arXiv subjects

Fayez Abu-Ajamieh

Publications and source records attributed to Fayez Abu-Ajamieh.

28 records · Page 2Linked to original sources

arXiv2023

A Proposed Renormalization Scheme for Non-local QFTs and Application to the Hierarchy Problem

We propose a renormalization scheme for non-local Quantum Field Theories (QFTs) with infinite derivatives inspired by string theory. Our Non-locality Renormalization Scheme (NRS) is inspired by Dimensional Regularization (DR) in local QFTs and is shown to significantly improve the UV behavior of non-local QFTs. We illustrate the scheme using simple examples from the phi3 and phi4 theories, then we evaluate the viability of NRS-enhanced non-local QFTs to solve the hierarchy problem using a simplified toy model. We find that non-locality protects the mass of a light scalar from receiving large corrections from any UV sector to which it couples, as long as the non-locality scale M is sufficiently smaller than the scale of the UV sector. We also find that NRS eliminates any large threshold corrections from the IR sector

hep-th↗

arXiv2022

The Scale of New Physics from the Higgs Couplings to $γγ$ and $γZ$

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 and the top quark; to the Higgs couplings to $γγ$ and $γZ$. We find that while the HL-LHC might be able to find new physics in the $γZ$ sector, the scale of new physics in both sectors is mostly beyond its reach. However, accurate measurements of the leading couplings of the two sectors in the HL-LHC can place stringent limits on both the scale of new physics and on other Higgs couplings that are difficult to measure. In addition, the scale of new physics is mostly within the reach of the $100$ TeV collider.

hep-ph↗

arXiv2022

Snowmass 2021 White Paper: Higgs Coupling Sensitivities and Model-Independent Bounds on the Scale of New Physics

In this Snowmass white paper, we describe how unitarity bounds can convert sensitivities for Higgs couplings at future colliders into sensitivities to the scale of new physics. This gives a model-independent consequence of improving these sensitivities and illustrate the impact they would have on constraining new physics. Drawing upon past successful applications of unitarity as a guide for future colliders (e.g. the Higgs mass bound and discovering it at the LHC), we hope this data will be useful in the planning for next generation colliders.

hep-ph↗

arXiv2022

The Scale of New Physics from the Higgs Couplings to gg

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 $\sim 10$ 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).

hep-ph↗

arXiv2021

Model-independent Veltman Condition, Naturalness and the Little Hierarchy Problem

We adopt a bottom-up Effective Field Theory (EFT) approach to derive a model-independent Veltman condition to cancel the quadratic divergences in the Higgs mass. We show using the equivalence theorem that all deviations in the Higgs couplings to the W and Z from the SM predictions should vanish. We argue based on tree-level unitarity, that any new physics that naturally cancels the quadratic divergences should be ~19 TeV. We show that the level of fine-tuning required is O(0.1- 1%) unless the UV sector has a symmetry that forces the satisfaction of the model-independent Veltman condition, in which case all fine-tuning is eliminated. We also conjecture that if no new physics that couples to the Higgs is found up to ~ 19 TeV, or if the Higgs couplings to the SM particles conform to the SM predictions, then either the Higgs does not couple to any UV sector or is fine-tuned.

hep-ph↗

arXiv2021

Higgs Coupling Measurements and the Scale of New Physics

A primary goal of present and future colliders is measuring the Higgs couplings to Standard Model (SM) particles. Any observed deviation from the SM predictions for these couplings is a sign of new physics whose energy scale can be bounded from above by requiring tree-level unitarity. In this paper, we extend previous work on unitarity bounds from the Higgs cubic coupling to Higgs couplings to vector bosons and top quarks. We find that HL-LHC measurements of these couplings compatible with current experimental bounds may point to a scale that can be explored at the HL-LHC or a next-generation collider. Our approach is completely model-independent: we assume only that there are no light degrees of freedom below the scale of new physics, and allow arbitrary values for the infinitely many couplings beyond the SM as long as they are in agreement with current measurements. We also extend and clarify the methodology of this analysis, and show that if the scale of new physics is above the TeV scale, then the deviations can be described by the leading higher-dimension gauge invariant operator, as in the SM effective field theory.

hep-ph↗

arXiv2020

Probing Scalar and Pseudoscalar Solutions of the g-2 Anomaly

I investigate a class of models with scalar and pseudoscalar solutions to the g-2 anomaly in the mass range between 1 MeV and 40 GeV. In particular, I investigate the constraints from BaBar, beam dump experiments and from Z decay measured quantities. I find that most of the favored region in this mass range is excluded except for a small window between ~30 MeV and 200 MeV. This open window is expected to be covered by the proposed NA64 experiment. The results can be readily applied to other proposed solutions of the anomaly, such as solutions with Z0 or with the dark photon.

hep-ph↗

arXiv2018

The Light Radion Window

Inspired by the Contino-Pomarol-Rattazzi mechanism we explore scenarios with a very light (100 keV to 10 GeV) radion which could be associated with the suppression of the electroweak contribution to vacuum energy. We construct explicit, realistic models that realize this mechanism and explore the phenomenological constraints on this class of models. Compared with axion-like particles in this mass range, the bounds from SN 1987a and from cosmology can be much weaker, depending on the the mass of the radion and its coupling to other particles. With couplings suppressed by a scale lower than 100 TeV much of the mass window from 100 keV to 10 GeV is still open.

hep-ph↗

arXiv2018

The Radion as a Dark Matter Candidate

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 $\lesssim 1$ 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.

hep-ph↗

arXiv2017

Phenomenology of Bulk Scalar Singlets in the Randall Sundrum Model

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.

hep-ph↗