In models with gravitino as the lightest supersymmetric particle (LSP), the next-to-lightest supersymmetric particle (NLSP) can have a long lifetime and appear stable in collider experiments. We study the leptonic signatures of such a scenario with tau sneutrino as the NLSP, which is realized in the non-universal Higgs masses (NUHM) scenario. We focus on an interesting trilepton signature with two like-sign taus and an electron or a muon of the opposite sign. The neutralinos and charginos are quite heavy in the model considered, and the trilepton signal comes mostly from the slepton-sneutrino production. We identify the relevant backgrounds, taking into account tau decays, and devise a set of cuts to optimize this trilepton signal. We simulate signal and backgrounds at the Large Hadron Collider (LHC) with 14 TeV center-of-mass energy. Although the sleptons in this model are relatively light, $\mathcal{O}(100\mathrm{GeV})$, discovery is more demanding compared to typical neutralino LSP scenarios. The trilepton signal requires a large amount of accumulated data, at least $\sim 80{\mathrm{fb}}^{-1}$, at the center-of-mass (c.m.) energy of 14 TeV.

We propose a direct gauge mediation model based on an uplifted metastable supersymmetry (SUSY) breaking coupled to supergravity. A constant superpotential plays an essential role to fix the moduli as well as breaking SUSY and $R$ symmetry and the cancellation of the cosmological constant. Gaugino masses are generated at leading order of SUSY breaking scale, and comparable to the sfermion masses as in the ordinary gauge mediation. The Landau pole problem for QCD coupling can be easily solved since more than half of messengers become superheavy, which are heavier than the grand unified theory (GUT) scale.

The neutrino oscillation data are in very good agreement with the tribimaximal mixing pattern: ${sin}^2{\theta }_{23}=1/2$, ${sin}^2{\theta }_{12}=1/3$, and ${sin}^2{\theta }_{13}=0$. Attempts to generate this pattern based on finite family symmetry groups typically assume that the family symmetry is broken into different subgroups in the charged-lepton and the neutrino mass matrices. This leads to a technical problem, where the cross couplings between the Higgs fields responsible for the two symmetry breaking chains force their vacuum expectation values to align, upsetting the desired breaking pattern. Here, we present a class of models based on the semidirect product group $(S_3{)}^4⋊A_4$, where the lepton families belong to representations which are not faithful. In effect, the Higgs sector knows about the full symmetry while the lepton sector knows only about the $A_4$ factor group. This can solve the alignment problem without altering the desired properties of the family symmetry. Inclusion of quarks into the framework is straightforward and leads to small and arbitrary Cabibbo-Kobayashi-Maskawa mixing angles. Supersymmetry is not essential for our proposal, but the model presented is easily supersymmetrized, in which case the same family symmetry solves the supersymmetry flavor problem.

In some dark matter models, the coupling of the dark matter particle to the standard model Higgs determines the dark matter relic density while it is also consistent with dark matter direct-detection experiments. On the other hand, the seesaw model for generating the neutrino masses probably arises from a spontaneous symmetry breaking of global lepton number. The dark matter particle thus can significantly annihilate into massless Majorons when the lepton number-breaking scale and hence the seesaw scale are near the electroweak scale. This leads to an interesting interplay between neutrino physics and dark matter physics, and the annihilation mode has an interesting implication on dark matter searches.

We present a measurement of the $t\overline{t}$ production cross section multiplied by the branching ratio to tau lepton decaying semihadronically (${\tau }_h$) plus jets, $\sigma (p\overline{p}\to t\overline{t}+X)·\mathrm{BR}(t\overline{t}\to {\tau }_h+\mathrm{\text{jets}})$, at a center of mass energy $\sqrt{s}=1.96\mathrm{TeV}$ using $1{\mathrm{fb}}^{-1}$ of integrated luminosity collected with the D0 detector. Assuming a top quark mass of 170 GeV, we measure ${\sigma }_{t\overline{t}}·{\mathrm{BR}}_{{\tau }_h+j}={0.60}_{-0.22}^{+0.23}(\mathrm{stat}{)}_{-0.14}^{+0.15}(\mathrm{syst})\pm 0.04(\mathrm{lumi})\mathrm{pb}$. In addition, we extract the $t\overline{t}$ production cross section using the $t\overline{t}\to {\tau }_h+\mathrm{\text{jets}}$ topology, with the result ${\sigma }_{t\overline{t}}={6.9}_{-1.2}^{+1.2}(\mathrm{stat}{)}_{-0.7}^{+0.8}(\mathrm{syst})\pm 0.4(\mathrm{lumi})\mathrm{pb}$. These findings are in good agreement with standard model predictions and measurements performed using other top quark decay channels.

Current cosmic microwave background bounds on the sum of the neutrino masses assume a sudden reionization scenario described by a single parameter that determines the onset of reionization. We investigate the bounds on the neutrino mass in a more general reionization scenario based on a principal component approach. We found the constraint on the sum of the neutrino masses from cosmic microwave background data can be relaxed by $\sim 40\%$ in a generalized reionization scenario. Moreover, the amplitude of the rms mass fluctuations ${\sigma }_8$ is also considerably lower providing a better consistency with the low amplitude of the Sunyaev-Zel’dovich signal recently found by the South Pole Telescope.

Topological insulators and superconductors in different spatial dimensions and with different discrete symmetries have been fully classified recently, revealing a periodic structure for the pattern of possible types of topological insulators and superconductors, both in terms of spatial dimensions and in terms of symmetry classes. It was proposed that K theory is behind the periodicity. On the other hand, D-branes, a solitonic object in string theory, are also known to be classified by K theory. In this paper, by inspecting low-energy effective field theories realized by two parallel D-branes, we establish a one-to-one correspondence between the K-theory classification of topological insulators/superconductors and D-brane charges. In addition, the string theory realization of topological insulators and superconductors comes naturally with gauge interactions, and the Wess-Zumino term of the D-branes gives rise to a gauge field theory of topological nature, such as ones with the Chern-Simons term or the $\theta$ term in various dimensions. This sheds light on topological insulators and superconductors beyond noninteracting systems, and the underlying topological field theory description thereof. In particular, our string theory realization includes the honeycomb lattice Kitaev model in two spatial dimensions, and its higher-dimensional extensions. Increasing the number of D-branes naturally leads to a realization of topological insulators and superconductors in terms of holography (AdS/CFT).

I explain a generalization of Bjorken flow where the medium has finite transverse size and expands both radially and along the beam axis. If one assumes that the equations of viscous hydrodynamics can be used, with $p=ϵ/3$ and zero bulk viscosity, then the flow I describe can be developed into an exact solution of the relativistic Navier-Stokes equations. The local four-velocity in the flow is entirely determined by the assumption of symmetry under a subgroup of the conformal group.

In this paper, we continue the work begun in a previous article. We compute, in the formalism of local composite operators, the value of the asymmetry in the dimension two condensate for finite temperatures. We find a positive value for the asymmetry, which disappears when the temperature is increased. We also compute the value of the full dimension two condensate for higher temperatures, and we find that it decreases in absolute value, finally disappearing for sufficiently high temperature. We also comment on the temperature dependence of the electric and magnetic components of the condensate separately. We compare our results with the corresponding lattice date found by Chernodub and Ilgenfritz.

We report results of the first $3\times 3$ “multiangle” simulation of the evolution of neutrino flavor in the core-collapse supernova environment. In particular, we follow neutrino flavor transformation in the neutronization neutrino burst of an O-Ne-Mg core-collapse event. Though in a qualitative sense our results are consistent with those obtained in $3\times 3$ single-angle simulations, at least in terms of neutrino mass hierarchy dependence, performing multiangle calculations is found to reduce the adiabaticity of flavor evolution in the normal neutrino mass hierarchy, resulting in lower swap energies. Differences between single-angle and multiangle results are largest for the normal neutrino mass hierarchy. Our simulations also show that current uncertainties in the measured mass-squared and mixing angle parameters translate into uncertainties in neutrino swap energies. Our results show that at low ${\theta }_{13}$ it may be difficult to resolve the neutrino mass hierarchy using the O-Ne-Mg neutronization neutrino burst.

We perform three-dimensional relativistic hydrodynamical calculations of neutron star mergers to assess the reliability of an approximate treatment of thermal effects in such simulations by combining an ideal-gas component with zero-temperature, microphysical equations of state. To this end we compare the results of simulations that make this approximation to the outcome of models with a consistent treatment of thermal effects in the equation of state. In particular we focus on the implications for observable consequences of merger events like the gravitational-wave signal. It is found that the characteristic gravitational-wave oscillation frequencies of the postmerger remnant differ by about 50 to 250 Hz (corresponding to frequency shifts of 2 to 8 percent) depending on the equation of state and the choice of the characteristic index of the ideal-gas component. In addition, the delay time to black hole collapse of the merger remnant as well as the amount of matter remaining outside the black hole after its formation are sensitive to the description of thermal effects.

The annihilation cross section of thermal relic dark matter determines both its relic density and indirect detection signals. We determine how large indirect signals may be in scenarios with Sommerfeld-enhanced annihilation, subject to the constraint that the dark matter has the correct relic density. This work refines our previous analysis through detailed treatments of resonant Sommerfeld enhancement and the effect of Sommerfeld enhancement on freeze out. Sommerfeld enhancements raise many interesting issues in the freeze out calculation, and we find that the cutoff of resonant enhancement, the equilibration of force carriers, the temperature of kinetic decoupling, and the efficiency of self-interactions for preserving thermal velocity distributions all play a role. These effects may have striking consequences; for example, for resonantly-enhanced Sommerfeld annihilation, dark matter freezes out but may then chemically recouple, implying highly suppressed indirect signals, in contrast to naive expectations. In the minimal scenario with standard astrophysical assumptions, and tuning all parameters to maximize the signal, we find that, for force-carrier mass $m_{\varphi }=250\mathrm{MeV}$ and dark matter masses $m_X=0.1$, 0.3, and 1 TeV, the maximal Sommerfeld enhancement factors are $S_{\mathrm{eff}}=7$, 30, and 90, respectively. Such boosts are too small to explain both the PAMELA and Fermi excesses. Nonminimal models may require smaller boosts, but the bounds on $S_{\mathrm{eff}}$ could also be more stringent, and dedicated freeze out analyses are required. For concreteness, we focus on $4\mu$ final states, but we also discuss $4e$ and other modes, deviations from standard astrophysical assumptions and nonminimal particle physics models, and we outline the steps required to determine if such considerations may lead to a self-consistent explanation of the PAMELA or Fermi excesses.

Motivated by their effect on the gravitational wave signal emitted by cosmic strings, we study the dynamics of kinks on strings of different tensions meeting at junctions. The propagation of a kink through a $Y$ junction leads to the formation of three “daughter” kinks. Assuming a uniform distribution of the incoming wave vectors at the junction, we find there is a significant region of configuration space in which the sharpness of at least one of the daughter kinks is enhanced relative to the sharpness of the initial kink. For closed loops with junctions we show this leads to an exponential growth in time of very sharp kinks. Using numerical simulations of realistic, evolving cosmic string loops with junctions to calculate the distribution of kink amplitudes as a function of time, we show that loops of this kind typically develop several orders of magnitude of very sharp kinks before the two junctions collide. This collision, or other effects such as gravitational backreaction, may end the proliferation.

The secondary spectra of the gravitons induced by a waterfall-like field are computed and the general bounds on the spectral energy density of the tensor modes of the geometry are translated into explicit constraints on the amplitude and slope of the waterfall spectrum. The obtained results are compared with the primary gravitational wave spectra of the concordance model and of its neighboring extensions as well as with the direct LIGO/Virgo bounds on stochastic backgrounds of relic gravitons. Space-borne interferometers [such as LISA (Laser Interferometer Space Antenna), BBO (Big Bang Observer), and DECIGO (Deci-hertz Interferometer Gravitational Wave Observatory)] seem to be less relevant but their potential implications are briefly outlined.

Recent measurements performed with some direct dark matter detection experiments, e.g. CDMS-II and CoGENT (after DAMA/LIBRA), have unveiled a few events compatible with weakly interacting massive particles. The preferred mass range is around 10 GeV, with a quite large spin-independent cross section of ${10}^{-43}-{10}^{-41}{\mathrm{cm}}^2$. In this paper, we recall that a light dark matter particle with dominant couplings to quarks should also generate cosmic-ray antiprotons. Taking advantage of recent works constraining the Galactic dark matter mass profile on the one hand and on cosmic-ray propagation on the other hand, we point out that considering a thermal annihilation cross section for such low mass candidates very likely results in an antiproton flux in tension with the current data, which should be taken into account in subsequent studies.

We make use of the language of nonlinear realizations to analyze electroweak symmetry breaking scenarios in which a light dilaton emerges from the breaking of a nearly conformal strong dynamics and compare the phenomenology of the dilaton to that of the well-motivated light composite Higgs scenario. We argue that—in addition to departures in the decay/production rates into massless gauge bosons mediated by the conformal anomaly—characterizing features of the light dilaton scenario are enhancements in off-shell events at high invariant mass involving two longitudinally polarized vector bosons and a dilaton, and tree-level flavor violating processes. Accommodating both electroweak precision measurements and flavor constraints appears especially challenging in the ambiguous scenario in which the Higgs and the dilaton fields strongly mix. We show that warped higgsless models of electroweak symmetry breaking are explicit and tractable realizations of this limiting case. The relation between the naive radion profile often adopted in the study of holographic realizations of the light dilaton scenario and the actual dynamical dilaton field is clarified in the Appendix.

Heavy colored scalar particles, which exist in many models of new physics, can be pair produced at the LHC via gluon-gluon fusion and possibly form quarkoniumlike bound states. If the scalars are also charged under the electroweak gauge group, these bound states can then decay into electroweak bosons. This yields a resonant cross section for final states such as $\gamma \gamma$ that can exceed standard model backgrounds. This paper studies this process in the Manohar-Wise model of color-octet scalars (COS). Important threshold logarithms and final state Coulomb-like QCD interactions are resummed using effective field theory. We compute the resummed cross section for gluon-gluon fusion to COS pairs at the LHC as well as the resonant cross section for octetonium decaying to $\gamma \gamma$. The latter cross section exceeds the standard model diphoton cross section when the COS mass is less than 500 (350) GeV for $\sqrt{s}=14(7)\mathrm{TeV}$. Nonobservation of resonances below these energies can significantly improve existing bounds on COS masses.

Grand unified theories where the neutrino mass is given by type II seesaw have the potential to provide interesting connections between the neutrino and charged fermion sectors. We explore the possibility of having a dominant type II seesaw contribution in supersymmetric $SO(10)$. We show that this can be achieved in the model where symmetry breaking is triggered by 54 and 45 dimensional representations, without the need for additional fields other than those already required to have a realistic charged fermion mass spectrum. Physical consequences, such as the implementation of the Bajc, Senjanović, and Vissani mechanism, the possibility of the fields responsible for type II seesaw dominance being messengers of supersymmetry breaking, and the realization of baryo and leptogenesis in these theories, are discussed.

Relative phases of amplitudes for $D$ meson decays to a light pseudoscalar meson $P$ and a light vector meson $V$ decaying to two pseudoscalar mesons will lead to characteristic interferences on the three-body Dalitz plot. These phases may be compared with predictions of a flavor-symmetric treatment which extracts contributing amplitudes and their relative phases from a fit to $D\to PV$ decay rates. Good agreement was found previously for the cases of $B^0\to K^{+}{\pi }^{-}{\pi }^0$ and $D^0\to {\pi }^{+}{\pi }^{-}{\pi }^0$. The present work is devoted to the decays $D^0\to K_S{\pi }^{+}{\pi }^{-}$ and $D^0\to {\pi }^0{K}^{+}{K}^{-}$, for which agreement is not found. Several suggestions are offered for this discrepancy.

We extract new parton distribution functions (PDFs) of the proton by global analysis of hard scattering data in the general-mass framework of perturbative quantum chromodynamics. Our analysis includes new theoretical developments together with the most recent collider data from deep-inelastic scattering, vector boson production, and single-inclusive jet production. Because of the difficulty in fitting both the D0 Run-II $W$ lepton asymmetry data and some fixed-target DIS data, we present two families of PDFs, CT10 and CT10W, without and with these high-luminosity $W$ lepton asymmetry data included in the global analysis. With both sets of PDFs, we study theoretical predictions and uncertainties for a diverse selection of processes at the Fermilab Tevatron and the CERN Large Hadron Collider.