We compute the triple ℙomeron vertex from the Wilson line formalism, including both planar and nonplanar contributions, and get perfect agreement with the result obtained in the Extended Generalized Logarithmic Approximation based on Reggeon calculus.

We report a measurement of inclusive charged current interactions of muon neutrinos on carbon with an average energy of 0.8 GeV using the Fermilab Booster Neutrino Beam. We compare our measurement with two neutrino interaction simulations: NEUT and NUANCE. The charged current interaction rates (product of flux and cross section) are extracted by fitting the muon kinematics, with a precision of 6%–15% for the energy dependent and 3% for the energy integrated analyses. We also extract charged current inclusive interaction cross sections from the observed rates, with a precision of 10%–30% for the energy dependent and 8% for the energy integrated analyses. This is the first measurement of the charged current inclusive cross section on carbon around 1 GeV. These results can be used to convert previous SciBooNE cross-section ratio measurements to absolute cross-section values.

QCD string is formed at distances larger than the confinement scale and can be described by the Polchinski–Strominger effective string theory with a nonpolynomial action, which has nevertheless a well-defined semiclassical expansion around a long-string ground state. We utilize modern ideas about the Wilson-loop/scattering-amplitude duality to calculate scattering amplitudes and show that the expansion parameter in the effective string theory is small in the Regge kinematical regime. For the amplitudes we obtain the Regge behavior with a linear trajectory of the intercept $(d-2)/24$ in $d$ dimensions, which is computed semiclassically as a momentum-space Lüscher term, and discuss an application to meson scattering amplitudes in QCD.

We extend Lorentz-violating supersymmetry models to include vector superfields. The $CPT$-preserving model generalizes easily, while the obvious attempt at generalizing the $CPT$-violating model meets serious obstructions. Generalizations of the $CPT$-preserving but Lorentz-violating model to higher dimensions are also straightforward. Compactification is used to reduce the six-dimensional theory to an $\mathcal{N}=2$ Lorentz-violating theory in four dimensions, while the ten-dimensional theory is used to produce an $\mathcal{N}=4$ Lorentz-violating theory. This may be useful in future constructions involving AdS/CFT correspondence with Lorentz violation.

We propose moving all the ${\gamma }_5$ matrices to the rightmost position before continuing the dimension and show that this simple prescription will enable the dimension regularization scheme proposed by ’t Hooft and Veltman to be consistent with gauge invariance.

Recently, a generally covariant reformulation of two-dimensional flat spacetime free scalar field theory known as parametrized field theory was quantized using loop quantum gravity (LQG) type “polymer” representations. Physical states were constructed, without intermediate regularization structures, by averaging over the group of gauge transformations generated by the constraints, the constraint algebra being a Lie algebra. We consider classically equivalent combinations of these constraints corresponding to a diffeomorphism and a Hamiltonian constraint, which, as in gravity, define a Dirac algebra. Our treatment of the quantum constraints parallels that of LQG and obtains the following results, expected to be of use in the construction of the quantum dynamics of LQG: (i) the (triangulated) Hamiltonian constraint acts only on vertices, its construction involves some of the same ambiguities as in LQG and its action on diffeomorphism invariant states admits a continuum limit, (ii) if the regulating holonomies are in representations tailored to the edge labels of the state, all previously obtained physical states lie in the kernel of the Hamiltonian constraint, (iii) the commutator of two (density weight 1) Hamiltonian constraints as well as the operator correspondent of their classical Poisson bracket converge to zero in the continuum limit defined by diffeomorphism invariant states, and vanish on the Lewandowski-Marolf habitat, (iv) the rescaled density 2 Hamiltonian constraints and their commutator are ill-defined on the Lewandowski-Marolf habitat despite the well-definedness of the operator correspondent of their classical Poisson bracket there, (v) there is a new habitat which supports a nontrivial representation of the Poisson-Lie algebra of density 2 constraints.

We present a framework for the study of lensing in spherically symmetric spacetimes within the context of $f(R)$ gravity. Equations for the propagation of null geodesics, together with an expression for the bending angle, are derived for any $f(R)$ theory and then applied to an exact spherically symmetric solution of $R^n$ gravity. We find that for this case more bending is expected for $R^n$ gravity theories in comparison to general relativity and is dependent on the value of $n$ and the value of the distance of closest approach of the incident null geodesic.

In a model of an Abelian vector boson with a Maxwell kinetic term and non-negative mass-squared it is demonstrated that, under fairly general conditions during inflation, a scale-invariant spectrum of perturbations for the components of a vector field, massive or not, whose kinetic function (and mass) is modulated by the inflaton field is an attractor solution. If the field is massless, or if it remains light until the end of inflation, this attractor solution also generates anisotropic stress, which can render inflation weakly anisotropic. The above two characteristics of the attractor solution can source (independently or combined together) significant statistical anisotropy in the curvature perturbation, which may well be observable in the near future.

We derive accurate semianalytic formulas for the power spectra from two-field inflation assuming an arbitrary potential and arbitrary noncanonical kinetic terms, and we use them both to build phenomenological intuition and to constrain classes of two-field models using WMAP data. Using covariant formalism, we first develop a framework for understanding the background field kinematics and introduce a “slow-turn” approximation. Next, we find covariant expressions for the evolution of the adiabatic/curvature and entropy/isocurvature modes, and we discuss how the evolution of modes can be inferred mostly from the background kinematics and the geometry of the field manifold. From these expressions, we derive semianalytic formulas for the curvature, isocurvature, and cross spectra, and the standard spectral observables, all to second order in the slow-roll and slow-turn approximations. In tandem, we show how our covariant formalism provides useful intuition into how the general features of the inflationary Lagrangian translate into distinct features in the observable power spectra. In particular, we find that key features of the power spectra can be directly read off from the nature of the roll path, the curve the field vector rolls along with respect to the two-dimensional field manifold. For example, models whose roll path makes a sharp turn around 60 e-foldings before the end of inflation tend to be ruled out because they produce stronger departures from scale invariance than are allowed by the latest CMB observations. Finally, we apply our formalism to confront four classes of two-field models with WMAP data, including doubly quadratic and quartic potentials and nonstandard kinetic terms, showing how whether a model is ruled out or not depends not only on certain features of the inflationary Lagrangian, but also on the initial conditions. Ultimately, for a two-field model to be consistent with observations, we show that it must possess the right balance of certain kinematical and dynamical behaviors, which we reduce to a set of functions that represent the main characteristics of any two-field model of inflation.

Primordial non-Gaussianity (NG) affects the large scale structure (LSS) of the Universe by leaving an imprint on the distribution of matter at late times. Much attention has been focused on using the distribution of collapsed objects (i.e. dark matter halos and the galaxies and galaxy clusters that reside in them) to probe primordial NG. An equally interesting and complementary probe however is the abundance of extended underdense regions or voids in the LSS. The calculation of the abundance of voids using the excursion set formalism in the presence of primordial NG is subject to the same technical issues as the one for halos, which were discussed e.g. in Ref. [51] [G. D’Amico, M. Musso, J. Noreña, and A. Paranjape, arXiv:1005.1203.]. However, unlike the excursion set problem for halos which involved random walks in the presence of one barrier ${\delta }_c$, the void excursion set problem involves two barriers ${\delta }_v$ and ${\delta }_c$. This leads to a new complication introduced by what is called the “void-in-cloud” effect discussed in the literature, which is unique to the case of voids. We explore a path integral approach which allows us to carefully account for all these issues, leading to a rigorous derivation of the effects of primordial NG on void abundances. The void-in-cloud issue, in particular, makes the calculation conceptually rather different from the one for halos. However, we show that its final effect can be described by a simple yet accurate approximation. Our final void abundance function is valid on larger scales than the expressions of other authors, while being broadly in agreement with those expressions on smaller scales.

We carry out global fits to the nonuniversal Higgs Model (NUHM), applying all relevant present-day constraints. We present global probability maps for the NUHM parameters and observables (including collider signatures, direct, and indirect detection quantities), both in terms of posterior probabilities and in terms of profile likelihood maps. We identify regions of the parameter space where the neutralino dark matter in the model is either binolike, or else higgsinolike with mass close to 1 TeV and a spin-independent scattering cross section $\sim {10}^{-9}–{10}^{-8}\mathrm{pb}$. We trace the occurrence of the higgsinolike region to be a consequence of a mild focusing effect in the running of one of the Higgs masses, the existence of which in the NUHM we identify in our analysis. Although the usual binolike neutralino is more prominent, higgsinolike dark matter cannot be excluded, however its significance strongly depends on the prior and statistics used to assess it. We note that, despite experimental constraints often favoring different regions of parameter space to the constrained minimal supersymmetric standard model, most observational consequences appear fairly similar, which will make it challenging to distinguish the two models experimentally.

We investigate the discovery potential of the LHC experiments for $R$-parity violating supersymmetric models with a stau as the lightest supersymmetric particle (LSP) in the framework of minimal supergravity. We classify the final states according to their phenomenology for different $R$-parity violating decays of the LSP. We then develop event selection cuts for a specific benchmark scenario with promising signatures for the first beyond the standard model discoveries at the LHC. For the first time in this model, we perform a detailed signal over background analysis. We use fast detector simulations to estimate the discovery significance taking the most important standard model backgrounds into account. Assuming an integrated luminosity of $1{\mathrm{fb}}^{-1}$ at a center-of-mass energy of $\sqrt{s}=7\mathrm{TeV}$, we perform scans in the parameter space around the benchmark scenario we consider. We then study the feasibility to estimate the mass of the stau LSP. We briefly discuss difficulties, which arise in the identification of hadronic tau decays due to small tau momenta and large particle multiplicities in our scenarios.

We study the phenomenology of the neutral gauge sector of the four-site Higgsless model, based on the $SU(2{)}_L\times SU(2{)}_1\times SU(2{)}_2\times U(1{)}_Y$ gauge symmetry, at present colliders. The model predicts the existence of two neutral and four charged extra gauge bosons, $Z_{1,2}$ and $W_{1,2}^{\pm }$. We expand and update a previous study, by concentrating on the neutral sector. We derive new limits on $Z_{1,2}$-boson masses and couplings from recent direct searches at the Tevatron. We moreover estimate the discovery potential at the Tevatron with a project luminosity $L=10{\mathrm{fb}}^{-1}$, and at the 7 TeV LHC with $L=1{\mathrm{fb}}^{-1}$. In contrast to other Higgsless theories characterized by almost fermiophobic extra gauge bosons, the four-site model allows sizable $Z_{1,2}$-boson couplings to standard model fermions. Owing to this feature, we find that in the next 2 years the extra $Z_{1,2}$ bosons could be discovered in the favored Drell-Yan channel at the 7 TeV LHC for $Z_{1,2}$ masses in the TeV region, depending on model parameters.

We examine the use of hadronic event generators, such as Pythia or Herwig, to estimate the production rate of loosely bound hadronic molecules, such as the deuteron and the $X(3872)$. In the case of the deuteron, we point out that there are large uncertainties in the normalization of the predictions using event generators, because baryon pair distributions are not among the inputs used to tune the event generators. Predictions using Pythia for antideuteron production in ${\rm Y}$ decay are compared to measurements by the CLEO Collaboration. They suggest that Pythia overpredicts the probability of producing pairs of baryons, at least in ${\rm Y}$ decay into three gluons, and that the standard value of the coalescence parameter underpredicts the probability for formation of a deuteron from a neutron and proton with small relative momentum. In the case of the $X(3872)$, we discuss a proposed upper bound on the prompt cross section at the Tevatron that has been used as an argument against the $X(3872)$ being a loosely bound charm-meson molecule. We demonstrate that this proposed upper bound is invalid by showing that the analogous upper bound for the antideuteron would be smaller than the observed antideuteron cross section.

The construction of a Monte Carlo generator for high energy hadronic and nuclear collisions is discussed in detail. Interactions are treated in the framework of the Reggeon Field Theory, taking into consideration enhanced Pomeron diagrams which are resummed to all orders in the triple-Pomeron coupling. Soft and “semihard” contributions to the underlying parton dynamics are accounted for within the “semihard Pomeron” approach. The structure of cut enhanced diagrams is analyzed; they are regrouped into a number of subclasses characterized by positively-defined contributions which define partial weights for various “macro-configurations” of hadronic final states. An iterative procedure for a Monte Carlo generation of the structure of final states is described. The model results for hadronic cross sections and for particle production are compared to experimental data.

The transverse charge density in the pion can be represented as a dispersion integral of the imaginary part of the pion form factor in the timelike region. This formulation incorporates information from $e^{+}{e}^{-}$ annihilation experiments and allows one to reconstruct the transverse density much more accurately than from the spacelike pion form factor data alone. We calculate the transverse density using an empirical parametrization of the timelike pion form factor and estimate that it is determined to an accuracy of $\sim 10\%$ at a distance $b\sim 0.1\mathrm{fm}$, and significantly better at larger distances. The density is found to be close to that obtained from a zero-width $\rho$ meson pole over a wide range and shows a pronounced rise at small distances. The resulting two-dimensional image of the fast-moving pion can be interpreted in terms of its partonic structure in QCD. We argue that the singular behavior of the charge density at the center requires a substantial presence of pointlike configurations in the pion’s partonic wave function, which can be probed in other high-momentum transfer processes.

Deciding whether a model provides a good description of data is often based on a goodness-of-fit criterion summarized by a $p$-value. Although there is considerable confusion concerning the meaning of $p$-values, leading to their misuse, they are nevertheless of practical importance in common data analysis tasks. We motivate their application using a Bayesian argumentation. We then describe commonly and less commonly known discrepancy variables and how they are used to define $p$-values. The distribution of these are then extracted for examples modeled on typical data analysis tasks, and comments on their usefulness for determining goodness-of-fit are given.

In the eprint by Jean Alexandre [arXiv:1009.5834], a minimal extension of ($3+1$)-dimensional quantum electrodynamics has been proposed, which includes Lorentz violation (LV) in the form of higher-(spatial)-derivative isotropic terms in the gauge sector, suppressed by a mass scale $M$. The model can lead to dynamical mass generation for charged fermions. In this article, I elaborate further on this idea and I attempt to connect it to specific quantum-gravity models, inspired from string/brane theory. Specifically, in the first part of the article, I comment briefly on the gauge dependence of the dynamical mass generation in the approximations of J. Alexandre [arXiv:1009.5834.], and I propose a possible avenue for obtaining the true gauge-parameter-independent value of the mass by means of pinch technique argumentations. In the second part of the work, I embed the LV QED model into multibrane world scenarios with a view to provide a geometrical way of enhancing the dynamical mass to phenomenologically realistic values by means of bulk warp metric factors, in an (inverse) Randall-Sundrum hierarchy. Finally, in the third part of this paper, I demonstrate that such Lorentz-violating QED models may represent parts of a low-energy effective action (of Finsler-Born-Infeld type) of open strings propagating in quantum D0-particle stochastic space-time foam backgrounds, which are viewed as consistent quantum-gravity configurations. To capture correctly the quantum-fluctuating nature of the foam background, I replace the D0-recoil-velocity parts of this action by appropriate gradient operators in three-space, keeping the photon field part intact. This is consistent with the summation over world-sheet genera in the first-quantized string approach. I identify a class of quantum orderings which leads to the LV QED action of J. Alexandre, arXiv:1009.5834. In this way I argue, following the logic in that work, that the D-foam can lead to dynamically generated masses for charged-matter (fermionic) excitations interacting with it.

We study the original version of the Zee model, where both of the $SU(2{)}_L$ Higgs doublets are allowed to couple to the leptons, in the framework of the split fermion model in $M_4\times S_1/Z_2$ space-time. The neutrino masses are generated through 1-loop diagrams without introducing the right-handed neutrinos. By assuming an order one anarchical complex 5D Yukawa couplings, all the effective 4D Yukawa couplings are determined by the wave function overlap between the split fermions and the bulk scalars in the fifth dimension. The predictability of the Yukawa couplings is in sharp contrast to the original Zee model in 4D where the Yukawa couplings are unknown free parameters. This setup exhibits a geometrical alternative to the lepton flavor symmetry. By giving four explicit sets of the split fermion locations, we demonstrate that it is possible to simultaneously fit the lepton masses and neutrino oscillation data by just a handful free parameters without much fine tuning. Moreover, we are able to make definite predictions for the mixing angle ${\theta }_{13}$, the absolute neutrino masses, and the lepton flavor violation processes for each configuration.