While the third run of the Large Hadron Collider (LHC) is ongoing, the
model that extends the Standard Model remains so far unknown. Left-Right Models
(LRMs) introduce a new gauge sector, and can restore parity symmetry at high enough
energies. If LRMs are indeed realized in nature, the mediators of the new weak force can
be searched for in colliders via their direct production. We recast...
Left-Right (LR) theories are one of the successful beyond Standard Model (SM) frameworks that explain the origin of small neutrino masses and low-energy weak parity violation. However, the conventional LR theory faces a challenge due to the presence of flavor changing neutral currents (FCNCs). To address this, we have studied an Alternative LR model (ALRM), which avoids FCNC constraints. Our...
Many different theories beyond the Standard Model (SM) predict that new physics will manifest itself by decaying into final states involving leptons. Leptoquarks are predicted by many new physics theories to describe the similarities between the lepton and quark sectors of the SM. Right-handed Ws and heavy-neutrinos are also predicted by many extensions of the SM in the gauge sector, and...
In the first part of this talk I will describe a Left-Right symmetric model that provides an explanation for the mass hierarchy of the charged fermions within the framework of the Standard Model. This explanation is achieved through the utilization of both tree-level and radiative seesaw mechanisms. In this model, the tiny masses of the light active neutrinos are generated via a three-loop...
Many theories beyond the Standard Model predict new phenomena, such as heavy vectors or scalar, vector-like quarks, and leptoquarks in final states containing bottom or top quarks. Such final states offer great potential to reduce the Standard Model background, although with significant challenges in reconstructing and identifying the decay products and modelling the remaining background. The...
The absence of new particles in the LHC direct searches starts challenging the idea of Naturalness. In this talk, we present a solution to the hierarchy problem, where the new particles are third-generation-philic. Due to this feature, the mass bounds from the direct searches are much weaker and the required fine-tuning can be reduced drastically. The idea is realized with a concrete model...
I will discuss an Effective Field Theory which extends the SM by an Axion-Like Particle (ALP) and particularly focus on the coupling of a light ALP to top quarks.
We use high-energy LHC probes, and examine both the direct probe to this coupling in associated production of a top-pair with an ALP, and the indirect probe through loop-induced gluon fusion to an ALP leading to top pairs. Using the...
I will present theoretical calculations of total cross sections and top-quark transverse-momentum and rapidity distributions in the associated production of a top-antitop pair with a photon (t t~ γ production) in the SM and SMEFT.
The theory predictions include complete QCD and electroweak corrections at NLO as well as soft-gluon corrections at approximate NNLO. Implications for SM...
I will argue that coloured gravitational instantons compromise the standard axion solution to the strong CP problem and propose a companion axion model as the solution, that necessarily contains two axions. I will discuss some phenomenological and cosmological consequences of this model.
Based on - 2108.05549, 2109.12920, 2110.11014
Dimensionless fundamental constants can vary as a function of time if an ultralight field couples to the standard model. Using data on strontium, ytterbium and caesium atomic-clock transitions collected by the National Physical Laboratory in the UK, fine-structure constant and electron-to-proton mass ratio variations have been measured for about two weeks. These data enable the extraction of...
We study the contributions of an axion-like particle to the electroweak precision observables. The particle is assumed to couple with the standard model electroweak gauge bosons. It is found that the effects arise not only via the oblique $S$ and $U$ parameters but also via radiative corrections to the gauge couplings. Besides, the decay of $Z\to a\gamma$ affects the total width of the $Z$...
The positivity of the scattering amplitude is a necessary condition for a low-energy effective field theory (EFT) to be UV complete. The gravitational positivity bound provides quantitative "swampland" constraints for low-energy EFTs to be UV complete within quantum gravity. The condition can give significant constraint on a feebly interacting particle model and its UV completion. In this...
We review models of partial compositeness based on underlying four dimensional gauge theories with fermionic matter.
The matter content is chosen in such a way as to give rise to a Higgs boson as a pseudo-Nambu--Goldstone boson as well as a Dirac-like partner to the top quark. We discuss recent lattice results (by other groups) and their relevance to these constructions.
We conclude by...
Two major ingredients of a composite Higgs model are vacuum misalignment and partial compositeness. The former is essential to trigger the electroweak symmetry breaking, while the latter can explain the mass hierarchy of the quarks. The partial compositeness mechansim employes a mixing between the SM quarks and vector-like quarks, arising from a new confining sector, via four-Fermi operators....
In this talk I will present some models of weakly coupled scalar fields which are massless at the tree level, despite the fact that the scalar potential includes all renormalizable operators compatible with the symmetries, and that it exhibits no accidentally enhanced symmetries associated with pseudo-Nambu-Goldstone bosons (pNGBs). These accidentally light fields are close cousins of both...
The proposed LUXE experiment (LASER Und XFEL Experiment) at DESY, Hamburg, using the electron beam from the European XFEL, aims to probe QED in the non-perturbative regime created in collisions between high-intensity laser pulses and high-energy electron or photon beams. This setup also provides a unique opportunity to probe physics beyond the standard model. In this talk we show that by...
We suggest a new class of models "a Fermionic Portal Vector Dark Matter" (FPVDM) which extends the Standard Model (SM) with a minimal non-Abelian $SU(2)_D$ dark gauge sector. Since the mixing between the SM and dark scalars is negligibly small, the main connection between two sectors is established on the mixing between a Vector-Like (VL) fermionic doublet of $SU(2)_D$ dark group and their SM...
In the first part of the talk I will describe a Majoron-like extension of the Standard Model with an extra global U(1)X symmetry where neutrino masses are generated through an inverse seesaw mechanism at the 1-loop level. In contrast to the tree-level inverse seesaw, the framework contains dark matter candidates stabilized by a residual Z2 symmetry surviving spontaneous breaking of the U(1)X...
A holographic model of chiral symmetry breaking is used to study the dynamics plus the meson and baryon spectrum of the underlying strong dynamics in composite Higgs models. We impose perturbative running for the anomalous dimension of the quark condensate in a variety of theories with varying number of colours and flavours. We compare our results in detail to lattice simulations for: Sp(4)...
Effective field theories are an efficient framework for parametrising the effects of heavy new physics on low energy observables and have become one of the key pillars of the LHC programme. It has recently been appreciated that large portions of EFT parameter spaces are inconsistent with fundamental principles of S-matrix theory such as analyticity/causality and unitarity, and therefore cannot...
