusion of the $\mathrm{NO}\nu \mathrm{A}$ antineutrino run removes the wrong-octant solutions appearing with both right and wrong hierarchy. Adding T2K data to this resolves the wrong hierarchy-right octant solutions to a large extent. The remaining wrong-hierarchy solutions can be removed by combining $\mathrm{NO}\nu \mathrm{A}+\mathrm{T}2\mathrm{K}$ with atmospheric neutrino data. We demonstrate this using ICAL@INO as the prototype atmospheric neutrino detector. We find that the degeneracies can be resolved at the $2\sigma$ level by the combined data set, for the true parameter space considered in the study.

Based on data samples collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies $\sqrt{s}>4.4\mathrm{GeV}$, the processes $e^{+}{e}^{-}\to \omega {\chi }_{c1,2}$ are observed for the first time. With an integrated luminosity of $1074{\mathrm{pb}}^{-1}$ near $\sqrt{s}=4.42\mathrm{GeV}$, a significant $\omega {\chi }_{c2}$ signal is found, and the cross section is measured to be $(20.9\pm 3.2\pm 2.5)\mathrm{pb}$. With $567{\mathrm{pb}}^{-1}$ near $\sqrt{s}=4.6\mathrm{GeV}$, a clear $\omega {\chi }_{c1}$ signal is seen, and the cross section is measured to be $(9.5\pm 2.1\pm 1.3)\mathrm{pb}$, while evidence is found for an $\omega {\chi }_{c2}$ signal. The first errors are statistical, and the second are systematic. Due to low luminosity or low cross section at other energies, no significant signals are observed. In the $\omega {\chi }_{c2}$ cross section, an enhancement is seen around $\sqrt{s}=4.42\mathrm{GeV}$. Fitting the cross section with a coherent sum of the $\psi (4415)$ Breit-Wigner function and a phase-space term, the branching fraction $\mathcal{B}(\psi (4415)\to \omega {\chi }_{c2})$ is obtained to be of the order of $10^{-3}$.

We report new measurements of the total cross sections for $e^{+}{e}^{-}\to \mathrm{\Upsilon }(n\mathrm{S}){\pi }^{+}{\pi }^{-}$ ($n=1$, 2, 3) and $e^{+}{e}^{-}\to b\overline{b}$ from a high-luminosity fine scan of the region $\sqrt{s}=10.63–11.05\mathrm{GeV}$ with the Belle detector. We observe that the $\mathrm{\Upsilon }(n\mathrm{S}){\pi }^{+}{\pi }^{-}$ spectra have little or no nonresonant component and extract from them the masses and widths of $\mathrm{\Upsilon }(10860)$ and $\mathrm{\Upsilon }(11020)$ and their relative phase. We find $M_{10860}=(10891.1\pm 3.2_{-1.7}^{+0.6})\mathrm{MeV}/c^2$ and ${\mathrm{\Gamma }}_{10860}=(53.7_{-5.6-5.4}^{+7.1+1.3})\mathrm{MeV}$ and report first measurements $M_{11020}=(10987.5_{-2.5-2.1}^{+6.4+9.0})\mathrm{MeV}/c^2$, ${\mathrm{\Gamma }}_{11020}=(61_{-19-20}^{+9+2})\mathrm{MeV}$, and ${\varphi }_{11020}-{\varphi }_{10860}=({-1.0\pm 0.4}_{-0.1}^{+1.4})\mathrm{rad}$.