The large number of $B_c$ mesons observed by LHCb suggests a sizable cross section for producing doubly heavy baryons in the same experiment. Motivated by this, we estimate masses of the doubly heavy $J=1/2$ baryons ${\mathrm{\Xi }}_{cc}$, ${\mathrm{\Xi }}_{bb}$, and ${\mathrm{\Xi }}_{bc}$, and their $J=3/2$ hyperfine partners, using a method which accurately predicts the masses of ground-state baryons with a single heavy quark. We obtain $M({\mathrm{\Xi }}_{cc})=3627\pm 12\mathrm{MeV}$, $M({\mathrm{\Xi }}_{cc}^{*})=3690\pm 12\mathrm{MeV}$, $M({\mathrm{\Xi }}_{bb})=10162\pm 12\mathrm{MeV}$, $M({\mathrm{\Xi }}_{bb}^{*})=10184\pm 12\mathrm{MeV}$, $M({\mathrm{\Xi }}_{bc})=6914\pm 13\mathrm{MeV}$, $M({{\mathrm{\Xi }}^{\prime }}_{bc})=6933\pm 12\mathrm{MeV}$, and $M({\mathrm{\Xi }}_{bc}^{*})=6969\pm 14\mathrm{MeV}$. As a byproduct, we estimate the hyperfine splitting between $B_c^{*}$ and $B_c$ mesons to be $68\pm 8\mathrm{MeV}$. We discuss P-wave excitations, production mechanisms, decay modes, lifetimes, and prospects for detection of the doubly heavy baryons.

We study the associated production of real (isolated) or virtual photons (with their subsequent leptonic decay) and hadronic jets in proton-proton collisions at the LHC using the $k_T$-factorization approach of QCD. The consideration is based on the off-shell quark-gluon QCD Compton scattering subprocesses. In the case of virtual photon production, the contributions from $Z$ boson exchange as well as ${\gamma }^{*}-Z$ interference with the full spin correlations are included. The transversemomentum-dependent (TMD) quark and gluon densities in a proton are determined from the Kimber-Martin-Ryskin prescription or Catani-Ciafoloni-Fiorani-Marchesini (CCFM) equation. In the latter, we restrict to the case where the gluon-to-quark splitting occurs at the last evolution step and calculate the sea quark density as a convolution of the CCFM-evolved gluon distribution and the TMD gluon-to-quark splitting function. Our numerical predictions are compared with the recent experimental data taken by the ATLAS Collaboration. We discuss the theoretical uncertainties of our calculations and argue that further studies are capable of constraining the TMD parton densities in the proton.

The ground state and excited spectra of baryons containing three identical heavy quarks, $b$ or $c$, have been recently calculated in nonperturbative lattice QCD. The energy of positive and negative parity excitations has been determined with high precision. Lattice results constitute a unique opportunity to learn about the quark-confinement mechanism as well as elucidating our knowledge about the nature of the strong force. We analyze the nonperturbative lattice QCD results by means of heavy-quark static potentials derived using SU(3) lattice QCD. We make use of different numerical techniques for the three-body problem.

We report the first analysis of background data from DM-Ice17, a direct-detection dark matter experiment consisting of 17 kg of NaI(Tl) target material. It was codeployed with IceCube 2457 m deep in the South Pole glacial ice in December 2010 and is the first such detector operating in the Southern Hemisphere. The background rate in the $6.5–8.0{\mathrm{keV}}_{\mathrm{ee}}$ region is measured to be $7.9\pm 0.4\text{counts}/\text{day}/\mathrm{keV}/\mathrm{kg}$. This is consistent with the expected background from the detector assemblies with negligible contributions from the surrounding ice. The successful deployment and operation of DM-Ice17 establishes the South Pole ice as a viable location for future underground, low-background experiments in the Southern Hemisphere. The detector assembly and deployment are described here, as well as the analysis of the DM-Ice17 backgrounds based on data from the first two years of operation after commissioning, July 2011–June 2013.

EXO-200 is a single phase liquid xenon detector designed to search for neutrinoless double-beta decay of ${}^{136}\mathrm{Xe}$. Here, we report on a search for various Majoron-emitting modes based on 100 kg yr exposure of ${}^{136}\mathrm{Xe}$. A lower limit of $T_{1/2}^{{}^{136}\mathrm{Xe}}>1.2\times {10}^{24}\mathrm{yr}$ at 90% C.L. on the half-life of the spectral $\mathrm{index}=1$ Majoron decay was obtained, corresponding to a constraint on the Majoron-neutrino coupling constant of $|⟨g_{ee}^M⟩|<(0.8–1.7)\times {10}^{-5}$.

We report results of a search for light dark matter weakly interacting massive particles (WIMPs) with CDEX-1 experiment at the China Jinping Underground Laboratory, based on 53.9 kg-days of data from a $p$-type point-contact germanium detector enclosed by a NaI(Tl) crystal scintillator as anti-Compton detector. The event rate and spectrum above the analysis threshold of 475 eVee are consistent with the understood background model. Part of the allowed regions for WIMP-nucleus coherent elastic scattering at WIMP mass of 6–20 GeV are probed and excluded. Independent of interaction channels, this result contradicts the interpretation that the anomalous excesses of the CoGeNT experiment are induced by dark matter, since identical detector techniques are used in both experiments.

We study novel types of contributions to the partition function of the Maxwell system defined on a small compact manifold, such as a torus. These new terms cannot be described in terms of the physical propagating photons with two transverse polarizations. Rather, these novel contributions emerge as a result of tunneling events when transitions occur between topologically different but physically identical vacuum winding states. These new terms give an extra contribution to the Casimir pressure. The infrared physics in the system can be described in terms of the topological auxiliary nonpropagating fields $a_i(\mathbf{k})$ governed by Chern-Simons-like action. The system can be studied in terms of these auxiliary fields precisely in the same way as a topological insulator can be analyzed in terms of Berry’s connection ${\mathcal{A}}_i(\mathbf{k})$. We also argue that the Maxwell vacuum defined on a small four-torus behaves very much in the same way as a topological insulator with $\theta \ne 0$.

We study the structure of Yukawa matrices derived from the supersymmetric Yang-Mills theory on magnetized orbifolds, which can realize the observed quark and charged lepton mass ratios as well as the Cabibbo-Kobayashi-Maswaka (CKM) mixing angles, even with a small number of tunable parameters and without any critical fine-tuning. As a reason behind this, we find that the obtained Yukawa matrices possess a Froggatt-Nielsen-like structure with Gaussian hierarchies, which provides a suitable texture for them favored by the experimental data.

We analyze the peculiar infrared instability that characterizes stationary inhomogeneous flows when their velocity crosses the sound speed by decreasing values. For definiteness, we work in the context of one-dimensional atomic Bose condensates. These flows are unstable under ultra-low real frequency perturbations because of the unbounded mode amplification near the sonic horizon. This results in a condensation of low-frequency phonons which produces a spatially structured flow in the supersonic domain. Numerical simulations reveal that this zero-frequency undulation suppresses the instability when its spatial extension is infinite, and when its phase is near that of a “shadow soliton” solution attached to the sonic horizon. These phenomena are akin to the condensation of rotons in flowing superfluid ${}^4\mathrm{He}$ when exceeding the Landau velocity. They also pertain to shallow water waves propagating on transcritical flows.

Light scalar fields can naturally couple disformally to matter fields. Static, nonrelativistic sources do not generate a classical field profile for a disformally coupled scalar, and so such scalars are free from the constraints on the existence of fifth forces that are so restrictive for conformally coupled scalars. In this paper we show that disformally coupled scalars can still be studied and constrained through their microscopic interactions with fermions and photons, both in terrestrial laboratories and from observations of stars. The strongest constraint on the coupling scale comes from mono-photon searches at the LHC and requires $M\gtrsim {10}^2\mathrm{GeV}$.

We consider the stability of self-accelerating solutions to extended quasidilaton massive gravity in the presence of matter. By making a second metric dynamical in this model, matter can cause it to evolve from a Lorentzian to Euclidean signature, triggering a ghost instability. We study this possibility with scalar field matter as it can model a wide range of cosmological expansion histories. For the $\mathrm{\Lambda }\mathrm{CDM}$ expansion history, stability considerations substantially limit the available parameter space while for a kinetic-energy-dominated expansion, no choice of quasidilaton parameters is stable. More generally these results show that there is no mechanism intrinsic to the theory to forbid such pathologies from developing from stable initial conditions and that stability can only be guaranteed for particular choices for the matter configuration.

The stability and localization of the gravitational perturbations for a special brane system in Eddington-inspired Born-Infeld gravity were studied in Liu et al. [Phys. Rev. D 85, 124053 (2012)]. In this paper, we show that the gravitational perturbations for a general brane system are stable, the four-dimensional graviton (massless KK graviton) can be localized on the brane, and the mass spectra of massive KK gravitons are gapless and continuous. Two models are constructed as examples. In the first model, which is a generalization of Liu et al. [Phys. Rev. D 85, 124053 (2012)], the brane has no inner structure and there is no gravitational resonance (quasilocalized KK gravitons). In the second one, the background scalar field is a double kink when the parameter in the model approaches its critical value. Correspondingly, the brane has inner structure and some gravitational resonances appear.

We give a proof of the most general multiple-scalar field theory in a flat space-time free of Ostrogradski ghosts. We start from the assumption that the action is a functional of the scalar fields with up to second-order derivatives (which in general can have field equations with up to fourth-order derivatives), and arrive at the most general field theory that can be constructed such that the field equations have up to second-order derivatives. Naturally, this theory includes all physically viable multi-scalar field theories in flat space-time, in the sense that they do not suffer from the Ostrogradski instability [M. Ostrogradsky, Memoires de lAcademie Imperiale des Science de Saint-Petersbourg 4, 385 (1850)].

The discovery of a void of size $\sim 200h^{-1}\mathrm{Mpc}$ and average density contrast of $\sim -0.1$ aligned with the cold spot direction has been recently reported. It has been argued that, although the first-order integrated Sachs-Wolfe (ISW) effect of such a void on the cosmic microwave background is small, the second-order Rees-Sciama (RS) contribution exceeds this by an order of magnitude and can entirely explain the observed cold spot temperature profile. In this paper we examine this surprising claim using both an exact calculation with the spherically symmetric Lemaître-Tolman-Bondi metric, and perturbation theory about a background Friedmann-Robertson-Walker metric. We show that both approaches agree well with each other, and both show that the dominant temperature contribution of the postulated void is an unobservable dipole anisotropy. If this dipole is subtracted, we find that the remaining temperature anisotropy is dominated by the linear ISW signal, which is orders of magnitude larger than the second-order RS effect, and that the total magnitude is too small to explain the observed cold spot profile. We calculate the density and size of a void that would be required to explain the cold spot, and show that the probability of existence of such a void is essentially zero in $\mathrm{\Lambda }\mathrm{CDM}$. We identify the importance of a posteriori selection effects in the identification of the cold spot, but argue that even after accounting for them, a supervoid explanation of the cold spot is always disfavored relative to a random statistical fluctuation on the last scattering surface.

Stationary and axisymmetric solutions of relativistic rotating stars with strong mixed poloidal and toroidal magnetic fields are obtained numerically. Because of the mixed components of the magnetic field, the underlying stationary and axisymmetric spacetimes are no longer circular. These configurations are computed from the full set of the Einstein-Maxwell equations, Maxwell’s equations, and from first integrals and integrability conditions of the magnetohydrodynamic equilibrium equations. After a brief introduction of the formulation of the problem, we present the first results for highly deformed magnetized rotating compact stars.

Relativistic equations of Bethe-Salpeter type for hadron structure are most conveniently formulated in momentum space. The presence of confining interactions causes complications because the corresponding kernels are singular. This occurs not only in the relativistic case but also in the nonrelativistic Schrödinger equation where this problem can be studied more easily. For the linear confining interaction the singularity reduces to one of Cauchy principal value form. Although this singularity is integrable, it still makes accurate numerical solutions difficult. We show that this principal value singularity can be eliminated by means of a subtraction method. The resulting equation is much easier to solve and yields accurate and stable solutions. To test the method’s numerical efficiency, we perform a three-parameter least-squares fit of a simple linear-plus-Coulomb potential to the bottomonium spectrum.

After the extraordinary discovery of the Higgs boson at the LHC, the next goal is to pin down its underlying dynamics by measuring the Higgs self-couplings, along with its couplings to gauge and matter particles. As a prototype model of new physics in the scalar sector, we consider the two-Higgs doublet model with $CP$ conservation, and evaluate the prospects for measuring the trilinear scalar couplings among the $CP$-even Higgs bosons $h$ and $H$ (${\lambda }^{hhh}$, ${\lambda }^{hhH}$, ${\lambda }^{hHH}$) at LHC14. The continuum and resonant production of $CP$-even Higgs boson pairs, $hh$ and $hH$, offer complementary probes of the scalar potential away from the light-Higgs alignment limit. We identify the viable search channels at LHC14 and estimate their expected discovery sensitivities.

We propose a two-loop induced Zee-Babu-type neutrino mass model at the TeV scale. Although there is no dark matter candidate in the original Zee-Babu model, our model can include the dark matter by introducing an unbroken discrete $Z_2$ symmetry. The discrepancy between the experimental value of the muon anomalous magnetic moment (muon $g-2$) and its prediction in the standard model can be explained by contributions from additional vectorlike charged leptons which are necessary to give nonzero neutrino masses. The mass of vectorlike leptons to be slightly above 300 GeV is favored and allowed from the muon $g-2$ and the current LHC data. We find that from the structure of the neutrino mass matrix, doubly charged scalar bosons in our model can mainly decay into the same-sign and same-flavor dilepton plus missing transverse momentum. By measuring an excess of these events at the LHC, our model can be distinguished from the other models including doubly charged scalar bosons.

Several groups are carrying out experiments to observe and measure vacuum magnetic birefringence, predicted by quantum electrodynamics (QED). We have started running the new PVLAS apparatus installed in Ferrara, Italy, and have measured a noise floor value for the unitary field magnetic birefringence of vacuum $\mathrm{\Delta }{n}_u^{(\mathrm{vac})}=(4\pm 20)\times 10^{-23}{\mathrm{T}}^{-2}$ (the error represents a $1\sigma$ deviation). This measurement is compatible with zero and hence represents a new limit on vacuum magnetic birefringence deriving from nonlinear electrodynamics. This result reduces to a factor of 50 the gap to be overcome to measure for the first time the value of $\mathrm{\Delta }{n}_u^{(\mathrm{vac},\mathrm{QED})}$ predicted by QED: $\mathrm{\Delta }{n}_u^{(\mathrm{vac},\mathrm{QED})}=4\times {10}^{-24}{\mathrm{T}}^{-2}$. These birefringence measurements also yield improved model-independent bounds on the coupling constant of axion-like particles to two photons, for masses greater than 1 meV, along with a factor-2 improvement of the fractional charge limit on millicharged particles (fermions and scalars), including neutrinos.

We study the response of a class of topological systems to electromagnetic and gravitational sources, including torsion and curvature. By using the technology of anomaly polynomials, we derive the parity-odd response of a massive Dirac fermion in $d=2+1$ and $d=4+1$, which provides a simple model for a topological insulator. We discuss the covariant anomalies of the corresponding edge states, from a Callan-Harvey anomaly inflow, as well as a Hamiltonian spectral flow point of view. We also discuss the applicability of our results to other systems such as Weyl semimetals. Finally, using dimensional reduction from $d=4+1$, we derive the effective action for a $d=3+1$ time-reversal invariant topological insulator in the presence of torsion and curvature, and discuss its various physical consequences.