A new measurement of the inclusive production cross section for $pp\to t\overline{t}$ is performed at a center-of-mass energy of 7 TeV using data collected by the CMS experiment at the LHC. The analysis uses a data sample corresponding to an integrated luminosity of $36{\mathrm{pb}}^{-1}$, and is based on the final state with one isolated, high transverse momentum muon or electron, missing transverse energy, and hadronic jets. The $t\overline{t}$ content of the selected events is enhanced by requiring the presence of at least one jet consistent with $b$-quark hadronization. The measured cross section is $150\pm 9(\mathrm{stat})\pm 17(\mathrm{syst})\pm 6(\mathrm{lumi})\mathrm{pb}$ and is in agreement with higher-order QCD calculations. The combination of this measurement with a previous CMS result based on dileptons gives $154\pm 17(\mathrm{stat}+\mathrm{syst})\pm 6(\mathrm{lumi})\mathrm{pb}$.

If the observation by OPERA of apparently superluminal neutrinos is correct, the Lagrangian for second-generation leptons must break Lorentz invariance. We calculate the effects of an energy-independent change in the neutrino speed on another observable, the charged pion decay rate. The rate decreases by a factor $[1-\frac{3}{1-m_{\mu }^2/m_{\pi }^2}(⟨v_{\nu }⟩-1)]$, where $⟨v_{\nu }⟩$ is the (directionally averaged) neutrino speed in the pion’s rest frame. This provides a completely independent experimental observable that is sensitive to the same forms of Lorentz violation as a neutrino time-of-flight measurement.

The exchange of a light $t$-channel flavor-changing gauge boson, $V^{\prime }$, with mass $\sim m_{\mathrm{top}}$ remains a leading explanation for the anomalous forward-backward asymmetry in top-quark production at the Tevatron. Unlike other ideas, including heavier $t$-channel mediators, the light $V^{\prime }$ model is not easily seen in the $m_{t\overline{t}}$ distribution. We advocate a more promising strategy. While current analyses at hadron colliders may not be sensitive, we propose searching for a $jj$ resonance in association with single top that may allow discovery in existing data. Deviations in the lepton charge asymmetry in this sample should also be present.

We demonstrate the existence of an extra nonanomalous $U(1)$ gauge symmetry in a three-generation Pati-Salam model constructed with intersecting D6-branes in Type-IIA string theory on a $T^6/({\mathbb{Z}}_2\times {\mathbb{Z}}_2)$ orientifold. This extra $U(1)$ forbids all dimension-4, 5, and 6 operators which mediate proton decay in the MSSM. Moreover, this results in the effective promotion of baryon and lepton number to local gauge symmetries, which can potentially result in leptophobic and leptophilic $Z^{\prime }$ bosons observable at the LHC. Furthermore, it is not necessary to invoke $R$-parity to forbid the dimension-4 operators which allow rapid proton decay. However, $R$-parity may arise naturally from a spontaneously broken $U(1{)}_{B-L}$. Assuming the presence of $R$-parity, we then study the direct-detection cross-sections for neutralino dark matter, including the latest constraints from the XENON100 experiment. We find that these limits are now within required range necessary to begin testing the model.

In this paper we continue the study of perturbative renormalizations in an $\mathcal{N}=(0,2)$ supersymmetric model. Previously we analyzed one-loop graphs in the heterotically deformed $\mathit{C}\mathit{P}(N-1)\mathit{C}$ models. Now we extend the analysis of the $\beta$ function and appropriate $Z$ factors to two, and, in some instances, all loops in the limiting case $g^2\to 0$. The field contents of the model, as well as the heterotic coupling, remain the same, but the target space becomes flat. In this toy $\mathcal{N}=(0,2)$ model we construct supergraph formalism. We show, by explicit calculations up to two-loop order, that the $\beta$ function is one-loop-exact. We derive a nonrenormalization theorem valid to all orders. This nonrenormalization theorem is rather unusual since it refers to (formally) $D$ terms. It is based on the fact that supersymmetry combined with target space symmetries and flavor symmetries is sufficient to guarantee the absence of loop corrections. We analyze the supercurrent supermultiplet (i.e., the hypercurrent) providing further evidence in favor of the absence of higher loops in the $\beta$ function.

A fourth generation of standard model fermions is usually considered unlikely due to constraints from direct searches, electroweak precision measurements, and perturbative unitarity. We show that fermion mass textures consistent with all constraints may be obtained naturally in a model with four generations constructed from intersecting $D6$-branes on a $T^6/({\mathbb{Z}}_2\times {\mathbb{Z}}_2)$ orientifold. The Yukawa matrices of the model are rank 2, so that only the third- and fourth-generation fermions obtain masses at the trilinear level. The first two generations obtain masses via higher-order couplings and are therefore naturally lighter. In addition, we find that the third and fourth generations automatically split in mass, but do not mix at leading order. Furthermore, the standard model gauge couplings automatically unify at the string scale, and all the hidden-sector gauge groups become confining in the range ${10}^{13}–{10}^{16}\mathrm{GeV}$, so that the model becomes effectively a four-generation minimal supersymmetric standard model at low energies.

We argue that the Isham-Storey exact solution to bigravity does not describe black holes because the horizon is a singular surface. However, this is not a generic property of bigravity, but a property of a particular potential. More general potentials do accept regular black holes. For regular black holes, we compute the total energy and thermodynamical parameters. Phase transitions occur for certain critical temperatures. We also find a novel region on phase space describing up to 4 allowed states for a given temperature.

In the effective-one-body (EOB) approach, the dynamics of two compact objects of masses $m_1$ and $m_2$ and spins ${\mathbf{S}}_1$ and ${\mathbf{S}}_2$ is mapped into the dynamics of one test particle of mass $\mu =m_1{m}_2/(m_1+m_2)$ and spin ${\mathbf{S}}_{*}$ moving in a deformed Kerr metric with mass $M=m_1+m_2$ and spin ${\mathbf{S}}_{\mathrm{Kerr}}$. In a previous paper, we computed an EOB Hamiltonian for spinning black-hole binaries that (i) when expanded in post-Newtonian orders, reproduces the leading-order spin-spin coupling and the leading and next-to-leading order spin-orbit couplings for any mass ratio, and (iii) reproduces all spin-orbit couplings in the test-particle limit. Here we extend this EOB Hamiltonian to include next-to-next-to-leading spin-orbit couplings for any mass ratio. We discuss two classes of EOB Hamiltonians that differ by the way the spin variables are mapped between the effective and real descriptions. We also investigate the main features of the dynamics when the motion is equatorial, such as the existence of the innermost stable circular orbit and of a peak in the orbital frequency during the plunge subsequent to the inspiral.

We consider the effects of the quantum stress tensor fluctuations of a conformal field in generating gravity waves in inflationary models. We find a nonscale invariant, non-Gaussian contribution which depends upon the total expansion factor between an initial time and the end of inflation. This spectrum of gravity wave perturbations is an illustration of a negative power spectrum, which is possible in quantum field theory. We discuss possible choices for the initial conditions. If the initial time is taken to be sufficiently early, the fluctuating gravity waves are potentially observable both in the CMB radiation and in gravity wave detectors, and could offer a probe of trans-Planckian physics. The fact that they have not yet been observed might be used to constrain the duration and energy scale of inflation. However, this conclusion is contingent upon including the contribution of modes which were trans-Planckian at the beginning of inflation.

An in-depth characterization of coherent radio Cherenkov pulses from particle showers in dense dielectric media, referred to as the Askaryan effect, is presented. The time-domain calculation developed in this article is based on a form factor to account for the lateral dimensions of the shower. It is computationally efficient and able to reproduce the results of detailed particle shower simulations with high fidelity in most regions of practical interest, including Fresnel effects due to the longitudinal development of the shower. In addition, an intuitive interpretation of the characteristics of the Askaryan pulse is provided. We expect our approach to benefit the analysis of radio pulses in experiments exploiting the radio technique.

We revise the spin-dependent neutralino-nucleus elastic scattering comparing the formalisms and approximations found in literature for the momentum transfer dependent structure functions. We argue that one of the normalized structure functions of Divari, Kosmas, Vergados, and Skouras is all that one needs to correctly take into account the detailed nuclear physics information provided by shell-model calculations. The factorization of the particle physics degrees of freedom from the nuclear physics momentum dependent structure functions implied by this formalism allows for a better understanding of the so-called model independent method for setting upper limits. We further discuss the possibility of experiments with spin-dependent sensitivity like COUPP to test or set limits on the proton spin-dependent cross section in the framework of the stau coannihilation region of the constrained minimal supersymmetric standard model. For this model with $A_0=0$, we provide a fitting formula by which it is possible to convert an upper limit on the spin-independent cross section as a function of the neutralino mass directly into an exclusion plot in the ($m_{1/2}$, $\tan \beta$) plane.

We study the impact of the Randall-Sundrum setup on the width difference $\Delta {\Gamma }_s$ and the $CP$-violating phase ${\varphi }_s$ in the ${\overline{B}}_s^0$-$B_s^0$ system. Our calculations are performed in the general framework of an effective theory, based on operator product expansion. The results can thus be used for many new-physics models. We find that the correction to the magnitude of the decay amplitude ${\Gamma }_{12}^s$ is below 4% for a realistic choice of input parameters. The main modification in the $\Delta {\Gamma }_s/{\beta }_s$-plane is caused by a new $CP$-violating phase in the mixing amplitude, which allows for a better agreement with the experimental results of the CDF and D0 Collaborations from $B_s^0\to J/\psi \varphi$ decays. The best-fit value of the $CP$ asymmetry $S_{\psi \varphi }$ can be reproduced, while simultaneously the theoretical prediction for the semileptonic $CP$ asymmetry $A_{\mathrm{SL}}^s$ can enter the $1\sigma$ range.

We revisit the case of a light neutralino lightest supersymmetric particle in the framework of the minimal supersymmetric standard model. We consider a model with 11 free parameters. We show that all scenarios where the annihilation of light neutralinos rely mainly on the exchange of a light pseudoscalar are excluded by direct detection searches and by Fermi measurements of the $\gamma$-flux from dwarf spheroidal galaxies. On the other hand, we find scenarios with light sleptons that satisfy all collider and astroparticle physics constraints. In this case, the lower limit on the lightest supersymmetric particle mass is 12.6 GeV. We discuss briefly how the parameter space of the model could be further probed at the LHC.

We present next-to-next-to-leading-order (NNLO) results for an exclusive soft function that appears in a recently developed factorization theorem for transverse momentum distributions. The factorization theorem, derived using the Soft Collinear Effective Theory, involves both a soft function and unintegrated nucleon distribution functions fully differential in momentum coordinates. The soft function is given by the vacuum matrix element of soft Wilson lines and is also fully differential in all components. We give results and relevant technical details for the NNLO calculation of the soft function, including finite parts, and derive the corresponding anomalous dimension. These results are necessary for achieving low transverse momentum resummation at next-to-next-to-leading-logarithmic accuracy in this effective field theory approach with unintegrated distribution functions.

A correspondence between type IIB string theory with $N$ D7-branes on ${\mathbb{R}}^{1,3}\times \frac{{\mathbb{C}}^1}{Z_2}\times \frac{{\mathbb{T}}^2}{Z_2}\times \frac{{\mathbb{T}}^2}{Z_2}$ and pure $\mathcal{N}=1$ $SU(N)$ gauge theory in four dimensions is proposed and argued. First the supergravity background of unwrapped and at D7-branes with running axion and dilaton on ${\mathbb{R}}^{1,7}\times \frac{{\mathbb{C}}^1}{Z_2}$ is studied together with the corresponding $\mathcal{N}=1$ $SU(N)$ gauge theory in eight dimensions. The D7-branes are then wrapped over a 4-cycle on $\frac{{\mathbb{T}}^2}{Z_2}\times \frac{{\mathbb{T}}^2}{Z_2}$ which turns on all $F_1$, $F_3$, $H_3$, and $F_5$ fluxes of type IIB theory and induces torsion. The supergravity solutions are explicitly constructed with exact analytic expressions for all components of the metric and the fluxes. The background geometry of the four-dimensional gauge theory is compact and conformally Calabi-Yau. The internal space normal to the wrapped D7-branes at the infrared boundary is ${\mathbb{S}}^1$ whose radius is set by the nonperturbative scale of the gauge theory and spacetime is ${\mathbb{R}}^{1,3}$ at the ultraviolet boundary. The gauge coupling of the four-dimensional gauge theory is related to the gauge coupling of the eight-dimensional gauge theory and the volume of the 4-cycle. The gravity theory reproduces the renormalization group flow and the pattern of chiral symmetry breaking of the gauge theory and produces linear connement of quarks. The curvature is small and nearly constant and the supergravity flow is smooth in the infrared region where the gauge theory is strongly coupled and a dual gravity description is useful. String loop corrections are small for large $N$. The scale of string tension in four dimensions is of the same order as the scale of Kaluza-Klein masses.

The scattering of two Dashen-Hasslacher-Neveu baryons in the large $N$ Gross-Neveu model is solved exactly using the relativistic, time-dependent Hartree-Fock approach. Unlike the special case of kink-antikink scattering, the scattering of Dashen-Hasslacher-Neveu baryons is sensitive to the backreaction of the fermions bound inside the baryons. Correspondingly the solution is much more complicated than the kink-antikink scattering solutions, which can be expressed in terms of sinh-Gordon solitons. Nevertheless, we present a simple ansatz form that gives closed analytic expressions for both the space–time-dependent mean fields and the Dirac spinors for all continuum and bound states. The solution can also be applied to the scattering of polarons and solitons in conducting polymers.

The total energy of any acceptable self-gravitating physical system has to be finite. In GR, the static gravitational potential of a self-gravitating body goes as $1/r$ at large distances and any slower decrease leads to infinite energy. In this work we show that in modified gravity theories the situation can be much different. We show that there exist spherically symmetric solutions with finite total energy, featuring an asymptotic behavior slower than $1/r$ and generically of the form $r^{\gamma }$. This suggests that configurations with nonstandard asymptotics may well turn out to be physical. The effect is due to an extra field coupled only gravitationally, which allows for modifications of the static potential generated by matter, while counterbalancing the apparently infinite energy budget.

The observed density of dark matter is of the magnitude expected for a thermal relic weakly-interacting massive particle (WIMP). In addition, the observed baryon density is within an order of magnitude of the dark matter density. This suggests that the baryon density is physically related to a typical thermal relic WIMP dark matter density. We present a model which simultaneously generates thermal relic WIMP-like densities for both baryons and dark matter by modifying a large initial baryon asymmetry. Dark matter is due to O(100) GeV gauge singlet scalars produced in the annihilation of the O(TeV) colored scalars which are responsible for the final thermal WIMP-like baryon asymmetry. The requirement of no baryon washout implies that there are two gauge singlet scalars. The low-temperature transfer of the asymmetry to conventional baryons can be understood if the long-lived O(TeV) colored scalars have large hypercharge, $|Y|>4/3$. Production of such scalars at the LHC would be a clear signature of the model.

Accepting the fine-tuned cosmological constant hypothesis, we have recently proposed that this hypothesis can be tested if the dark matter freeze out occurs at the electroweak scale and if one were to measure an anomalous shift in the dark matter relic abundance. In this paper, we numerically compute this relic abundance shift in the context of explicit singlet extensions of the standard model and explore the properties of the phase transition which would lead to the observationally most favorable scenario. Through the numerical exploration, we explicitly identify a parameter space in a singlet extension of the standard model which gives order unity observable effects. We also clarify the notion of a temperature dependence in the vacuum energy.

We consider an $SU(3{)}_c\otimes SU(2{)}_L\otimes SU(2{)}_R\otimes U(1{)}_{B-L}$ left-right symmetric model with three Higgs scalars including an $SU(2{)}_L$ doublet, an $SU(2{)}_R$ doublet and an $SU(2{)}_L\otimes SU(2{)}_R$ bidoublet. In addition to usual $SU(2)$-doublet fermions, our model contains $SU(2)$-triplet fermions with Majorana masses. The neutral components of the left-handed triplets can contribute a canonical seesaw while the neutral components of the right-handed triplets associated with the right-handed neutrinos can contribute a double/inverse-type seesaw. Our model can be embedded into an $SO(10)$ grand unification theory where the triplets belong to the $\mathbf{45}=(\mathbf{1},\mathbf{3},\mathbf{1},0)\oplus (\mathbf{1},\mathbf{1},\mathbf{3},0)\oplus \dots$ representations.