The talk gives an overview of recent theoretical developments in effective field theory methods as applied to the electroweak sector, particularly to the mechanism of electroweak symmetry breaking, and to flavor changing processes.
I present a global likelihood function in the space of dimension-six Wilson coefficients in the Standard Model Effective Field Theory (SMEFT). The likelihood includes contributions from flavour-changing neutral current Bdecays, lepton flavour universality tests in charged- and neutral-current B and K decays, meson-antimeson mixing observables in the K, B, and D systems, direct CP...
We present a novel framework for carrying out global analyses of the Standard Model Effective Field Theory (SMEFT) at dimension-six: SMEFiT. This approach is based on the Monte Carlo replica method for deriving a faithful estimate of the experimental and theoretical uncertainties and enables one to construct the probability distribution in the space of the SMEFT degrees of freedom. As a proof...
In the context of the Standard Model effective field theory (SMEFT), we study the LHC sensitivity to four fermion operators involving heavy quarks by employing cross section measurements in the $t\overline{t}b\overline{b}$ final state. Starting from the measurement of total rates, we progressively exploit kinematical information and machine learning techniques to optimize the projected...
I will discuss developments in our understanding and construction of operator bases
The study of scattering amplitudes has advanced tremendously in recent years. Lorentz symmetry and unitarity have been shown to greatly constrain the structure of both massless- and massive-particle amplitudes. In this talk, I discuss the application of these methods to the formulation and calculation of Effective Field Theory amplitudes.
Requiring an analytic and unitary UV completion for a low energy effective field theory (EFT) can impose positivity bounds on the Wilson coefficients of the EFT. These positivity bounds take the form of constraints on combinations of the pole subtracted scattering amplitude and its derivatives, and are valid away from the forward limit and for any spins. Furthermore, positivity bounds with...
When dealing with effective Lagrangians it is often convenient to work with a basis, i.e., a complete set of independent operators. I will present BasisGen, a Python package for the automatic generation of operator bases in a general setting: it accepts any semisimple symmetry group and fields in any of its finite dimensional irreducible representations. It takes into account integration by...
In this talk, we present the universal one-loop effective action obtained by integrating out massive, non-degenerate multiplets, focusing on the coefficients of operators of dimension up to six composed of Standard Model fields. Our general results may be applied to loops of non-degenerate heavy fermions or bosons.
We discuss the relationship of our results (and their ongoing improvement) to...
Operators with the vertex $h Z_{\mu \nu} h Z^{\mu \nu}$ contributing to associated production of a Higgs boson with a transverse Z boson, do not interfere with the dominant longitudinal part of the $Zh$ amplitude at high energies. Here we explore how angular distributions related to the Z decay products can be used to recover the interference term and thus gain sensitivity to these operators.
My talk will cover EFT fits to Higgs & EW data. I will show fits at LO in the EFT expansion, separately for CP-even and CP-odd operators. I will then discuss issues with extending to the next order in EFT, focussing in particular on the effect of dimension-8 operators.
We calculate the total and partial inclusive Higgs widths at leading order in the Standard Model Effective Field Theory (SMEFT). We report results incorporating all SMEFT corrections for two and four body Higgs decays in this limit. The narrow width approximation is avoided and all phase space integrals are directly evaluated.
We want to establish the reach to possible deviations of the Higgs couplings from their SM values, to do this we look at processes with longitudinally polarised vector bosons in the final states at high energies.
Especially, our analysis is grounded on the observation that deviations from the Standard Model are characterised by an energy growing behaviour in the amplitudes, so that at higher...
There is increasing need to assess the impact and the interpretation of dim = 6 and dim = 8 operators within
the context of the Standard Model Effective Field Theory (SMEFT). The observational and mathematical consistency of a
construct based on dim = 6 and dim = 8 operators is critically examined in the light of known theoretical
results. The discussion includes elimination of redundant...
Direct searches for New Physics states have given so far negative results. There is a mass gap between SM fields and possible new states. The observed SM symmetry pattern and this mass gap justifies the use of electroweak effective Lagrangians. Implications of new, higher scales can be analyzed through next-to-leading order corrections to the Higgs Effective Theory, HEFT (also denoted as EW...
The collider phenomenology of a strongly interacting electroweak symmetry breaking sector is studied. We use the Electroweak Chiral Lagrangian (EChL) and the Inverse Amplitude Method (IAM). And generate a MadGraph v5 UFO model, which includes the beyond Standard Model (BSM) interactions via effective vertices in the framework of a Proca Lagrangian. The constants of the Proca Lagrangian are...
In this talk, we will discuss the present status of the di-Higgs searches at the LHC. We will quantify the prospects of witnessing signatures of these elusive modes in the $b \bar{b} \gamma \gamma$, $b \bar{b} \tau^+ \tau^-$, $b \bar{b} W W^*$, $W W^* \gamma \gamma$ and the $4W$ channels at the high luminosity run of the LHC (HL-LHC). We will emphasise the prospects of measuring the Higgs...
The ACME collaboration has recently reported a new bound on the electric dipole moment (EDM) of the electron, |d_e|<1.1×10^−29e⋅cm at 90% confidence level, reaching an unprecedented accuracy level. This can translate into new relevant constraints on theories beyond the SM laying at the TeV scale, even when they contribute to the electron EDM at the two-loop level. We use the EFT approach to...
I will discuss the measurements of the anomalous triple gauge couplings at Large Hadron
Collider focusing on the contribution of the CP-even and CP-odd O3W 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...
A major recent breakthrough in global fits of the quark and gluon structure of the proton has been the inclusion of a significant amount of precision LHC measurements. While these data provide important constraints, specially on the poorly-know gluon and antiquark PDFs, it is crucial to avoid any contamination from potential beyond the Standard Model (BSM) effects that could be present in the...
We compile information from low-energy observables sensitive to flavor-conserving 4-fermion operators with two or four leptons. Our analysis includes data from e+ e− colliders, neutrino scattering on electron or nucleon targets, atomic parity violation, parity-violating electron scattering, and the decay of pions, neutrons, nuclei and tau leptons. We recast these data as tree-level constraints...
We present a global analysis of the Higgs and electroweak sector based on LHC Run II and electroweak precision observables using the SFitter framework. We show which measurements provide the leading constraints on Higgs-related operators, and how the achieved LHC precision makes it necessary to combine rate measurements with electroweak precision observables.
Moreover, we estimate the reach...
Up to now, more than 150 fb$^{-1}$ of integrated luminosity have been collected by the CMS and ATLAS experiments at 13 TeV. These large data-sets allow challenging searches for subtle signs of generic physics beyond the standard model (BSM). A theoretical framework to describe such effects is provided by the standard model effective field theory (SMEFT) in which BSM physics is encoded via...
In this contribution I will discuss a number of issues that connect Higgs and top physics at present and future colliders. I will present the result of a fit to LHC data of the operator coefficients that modify the electro-weak couplings of the top and bottom quark and projections for the evolution of this fit at the HL-LHC and a future linear electron-positron collider. Finally, I will...
I will discuss the technically convenient setup for loop calculations in the EFT. First, I will present the proof that the R_xi gauge fixing can always be used in any EFT with linearly realised gauge symmetry and to any order in 1/Lambda expansion. Then, I will discuss the applications to SM-EFT on the example of systematic calculation of h->2 gamma and h->Zgamma decays: derivation of Feynman...
Using background-field method and super-heat-kernel expansion, we derive a master formula for the one-loop UV divergences of the bosonic dimension-six operators in Standard Model Effective Field Theory (SMEFT). This approach reduces the calculation of all the UV divergences to algebraic manipulations. Using this formula we corroborate results in the literature for the one-loop anomalous...
We study the effects of new physics in double Higgs production at future $e^+ e^-$ colliders. In the Standard Model the chiral limit ($m_e=0$) plays an important role for this process, being responsible for the smallness of the tree-level diagrams with respect to the 1-loop contributions. In our work, we consider the possibility of an enhancement due to the contribution of Standard Model...
Accurate measurements of high-energy reactions are potentially powerful indirect probes of heavy new physics parametrised by the SMEFT. I will summarise the status of the design of searches implementing this idea in di-lepton and in di-boson final states at the LHC and HL-LHC and I will illustrate their potential mass reach on concrete new physics scenarios. A substantial progress is possible...
New physics can manifest itself by an appreciable increase of the decay rate
of top quarks in rare flavour-changing final states. Exploiting the large top
quark production rate at the LHC, we bound four-fermion operators using
different signal regions of the latest LHC searches for $t \to Zj$. We also
provide prospects for the high-luminosity LHC to test these as well as four-fermion
operators...
Anomalous Higgs couplings precipitate unitarity violation in a multitude of processes. These include, in particular, high multiplicity (2 → more than 2) processes involving longitudinal vectors, where unitarity violation manifests in cross-sections that grow too quickly with energy. Using EFT―which provides a transparent and systematic parameterization of the energy growth―we explore how to...
An important part of the LHC legacy will be precise limits on indirect effects of new physics, framed for instance in terms of an effective field theory. These measurements often involve many theory parameters and observables, which makes them challenging for traditional analysis methods. We discuss the underlying problem of “likelihood-free” inference and present powerful new analysis...
