The discovery of the Higgs boson with the mass of about 125 GeV completed the particle content predicted by the Standard Model. Even though this model is well established and consistent with many measurements, it is not capable to solely explain some observations. Many extensions of the Standard Model addressing such shortcomings introduce additional Higgs bosons, beyond-the-Standard-Model...

We discuss the accumulating evidence for a new Higgs boson at $\sim 95$ GeV and how it could be realized in simple Higgs sector extensions. We discuss the physics implications for the LHC and future $e^+e^-$ colliders.

We present searches from the CMS experiment, performed with data collected during LHC Run 2 at a centre-of-mass energy of 13 TeV, for rare Higgs bosons decays into light pseudoscalars. A variety of final states are explored, probing both boosted and resolved topologies.

We study the interaction between the inert Higgs doublet (IDM) dark matter and a vector-like SU(2) triplet lepton (VLL), both of which are Z2-odd. The vector current of the VLL with the Z-boson rules out a fermionic or two-component dark matter scenario. However, a compressed mass spectrum and a sufficiently small Yukawa coupling allows co-annihilation and late decay of the VLL into the IDM...

We analyze possible signatures of an ALP with masses above $\sim 400$ GeV at the (HL-)LHC in the $t \bar t$ decay channel. In particular, we demonstrate that such an ALP could be distinguished from a CP-even Higgs boson with the same mass and the same $t \bar t$ cross section with the help of $m_{tt}$ distributions. We obtain new limits on the effective ALP couplings to top quarks and gluons.

In this talk we investigate the capability of the new ATLAS searches for

$A \to ZH$ decays in $ell^+ \ell^- t \bar t$ and $\nu \nu b \bar b$

final states to probe the electroweak phase transition in the early

Universe. In the framework of the Two Higgs Doublet Model (2HDM), we

investigate the impact of the new searches on the 2HDM parameter space,

paying special attention to...

The event rates and kinematics of Higgs boson production and decay processes at the LHC are sensitive probes of possible new phenomena beyond the Standard Model (BSM). This talk presents precise measurements of Higgs boson production and decay rates, obtained using the full Run 2 and partial Run 3 pp collision dataset collected by the ATLAS experiment at 13 TeV and 13.6 TeV. These include...

FlexibleSUSY is a framework for an automated computation of physical quantities in non-supersymmetric and supersymmetric models starting from the most basic building blocks, namely the particle content and the Lagrangian. Among a plethora of observables that it supports it is also capable of computing decay widths of Higgs sector particles with precision comparable to experimental...

In a supersymmetric theory, large mass hierarchies can lead to large uncertainties in fixed-order calculations of the SM-like Higgs mass. A reliable prediction is then obtained by performing the calculation in an effective field theory (EFT) framework, involving the matching to the full supersymmetric theory at the high scale to include contributions from the heavy particles, and a subsequent...

This talk presents precise measurement of the properties of the Higgs boson, including its mass, total width, spin, and CP quantum number. The measurements are performed in various Higgs boson production and decay modes, as well as their combinations. Observation of deviations between these measurements and Standard Model (SM) predictions would be a sign of possible new phenomena beyond the SM

The trilinear Higgs coupling offers a unique opportunity to probe the structure of the Higgs sector and study the nature of the electroweak phase transition. Recently, it was also shown that confronting the prediction for the trilinear Higgs coupling with the latest experimental bounds opens a powerful new way to probe possible effects of BSM Physics arising from extended Higgs sectors, going...

We present searches from the CMS experiment, performed with data collected during LHC Run 2 at a centre-of-mass energy of 13 TeV, for resonant and nonresonant di-Higgs production. A variety of final states are explored, probing both boosted and resolved topologies.

In the Standard Model, the ground state of the Higgs field is not found at zero but instead corresponds to one of the degenerate solutions minimising the Higgs potential. In turn, this spontaneous electroweak symmetry breaking provides a mechanism for the mass generation of nearly all fundamental particles. The Standard Model makes a definite prediction for the Higgs boson self-coupling and...

We analyze the impact of one-loop corrections to triple Higgs bosons on the di-Higgs production cross section at $e^+e^-$ colliders within the two Higgs doublet model (2HDM). In particular, we study the production cross section of two SM-like Higgs bosons together with a $Z$ boson at the ILC. The one-loop triple Higgs couplings are calculated using the one-loop effective potential, and in the...

We explore the real-singlet extension of the Standard Model without a Z2 symmetry (RxSM), as a model to reconstruct the Higgs potental and explain the baryon asymmetry of the Universe. First, we determine regions of parameter space that allow a Strong First-Order Electroweak Phase Transition (SFOEWPT) using the public tools CosmoTransitions and TransitionListener, including also relevant...

The trilinear Higgs coupling is a crucial tool to investigate the structure of the Higgs sector and the nature of the electroweak phase transition, and to probe the parameter space of Beyond-the-Standard-Model (BSM) theories. The vast number of BSM models for which it is relevant to compute the trilinear coupling motivates the automation of its calculation. While calculations are possible at...

We investigate the reliability of a comparison between the experimental results and the theoretical predictions for the pair production of the 125 GeV Higgs boson at the LHC. Recent experimental results for di-Higgs production provide already sensitivity to triple Higgs couplings (THCs) in models beyond the Standard Model (BSM). In our analysis within the Two Higgs Doublet Model (2HDM) we find...

Understanding the shape of the Higgs potential and the nature of the electroweak phase transition in theories beyond the Standard Model requires experimental information on the trilinear Higgs boson self-coupling $\kappa_3$ and the quartic self-coupling $\kappa_4$. Although triple Higgs production suffers from small cross-section rates, it can establish the first experimental bounds on...

Domain walls are a type of topological defects that can arise in the

early universe after the spontaneous breaking of a discrete symmetry. This occurs in several beyond Standard Model theories with an

extended Higgs sector such as the Next-to-Two-Higgs-Doublet model

(N2HDM). In this talk I will discuss the domain wall solution related

to the singlet scalar of the N2HDM as well as...

We present a detailed study of the precision calculations of higher-order contributions to effective potential with the application of three-dimensional effective field theories (3D EFTs). Our work focuses on the thermodynamic quantification and description of electroweak phase transitions in the early Universe for the complex singlet extended Standard Model (cxSM). In particular, we address...

Computing the decay rate of a meta-stable state is a well-known problem with relevance in various areas of physics. The decay rate is dominated by an exponential factor called the bounce action. Determining the bounce action for a given potential and meta-stable vacuum involves solving a set of partial differential equations with intricate boundary conditions. There are several dedicated...

The evolution of the early Universe around the electroweak epoch is an ideal testbed for physics beyond the Standard Model and in particular extended scalar sectors. The Universe may have experienced a sequence of phases of exotic nature, one of these being an intermediate phase where the electromagnetic charge is not conserved.

In my talk, intermediate $U(1)_\mathrm{em}$ charge-breaking...

Very detailed measurements of Higgs boson coupling and kinematical properties can be performed using the data collected with the ATLAS experiment, exploiting a variety of final states and production modes, and probing different regions of the phase space with increasing precision. These measurements can then be combined to exploit the specific strength of each channel, thus providing the most...

In this work we explore the phenomenological implications at future e+eโ colliders of assuming anomalous couplings of the Higgs boson to gauge bosons HVV and HHVV (V = W, Z) given by the ฮบ-modifiers with respect to the Standard Model couplings, ฮบV and ฮบ2V, respectively. For this study we use the Higgs Effective Field Theory (HEFT) where these two ฮบ parameters are identified with the two most...

Various extensions of the Standard Model predict the existence of additional Higgs bosons. If these additional Higgs bosons are sufficiently heavy, an important search channel is the di-top final state. In this channel, interference effects between the signal and the corresponding QCD background process are important. If more than one heavy scalar is present, besides the signal-background...

We present searches from the CMS experiment, performed with data collected during LHC Run 2 at a centre-of-mass energy of 13 TeV, for additional Higgs bosons. A variety of states are searched for, at masses both above and below 125 GeV.