Dark matter charged under a new gauge sector, as motivated by recent data, suggests a rich GeV-scale “dark sector” weakly coupled to the standard model by gauge kinetic mixing. The new gauge bosons can decay to standard model leptons, but this mode is suppressed if decays into lighter “dark sector” particles are kinematically allowed. These particles in turn typically have macroscopic decay lifetimes that are constrained by two classes of experiments, which we discuss. Lifetimes of $10\mathrm{cm}\lesssim c\tau \lesssim {10}^8\mathrm{cm}$ are constrained by existing terrestrial beam-dump experiments. If, in addition, dark matter captured in the Sun (or Earth) annihilates into these particles, lifetimes up to $\sim {10}^{15}\mathrm{cm}$ are constrained by solar observations. These bounds span 14 orders of magnitude in lifetime, but they are not exhaustive. Accordingly, we identify promising new directions for experiments including searches for displaced di-muons in $B$ factories, studies at high-energy and -intensity proton beam dumps, precision gamma-ray and electronic measurements of the Sun, and milli-charge searches reanalyzed in this new context.

We derive the nonuniversal gaugino mass ratios in a supergravity (SUGRA) framework where the Higgs superfields belong to the nonsinglet representations $\mathbf{54}$ and $\mathbf{770}$ in an $SO(10)$ grand unified theory (GUT). We evaluate the ratios for the phenomenologically viable intermediate breaking chain $SU(4{)}_C\times SU(2{)}_L\times SU(2{)}_R(G_{422})$. After a full calculation of the gaugino mass ratios, noting some errors in the earlier calculation for $\mathbf{54}$, we obtain, using the renormalization group equations, interesting low scale phenomenology of such breaking patterns. Here, we assume the breaking of the $SO(10)$ GUT group to the intermediate gauge group and that to the standard model take place at the GUT scale itself. We also study the collider signatures in multilepton channels at the Large Hadron Collider (LHC) for some selected benchmark points allowed by the cold dark-matter relic density constraint provided by the WMAP data and compare these results with the minimal supergravity (mSUGRA) framework with similar gluino masses indicating their distinguishability in this regard.

We consider extension of the standard model $SU(2{)}_l\times SU(2{)}_h\times U(1)$ where the first two families of quarks and leptons transform according to the $SU(2{)}_l$ group and the third family according to the $SU(2{)}_h$ group. In this approach, the largeness of top-quark mass is associated with the large vacuum expectation value of the corresponding Higgs field. The model predicts almost degenerate heavy $W^{\prime }$ and $Z^{\prime }$ bosons with nonuniversal couplings, and extra Higgs bosons. We present in detail the symmetry breaking mechanism, and carry out the subsequent phenomenology of the gauge sector. We compare the model with electroweak precision data, and conclude that the extra gauge bosons and the Higgs bosons whose masses lie in the TeV range, can be discovered at the LHC.

We have computed the full one-loop corrections (electroweak as well as QCD) to processes contributing to the relic density of dark matter in the minimal supersymmetric standard model where the lightest supersymmetric particle is the lightest neutralino. We cover scenarios where the most important channels are those with gauge boson pair production. This includes the case of a bino with some wino admixture, a Higgsino and a wino. In this paper we specialize to the case of light dark matter much below the TeV scale. The corrections can have a non-negligible impact on the predictions and should be taken into account in view of the present and forthcoming increasing precision on the relic density measurements. Our calculations are made with the help of SLOOPS, an automatic tool for the calculation of one-loop processes in the minimal supersymmetric standard model. The renormalization scheme dependence of the results as concerns $\tan \beta$ is studied.

Motivated by recent measurements of the top quark forward-backward asymmetry at the Tevatron, we study how $t$-channel new physics can contribute to a large value. We concentrate on a theory with an Abelian gauge boson that possesses flavor changing couplings between up and top quarks but satisfies flavor physics constraints. Collider constraints are strong, but can be accommodated with the aid of small flavor-diagonal couplings. We find that $M_{Z^{\prime }}\approx 160\mathrm{GeV}$ can yield a total lab-frame asymmetry of $\sim 18\%$ without conflicting with other observables. There are implications for future collider searches, including exotic top quark decays, like-sign top quark production, and detailed measurements of the top production cross section. An alternate model with a gauged non-Abelian flavor symmetry has similar phenomenology, but lacks the like-sign top signal.

We consider a supersymmetric (SUSY) scenario including right-handed neutrinos, one of whose scalar superpartners is the lightest SUSY particle. The distinguishing feature in the collider signal of SUSY in such a case is not missing energy but a pair of charged tracks corresponding to the next-to-lightest SUSY particle, when it is, as in the case considered, a stau. Following up on our recent work on neutralino reconstruction in such cases, we explore the possibility of reconstructing charginos, too, through a study of transverse mass distributions in specified final states. The various steps of isolating the transverse momenta of neutrinos relevant for this are outlined, and regions of the parameter space where our procedure works are identified.

$1/N_c$ baryon mass relations are compared with lattice simulations of baryon masses using different values of the light-quark masses, and hence different values of $SU(3)$ flavor-symmetry breaking. The lattice data clearly display both the $1/N_c$ and $SU(3)$ flavor-symmetry breaking hierarchies. The validity of $1/N_c$ baryon mass relations derived without assuming approximate $SU(3)$ flavor symmetry also can be tested by lattice data at very large values of the strange quark mass. The $1/N_c$ expansion constrains the form of discretization effects; these are suppressed by powers of $1/N_c$ by taking suitable combinations of masses. This $1/N_c$ scaling is explicitly demonstrated in the present work.

This paper focuses on disagreement between theoretical predictions and experimental results of the production properties of $B_c$ meson. Hadronic decays of $B_c$ are used to separate predictions of production cross section and predictions of branching ratio. The branching ratios of $B_c$ decays to $J/\psi +\pi$ and to $J/\psi +3\pi$ are also presented.

We explore for the first time the possibilities to measure an intermediate-mass ($m_H=115–140\mathrm{GeV}/c^2$) standard model Higgs boson in electromagnetic proton-lead ($p\mathrm{Pb}$) interactions at the CERN Large Hadron Collider (LHC) via its $b\overline{b}$ decay. Using equivalent Weizsäcker-Williams photon fluxes and Higgs effective field theory for the coupling $\gamma \gamma \to H$, we obtain a leading-order cross section of the order of 0.3 pb for exclusive Higgs production in elastic ($p\mathrm{Pb}\stackrel{\gamma \gamma }{\to }XH\mathrm{Pb}$) and semielastic ($p\mathrm{Pb}\stackrel{\gamma \gamma }{\to }XH\mathrm{Pb}$) processes at $\sqrt{s_{NN}}=8.8\mathrm{TeV}$. After applying various kinematics cuts to remove the main backgrounds ($\gamma \gamma \to b\overline{b}$ and misidentified $\gamma \gamma \to q\overline{q}$ events), we find that a Higgs boson with $m_H=120\mathrm{GeV}/c^2$ could be observed in the $b\overline{b}$ channel with a $3\sigma$ significance integrating $300{\mathrm{pb}}^{-1}$ with an upgraded $p\mathrm{A}$ luminosity of ${10}^{31}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$. We also provide for the first time semielastic Higgs cross sections, along with elastic $t\overline{t}$ cross sections, for electromagnetic $pp$, $p\mathrm{A}$ and AA collisions at the LHC.

Tests of gravity on large scales in the Universe can be made using both imaging and spectroscopic surveys. The former allow for measurements of weak lensing, galaxy clustering and cross correlations such as the integrated Sachs-Wolfe effect. The latter probe galaxy dynamics through redshift-space distortions. We use a set of basic observables, namely, lensing power spectra, galaxy-lensing and galaxy-velocity cross-spectra in multiple redshift bins (including their covariances), to estimate the ability of upcoming surveys to test gravity theories. We use a two-parameter description of gravity that allows for the Poisson equation and the ratio of metric potentials to depart from general relativity. We find that the combination of imaging and spectroscopic observables is essential in making robust tests of gravity theories. The range of scales and redshifts best probed by upcoming surveys is discussed. We also compare our parametrization to others used in the literature, in particular, the $\gamma$ parameter modification of the growth factor.

Since the energy momentum tensor of a magnetic field always contains a spin-2 component in its anisotropic stress, stochastic primordial magnetic field (PMF) in the early universe must generate stochastic gravitational-wave (GW) background. This process will greatly affect the relic gravitational wave (RGW), which is one of the major scientific goals of the laser interferometer GW detections. Recently, the fifth science (S5) run of laser interferometer gravitational-wave observatory (LIGO) gave a latest upper limit ${\Omega }_{\mathrm{GW}}<6.9\times {10}^{-6}$ on the RGW background. Utilizing this upper limit, we derive new PMF limits: for a scale of galactic cluster $\lambda =1\mathrm{Mpc}$, the amplitude of PMF, that produced by the electroweak phase transition, has to be weaker than $B_{\lambda }\le 4\times {10}^{-7}\mathrm{G}$; for a scale of supercluster $\lambda =100\mathrm{Mpc}$, the amplitude of PMF has to be weaker than $B_{\lambda }\le 9\times {10}^{-11}\mathrm{G}$. In this manner, GW observation has potential to make interesting contributions to the study of primordial magnetic field.

The status and parameters of the scalar, vector, and tensor mesonic resonances are obtained in the multichannel analysis of processes $\pi \pi \to \pi \pi$, $K\overline{K}$, $\eta \eta$, and $\eta {\eta }^{\prime }$ and compared with other results. For example, we obtained the $f_0(600)$ meson with mass $774\pm 15\mathrm{MeV}$ and width $988\pm 36\mathrm{MeV}$ (the pole position on sheet II is $596-i494\mathrm{MeV}$) and the first $\rho$-like meson with mass $1275\pm 32\mathrm{MeV}$ and total width $304\pm 24\mathrm{MeV}$, which differ significantly from the mean value $1459\pm 11\mathrm{MeV}$ cited in the Particle Data Group tables. Spectroscopic implications from results of these analyses and possible classification of the resonance states in terms of the SU(3) multiplets are also discussed.

The temperature of the upper atmosphere affects the height of primary cosmic ray interactions and the production of high-energy cosmic ray muons which can be detected deep underground. The MINOS far detector at Soudan, MN, has collected over $67\times {10}^6$ cosmic ray induced muons. The underground muon rate measured over a period of five years exhibits a 4% peak-to-peak seasonal variation which is highly correlated with the temperature in the upper atmosphere. The coefficient, ${\alpha }_T$, relating changes in the muon rate to changes in atmospheric temperature was found to be ${\alpha }_T=0.873\pm 0.009(\mathrm{stat})\pm 0.010(\mathrm{syst})$. Pions and kaons in the primary hadronic interactions of cosmic rays in the atmosphere contribute differently to ${\alpha }_T$ due to the different masses and lifetimes. This allows the measured value of ${\alpha }_T$ to be interpreted as a measurement of the $K/\pi$ ratio for $E_p\gtrsim 7\mathrm{TeV}$ of ${0.12}_{-0.05}^{+0.07}$, consistent with the expectation from collider experiments.

We investigate the hypothesized existence of an $S$ matrix for gravity and some of its expected general properties. We first discuss basic questions regarding the existence of such a matrix, including those of infrared divergences and description of asymptotic states. Distinct scattering behavior occurs in the Born, eikonal, and strong gravity regimes, and we describe aspects of both the partial wave and momentum space amplitudes, and their analytic properties, from these regimes. Classically the strong gravity region would be dominated by the formation of black holes, and we assume its unitary quantum dynamics is described by corresponding resonances. Masslessness limits some powerful methods and results that apply to massive theories, though a continuation path implying crossing symmetry plausibly still exists. Physical properties of gravity suggest nonpolynomial amplitudes, although crossing and causality constrain (with modest assumptions) this nonpolynomial behavior, particularly requiring a polynomial bound in complex $s$ at fixed physical momentum transfer. We explore the hypothesis that such behavior corresponds to a nonlocality intrinsic to gravity, but consistent with unitarity, analyticity, crossing, and causality.

It is argued that the appropriate macroscopic description of half-Bogomol’nyi-Prasad-Sommerfeld mesonic chiral operators in generic $d=4$ $\mathcal{N}=1$ toric gauge theories is in terms of the geometric quantization of smooth horizonless configurations. The relevance of different ensemble macroscopic descriptions is emphasized: Lorentzian vs Euclidean configurations as (semiclassical) microstates vs saddle points in a Euclidean path integral.

Small black holes in heterotic string theory have a vanishing horizon area at the supergravity level, but the horizon is stretched to the finite radius ${\mathrm{AdS}}_2\times S^{D-2}$ geometry once higher curvature corrections are turned on. This has been demonstrated to give good agreement with microscopic entropy counting. Previous considerations, however, were based on the classical local solutions valid only in the vicinity of the event horizon. Here we address the question of global existence of extremal black holes in the $D$-dimensional Einstein-Maxwell-Dilaton theory with the Gauss-Bonnet term introducing a variable dilaton coupling $a$ as a parameter. We show that asymptotically flat black holes exist only in a bounded region of the dilaton couplings $0<a<a_{\mathrm{cr}}$,where $a_{\mathrm{cr}}$ depends on $D$. For $D\ge 5$ (but not for $D=4$) the allowed range of $a$ includes the heterotic string values. For $a>a_{\mathrm{cr}}$ numerical solutions meet weak naked singularities at finite radii $r=r_{\mathrm{cusp}}$ (spherical cusps), where the scalar curvature diverges as $|r-r_{\mathrm{cusp}}{|}^{-1/2}$. For $D\ge 7$ cusps are met in pairs, so that solutions can be formally extended to asymptotically flat infinity choosing a suitable integration variable. We show, however, that radial geodesics cannot be continued through the cusp singularities, so such a continuation is unphysical.

We study the thermodynamic stability of the Kerr-anti-de Sitter black hole from the perturbative corrections to the gravitational partition function. The line of critical stability is identified by the appearance of a negative mode of the Euclidean action that renders the partition function ill defined. The eigenvalue problem, consisting of a system of three coupled partial differential equations for the metric perturbations, is solved numerically. The agreement with the standard condition of thermodynamic stability in the grand-canonical ensemble is remarkable. The results illustrate the physical significance of gravitational partition functions for rotating spacetimes beyond the instanton approximation. At a classical level, the results also imply that the Gregory-Laflamme instability of the Kerr string persists up to extremality, the range of unstable modes increasing with the angular momentum.

The recent data from PAMELA and Fermi-LAT can be interpreted as evidence of new astrophysical sources of high energy positrons. In that case, such astrophysical positrons constitute an additional background against the positrons from dark matter annihilation. In this paper, we study the effect of that background on the prospects for the detection of a positron dark matter signal in future experiments. In particular, we determine the new regions in the (mass, $⟨\sigma v⟩$) plane that are detectable by the AMS-02 experiment for several dark matter scenarios and different propagation models. We find that, due to the increased background, these regions feature annihilation rates that are up to a factor of 3 larger than those obtained for the conventional background. That is, an astrophysical interpretation of the present data by PAMELA and Fermi-LAT implies that the detection of positrons from dark matter annihilation is slightly more challenging than previously believed.

We generalize the Swiss-cheese cosmologies so as to include nonzero linear momenta of the associated boundary surfaces. The evolution of mass scales in these generalized cosmologies is studied for a variety of models for the background without having to specify any details within the local inhomogeneities. We find that the final effective gravitational mass and size of the evolving inhomogeneities depends on their linear momenta but these properties are essentially unaffected by the details of the background model.

We constrain the maximum flux from extragalactic neutrino point sources by using diffuse neutrino flux limits. We show that the maximum flux from extragalactic point sources is $E^2(d{N}_{\nu }/dE)\le 1.4\times {10}^{-9}(L_{\nu }/2\times {10}^{43}\mathrm{erg}/\mathrm{s}{)}^{1/3}\mathrm{GeV}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$ from individual point sources with average neutrino luminosity per decade, $L_{\nu }$. It depends only slightly on factors such as the inhomogeneous matter density distribution in the local universe, the luminosity distribution, and the assumed spectral index. The derived constraints are at least 1 order of magnitude below the current experimental limits from direct searches. Significant constraints are also derived on the number density of neutrino sources and on the total neutrino power density.