The detection of electromagnetic pulses from high energy showers is used as a means to search for ultrahigh energy cosmic ray and neutrino interactions. An approximate formula has been obtained to numerically evaluate the radio pulse emitted by a charged particle that instantaneously accelerates, moves at constant speed along a straight track, and halts again instantaneously. The approximate solution is applied to the particle track after dividing it in smaller subintervals. The resulting algorithm [often referred to as the Zas-Halzen-Stanev (ZHS) algorithm] is also the basis for most of the simulations of the electric field produced in high energy showers in dense media. In this work, the electromagnetic pulses as predicted with the ZHS algorithm are compared to those obtained with an exact solution of the electric field produced by a charged particle track. The precise conditions that must apply for the algorithm to be valid are discussed and its accuracy is addressed. This comparison is also made for electromagnetic showers in dense media. The ZHS algorithm is shown to describe Cherenkov radiation and to be valid for most situations of interest concerning detectors searching for ultrahigh energy neutrinos. The results of this work are also relevant for the simulation of pulses emitted from air showers.

We present the first results in the search for relativistic magnetic monopoles with the IceCube detector, a subsurface neutrino telescope located in the South Polar ice cap containing a volume of $1{\mathrm{km}}^3$. This analysis searches data taken on the partially completed detector during 2007 when roughly $0.2{\mathrm{km}}^3$ of ice was instrumented. The lack of candidate events leads to an upper limit on the flux of relativistic magnetic monopoles of ${\Phi }_{90\%\mathrm{C}.\mathrm{L}.}\sim 3\times {10}^{-18}{\mathrm{cm}}^{-2}{\mathrm{sr}}^{-1}{\mathrm{s}}^{-1}$ for $\beta \ge 0.8$. This is a factor of 4 improvement over the previous best experimental flux limits up to a Lorentz boost $\gamma$ below ${10}^7$. This result is then interpreted for a wide range of mass and kinetic energy values.

We examine a possibility to discover a Kaluza-Klein (KK) excitation of gluon in a warped extra-dimension model at the Large Hadron Collider, focusing on a decay channel of the KK gluon into a $b$-quark pair. It is known that, in a certain extension of the warped extra-dimension model, the third generation quarks could strongly couple to the KK gluon, as a result of appropriate bulk fermion mass parameters. Taking account of kinematical cuts to reduce background events, we show the model parameter space, which leads to a significance larger than $5\sigma$ with the integrated luminosity of $10(100){\mathrm{fb}}^{-1}$.

The Bethe-Salpeter approach allows for quantum-field theoretic descriptions of relativistic bound states; its inherent complexity, however, usually prevents the finding of exact solutions. Under suitable simplifying assumptions about the systems discussed, we derive analytically examples of rigorous solutions to the instantaneous homogeneous Bethe-Salpeter equation by relating tentative solutions to the interactions responsible for the formation of bound states.

We study the indirect effects of new physics on the phenomenology of the recently discovered “Higgs-like” particle. In a model-independent framework these effects can be parametrized in terms of an effective Lagrangian at the electroweak scale. In a theory in which the $SU(2{)}_L\times U(1{)}_Y$ gauge symmetry is linearly realized they appear at lowest order as dimension-six operators, containing all the standard model fields including the light scalar doublet, with unknown coefficients. We discuss the choice of operator basis which allows us to make better use of all the available data to determine the coefficients of the new operators. We illustrate our present knowledge of those by performing a global five-parameter fit to the existing data which allows simultaneous determination of the Higgs couplings to gluons, electroweak gauge bosons, bottom quarks, and tau leptons. We find that for all scenarios considered the standard model predictions for each individual Higgs coupling and observable are within the corresponding 90% C.L. allowed range, the only exception being the Higgs branching ratio into two photons for the scenario with standard couplings of the Higgs to fermions. We finish by commenting on the implications of the results for unitarity of processes at higher energies.

We present a lattice QCD calculation of the parameters of the $\rho$ meson decay. The study is carried out on spatially asymmetric boxes using nHYP-smeared clover fermions with two mass-degenerate quark flavors. Our calculations are carried out at a pion mass $m_{\pi }=304(2)\mathrm{MeV}$ on the set of lattices $V={24}^2\times \eta 24\times 48$ with $\eta =1.0$, 1.25, and 2.0 with lattice spacing $a=0.1255(7)\mathrm{fm}$. The resonance mass $m_{\rho }=827(3)(5)\mathrm{MeV}$ and coupling constant $g_{\rho \pi \pi }=6.67(42)$ are calculated using the $P$-wave scattering phase shifts. We construct a $2\times 2$ correlation matrix to extract the energy of the scattering states and compute the phase shifts using the finite volume formula. By varying the degree of asymmetry, we are able to compute a set of phase shifts that are evenly distributed throughout the spectral region where the $\rho$ decays.

In processes involving small-$x$ partons, like in deep inelastic scattering and in hadronic collisions at high energy, the final state can be expressed in terms of correlators of Wilson lines. We study such high-point correlators evolving according to the JIMWLK equation and we confirm the results of previous numerical and analytic work, by using an independent method, that the solution to the JIMWLK equation can be very well approximated by an appropriate Gaussian wave function. We explore both fixed and running coupling evolution, where in the latter the scale is set according to various prescriptions. As a byproduct, we also numerically confirm to high accuracy the validity of the law governing the behavior of the $S$-matrix close to the unitarity limit, the Levin-Tuchin formula. We furthermore outline how to calculate correlators with open color indices.

In the minimal supersymmetric standard model (MSSM), the Higgs couplings to down-type quarks and leptons, normalized with respect to their corresponding Standard Model values, coincide at tree level and this degeneracy is only slightly broken at the quantum level. Motivated by the latest results of the Higgs searches at the LHC and Tevatron, we explore the possibility of disentangling these couplings from each other by considering a scenario in which supersymmetry is broken spontaneously at a low scale. In such a scenario, all the Higgs couplings, except the ones to the $Z$ and $W$ bosons, receive tree level corrections that depend on the MSSM soft parameters. In particular, the corrections to the Yukawa couplings depend on the $A$-term soft parameter for the corresponding fermion, allowing for the freedom to break their usual relations, even in the MSSM decoupling limit. We highlight the main features of this scenario in terms of a benchmark point for which the normalized Higgs coupling to the tau leptons is depleted, the coupling to photons is enhanced, while all the other Higgs couplings, including the one to the bottom quarks, are close to their corresponding standard model values. We also discuss the experimental bounds arising mainly from di-tau searches and comment on the discovery/exclusion prospects at the LHC.

Cosmic ray signals from dipole-interacting dark matter annihilation are considered in the positron, antiproton, and photon channels. The predicted signals in the positron channel could nicely account for the excess of positron fraction from Fermi LAT, PAMELA, HEAT, and AMS-01 experiments for the dark matter mass larger than 100 GeV with a boost (enhancement) factor of 30–80. No excess of antiproton over proton ratio at the experiments also gives a severe restriction for this scenario. With the boost factors, the predicted signals from Galactic halo and signals as monoenergetic gamma-ray lines (monochromatic photons) for the region close to the Galactic center are investigated. The gamma-ray excess of recent tentative analyses based on Fermi LAT data and the potential probe of the monochromatic lines at a planned experiment, AMS-02, are also considered.

Using a sample of $1.06\times {10}^8$ ${\psi }^{\prime }$ mesons collected with the BESIII detector at the BEPCII $e^{+}{e}^{-}$ collider and ${\chi }_{cJ}$ mesons produced via radiative transitions from the ${\psi }^{\prime }$, we report the first observation for ${\psi }^{\prime }\to \overline{p}{K}^{+}{\Sigma }^0+\mathrm{c}.\mathrm{c}.$ (charge conjugate), as well as improved measurements for the ${\chi }_{cJ}$ hyperon decays ${\chi }_{cJ}\to \overline{p}{K}^{+}\Lambda +\mathrm{c}.\mathrm{c}.$ The branching fractions are measured to be $\mathcal{B}({\psi }^{\prime }\to \overline{p}{K}^{+}{\Sigma }^0+\mathrm{c}.\mathrm{c}.)=(1.67\pm 0.13\pm 0.12)\times {10}^{-5}$, $\mathcal{B}({\chi }_{c0}\to \overline{p}{K}^{+}\Lambda +\mathrm{c}.\mathrm{c}.)=(13.2\pm 0.3\pm 1.0)\times {10}^{-4}$, $\mathcal{B}({\chi }_{c1}\to \overline{p}{K}^{+}\Lambda +\mathrm{c}.\mathrm{c}.)=(4.5\pm 0.2\pm 0.4)\times {10}^{-4}$, and $\mathcal{B}({\chi }_{c2}\to \overline{p}{K}^{+}\Lambda +\mathrm{c}.\mathrm{c}.)=(8.4\pm 0.3\pm 0.6)\times {10}^{-4}$, where the first error is statistical, and the second is systematic. In the decay of ${\chi }_{c0}\to \overline{p}{K}^{+}\Lambda +\mathrm{c}.\mathrm{c}.$, an anomalous enhancement near threshold is observed in the invariant mass distribution of $\overline{p}\Lambda +\mathrm{c}.\mathrm{c}.$, which cannot be explained by phase space.

In this paper we consider nonanticommutative field theories in $\mathcal{N}=2$ superspace formalism on three-dimensional manifolds with a boundary. We modify the original Lagrangian in such a way that it preserves half the supersymmetry even in the presence of a boundary. We also analyze the partial breaking of supersymmetry caused by nonanticommutativity between fermionic coordinates. Unlike in four dimensions, in three dimensions a theory with $\mathcal{N}=1/2$ supersymmetry cannot be obtained by a nonanticommutative deformation of an $\mathcal{N}=1$ theory. However, in this paper we construct a three-dimensional theory with $\mathcal{N}=1/2$ supersymmetry by studying a combination of nonanticommutativity and boundary effects, starting from $\mathcal{N}=2$ supersymmetry.

One of the challenges of collider physics is to unambiguously associate detector-based objects with the corresponding elementary physics objects. A particular example is the association of calorimeter-based objects such as “jets,” identified with a standard (IR-safe) jet algorithm, with the underlying physics objects, which may be QCD-jets (arising from a scattered parton), electrons, photons or, as discussed here, photon-jets (a group of collinear photons). This separation is especially interesting in the context of Higgs search, where the signal includes events with two photons (in the Standard Model) as well as events with two photon-jets (in a variety of Beyond the Standard Model scenarios), while QCD provides ever-present background. Here we describe the implementation of techniques from the rapidly evolving area of jet substructure studies, not only to enhance the more familiar photon-QCD separation, but also to separately distinguish photon-jets, i.e., to separate usual jets into three categories: single photons, photon-jets and QCD-jets. The efficacy of these techniques for separation is illustrated through studies of simulated data.

We provide further numerical evidence which shows that $R^n$ models in $f(R)$ metric gravity produce a late time acceleration in the Universe or a matter domination era (usually a transient one) but not both. Our results confirm the findings of Amendola et al. [Phys. Rev. Lett. 98, 131302 (2007); Phys. Rev. D 75, 083504 (2007); Int. J. Mod. Phys. D 16, 1555 (2007)], but using a different approach that avoids the mapping to scalar-tensor theories of gravity, and therefore, spares us from any discussion or debate about frames (Einstein vs Jordan) which are endemic in this subject. This class of models has been used extensively in the literature as an alternative to dark energy, but should be considered ruled out for being inconsistent with the observations. Finally, we discuss a caveat in the analysis by Faraoni [Phys. Rev. D 83, 124044 (2011)], which was used to further constrain these models by using a chameleon mechanism.

A massive, self-interacting scalar field has been considered as a possible candidate for the dark matter in the universe. We present an observational constraint to the model arising from strong lensing observations in galaxies. The result points to a discrepancy in the properties of scalar field dark matter halos for dwarf and lens galaxies, mainly because halo parameters are directly related to physical quantities in the model. This is an important indication that it becomes necessary to have a better understanding of halo evolution in scalar field dark matter models, where the presence of baryons can play an important role.

Recent measurements of semileptonic $B$-meson decays into $\tau$ leptons are somewhat higher than expected in the standard model. Although the deviations are less than $3\sigma$, they suggest the possibility of new physics affecting primarily the $\tau$ lepton. In this paper we examine these results within the context of nonuniversal left-right models. We find that strong constraints from $b\to s\gamma$ on $W\mathrm{\text{−}}{W}^{\prime }$ mixing lead to a prediction of approximately equal enhancements for the $B\to D\tau \nu$ and the $B\to D^{\star }\tau \nu$ modes. The model predicts approximately the same enhancement for the inclusive semileptonic rate $\overline{B}\to X_c\tau \nu$ as well as for the leptonic decay $B_c^{-}\to {\tau }^{-}\nu$. An enhancement in the leptonic decay $B^{-}\to {\tau }^{-}\nu$ is also possible but is not uniquely correlated with the other modes. For this explanation to be viable, the mass of the nonuniversal $W^{\prime }$ would be below 1 TeV, within LHC reach.

We investigate the scope of the Large Hadron Collider in probing the parameter space of a 4-site model supplemented by one composite Higgs state. We concentrate on the yield of “mixed” diboson production giving three leptons and missing (transverse) energy in the final state, i.e., events induced via the subprocess $q{\overline{q}}^{\prime }\to l^{+}{\nu }_l{l}^{\prime +}{l}^{\prime -}+\mathrm{c}.\mathrm{c}.$, where $q$, $q^{\prime }$ are quarks and $l$, $l^{\prime }=e$, $\mu$ in all possible combinations, a signature which enables the production in the intermediate steps of all additional—with respect to the standard model—neutral and charged gauge bosons belonging to the spectrum of this scenario. We not only find this channel to be accessible over the background but also show that, after a dedicated cut-based analysis, kinematical reconstruction of all such resonances is always possible. We finally compare the yield of the mixed diboson mode to that of the “charged” diboson one and find that the former is of lesser scope than the latter at smaller gauge boson masses but it overcomes it at higher values, thereby revealing itself as a viable search mode covering new regions of parameter space.

The photon impact factor for the Balitsky-Fadin-Kuraev-Lipatov pomeron is calculated in the next-to-leading order approximation using the operator expansion in Wilson lines. The result is represented as a next-to-leading order $k_T$-factorization formula for the structure functions of small-$x$ deep inelastic scattering.

We study the Wilson line response in the holographic superconducting phase transitions in the Gauss-Bonnet gravity. In the black brane background case, the Little-Parks periodicity is independent of the Gauss-Bonnet parameter, while in the anti–de Sitter soliton case, there is no evidence for the Little-Parks periodicity. We further study the impact of the Gauss-Bonnet term on the holographic phase transitions quantitatively. For a given Wilson line, a bigger Gauss-Bonnet coefficient makes the phase transition easier for the black brane background while harder for the soliton background. For a given chemical potential, the response to the Wilson line is less sensitive for a bigger Gauss-Bonnet coefficient in the black brane case while the response is more sensitive in the soliton case. And more, a bigger Gauss-Bonnet coefficient makes the superconducting state more stable for both the black brane and the soliton backgrounds.

The connection of maximally supersymmetric Yang-Mills theory to the (2,0) theory in six dimensions has raised the possibility that it might be perturbatively ultraviolet finite in five dimensions. We test this hypothesis by computing the coefficient of the first potential ultraviolet divergence of planar (large $N_c$) maximally supersymmetric Yang-Mills theory in $D=5$, which occurs at six loops. We show that the coefficient is nonvanishing. Furthermore, the numerical value of the divergence falls very close to an approximate exponential formula based on the coefficients of the divergences through five loops. This formula predicts the approximate values of the ultraviolet divergence at loop orders $L>6$ in the critical dimension $D=4+6/L$. To obtain the six-loop divergence we first construct the planar six-loop four-point amplitude integrand using generalized unitarity. The ultraviolet divergence follows from a set of vacuum integrals, which are obtained by expanding the integrand in the external momenta. The vacuum integrals are integrated via sector decomposition, using a modified version of the FIESTA program.

The dynamics of extended bodies endowed with multipolar structure up to the mass quadrupole moment is investigated in the Schwarzschild background according to Dixon’s model, extending previous works. The whole set of evolution equations is numerically integrated under the simplifying assumptions of constant frame components of the quadrupole tensor and that the motion of the center of mass be confined on the equatorial plane, the spin vector being orthogonal to it. The equations of motion are also solved analytically in the limit of small values of the characteristic length scales associated with the spin and quadrupole with respect to the background curvature characteristic length. The results are qualitatively and quantitatively different from previous analyses involving only spin structures. In particular, the presence of the quadrupole turns out to be responsible for the onset of a nonzero spin angular momentum, even if initially absent.