Search

In this paper, we use an Effective Field Theory (EFT) approach to evaluate the viability of the Higgs to account for the g − 2 anomaly. Although the SM contribution of the Higgs to the muon's magnetic dipole moment is negligible, using a bottom-up EFT, we show that given the current level of experimental limits on the Higgs sector, the Higgs can still yield a viable solution to the g − 2 anomaly if its couplings to the rest of the SM particles are allowed to deviate from their SM predictions. Such a solution would only require an O (1) fine-tuning. Further, applying unitarity arguments, we show that such a solution would indicate a scale of New Physics (NP) of ∼ 5–8 TeV, which could be lowered to ∼ 3.4–4 TeV if the Higgs couplings to the W and Z are assumed to conform to their SM predictions. We show that such a scenario could yield significant enhancement to the di-Higgs production in muon colliders, thus providing further motivation for its consideration. A key takeaway of this study is to highlight the importance of measuring the μ ̄ μ h h coupling in future experiments. [ABSTRACT FROM AUTHOR]

Di-Higgs couplings to fermions of the form h 2 f ‾ f are absent in the Standard Model, however, they are present in several physics Beyond Standard Model (BSM) extensions, including those with vector-like fermions. In Effective Field Theories (EFTs), such as the Standard Model Effective Field Theory (SMEFT) and the Higgs Effective Field Theory (HEFT), these couplings appear at dimension 6 and can in general, be flavour-violating (FV). In the present work, we employ a bottom-up approach to investigate the FV in the lepton and quarks sectors through the di-Higgs effective couplings. We assume that all FV arises from this type of couplings and assume that the Yukawa couplings Y i j are given by their SM values, i.e. Y i j = 2 m i δ i j / v. In the lepton sector, we set upper limits on the Wilson coefficients C l l ′ from l → 3 l ′ decays, l → l γ decays, muonium oscillations, the (g − 2) μ anomaly, LEP searches, muon conversion in nuclei, FV Higgs decays, and Z decays. We also make projections on some of these coefficients from Belle II, the Mu2e experiment and the LHC's High Luminosity (HL) run. In the quark sector, we set upper limits on the Wilson coefficients C q q ′ from meson oscillations and from B -physics searches. A key takeaway from this study is that current and future experiments should set out to measure the effective di-Higgs couplings C f f ′ , whether these couplings are FV or flavour-conserving. We also present a matching between our formalism and the SMEFT operators and show the bounds in both bases. [ABSTRACT FROM AUTHOR]

I investigate a class of models with scalar and pseudoscalar solutions to the g − 2 anomaly for both the muon and the electron over the mass range of perturbativity ( m ϕ ≲ 50 GeV), with Yukawa couplings proportional to the lepton's mass. In particular, I investigate the constraints from BaBar, beam dump experiments, Z decay measured quantities, LEP mono- γ searches, e e ⟶ τ τ γ searches, and solar and horizontal branch (HB) star bounds. For a pseudoscalar, I find that no region in the parameter space can simultaneously provide a solution for both the electron and the muon anomalies while maintaining the required form of the couplings, and therefore, the pseudoscalar solution is disfavored. On the other hand, I find for the scalar case that there is an open window above ~30 MeV in the allowed region, but with significant tension with experiment for the region m ϕ ≳ 10 GeV. In addition, there is a smaller window between ~350 KeV and 1 MeV that is not ruled out by cosmological observations. Part of the first open window is expected to be covered by the proposed NA64 experiment. Similar analysis can be readily applied to other proposed solutions to the anomaly, such as solutions with Z ′ or with the dark photon. [ABSTRACT FROM AUTHOR]

I study a class of Randall–Sundrum (RS) models with Spontaneous Breaking of Scale Invariance (SBSI). This class of models implements the Contino–Pomarol–Rattazzi (CPR) mechanism to achieve SBSI through the small running of an external close-to-marginal scale-breaking operator that leads to a light dilaton/radion with couplings to matter suppressed by the small running. I show that for radion masses ≲ 1  KeV, it can serve as a dark matter (DM) candidate, with a lifetime longer than the age of the universe, and show that the experimental bounds from LHC, non-Newtonian gravity and Axion-Like Particle (ALP) searches allow for the existence of such a radion. In spite of the small relic abundance of the light radion produced in this model, we show that it could be possible to obtain the required abundance through additional assumptions, an issue we postpone to the future. [ABSTRACT FROM AUTHOR]

We present a Randall-Sundrum toy model with an added scalar singlet that couples only to KK fermions in the bulk. Such a scalar would nontrivially affect radion phenomenology. In addition, we examine the radion phenomenology in light of the new scalar and show how this scalar could present another probe to search for the radion. [ABSTRACT FROM AUTHOR]

Measuring the Higgs couplings accurately at colliders is one of the best routes for finding physics Beyond the Standard Model (BSM). If the measured couplings deviate from the SM predictions, then this would give rise to energy-growing processes that violate tree-level unitarity at some energy scale, indicating new physics. In this paper, we extend previous work on unitarity bounds from the Higgs potential and the Higgs couplings to vector bosons, the top quark, γγ and γZ ; to the Higgs coupling to gg. We show that the scale of new physics could be as low as ∼10 TeV, which although beyond the reach of the LHC, is well within the reach of the future 100-TeV collider, and can also be probed indirectly in the High Luminosity LHC (HL-LHC). [ABSTRACT FROM AUTHOR]