Implications of Vector Boson Scattering Unitarity in Composite Higgs Models

The strong nature of Composite Higgs models manifests at high energies through the growing behavior of the scattering amplitudes of longitudinally polarized weak bosons that leads to the formation of composite resonances as well as non-resonant strong effects. In this work the unitarity of these scattering amplitudes is used as a tool to assess the profile of the composite spectrum of the theory, including non-resonant enhancements, vector resonances and the CP-even scalar excitation. These three signatures are then studied in realistic scattering processes at hadron colliders, aiming to estimate the potential to exclude dynamically motivated scenarios of Composite Higgs models.Comment: 27 pages, 16 figure

Constraining scalar resonances with top-quark pair production at the LHC

Constraints on models which predict resonant top-quark pair production at the LHC are provided via a reinterpretation of the Standard Model (SM) particle level measurement of the top-anti-top invariant mass distribution, $m(t\bar{t})$. We make use of state-of-the-art Monte Carlo event simulation to perform a direct comparison with measurements of $m(t\bar{t})$ in the semi-leptonic channels, considering both the boosted and the resolved regime of the hadronic top decays. A simplified model to describe various scalar resonances decaying into top-quarks is considered, including CP-even and CP-odd, color-singlet and color-octet states, and the excluded regions in the respective parameter spaces are provided.Comment: 34 pages, 17 figure

Vector-Vector scattering at the LHC with two charged leptons and two neutrinos in the final state

A complete parton level analysis of 2l2v2j and 4l2j, l = mu,e production at the LHC is presented, including all processes at order alpha^6, alpha^4*alpha_s^2. The infinite Higgs mass scenario, which is considered as a benchmark for strong scattering theories and is the limiting case for composite Higgs models, and one example of Strongly Interacting Light Higgs models are confronted with the Standard Model light Higgs predictions. This analysis is combined with the results in the lv4j, the ll4j and the 3lv2j channels presented in previous papers, in order to determine whether these alternative Higgs frameworks can be detected as an excess of events in boson--boson scattering.Comment: Version accepted by JHE

Diboson Signals via Fermi Scale Spin-One States

ATLAS and CMS observe deviations from the expected background in diboson invariant mass searches of new resonances around 2 TeV. We provide a general analysis of the results in terms of spin-one resonances and find that Fermi scale composite dynamics can be the culprit. The analysis and methodology can be employed for future searches at run two of the Large Hadron Collider.Comment: Version to match the published one in PRD. Note that we use an effective theory and therefore our analysis is largely model-independent and applies not only to technicolor but also to composite (goldstone) Higgs as well as to elementary extensions that appeared later in the literature. LaTeX, 2 columns, 4 pages, 5 figure

Testing a dynamical origin of Standard Model fermion masses

We discuss a test of the Standard Model fermion mass origin in models of dynamical electroweak symmetry breaking. The couplings of composite pseudoscalar resonances to top quarks allow to distinguish high-scale Extended-Technicolor-type fermion mass generation from fermion partial compositeness and low-scale mass generation via an induced vacuum expectation value of a doublet coupled to the composite sector. These different possible origins of fermion masses are thus accessible via weak-scale physics searched for at the LHC.Comment: 6 pages, 3 figures. Discussion of fermion partial compositeness added, typos improve

Anomalous dimensions of potential top-partners

We discuss anomalous dimensions of top-partner candidates in theories of Partial Compositeness. First, we revisit, confirm and extend the computation by DeGrand and Shamir of anomalous dimensions of fermionic trilinears. We present general results applicable to all matter representations and to composite operators of any allowed spin. We then ask the question of whether it is reasonable to expect some models to have composite operators of sufficiently large anomalous dimension to serve as top-partners. While this question can be answered conclusively only by lattice gauge theory, within perturbation theory we find that such values could well occur for some specific models. In the Appendix we collect a number of practical group theory results for fourth-order invariants of general interest in gauge theories with many irreducible representations of fermions.Comment: 21 pages, 4 figures, 6 tables V2: Added Table 3,4,5, equation (9) and various comments in reply to questions and suggestions raised by the two Referees of SciPost. Two references also added. V3: Typo in footnote 6 corrected. Final version in SciPos

A partially composite Goldstone Higgs

We consider a model of dynamical electroweak symmetry breaking with a partially composite Goldstone Higgs. The model is based on a strongly-interacting fermionic sector coupled to a fundamental scalar sector via Yukawa interactions. The SU(4) x SU(4) global symmetry of these two sectors is broken to a single SU(4) via Yukawa interactions. Electroweak symmetry breaking is dynamically induced by condensation due to the strong interactions in the new fermionic sector which further breaks the global symmetry SU(4) to Sp(4). The Higgs boson arises as a partially composite state which is an exact Goldstone boson in the limit where SM interactions are turned off. Terms breaking the SU(4) global symmetry explicitly generate a mass for the Goldstone Higgs. The model realizes in different limits both (partially) composite Higgs and (bosonic) Technicolor models, thereby providing a convenient unified framework for phenomenological studies of composite dynamics. It is also a dynamical extension of the recent elementary Goldstone-Higgs model.Comment: 7 pages, 7 figure