Sherif Elgammal | Searcharxiv

arXiv2024

Search for the production of dark matter in the framework of Mono-Z$^{\prime}$ portal at the ILC simulated electron-positron collisions at $\sqrt{s} = 500$ GeV

In the present work, we study the possible production of the light neutral gauge boson (Z$^{\prime}$) candidates, which originated from a simplified-model scenario based on the Mono-Z$^{\prime}$ model, in association with dark matter. This study has been performed by studying events with dimuon plus missing transverse energy produced in the simulated electron-positron collisions at the foreseen International Linear Collider (ILC), operating at 500 GeV center of mass energy and integrated luminosity of 1000 fb$^{-1}$. In case no new physics has been discovered, we set upper limits at 95\% confidence level on the masses of various particles in the model as, spin-1 (Z$^{\prime}$), as well as the fermionic dark matter.

hep-ph↗

arXiv2018

$H_0$ Tension and the Phantom Regime: A Case Study In Terms of an Infrared $f(T)$ Gravity

We propose an $f(T)$ teleparallel gravity theory including a torsional infrared (IR) correction. We show that the governing Friedmann's equations of a spatially flat universe include a phantom-like effective dark energy term sourced by the torsion IR correction. As has been suggested, this phantom phase does indeed act as to reconcile the tension between local and global measurements of the current Hubble value $H_0$. The resulting cosmological model predicts an electron scattering optical depth $τ_e\thickapprox 0.058$ at reionization redshift $z_{re} \sim 8.1$, in agreement with observations. The predictions are however in contradiction with baryon acoustic oscillations (BAO) measurements, particularly the distance indicators. We argue that this is the case with any model with a phantom dark energy model that has effects significant enough at redshifts $z \lesssim 2$ as to be currently observable. The reason being that such a scenario introduces systematic differences in terms of distance estimates in relation to the standard model; e.g., if the angular diameter distance to the recombination era is to be kept constant while $H_0$ is increased in the context of a phantom scenario, the distances there are systematically overestimated to all objects at redshifts smaller than recombination. But no such discrepancies exist between $Λ$CDM predictions and current data for $z \lesssim 2$.

gr-qc↗