We show that study of the atmospheric neutrinos in the 10–100 GeV energy range by DeepCore subarray of the IceCube Neutrino Observatory can substantially constrain the mixing of sterile neutrinos of mass $\sim 1\mathrm{eV}$ with active neutrinos. In the scheme with one sterile neutrino we calculate ${\nu }_{\mu }$ and ${\overline{\nu }}_{\mu }$ oscillation probabilities as well as zenith angle distributions of ${\nu }_{\mu }^{\mathrm{CC}}$ (charge current) events in different energy intervals in DeepCore. The distributions depend on the mass hierarchy of active neutrinos. Therefore, in principle, the hierarchy can be identified, if ${\nu }_s$ exists. After a few years of exposure the DeepCore data will allow us to exclude the mixing of $|U_{\mu 4}{|}^2\ge 0.02$ indicated by the LSND/MiniBooNE results. Combination of the DeepCore and high-energy IceCube data will further improve sensitivity to ${\nu }_s$ mixing parameters.

Using a data sample containing $1.06\times {10}^8$ ${\psi }^{\prime }$ events collected with the BESIII detector at the BEPCII electron-positron collider, we search for a light exotic particle $X$ in the process ${\psi }^{\prime }\to {\pi }^{+}{\pi }^{-}J/\psi$, $J/\psi \to \gamma X$, $X\to {\mu }^{+}{\mu }^{-}$. This light particle $X$ could be a Higgs-like boson $A^0$, a spin-1 $U$ boson, or a pseudoscalar sgoldstino particle. In this analysis, we find no evidence for any ${\mu }^{+}{\mu }^{-}$ mass peak between the mass threshold and $3.0\mathrm{GeV}/c^2$. We set 90%-confidence-level upper limits on the product-branching fractions for $J/\psi \to \gamma A^0$, $A^0\to {\mu }^{+}{\mu }^{-}$ which range from $4\times {10}^{-7}$ to $2.1\times {10}^{-5}$, depending on the mass of $A^0$, for $M(A^0)<3.0\mathrm{GeV}/c^2$. Only one event is seen in the mass region below $255\mathrm{MeV}/c^2$, and this has a ${\mu }^{+}{\mu }^{-}$ mass of $213.3\mathrm{MeV}/c^2$ and the product-branching-fraction upper limit $5\times {10}^{-7}$.

We search for the rare decay of the $D^0$ meson to two photons, $D^0\to \gamma \gamma$, and present a measurement of the branching fraction for a $D^0$ meson decaying to two neutral pions, $B(D^0\to {\pi }^0{\pi }^0)$. The data sample analyzed corresponds to an integrated luminosity of $470.5{\mathrm{fb}}^{-1}$ collected by the BABAR detector at the PEP-II asymmetric-energy $e^{+}{e}^{-}$ collider at SLAC. We place an upper limit on the branching fraction, $B(D^0\to \gamma \gamma )<2.2\times {10}^{-6}$, at 90% confidence level. This limit improves on the existing limit by an order of magnitude. We also find $B(D^0\to {\pi }^0{\pi }^0)=(8.4\pm 0.1\pm 0.4\pm 0.3)\times {10}^{-4}$.

We report measurements of branching fractions and time-dependent $CP$ asymmetries in $B^0\to D^{+}{D}^{-}$ and $B^0\to D^{*\pm }{D}^{\mp }$ decays using a data sample that contains $(772\pm 11)\times {10}^{6}B\overline{B}$ pairs collected at the ${\rm Y}(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We determine the branching fractions to be $\mathcal{B}(B^0\to D^{+}{D}^{-})=(2.12\pm 0.16\pm 0.18)\times {10}^{-4}$ and $\mathcal{B}(B^0\to D^{*\pm }{D}^{\mp })=(6.14\pm 0.29\pm 0.50)\times {10}^{-4}$. We measure $CP$ asymmetry parameters ${\mathcal{S}}_{D^{+}{D}^{-}}=-{1.06}_{-0.14}^{+0.21}\pm 0.08$ and ${\mathcal{C}}_{D^{+}{D}^{-}}=-0.43\pm 0.16\pm 0.05$ in $B^0\to D^{+}{D}^{-}$ and ${\mathcal{A}}_{D^{*}D}=+0.06\pm 0.05\pm 0.02$, ${\mathcal{S}}_{D^{*}D}=-0.78\pm 0.15\pm 0.05$, ${\mathcal{C}}_{D^{*}D}=-0.01\pm 0.11\pm 0.04$, $\Delta {\mathcal{S}}_{D^{*}D}=-0.13\pm 0.15\pm 0.04$ and $\Delta {\mathcal{C}}_{D^{*}D}=+0.12\pm 0.11\pm 0.03$ in $B^0\to D^{*\pm }{D}^{\mp }$, where the first uncertainty is statistical and the second is systematic. We exclude the conservation of $CP$ symmetry in both decays at equal to or greater than $4\sigma$ significance.

We study two $1/N_c$ effects on the meson spectra by using the anti-de Sitter/conformal field theory correspondence where the $1/N_c$ corrections from the chiral condensate and the quark density are controlled by the gravitational backreaction of the massive scalar field and $U(1)$ gauge field, respectively. The dual geometries with zero and nonzero current-quark masses are obtained numerically. We discuss meson spectra and binding energy of heavy quarkonium with the subleading corrections in the hard wall model.

We use the duality between color and kinematics to simplify the construction of the complete four-loop four-point amplitude of $\mathcal{N}=4$ super-Yang-Mills theory, including the nonplanar contributions. The duality completely determines the amplitude’s integrand in terms of just two planar graphs. The existence of a manifestly dual gauge-theory amplitude trivializes the construction of the corresponding $\mathcal{N}=8$ supergravity integrand, whose graph numerators are double copies (squares) of the $\mathcal{N}=4$ super-Yang-Mills numerators. The success of this procedure provides further nontrivial evidence that the duality and double-copy properties hold at loop level. The new form of the four-loop four-point supergravity amplitude makes manifest the same ultraviolet power counting as the corresponding $\mathcal{N}=4$ super-Yang-Mills amplitude. We determine the amplitude’s ultraviolet pole in the critical dimension of $D=11/2$, the same dimension as for $\mathcal{N}=4$ super-Yang-Mills theory. Strikingly, exactly the same combination of vacuum integrals (after simplification) describes the ultraviolet divergence of $\mathcal{N}=8$ supergravity as the subleading-in-$1/N_c^2$ single-trace divergence in $\mathcal{N}=4$ super-Yang-Mills theory.

We analyzed the $S_3$ invariant Higgs potential with $S_3$ singlet and doublet Higgs. We obtained a relation $(|v_1|/|v_2|{)}^2=-\sin 2{\varphi }_2/\sin 2{\varphi }_1$ from this $S_3$ invariant Higgs potential, where $v_1$, $v_2$ and ${\varphi }_1$, ${\varphi }_2$ are vacuum expectation values and phases of $S_3$ doublet Higgs, respectively. This relation could be satisfied exactly by the results $|v_1|/|v_2|=0.207$, ${\varphi }_1=-74.9°$, and ${\varphi }_2=0.74°$ obtained from our previous work analyzing the quark/lepton mass and mixing in the $S_3$ invariant Yukawa interaction. Furthermore, the relation $v_S\sim v_D=\sqrt{|v_1{|}^2+|v_2{|}^2}=174\mathrm{GeV}$ is obtained, and then the coupling strength of the Higgs to the top quark $g_{H_{S}tt}=m_t/v_S$ is altered by a factor $\sqrt{2}$ from the standard value. Introducing the $S_3$ doublet Higgs, flavor changing neutral currents are produced at tree level. The predicted branching ratios for rare decays ${\mu }^{-}\to e^{-}{e}^{+}{e}^{-}$, $K_L^0\to {\mu }^{+}{\mu }^{-}$, etc., induced by the flavor changing neutral currents, are sufficiently below the present experimental upper bounds.

We study high energy charged particle collisions near the horizon in an electromagnetic field around a rotating black hole and reveal the condition of the fine-tuning to obtain arbitrarily large center-of-mass (CM) energy. We demonstrate that the CM energy can be arbitrarily large as the uniformly magnetized rotating black hole arbitrarily approaches maximal rotation under the situation that a charged particle plunges from the innermost stable circular orbit (ISCO) and collides with another particle near the horizon. Recently, Frolov [Phys. Rev. D 85, 024020 (2012)] proposed that the CM energy can be arbitrarily high if the magnetic field is arbitrarily strong, when a particle collides with a charged particle orbiting the ISCO with finite energy near the horizon of a uniformly magnetized Schwarzschild black hole. We show that the charged particle orbiting the ISCO around a spinning black hole needs arbitrarily high energy in the strong field limit. This suggests that Frolov’s process is unstable against the black hole spin. Nevertheless, we see that magnetic fields may substantially promote the capability of rotating black holes as particle accelerators in astrophysical situations.

We point out that the temperature fluctuations of cosmic microwave background can be generated in a way that is different from the one usually assumed in slow-roll inflation. Our mechanism is based on vacuum fluctuations of fields which are at rest at the bottom of the potential, such as Kaluza-Klein modes or string excited states. When there are a large number (typically of order $N\sim {10}^{14}$) of fields with small mass in units of Hubble parameter during the inflationary era, this effect can give significant contributions to the cosmic microwave background temperature fluctuations. This number $N$ makes it possible to enhance scalar perturbation relative to tensor perturbation. Comparison with the observed amplitudes suggests that models with string scale of order ${10}^{-5}$ of four-dimensional Planck scale are favorable.

We reconstruct the shape of the primordial power spectrum of curvature perturbations in extended cosmological models, including addition of massive neutrinos, extra relativistic species, or varying primordial helium abundance, from the latest cosmic microwave background data from the Wilkinson Microwave Anisotropy Probe, the Atacama Cosmology Telescope, and the South Pole Telescope. We find that a scale-invariant primordial spectrum is disfavored by the data at 95% confidence level even in the presence of massive neutrinos, however it can lie within the 95% confidence region if the effective number of relativistic species or the primordial helium abundance is allowed to vary freely. The constraints on the extension parameters from $\mathrm{WMAP}7+\mathrm{ACT}+H_0+\mathrm{BAO}$ are the total mass of neutrinos $\sum _{}^{}{m}_{\nu }<0.48\mathrm{eV}$ (95% C.L.), the effective number of relativistic species $N_{\mathrm{eff}}=4.50\pm 0.81$, and the primordial helium abundance $Y_p=0.303\pm 0.075$. The constraints from $\mathrm{WMAP}7+\mathrm{SPT}+H_0+\mathrm{BAO}$ are $\sum _{}^{}{m}_{\nu }<0.45\mathrm{eV}$ (95% C.L.), $N_{\mathrm{eff}}=3.86\pm 0.63$, and $Y_p=0.277\pm 0.050$.

We compare observables to the finite size scaling hypothesis in SU(2) lattice gauge theory with two Dirac fermions in the adjoint representation. The fits that we obtain yield an estimate of the anomalous mass dimension that is consistent with four loop perturbation theory: $\gamma =0.50\pm 0.26$, with the error due to systematic uncertainties in the finite size scaling analysis. The result is consistent with Schrödinger functional studies and perturbative results.

We review the status of the phenomenology of light neutralinos in an effective minimal supersymmetric extension of the standard model at the electroweak scale, in light of new results obtained at the CERN Large Hadron Collider. First, we consider the impact of the new data obtained by the CMS Collaboration on the search for the Higgs-boson decay into a tau pair, and by the CMS and LHCb Collaborations on the branching ratio for the decay $B_s\to {\mu }^{+}+{\mu }^{-}$. Then, we examine the possible implications of the excess of events found by the ATLAS and CMS Collaborations in a search for a standard-model (SM)-like Higgs boson around a mass of 126 GeV, with a most likely mass region (95% C.L.) restricted to 115.5–131 GeV (global statistical significance about $2.3\sigma$). From the first set of data, we update the lower bound of the neutralino mass to be about 18 GeV. From the second set of measurements, we derive that the excess around $m_H^{\mathrm{SM}}=126\mathrm{GeV}$, which however needs a confirmation by further runs at the LHC, would imply a neutralino in the mass range $18\mathrm{GeV}\lesssim m_{\mathcal{X}}\lesssim 38\mathrm{GeV}$, with neutralino-nucleon elastic cross sections fitting well the results of the dark matter direct search experiments DAMA/LIBRA and CRESST.

Recently the ATLAS and CMS collaborations presented preliminary results of standard model Higgs searches and reported excesses of events for a Higgs boson at 124–126 GeV. Such a Higgs mass can be naturally realized, simultaneously explaining the muon $g-2$ anomaly, in gauge-mediated SUSY-breaking models with extra vectorlike matters. Upper bounds are obtained on the gluino mass, $m_{\tilde{g}}\lesssim 1.2(1.8)\mathrm{TeV}$, and on the extra vectorlike quark mass, $M_{Q^{\prime }}\lesssim 1.0(1.8)\mathrm{TeV}$, in the parameter region where the Higgs boson mass is 124–126 GeV and the muon $g-2$ is consistent with the experimental value at the $1\sigma$ ($2\sigma$) level. The LHC prospects are explored in the parameter region. It is found that some of the regions are already excluded by the LHC, and most of the parameter space is expected to be covered at $\sqrt{s}=14\mathrm{TeV}$. A study on the extra vectorlike quarks, especially current bounds on their masses and prospects for future searches, is also included.

We investigate planar quantum electrodynamics with two degenerate staggered fermions in an external magnetic field on the lattice. We argue that in external magnetic fields there is dynamical generation of mass for two-dimensional massless Dirac fermions in the weak-coupling region. We extrapolate our lattice results to the quantum Hall effect in graphene.

We compute the corrections of thermal photons on the effective potential for the linear sigma model of QCD. Since we are interested in temperatures lower than the confinement temperature, we consider the scalar fields to be out of equilibrium. We find that the induced thermal terms in the effective potential can stabilize the pion string, a string configuration which is unstable in the vacuum. Our results are applicable in a more general context and demonstrate that topological defect configurations arising in a wider class of field theories can be stabilized by thermal effects.

We consider cones over manifolds admitting real Killing spinors and instanton equations on connections on vector bundles over these manifolds. Such cones are manifolds with special (reduced) holonomy. We generalize the scalar ansatz for a connection proposed by Harland and Nölle [D. Harland and C. Nölle, J. High Energy Phys. 03 (2012) 082.] in such a way that instantons are parametrized by constrained matrix-valued functions. Our ansatz reduces instanton equations to matrix model equations which can be further reduced to Newtonian mechanics with particle trajectories obeying first-order gradient flow equations. Generalizations to Kähler-Einstein manifolds and resolved Calabi-Yau cones are briefly discussed. Our construction allows one to associate quiver gauge theories with special holonomy manifolds via dimensional reduction.

Nothing—the absence of spacetime—can be either an endpoint of tunneling, as in the bubble of nothing, or a starting point for tunneling, as in the quantum creation of a universe. We argue that these two tunnelings can be treated within a unified framework, and that, in both cases, nothing should be thought of as the limit of anti-de Sitter space in which the curvature length approaches zero. To study nothing, we study decays in models with perturbatively stabilized extra dimensions, which admit not just bubbles of nothing—topology-changing transitions in which the extra dimensions pinch off and a hole forms in spacetime—but also a whole family of topology-preserving transitions that nonetheless smoothly hollow out and approach the bubble of nothing in one limit. The bubble solutions that are close to this limit, bubbles of next-to-nothing, give us a controlled setting in which to understand nothing. Armed with this understanding, we are able to embed proposed mechanisms for the reverse process, tunneling from nothing to something, within the relatively secure foundation of the Coleman-De Luccia formalism and show that the Hawking-Turok instanton does not mediate the quantum creation of a universe.

Any theory invoked to explain cosmic acceleration predicts consistency relations between the expansion history, structure growth, and all related observables. Currently there exist high-quality measurements of the expansion history from type Ia supernovae, the cosmic microwave background temperature and polarization spectra, and baryon acoustic oscillations. We can use constraints from these data sets to predict what future probes of structure growth should observe. We apply this method to predict what range of cosmic shear power spectra would be expected if we lived in a $\Lambda \mathrm{CDM}$ universe, with or without spatial curvature, and what results would be inconsistent and therefore falsify the model. Though predictions are relaxed if one allows for an arbitrary quintessence equation of state $-1\le w(z)\le 1$, we find that any observation that rules out $\Lambda \mathrm{CDM}$ due to excess lensing will also rule out all quintessence models, with or without early dark energy. We further explore how uncertainties in the nonlinear matter power spectrum, e.g. from approximate fitting formulas such as Halofit, warm dark matter, or baryons, impact these limits.

An early stage of kinetic energy domination for inflation is applied to single-field quadratic and hybrid-type potentials considering only the amount of inflation necessary to solve the problems of the standard cosmological scenario. Using initial conditions inside the 1-sigma interval of the best-fit cosmological parameters for the potentials, low values for the quadrupole component can be obtained.

We find the best-fit cosmological parameters for a scenario of inflation with only the sufficient amount of accelerated expansion for the $\lambda {\varphi }^4$ potential. While for the simplest scenario of chaotic inflation all observable primordial fluctuations cross the Hubble horizon during the slow-roll epoch, for the scenario of just-enough inflation the slow-roll conditions are violated at the largest length scales. Performing a numerical mode-by-mode integration for the perturbations on the largest scales and comparing the predicted anisotropies of the cosmic microwave background to results from the WMAP 7-yr data analysis, we find the initial conditions in agreement with current cosmological data. In contrast to the simplest chaotic model for the quartic potential, the just-enough inflation scenario is not ruled out. Although this scenario naturally gives rise to a modification of the first multipoles, for a quartic potential it cannot explain the lack of power at the largest angular scales.