We explore the potential for the discovery of a dilaton $mathcalO(200-500)$ GeV in a classical scale/conformal invariant extension of the Standard Model by investigating the size of the corresponding breaking scale $Lambda$ at the LHC, extending a previous analysis. In particular, we address the recent bounds on $Lambda$ derived from Higgs boson searches. We investigate if such a dilaton can be produced via gluon-gluon fusion, presenting rates for its decay either into a pair of Higgs bosons or into two heavy gauge bosons, which can give rise to multi-leptonic final states. A detailed analysis via PYTHIA-FastJet has been carried out of the dominant Standard Model backgrounds, at a centre of mass energy of 14 TeV. We show that early data of $sim 20$ fb$^-1$ can certainly probe the region of parameter space where such a dilaton is allowed. A conformal scale of 5 TeV is allowed by the current data, for almost all values of the dilaton mass investigated.

We investigate the semiclassical approach to the lensing of photons in a spherically symmetric gravitational background, starting from Born level and include in our analysis the radiative corrections obtained from the electroweak theory for the graviton/photon/photon vertex

We test a class of holographic models for the very early Universe against cosmological observations and find that they are competitive to the standard cold dark matter model with a cosmological constant (ΛCDM) of cosmology. These models are based on three-dimensional perturbative superrenormalizable quantum field theory (QFT), and, while they predict a different power spectrum from the standard power law used in ΛCDM, they still provide an excellent fit to the data (within their regime of validity). By comparing the Bayesian evidence for the models, we find that ΛCDM does a better job globally, while the holographic models provide a (marginally) better fit to the data without very low multipoles (i.e., l≲30), where the QFT becomes nonperturbative. Observations can be used to exclude some QFT models, while we also find models satisfying all phenomenological constraints: The data rule out the dual theory being a Yang-Mills theory coupled to fermions only but allow for a Yang-Mills theory coupled to nonminimal scalars with quartic interactions. Lattice simulations of 3D QFTs can provide nonperturbative predictions for large-angle statistics of the cosmic microwave background and potentially explain its apparent anomalies.

We investigate the extended Higgs sectors, specially the charged Higgs sector in a supersymmetric $Y=0$ $SU(2)$ triplet and a Standard Model (SM) gauge singlet extension of SM. We show that in this model the allowed data for the Higgs boson interaction eigenstates tend to group into separate blocks for $SU(2)$ triplet, doublet and singlet. The triplet sector has two degenerate paired states, each pair composed of a mostly-triplet charged Higgs and of a mostly-triplet scalar or pseudoscalar state. The mostly-doublet sector involves a Standard Model like Higgs of 125 GeV and extra mass-degenerate states, composed of a charged, a scalar and a pseudoscalar. The CP-odd component of the singlet scalar, after supersymmetry breaking, takes the role of a pseudo-Nambu-Goldstone mode in the $Z_3$ symmetric case, while the CP-even one becomes decoupled. In a second part of our study we investigate the different decay processes allowed to a charged Higgs boson of this model. Specifically, we search for general signatures of the TNMSSM in order to distinguish among Higgs fields belonging to $SU(2)$ doublet, triplet and singlet representations at the LHC. We also propose few golden plated final state modes carrying the distinctive signatures of this model which could be investigated in collider searches. We also show how in the decoupling limit of the triplet ($|lambda_T| simeq 0$) affects the decays as well as the production channels at the LHC.

We present a complete study of the one graviton-two neutral gauge bosons vertex at 1-loop level in the electroweak theory. This vertex provides the leading contribution to the interaction between the standard model and gravity, mediated by the trace anomaly, at first order in the inverse Planck mass and at second order in the electroweak expansion. At the same time, these corrections are significant for precision studies of models with low scale gravity at the LHC. We show, in analogy with previous results in the QED and QCD cases, that the anomalous interaction between gravity and the gauge current of the standard model, due to the trace anomaly, is mediated, in each gauge-invariant sector, by effective massless scalar degrees of freedom. We derive the Ward and Slavnov-Taylor identities characterizing the vertex. Our analysis includes the contributions from the improvements of the scalar sector, induced by a conformally coupled Higgs sector in curved space.

We investigate the mapping of conformal correlators and of their anomalies from configuration to momen- tum space for general dimensions, focusing on the anomalous correlators TOO, TVV - involving the energy- momentum tensor (T ) with a vector (V ) or a scalar operator (O) - and the 3-graviton vertex T T T . We compute the T OO, T V V and T T T one-loop vertex functions in dimensional regularization for free field theories involving conformal scalar, fermion and vector fields. Since there are only one or two independent tensor structures solv- ing all the conformal Ward identities for the T OO or T V V vertex functions respectively, and three independent tensor structures for the T T T vertex, and the coefficients of these tensors are known for free fields, it is possible to identify the corresponding tensors in momentum space from the computation of the correlators for free fields. This works in general d dimensions for T OO and T V V correlators, but only in 4 dimensions for T T T , since vector fields are conformal only in d = 4. In this way the general solution of the Ward identities including anomalous ones for these correlators in (Euclidean) position space, found by Osborn and Petkou is mapped to the ordinary diagrammatic one in momentum space. We give simplified expressions of all these correlators in configuration space which are explicitly Fourier integrable and provide a diagrammatic interpretation of all the contact terms arising when two or more of the points coincide. We discuss how the anomalies arise in each approach. We then outline a general algorithm for mapping correlators from position to momentum space, and illustrate its application in the case of the V V V and T OO vertices. The method implements an intermediate regularization - similar to differential regularization - for the identification of the integrands in momentum space, and one extra regulator. The relation between the ordinary Feynman expansion and the logarithmic one generated by this approach are briefly discussed.

We investigate the Standard Model in the nearly conformal limit, in which conformal symmetry is broken only by the dilatation anomaly, through a hierarchy of anomalous Ward identities for the divergence of its dilatation current. In this approximation, the identities allow to extract the coupling of the dilaton to the trace anomaly, which we compute up to the quartic order in the conformal breaking scale. Our approach can be easily extended to discuss the anomaly contributions to the dilaton effective action to an arbitrarily high order. They allow to make a distinction between the Higgs and a dilaton at a phenomenological level.

We extend a previous phenomenological analysis of photon lensing in an external gravitational background to the case of a massless neutrino, and propose a method to incorporate radiative effects in the classical lens equations of neutrinos and photons. The study is performed for a Schwarzschild metric, generated by a point-like source, and expanded in the Newtonian potential at first order. We use a semiclassical approach, where the perturbative corrections to neutrino scattering, evaluated at one-loop in the Standard Model, are compared with the Einstein formula for the deflection using an impact parameter formulation. For this purpose, we use the renormalized expression of the graviton/fermion/fermion vertex presented in previous studies. We show the agreement between the classical and the semiclassical formulations, for values of the impact parameter $b_h$ of the neutrinos of the order of $b_hsim 20$, measured in units of the Schwarzschild radius. The analysis is then extended with the inclusion of the post Newtonian corrections in the external gravity field, showing that this extension finds application in the case of the scattering of a neutrino/photon off a primordial black hole. The energy dependence of the deflection, generated by the quantum corrections, is then combined with the standard formulation of the classical lens equations. We illustrate our approach by detailed numerical studies, using as a reference both the thin lens and the nonlinear Virbhadra-Ellis lens.

We consider a class of minimal abelian extensions of the Standard Model with an extra neutral gauge boson $Z'$ at the TeV scale. In these scenarios an extended scalar sector and heavy right-handed neutrinos are naturally envisaged. We present some of their striking signatures at the Large Hadron Collider, the most interesting arising from a $Z'$ decaying to heavy neutrino pairs as well as a heavy scalar decaying to two Standard Model Higgses. Using renormalisation group methods, we characterise the high energy behaviours of these extensions and exploit the constraints imposed by the embedding into a wider GUT scenario.

We compute the dark matter relic densities of neutralinos and axions in a supersymmetric model with a gauged anomalous U(1) symmetry.

We study the high-energy behaviour of a class of anomaly-free abelian extensions of the Standard Model. We focus on the interplay among the phenomenological characterisation of the model and the use of precise renormalisation group methods. Using as boundary conditions regions of the parameter space at the verge of current LHC probe, interesting unification patterns emerge linked to thresholds belonging to a SO(10) grand unification theory (GUT). We stress how the evolution of the mixing between the two abelian factors may provide a valuable tool to address the candidate high-energy embedding. The emerging unification scenarios are then challenged to be perturbative and to allow for a stable vacuum.

We close a gap in previous studies of nonsupersymmetric $cal N=0$ quiver gauge theories from a phenomenological point of view aimed at acquiring specific proposals for models beyond the Standard Model (BSM). Because $SU(3)$ is the gauge group of QCD we fix $N=3$ and vary only the $Z_p$ abelian orbifold. The values $1 leq p leq 7$ have been previously fully discussed as well as one special case, discovered by happenstance, of $p=12$. The values $p = 8$ and $p=9$ are discussed comprehensively in the present paper including the electroweak mixing angle, gauge coupling unification, spontaneous symmetry breakdown to the standard model, and the occurrence of three quark-lepton families. Two promising quiver node identifications are discovered for $p=8$ and three for $p=9$. All of these merit further study as BSM candidates.

Abstract: We discuss the signature of the anomalous breaking of the superconformal symmetry in N = 1 super Yang Mills theory, mediated by the Ferrara-Zumino hypercurrent (J ) with two vector (V) supercurrents (J VV) and its manifestation in the anomaly action, in the form of anomaly poles. This allows to investigate in a unified way both conformal and chiral anomalies. The analysis is performed in parallel to the Standard Model, for comparison. We investigate, in particular, massive deformations of the N = 1 theory and the spectral densities of the anomaly form factors which are extracted from the components of this correlator. In this extended framework it is shown that all the anomaly form factors are characterized by spectral densities which flow with the mass deformation. In particular, the continuum contributions from the two-particle cuts of the intermediate states turn into poles in the zero mass limit, with a single sum rule satisfied by each component. Non anomalous form factors, instead, in the same anomalous correlators, are characterized by non-integrable spectral densities. These tend to uniform distributions as one moves towards the conformal point, with a clear dual behaviour. As in a previous analysis of the dilaton pole of the Standard Model, also in this case the poles can be interpreted as signaling the exchange of a composite dilaton/axion/dilatino (ADD) multiplet in the effective Lagrangian. The pole-like behaviour of the anomaly form factors is shown to be a global feature of the correlators, present at all energy scales, due to the sum rules.

We present a brief overview of axion models associated to anomalous abelian (gauge) symmetries, discussing their main phenomenological features.

We point out that when doubly-charged bileptons are pair produced at the LHC, kinematics dictate that they are both almost at rest in the lab frame and therefore their decays lead to final state muons in a characteristic X-shape with only very tiny track curvature because of the high muon energies. Such X-events have essentially no standard model background and provide a smoking gun for the 331 model.

We study a class of non-exotic minimal $U(1) '$ extensions of the Standard Model, which includes all scenarios that are anomaly-free with the ordinary fermion content augmented by one Right-Handed neutrino per generation, wherein the new Abelian gauge group is spontaneously broken by the non-zero Vacuum Expectation Value of an additional Higgs singlet field, in turn providing mass to a $Z'$ state. By adopting the $B-L$ example, whose results can be recast into those pertaining to the whole aforementioned class, and allowing for both scalar and gauge mixing, we first extract the surviving parameter space in presence of up-to-date theoretical and experimental constraints. Over the corresponding parameter configurations, we then delineate the high energy behaviour of such constructs in terms of their stability and perturbativity. Finally, we highlight key production and decay channels of the new states entering the spectra of this class of models, i.e., heavy neutrinos, a second Higgs state and the $Z'$, which are amenable to experimental investigation at the Large Hadron Collider. We therefore set the stage to establish a direct link between measurements obtainable at the Electro-Weak scale and the dynamics of the underlying model up to those where a Grand Unification Theory embedding a $U(1)'$ can be realised.