We present a family of new rotating black hole solutions to Einstein’s equations that generalizes the Kerr-Newman spacetime to include an anisotropic matter. The geometry is obtained by employing the Newman-Janis algorithm. In addition to the mass, the charge, and the angular momentum, an additional hair exists thanks to the negative radial pressure of the anisotropic matter. The properties of the black hole are analyzed in detail including thermodynamics. This black hole can be used as a better engine than the Kerr-Newman one in extracting energy.

The presence of a significant amount of gravitational radiation in the early Universe affects the total energy density and hence the expansion rate in the early epoch. In this work, we develop a physical model to connect the number of relativistic degrees of freedom $N_{\mathrm{eff}}$ with the amplitude and shape of the primordial tensor power spectrum, and use the cosmic microwave background temperature and polarization data from Planck and the BICEP2/KECK Array and the primordial deuterium measurements from damped Lyman-$\alpha$ systems to constrain this model. We find that with the extra relation $\mathrm{\Delta }{N}_{\mathrm{eff}}(r,n_{\mathrm{t}})$, the tensor-to-scalar ratio $r$ is constrained to be $r<0.07$ ($3\sigma$ C.L.) and the tilt of the tensor power spectrum is $n_{\mathrm{t}}=-0.01\pm 0.31$ ($1\sigma$ C.L.) for $Planck+\mathrm{BICEP}2+\mathrm{KECK}+[\mathrm{D}/\mathrm{H}]$ data. This achieves a much tighter constraint on the tensor spectrum and provides a stringent test for cosmic inflation models. In addition, the current constraint on $N_{\mathrm{eff}}=3.122\pm 0.171$ excludes the possibility of a fourth neutrino species at more than $5\sigma$ C.L.

We calculate the complete $T$ matrices of pion-nucleon ($\pi N$) scattering to the third order in heavy baryon SU(3) chiral perturbation theory. The baryon mass in the chiral limit $M_0$ and the low-energy constants are determined by fitting to phase shifts of $\pi N$ and the experimental octet-baryon masses simultaneously. By using these constants, we obtain the pion-nucleon sigma terms, ${\sigma }_{\pi N}=(34.57\pm 11.85)\mathrm{MeV}$ . We also find a very small strangeness content of the proton, $y\simeq 0$. The scattering lengths and the scattering volumes are predicted, which turn out to be in good agreement with those of other approaches and the available experimental data. The contributions from the third-order amplitudes are discussed in detail. We find that the contributions from the internal kaon lines of one-loop diagrams and the counterterms of the third order are sizeable. In addition, the issue of convergence is also discussed.

We study multiscalar models of radius stabilization, with an eye toward application to novel extra-dimensional models of symmetry breaking. With inspiration from holography, we construct a multiscalar effective potential that is a function of UV-brane values of the scalar fields and that takes into account bulk gravitational backreaction. We study extrema of this potential and additionally provide a “superpotential” method for generating static solutions for the extra-dimensional geometry. We apply these methods to some simple models of the Higgs mechanism where the Higgs itself plays a nontrivial role in radius stabilization. We conclude that mass mixing of the Higgs and radion is generic unless additional symmetries are imposed. We focus on models with a moderate gap between the electroweak and Kaluza-Klein scale, as required by phenomenological constraints. We note that tuning of the Higgs mass relative to the Kaluza-Klein scale is related to various classes of tuning of 5D parameters, with different resulting spectra and phenomenologies.

We study a new mechanism to discover dark photon fields by resonantly triggering two-photon transitions in cold gas preparations. Using coherently prepared cold parahydrogen, the coupling sensitivity for sub-meV mass dark photon fields can be advanced by orders of magnitude with a modified light-shining-through-wall setup. We calculate the effect of a background dark photon field on the dipole moment and corresponding transition rate of cold parahydrogen pumped into its first vibrational excited state by counter-propagating laser beams. The nonlinear amplification of two-photon emission triggered by dark photons in a cold parahydrogen sample is numerically simulated to obtain the expected dark photon coupling sensitivity.

We study the effective potential and the renormalization group (RG) improvement to the effective potential of a Higgs boson in a singlet-doublet fermion dark matter extension of the Standard Model (SM), and in general singlet-doublet fermion extension models with several copies of doublet fermions or singlet fermions. We study the stability of the electroweak vacuum with the RG-improved effective potential in these models beyond the SM. We study the decay of the electroweak vacuum using the RG-improved effective potential in these models beyond the SM. In this study we consider the quantum correction to the kinetic term in the effective action and consider the RG improvement of the kinetic term. Combining all these effects, we find that the decay rate of the false vacuum is slightly changed when calculated using the RG-improved effective action in the singlet-doublet fermion dark matter model. In general singlet-doublet fermion extension models, we find that the presence of several copies of doublet fermions can make the electroweak vacuum stable if the new Yukawa couplings are not large. If the new Yukawa couplings are large, the electroweak vacuum can be turned into metastable or unstable again by the presence of extra fermions.

Experimental probes of the recently discovered Higgs boson show that its behavior is close to that of the Standard Model (SM) Higgs particle. Extensions of the SM which include extra Higgs bosons are constrained by these observations, implying either the decoupling of the heavy nonstandard Higgs particles or the realization of alignment, associated with vanishing mixing of the SM-like Higgs boson with the nonstandard ones. Quite generally, alignment is not enforced by symmetry considerations and hence it is interesting to look for dynamical ways in which this condition can be realized. We show that this is possible in the Next-to-Minimal Supersymmetric Standard Model (NMSSM), in which alignment is achieved for values of the coupling of the Higgs fields to the singlet field that become large close to the Grand Unification (GUT) scale. This, in turn, can be explained by the composite nature of the Higgs fields, with a compositeness scale close to the GUT scale. In this article we present this dynamical scenario and discuss its phenomenological properties.

It has been shown that the data from the LHC do not rule out a chiral sequential fourth generation of fermions that obtain their masses through an identical mechanism as the other three generations do. However, this is possible only if the scalar sector of the Standard Model is suitably enhanced, like embedding it in a type-II two-Higgs doublet model. In this article, we try to show that double Higgs production (DHP) can unveil the existence of such a hidden fourth generation in a very efficient way. While the DHP cross section in the SM is quite small, it is significantly enhanced with a fourth generation. We perform a detailed analysis of the dependence of the DHP cross section on the model parameters and show that either a positive signal of DHP is seen in the early next run of the LHC or the model is ruled out.

We discuss a possibility of restricting parameters in $\mathcal{N}=2$ supergravity based on axion observations. We, accordingly, derive conditions that prepotential and gauge couplings should satisfy. Such conditions not only allow us to constrain the theory but also provide the lower bound of the $\mathcal{N}=2\to \mathcal{N}=1$ breaking scale.

Recently Bauer et al. [arXiv:1909.13022] proposed ANUBIS, an auxiliary detector to be installed in one of the shafts above the ATLAS or CMS interaction point, as a tool to search for long-lived particles. Here, we study the sensitivity of this proposal for long-lived heavy neutral leptons (HNLs) in both minimal and extended scenarios. We start with the minimal HNL model where both production and decay of the HNLs are mediated by active-sterile neutrino mixing, before studying the case of right-handed neutrinos in a left-right symmetric model. We then consider a $U(1{)}_{B-L}$ extension of the Standard Model (SM). In this model HNLs are produced from the decays of the mostly SM-like Higgs boson, via mixing in the scalar sector of the theory. In all cases, we find that ANUBIS has sensitivity reach comparable to the proposed MATHUSLA detector. For the minimal HNL scenario, the contributions from $W$’s decaying to HNLs are more important at ANUBIS than at MATHUSLA, extending the sensitivity to slightly larger HNL masses at ANUBIS.

The Roper state is extracted with valence overlap fermions on a $2+1$-flavor domain-wall fermion lattice (spacing $a=0.114\mathrm{fm}$ and $m_{\pi }=330\mathrm{MeV}$) using both the sequential empirical Bayes (SEB) method and the variational method. The results are consistent, provided that a large smearing-size interpolation operator is included in the variational calculation to have better overlap with the lowest radial excitation. The SEB and variational calculation with large smearing size are also carried out for an anisotropic clover lattice with similar parameters (spatial lattice spacing $a_s=0.12\mathrm{fm}$ and pion mass $m_{\pi }=396\mathrm{MeV}$) and obtain consistent results. However, these calculations with clover fermions give a Roper mass of $m_R=1.92(6)\mathrm{GeV}$, while the same approach with overlap fermions finds the Roper $\approx 280\mathrm{MeV}$ lower, at $m_R=1.64(9)\mathrm{GeV}$, for identical valence pion mass. The fact that the prediction of the Roper state by overlap fermions is consistently lower than those of clover fermions, chirally improved fermions, and twisted-mass fermions over a wide range of pion masses has been dubbed a “Roper puzzle.” To understand the origin of this difference, we study the hairpin $Z$-diagram in the isovector scalar meson ($a_0$) correlator in the quenched approximation. The lack of quark loops in the quenched approximation turns the $a_0$ correlator negative; giving rise to a ghost “would-be” $\eta \pi$ state. Comparing the $a_0$ correlators for valence clover and overlap fermions, at a valence pion mass of 290 MeV, on three quenched Wilson-gauge lattices, we find that the spectral weight of the ghost state with clover fermions is smaller than that of the overlap at $a=0.12\mathrm{fm}$ and 0.09 fm—the ratios of the Wilson ghost-state magnitudes (correlator minima) are about half of those of overlap—whereas, the whole $a_0$ correlators of clover and overlap at $a=0.06\mathrm{fm}$ coincide within errors. This suggests that chiral symmetry is restored for clover at $a\le 0.06\mathrm{fm}$ and that the Roper mass should agree between clover and overlap fermions toward the continuum limit. We conclude that the present work supports a resolution of the “Roper puzzle” due to $Z$-graph type chiral dynamics. This entails coupling to higher components in the Fock space (e.g., $N\pi$, $N\pi \pi$ states) to induce the effective flavor-spin interaction between quarks as prescribed in the chiral quark model, resulting in the parity-reversal pattern as observed in the experimental excited states of $N$, $\mathrm{\Delta }$ and $\mathrm{\Lambda }$.

The spin-dependent operators for heavy quarkonium hybrids have been recently obtained in a nonrelativistic effective field theory approach up to next-to-leading order in the heavy-quark mass expansion. In the effective field theory for hybrids several operators not found in standard quarkonia appear, including an operator suppressed by only one power of the heavy-quark mass. We compute the matching coefficients for these operators in the short heavy-quark-antiquark distance regime, $r\ll 1/{\mathrm{\Lambda }}_{\mathrm{QCD}}$, by matching weakly coupled potential nonrelativistic QCD to the effective field theory for hybrids. In this regime the perturbative and nonperturbative contributions to the matching coefficients factorize, and the latter can be expressed in terms of purely gluonic correlators whose form we explicitly calculate with the aid of the transformation properties of the gluon fields under discrete symmetries. We detail our previous comparison with direct lattice computations of the charmonium hybrid spectrum, from which the unknown nonperturbative contributions can be obtained, and extend it to datasets with different light-quark masses.

Stimulated by the state $Y(4626)$ recently reported by the Belle Collaboration, we utilize a multiquark color flux-tube model with a multibody confinement potential and one-gluon-exchange interaction to make an exhaustive investigation on the diquark-antidiquark state $[cs][\overline{c}\overline{s}]$. Numerical results indicate that the spatial configuration of the states $[cs][\overline{c}\overline{s}]$ like a dumbbell, the larger the orbital excitation $L$, the farther the distance between the diquark $[cs]$ and the antidiquark $[\overline{c}\overline{s}]$, the more clearer the shape. The mixing of the color configurations ${[[cs{]}_{{\overline{\mathbf{3}}}_c}[\overline{c}\overline{s}{]}_{{\mathbf{3}}_c}]}_{\mathbf{1}}$ and ${[[cs{]}_{{\mathbf{6}}_c}[\overline{c}\overline{s}{]}_{{\overline{\mathbf{6}}}_c}]}_{\mathbf{1}}$ in the ground states is strong, while the color configuration ${[[cs{]}_{{\overline{\mathbf{3}}}_c}[\overline{c}\overline{s}{]}_{{\mathbf{3}}_c}]}_{\mathbf{1}}$ is absolutely predominant in the excited states. The states $Y(4626)$, $Y(4630)$, and $Y(4660)$ can be uniformly described as the $P$-wave tetraquark state $[cs][\overline{c}\overline{s}]$ with $1^{--}$. The states $Y(4626)$ and $Y(4630)$ can be described as the same state consisting of a scalar $[cs]$ and a scalar $[\overline{c}\overline{s}]$, while the state $Y(4660)$ is made of a scalar $[cs]$ ($[\overline{c}\overline{s}]$) and an axial-vector $[\overline{c}\overline{s}]$ ($[cs]$). Their hidden-bottom partner is predicted in the model calculation. The states $X(4140)$, $X(4274)$, $X(4350)$, $X(4500)$, and $X(4700)$ are also discussed.

The $n=2$ and $n=3$ levels for muonic helium are calculated using a potential that includes all one-loop and recoil effects. Electronic vacuum polarization corrections are calculated using an extension of the Kinoshita and Nio method. For $n=2$, the results are $2p_{1/2}-2s_{1/2}=1374.24\pm 1.4\mathrm{meV}$ and $2p_{3/2}-2s_{1/2}=1520.83\pm 1.4\mathrm{meV}$, essentially in agreement with the latest summary of the current calculations. The $n=3$ results are summarized in tabular form and give $3p_{1/2}-3s_{1/2}=394.48\pm 0.43\mathrm{meV}$ and $3d_{3/2}-3p_{3/2}=111.40\mathrm{meV}$.

We point out that the LDMX (Light Dark Matter eXperiment) detector design, conceived to search for sub-GeV dark matter, will also have very advantageous characteristics to pursue electron-nucleus scattering measurements of direct relevance to the neutrino program at DUNE and elsewhere. These characteristics include a 4-GeV electron beam, a precision tracker, electromagnetic and hadronic calorimeters with near $2\pi$ azimuthal acceptance from the forward beam axis out to $\sim 40°$ angle, and low reconstruction energy threshold. LDMX thus could provide (semi)exclusive cross section measurements, with detailed information about final-state electrons, pions, protons, and neutrons. We compare the predictions of two widely used neutrino generators (genie, gibuu) in the LDMX region of acceptance to illustrate the large modeling discrepancies in electron-nucleus interactions at DUNE-like kinematics. We argue that discriminating between these predictions is well within the capabilities of the LDMX detector.

A search is presented for pair production of long-lived neutral particles using $33{\mathrm{fb}}^{-1}$ of $\sqrt{\mathrm{s}}=13\mathrm{TeV}$ proton–proton collision data, collected during 2016 by the ATLAS detector at the LHC. This search focuses on a topology in which one long-lived particle decays in the ATLAS inner detector and the other decays in the muon spectrometer. Special techniques are employed to reconstruct the displaced tracks and vertices in the inner detector and in the muon spectrometer. One event is observed that passes the full event selection, which is consistent with the estimated background. Limits are placed on scalar boson propagators with masses from 125 GeV to 1000 GeV decaying into pairs of long-lived hidden-sector scalars with masses from 8 GeV to 400 GeV. The limits placed on several low-mass scalars extend previous exclusion limits in the range of proper lifetimes $c\tau$ from 5 cm to 1 m.

We investigate four-dimensional near-conformal dynamics by means of the large-charge limit. We first introduce and justify the formalism in which near-conformal invariance is insured by adding a dilaton and then determine the large-charge spectrum of the theory. The dilaton can also be viewed as the radial mode of the effective field theory. We calculate the two-point functions of charged operators. We discover that the mass of the dilaton, parametrizing the near-breaking of conformal invariance, induces a novel term that is logarithmic in the charge. One can therefore employ the large-charge limit to explore near-conformal dynamics and determine dilaton-related properties.

It has been suggested that amplitudes for quantum higher-spin massive particles exchanging gravitons lead, via a classical limit, to results for scattering of spinning black holes in general relativity, when the massive particles are in a certain way minimally coupled to gravity. Such limits of such amplitudes suggest, at least at lower orders in spin, up to second order in the gravitational constant $G$, that the classical aligned-spin scattering function for an arbitrary-mass-ratio two-spinning-black hole system can be obtained by a simple kinematical mapping from that for a spinning test black hole scattering off a stationary background Kerr black hole. Here we test these suggestions, at orders beyond the reach of the post-Newtonian and post-Minkowskian results used in their initial partial verifications, by confronting them with results from general-relativistic “self-force” calculations of the linear perturbations of a Kerr spacetime sourced by a small orbiting body, here considering only results for circular orbits in the equatorial plane. We translate between scattering and circular-orbit results by assuming the existence of a local-in-time canonical Hamiltonian governing the conservative dynamics of generic (bound and unbound) aligned-spin orbits, while employing the associated first law of spinning binary mechanics. To the extent possible with available self-force results, we confirm, through linear order in the mass ratio, some previous conjectures which would begin to fill in the spin-dependent parts of the conservative dynamics for arbitrary-mass-ratio aligned-spin binary black holes at the fourth-and-a-half and fifth post-Newtonian orders.

The symmetron is a typical example of screened modified gravity, wherein the symmetron force is dynamically suppressed in dense environments. This allows it to hide in traditional tests of gravity. However, the past decade has seen great experimental progress toward measuring screened forces in the laboratory or in space. Screening relies on nonlinearities in the equation of motion, which significantly complicates the theoretical analysis of such forces. Here, we present a calculation of the symmetron force between a dense plate and sphere surrounded by vacuum. This is done via semianalytical approaches in two limiting cases, based on the size of the sphere: large spheres are analyzed via the proximity force approximation, whilst small spheres are treated as screened test particles. In the intermediate regime we solve the problem numerically. Our results allow us to make contact with Casimir force experiments, which often employ a plate and sphere configuration for practical reasons, and may therefore be used to constrain symmetrons. We use our results to forecast constraints on the symmetron’s parameters for a hypothetical Casimir experiment that is based on the current state of the art. The forecasts compare favorably to other leading laboratory tests of gravity, particularly atom interferometry and bouncing neutrons. We thus conclude that near-future Casimir experiments will be capable of placing tight new bounds on symmetrons. Our results for the symmetron force are derived in a scale-invariant way, such that although we here focus on Casimir experiments, they may be applied to any other plate-sphere system, ranging from microscopic to astrophysical scales.

In this paper we present a simple but exact model of quasisingle field inflation [X. Chen and Y. Wang, Quasi-single field inflation and non-Gaussianities, J. Cosmol. Astropart. Phys. 04 (2010) 027, X. Chen and Y. Wang, Large non-Gaussianities with intermediate shapes from quasisingle field inflation, Phys. Rev. D 81, 063511 (2010)], in which the couplings between perturbations are completely controlled, and for instance can be made constant with any desired value. This provides a way to numerically implement quasisingle field inflation and to test its predictions in various regimes. We find that the numerics agree to high accuracy with the analytical predictions for the shape of the bispectrum, given a fixed overall scale. Also, we find reasonable agreement for the amplitude of the isosceles bispectrum, given a fixed base side.