1,720,990 research outputs found
Radiative corrections to the lightest KK states in the T**2 / Z(2) x Z(2)-prime) orbifold
Full text linkWe study radiative corrections localized at the fixed points of the orbifold for the field theory in six dimensions with two dimensions compactified on the T-2/(Z(2) x Z(2)') orbifold in a specific realistic model for low energy physics that solves the proton decay and neutrino mass problem. We calculate corrections to the masses of the lightest stable KK modes, which could be the candidates for dark matter
Phase transitions in perturbative walking dynamics
No full textIn this paper, we investigate the dynamics of the confinement-deconfinement phase transition in a toy model where the walking dynamics is realized perturbatively. We study the properties of the phase transition focusing on the possible cosmological signatures it can provide. Interestingly the model is well under perturbative control only when the mass of the lightest field — the dilaton/scalon is much lighter than the rest of the fields and the phase transition proceeds slowly leading to strong signals in the stochastic gravitational wave spectrum
Nonlinear QED and physical Lorentz invariance
No full textThe spontaneous breakdown of 4-dimensional Lorentz invariance in the framework of QED with the nonlinear vector potential constraint A(mu)(2) = M-2 (where M is a proposed scale of the Lorentz violation) is shown to manifest itself only as some noncovariant gauge choice in the otherwise gauge invariant (and Lorentz invariant) electromagnetic theory. All the contributions to the photon-photon, photon-fermion, and fermion-fermion interactions violating the physical Lorentz invariance happen to be exactly cancelled with each other in the manner observed by Nambu long ago for the simplest tree-order diagrams-the fact which we extend now to the one-loop approximation and for both the timelike (M-2 > 0) and spacelike (M-2 < 0) Lorentz violations. The way to reach the physical breaking of the Lorentz invariance in the pure QED case (and beyond) treated in the flat Minkowskian space-time is also discussed in some detail
Flavor physics in SO(10) GUTs with suppressed proton decay due to gauged discrete symmetry
No full textGeneric SO(10) GUT models suffer from the problem that Planck scale induced non-renormalizable proton decay operators require extreme suppression of their couplings to be compatible with present experimental upper limits. One way to resolve this problem is to supplement SO(10) by simple gauged discrete symmetries which can also simultaneously suppress the renormalizable R-parity violating ones when they occur and make the theory "more natural". Here we discuss the phenomenological viability of such models. We first show that for both classes of models, e.g the ones that use 16H or 126H to break B-L symmetry, the minimal Higgs content which is sufficient for proton decay suppression is inadequate for explaining fermion masses despite the presence of all apparently needed couplings. We then present an extended 16H model, with three {\bf 10} and three {\bf 45}-Higgs, where is free of this problem. We propose this as a realistic and "natural" model for fermion unification and discuss the phenomenology of this model e.g. its predictions for neutrino mixings and lepton flavor violation
Precision diboson measurements at hadron colliders
Full text linkWe discuss the measurements of the anomalous triple gauge couplings at Large Hadron Collider focusing on the contribution of the O-3W and O-3 (W) over tilde operators. These deviations were known to be particularly hard to measure due to their suppressed interference with the SM amplitudes in the inclusive processes, leading to approximate flat directions in the space of these Wilson coefficients. We present the prospects for the measurements of these interactions at HL-LHC and HE-LHC using exclusive variables sensitive to the interference terms and taking carefully into account effects appearing due to NLO QCD corrections
Resolving gluon fusion loops at current and future hadron colliders
No full textInclusive Higgs measurements at the LHC have limited resolution on the gluon fusion loops, being unable to distinguish the long-distance contributions mediated by the top quark from possible short-distance new physics effects. Using an Effective Field Theory (EFT) approach we compare several proposed methods to lift this degeneracy, including tt ̄ h and boosted, off-shell and double Higgs production, and perform detailed projections to the High-Luminosity LHC and a future hadron collider. In addition, we revisit off-shell Higgs production. Firstly, we point out its sensitivity to modifications of the top-Z couplings, and by means of a general analysis we show that the reach is comparable to that of tree-level processes such as tt ̄ Z production. Implications for composite Higgs models are also discussed. Secondly, we assess the regime of validity of the EFT, performing an explicit comparison for a simple extension of the Standard Model containing one vector-like quark
Taming the off-shell Higgs boson
No full textWe study the off-shell Higgs data in the process pp → h(*) → Z(*)Z(*) → 4l, to constrain deviations of the Higgs couplings. We point out that this channel can be used to resolve the long- and short-distance contributions to Higgs production by gluon fusion and can thus be complementary to in measuring the top Yukawa coupling. Our analysis, performed in the context of effective field theory, shows that current data do not allow drawing any model-independent conclusions. We study the prospects at future hadron colliders, including the high-luminosity LHC and accelerators with higher energy, up to 100 TeV. The available QCD calculations and the theoretical uncertainties affecting our analysis are also briefly discussed
Effective field theory analysis of double Higgs production via gluon fusion
Full text linkWe perform a detailed study of double Higgs production via gluon fusion in the Effective Field Theory (EFT) framework where effects from new physics are parametrized by local operators. Our analysis provides a perspective broader than the one followed in most of the previous analyses, where this process was merely considered as a way to extract the Higgs trilinear coupling. We focus on the channel and perform a thorough simulation of signal and background at the 14 TeV LHC and a future 100 TeV proton-proton collider. We make use of invariant mass distributions to enhance the sensitivity on the EFT coefficients and give a first assessment of the impact of jet substructure techniques on the results. The range of validity of the EFT description is estimated, as required to consistently exploit the high-energy range of distributions, pointing out the potential relevance of dimension-8 operators. Our analysis contains a few important improvements over previous studies and identifies some inaccuracies there appearing in connection with the estimate of signal and background rates. The estimated precision on the Higgs trilinear coupling that follows from our results is less optimistic than previously claimed in the literature. We find that a ~30% accuracy can be reached on the trilinear coupling at a future 100 TeV collider with 3 ab^-1. Only an O(1) determination seems instead possible at the LHC with the same amount of integrated luminosity
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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