This talk will present the latest results on searches for additional Higgs bosons with low mass by the ATLAS and CMS experiments at the LHC. It will include searches for the 125 GeV Higgs boson decaying to lower-mass scalars.
Experimental measurements of multiboson interactions serve as tests for the Standard Model (SM) electroweak sector and its mechanism of spontaneous symmetry breaking (EWSB). One direct avenue to probe this sector is through the study of weak boson polarizations, offering a direct insight into EWSB. As longitudinal polarization modes only exist for massive bosons, they are directly linked to...
In this study, we explore the signatures of a light fermiophobic Higgs boson within the type-I two-Higgs-doublet model at the HL-LHC. Our parameter scan identifies a mass range between 1 and 10 GeV, challenging to detect due to soft decay products. We propose a discovery channel with the final state consisting of four photons, one lepton, and missing transverse momentum. However, the merger of...
The lattice studies provided evidence of a smooth crossover between the hadronic and quark-gluon phases at high temperatures and zero chemical potential for baryonic number. We argue that these simulations might not rule out relatively weekly first-order phase transition. This first-order QCD phase transition may lead to cosmic separation of phases, creating temporarily macroscopic domains...
The first idea relates to the asymmetric dark matter mass scale. To explain the cosmological coincidence between the ordinary and dark matter mass densities, one needs a rationale for why the dark matter mass scale is of the order of the proton mass. I present an analysis of how infrared fixed points in the running of the ordinary and dark QCD coupling constants can be used to achieve this...
To explore BSM scenarios from underlying strong dynamics, the key ingredients are new particles as composite states. Extended Higgs sectors with pNGB Higgses can give distinctive signatures at colliders, for example in the double-Higgs production process, and can be linked to the thermal history of the Universe for triggering a strong first order EW phase transition.
The scattering of neutral particles by an atomic nucleus can lead to electronic ionisation and excitation through a process known as the Migdal effect. I will describe the necessity of revisiting previous calculations to provide more accurate predictions which allow for large nuclear recoil velocities and incorporate the effects of multiple ionisation. These results are relevant for dark...
Solar neutrinos induce elastic neutrino-electron scattering in dark matter direct detection experiments, resulting in detectable event rates at current facilities. In this talk, I will present an analysis of recent data from the XENONnT, LUX-ZEPLIN, and PandaX-4T experiments from which we derive stringent constraints on several U(1)′ extensions of the Standard Model, accommodating new...
The Euclid mission satellite was launched on July 1st, 2023 from Cape Canaveral, Florida, with a Space X Falcon 9 rocket . After one month journey it is set in its orbit around the Sun-Earth L2 point and has already finished its commissioning period. Euclid survey started in February 2024 and will map 15000 deg2 of the sky in the following six years observing more than 1 billion galaxies with...
In this talk, the potential for detecting sub-GeV dark matter through the QUEST-DMC experiment will be explored. The experiment employs a novel approach, utilizing superfluid Helium-3 (He-3) alongside quantum sensors. Superfluid He-3 is highlighted as an optimal medium for sub-GeV dark matter searches, particularly effective in spin-dependent interactions. The presentation will cover the...
We study how the recent experimental results constrain the
gauge sectors of $U(1)$ extensions of the standard model
using a novel representation of the parameter space.
We determine the bounds on the mixing angle between the massive
gauge bosons, or equivalently, the new gauge coupling as a function of
the mass $M_{Z'}$ of the new neutral gauge boson $Z'$ in the
approximate range...
I discuss a grand unified theory that assigns a separate $SU(5)$ gauge group to each fermion family. The equality of the gauge couplings at the unification scale is enforced by means of a cyclic $\mathbb{Z}_3$ symmetry. Such tri-unification reconciles the idea of gauge non-universality with gauge coupling unification, opening the possibility to build consistent non-universal descriptions of...
Triality models are motivated by flavour structure theories. They produce charged lepton flavour violation channels mediated by a doubly charged scalar. However, the triality charges forbid decays such as muon to electron conversions, avoiding stringent experimental bounds. We have calculated predictions of charged lepton violation in this scenario and show the complementarity between Belle II...
Building on the successes of the FASER and SND@LHC experiments, proposed programs at CERN's Forward Physics Facility (FPF) can build the world's largest dataset of neutrino deep-inelastic scattering ($\nu$DIS) in the TeV range for all neutrino flavors. These data will enable novel tests of neutrino-matter interactions but also complement ongoing short-baseline programs at FNAL as well as...
Determination of the nature of dark matter is one of the most fundamental problems of particle physics and cosmology. This talk presents searches for dark matter particles associated with the production of a Higgs or a dark Higgs. The results are based on proton-proton collisions recorded at sqrt(s) = 13 TeV with the CMS detector at the Large Hadron Collider.
ATLAS is one of the main experiments at the Large Hadron Collider, with focus on Standard Model (SM) measurements and searches for new physics at the TeV scale.
One of the most active fields currently is the search for Higgs boson pair production. Models with an extended Higgs sector predict that Higgs boson pairs are produced via the decay of new heavy scalars. Models with extra dimensions...
A pseudo Nambu-Goldstone boson (PNGB) coupled to a confining gauge group via an anomalous term is characterised, during the confining phase transition, by a temperature dependent mass $m(T) \propto T^{-n}$ with values of $n$ not far from $n\sim 3$. We study the possibility that a hidden gauge group undergoing confinement at present time could provide a suitable time-varying mass to a dark...
The existence of dark matter in our Universe and the existence of an asymmetry between nucleons and antinucleons are two of the most solid evidences for physics beyond the Standard Model. Many mechanisms have been proposed to explain these two phenomena. On the other hand, these mechanisms typically involve different particles and different energy scales, therefore the observed similarity...
Novel bounds on CP-odd fermionic couplings of ALPs and of a general singlet scalar are presented and compared. In both cases, we improve present constraints by several orders of magnitude. The impact of an additional Peccei-Quinn symmetry will be discussed as well.
Scattering and decay processes of thermal bath particles in the early universe can dump relativistic degrees of freedom in the primordial plasma. This talk will focus on the QCD axion and it will feature recent and significant improvements in the predicted amount of axion dark radiation. First, I will present novel calculations for the production rate across the different energy scales during...
Compact stellar objects like Supernovae (SN) and Neutron Stars (NS) are believed to cool by emitting axions via processes emission of neutrinos and possibly emission of axions, if they exist. In this talk, we study a previously overlooked contribution to the photo-production channel of interactions like $\gamma N \to N \nu \nu$ and $\gamma N \to Na$. This originates from the unavoidable...
The Tunneling Potential formalism offers an alternative to the Euclidean bounce formalism for calculating tunneling actions. These actions govern the exponential suppression of metastable vacua decay in quantum field theory. In this talk, I will discuss how this formalism elegantly describes gravitational effects on vacuum decay, bubble-of-nothing decays, domain walls, and more.
First-order phase transitions proceed via bubble nucleation. This is true regardless of whether the transition is happening in your kettle or on a cosmological scale in the very early universe. I will give an overview of our present understanding of bubble nucleation within quantum field theory, including both long-standing theoretical questions and recent progress.
We are currently witnessing the dawn of a new era in astrophysics and cosmology, started by the first LIGO/Virgo/KAGRA observations of Gravitational Waves (GW). Very recently, also the detection of a stochastic background of GWs at very low frequencies was announced by the Pulsar Timing Array collaborations. In this talk, I will discuss how such signals are produced in cosmological phase...
In this talk I will discuss PRyMordial: a program dedicated to the computation of observables in the early universe with a focus on the cosmological era of Big Bang Nucleosynthesis (BBN). The code is the first of its kind written in python and offers fast and precise evaluation of both the BBN light-element abundances and the effective number of relativistic degrees of freedom. PRyMordial was...
The dynamics of the Higgs and other light scalar fields during inflation can have important cosmological consequences, but because of the infrared problem, they cannot be computed using perturbation theory. A powerful alternative is the stochastic Starobinsky-Yokoyama approach, which is based on the observation that on superhorizon distances the field behaves classically, with a noise term...
Any light species in thermal equilibrium in the early universe, such as an axion, will contribute to the effective number of relativistic species, $N_\textrm{eff}$. In the context of the Axiverse, potentially hundreds of axions exist in the spectrum of nature and can thermalize with the Standard Model bath, but Planck data constrains the number of additional scalars to nine. Do they all...
Light relics produced by freeze-in, while more dependent on both the specific BSM physics scenario and the reheating temperature than freeze-out, are generic for models in which the light relic couples to the SM plasma more weakly than necessary for full thermalization. In particular, rates for light relic production associated with non-renormalizable interactions typical of BSM scenarios can...
We discuss some examples of how gravitational waves from either phase transitions or cosmological relics such as cosmic strings or domain walls, may be used to probe a variety of new physics ranging from neutrino mass, grand unification, inflation or even quantum gravity. The recent Pulsar Timing Array results from experiments such as NANOgrav may be the first indication of such signals.
The LISA mission has been adopted, with launch scheduled in 2035. This leaves us with just a decade to complete the data analysis pipelines and prepare the science interpretation of the potentially observed signals. In this talk we will briefly review the status of the mission, some possible data analysis approaches to isolate the primordial stochastic GW background (SGWB), and some potential...
An integral part of the BSM physics model building is testing if the new models can provide the answer to the origin of the baryon asymmetry in the universe (BAU). This test requires solving the CP-violating out-of-equilibrium particle distributions near the expanding phase transition front. The quantum transport theory for this purpose, the semiclassical method, is well understood and...
I will review recent progress in the model-independent constraining of the properties of neutron-star matter using ab-initio tools from theoretical particle and nuclear physics. In particular, I will discuss results from a new study employing Bayesian inference methods and taking input from both electromagnetic and gravitational-wave observations, which point to the rapid conformalization of...
Pulsars are rapidly rotating, highly-magnetized neutron stars which emit electromagnetic radiation in the form of highly collimated beams, mainly observed in the radio wavelength regime. Pulsars can be instrumental in solving the puzzle, which has perplexed the minds of the scientific community for almost a century – dark matter. The ultralight scalar field dark matter (also known as "fuzzy"...
Cosmic microwave background (CMB) photons can convert into axion-like particles as they cross the halo magnetic fields of non-linear structure. Resonant conversion occurs when the axion mass matches the photon plasma mass, induced by the ionized gas within halos, leading to a frequency-dependent transition probability. Therefore, axions induce a frequency-dependent anisotropic screening of the...
We discuss how we can explore electroweak phase transitions (EWPTs) via collider experiments and gravitational wave (GW) observations. The nature of the EWPT is important to understand the thermal history of the early Universe and to determine the scenario of baryogenesis. To obtain model independent results, we focus on an effective field theoretical approach, which is known as the nearly...
We discuss the possibility of a First Order Electroweak Phase Transition (FOEWPT) in the early universe, as required for EW baryogenesis, in the framework of the 2HDM. One corresponding prediction, the decay $A \to Z H$ with $H \to t \bar t$ may have been observed at the LHC. We present the phenomenological consequences for the detection of gravitational waves at LISA, as well as the prospects...
Extended scalar sectors can yield baryogenesis at the EW scale. This is generally related to their providing the needed departure from thermal equilibrium (absent in the SM) via a first-order EW phase transition. Yet, BSM sources of CP violation are also required for baryogenesis, despite being very strongly constrained experimentally by electric dipole moments (EDMs). I show that extended...
Conformal UV completions of Standard Model extensions have interesting implications on small and bigger scale hierarchies. The talk will cover general features which will be exemplified by model realizations.
In this talk I will review a few aspects of Coherent Elastic neutrino-Nucleus Scattering (CEvNS). In particular I will focus on measurements using neutrino beams from pion decay-in-flight, as those used at FNAL. I will show that, combined with directional detectors, these beams offer an avenue for CEvNS measurements at a different energy scale. Such measurements will provide complementary...
The Pulsar Timing Array signal at the nHz frequency can be described by the first order phase transition of a conformal sector with a confinement scale around the GeV. We model this effect in a 5D warped theory with an IR dark brane at the GeV scale. The dark sector, located in the dark brane, interacts only gravitationaly with the SM. A simple model of a fermionic dark matter is presented,...
Higgs-boson pairs are dominantly produced via gluon fusion at hadron colliders, i.e. via a loop-induced process. This process will constitute the first direct access to the trilinear Higgs self-interaction. In recent years the NLO QCD corrections involving the full top-mass dependence became available by means of numerical integrations, since analytical methods available so far are not capable...
I will discuss entanglement between two final-state particles in 2 to 2 scattering, induced by the S-matrix which depends on both the momentum and flavor degrees of freedom. I will describe different ways to quantify the entanglement in such a system and the resulting constraints on the interactions' structure. An example of scalar scattering in 2HDM will be discussed.
In recent years, interest in vector like quaks (VLQs) has been increasing, due to their contributions to
new physics effects that can be tested in experiments at LHC and High-Lumi LHC. The existence of VLQs leads to flavour-changing neutral currents at tree level and deviations from unitarity of the CKMmatrix, introducing rich phenomenological implications. In my talk I shall address some of...
Flavour (and CP) symmetries can be the key to understand fermion masses and mixing. In theories beyond the Standard Model they can also be crucial in order to understand, for example, the suppression of certain flavour-violating signals and the correlation among the generated amount of baryon asymmetry of the Universe and the size of CP violation, potentially observable in neutrino...
The current LHC Higgs data suggest that the couplings of the observed
125 GeV Higgs boson must be remarkably close to the Standard Model
(SM) expectations. This implies that any Beyond-the-Standard-Model
physics due to an extended Higgs sector must lead to the so-called SM
alignment limit, where one of the Higgs bosons behaves exactly like
that of the SM. In the context of the Two Higgs...
The Weinberg 3HDM potential may lead to spontaneous CP violation. The terms thus inducing CP violation are constrained by the measured properties of the discovered scalar at 125 GeV. In a wide range of parameter space, the potential leads to one or two light neutral states (below 125 GeV) that have a considerable admixture of CP-odd fields. The potential can accommodate a light state at 95...
The asymmetries in out-of-equilibrium decays or scatterings necessary for lepto/baryogenesis can only occur in sufficiently complex particle models, where irreducible phases of couplings are possible. Imaginary kinematics is required in loop diagrams. Even when these ingredients are present, the resulting asymmetry may vanish due to the $CPT$ and unitarity constraints. In this talk, we show...
After the discovery of a particle that complies with the properties of the Standard Model Higgs particle, particle physics has entered an exciting era. Both theoretical and experimental uncertainties in principle still leave room for additional particles where the scalar sector can be augmented by additional particle content. In this talk, I focus on scenarios with singlet extensions. I will...
In this talk I will review several scenarios for DM that can be tested in the next generation of colliders and direct detection experiments.
UV Priors for Light Scalars (and how they might be screened)
The recent advent of gravitational-wave observations allows testing gravity in a strongly relativistic regime, but decoupling - which beautifully explains why low-energy measurements are largely insensitive to UV details - seems to thwart the extraction of fundamental insights about UV physics from astrophysical or cosmological...
Characteristic patterns can emerge in the spectral shape of the stochastic gravitational wave (GW) background through various mechanisms. For instance, the GW background generated via second-order scalar perturbations, often discussed in the context of primordial black hole formation, exhibits a distinct spectral shape. Additionally, scalar-induced GWs excited during inflation and specific...
I will discuss the possibility of dynamically generating arbitrarily small Yukawa couplings in the framework of trans-Planckian asymptotic safety. This effective mechanism may provide an interesting alternative to other dynamical means to generate small neutrino masses, e.g., the see-saw mechanism, and can be applied to various new physics scenarios requiring feeble Yukawa interactions...
A successful measurement of the Stochastic Gravitational Wave Background (SGWB) in Pulsar Timing Arrays (PTAs) would open up a new window through which to test the predictions of General Relativity (GR). Astrometry on the other side also holds the potential for testing fundamental physics through the effects of the Stochastic Gravitational Wave Background (SGWB) in the ∼ 1 − 100 nHz frequency...
The Standard Model Effective Field Theory (SMEFT) provides a powerful theoretical framework for interpreting subtle deviations from the Standard Model and searching for heavy new physics at the LHC. Accurate interpretations of LHC data, however, rely on the precise knowledge of the proton structure in terms of parton distribution functions (PDFs). I will discuss the interplay between PDFs...
I will discuss the inaugural investigation of BSM radiation processes, framed as a generalized, process- and model-independent parton shower algorithm within Herwig7, based on direct translations of UFO constructs via Herwig's "ufo2herwig" module. Additionally, I will address some phenomenological aspects of employing BSM parton showers, particularly in the context of models with extended...
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...
I will discuss the first combined interpretation of multiboson production at colliders in the Standard Model Effective Field Theory framework. We find that triboson measurements contribute signifincantly towards pinning down possible new interactions. We quantify how, in addition to the precise diboson measurements from the LEP and LHC experiments, they offer complementary and competitive...
