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Nidal Chamoun

Publications and source records attributed to Nidal Chamoun.

18 recordsLinked to original sources
arXiv2026

Z'-Mediated Slepton and Sneutrino Signatures at HL-LHC

We investigate the discovery potential of a heavy $Z'$ boson as a portal to charged sleptons and right-handed sneutrinos within the $B-L$ Supersymmetric Standard Model (BLSSM) at the High-Luminosity LHC. Using a detector-level simulation and Boosted Decision Trees to suppress Standard Model backgrounds, we find that the direct slepton decay $pp \to Z' \to \tilde{\ell}^+\tilde{\ell}^- \to 2\ell + E_{\rm T}^{\rm miss}$ yields a significance exceeding $5\sigma$ at 3000 fb$^{-1}$, while the cascade $(\mbox{multileptons} + E_{\rm T}^{\rm miss})$ mode is unobservable due to rate suppression. For right-handed sneutrinos, the hadronic channel $pp \to Z' \to \tilde{\nu}_R\tilde{\nu}_I \to 2\ell + 4j + E{\rm T}^{\rm miss}$ emerges as the most promising signature. These results establish the $2\ell + E_{\rm T}^{\rm miss}$ and $2\ell + 4j + E_{\rm T}^{\rm miss}$ final states as the principal discovery channels for the scalar leptonic sector of the BLSSM at the HL-LHC.

hep-ph↗
arXiv2026

A Comparative Study of Correlation and Relativistic Effects on Atomic Ionization Energy

This study investigates the interplay between relativistic effects and electron correlation effects on the first ionization energies of heavy atoms (Au through Rn, Z = 79-86). We perform two complementary analyses: (1) comparing relativistic corrections computed at both the Hartree-Fock (HF) and coupled cluster CCSD(T) levels to assess how correlation influences the magnitude of relativistic corrections, and (2) comparing correlation corrections computed within both non-relativistic and relativistic frameworks to determine how relativity influences the magnitude of correlation corrections. Our results reveal a striking non-linear relationship between these two effects. Specifically, the combined effect of relativity and correlation on ionization energy does not equal the sum of their individual contributions. This non-additivity indicates that relativistic and correlation effects are not independent; they interact in complex ways that depend on the atomic system. We find that for some atoms, the two effects enhance each other, while for others they partially cancel. Moreover, the order in which one may add "separate" effects also counts, in that adding "pure" relativistic effects to the remaining outcome (including correlation) would give a different result than when adding "pure" correlation effects to the remaining outcome (including relativity). These findings demonstrate that relativistic and correlation effects are inherently non-additive, reflecting the non-linearity of the quantum many-body problem. Accurate computational predictions of ionization energies in heavy-element systems thus require simultaneous treatment of both effects rather than treating them as independent contributions.

physics.atom-ph↗
arXiv2026

Constraining nonminimal f(T) gravity from Primordial Nucleosynthesis to Late-Universe observations

We present a multi-epoch test of f(T) gravity with nonminimal torsion-matter coupling, combining early- and late-Universe observations. At the MeV scale, Big-Bang Nucleosynthesis constrains the fractional variation of the weak freeze-out temperature, |{\delta}{\tau}_f/{\tau}_f|, thereby mapping light-element abundances into limits on deviations from the standard expansion history. At low redshift, we confront the model with type Ia supernovae, baryon acoustic oscillations, and cosmic-chronometer data, which respectively probe distances, the late-time standard ruler, and the Hubble rate. Independent analyses highlight the complementary roles of each dataset, while a joint SNe Ia + BAO + CC fit breaks degeneracies and yields the tightest combined bounds. As an illustration, we examine two representative torsion-modified gravity scenarios: BBN strongly limits large departures from standard cosmology, whereas late-time probes remain compatible with a near-{\Lambda}CDM background. This unified approach demonstrates the power of linking early-Universe nuclear physics with precision cosmological observables in assessing torsional extensions of gravity.

astro-ph.CO↗
arXiv2026

Cosmological Constraints on f(T,B) Gravity from Observations of Early and Late Universe

We present a unified framework that combines early- and late-Universe observations to constrain three functional realizations of f(T,B) gravity: the linear, quadratic, and general power-law models. First, constraints on deviations from the standard weak interaction freeze-out temperature are derived using the most recent measurements of the primordial helium-4 mass fraction. Second, we perform a joint analysis incorporating five priors: Type Ia supernovae, baryon acoustic oscillations, cosmic chronometers, Big Bang Nucleosynthesis, and Cosmic Microwave Background in order to place bounds on the model parameters. The joint likelihood analysis significantly tightens the constraints compared to individual datasets. Third, we test the null, strong, and dominant energy conditions to evaluate the physical viability of the best-fit solutions across the cosmic redshift range. Our results show that all three f(T,B) models are consistent with current observations and exhibit stable behavior under the energy-condition criteria, supporting torsion-boundary modified gravity as a robust and viable alternative to General Relativity.

astro-ph.CO↗
arXiv2026

Quantum Study of Dispersion-Corrected Electronic and Optical Properties of syn- and anti- B18H22 Clusters with/without Sulfur Doping for Tunable Optoelectronics

This study presents a detailed quantum chemical investigation of the electronic and excited-state properties of syn- and anti-isomers of the borane cluster B18H22 and their sulfur-doped derivatives. Using the PB86/def2-SVP level of theory with dispersion corrections, the research examines how sulfur substitution and non-covalent interactions influence cluster stability, electronic structure, spectra, and optoelectronic potential. Comparative analysis of the syn- and anti-isomers reveals the impact of molecular conformation on frontier molecular orbitals and related energetic and photophysical properties. Sulfur doping is shown to enhance charge delocalization, stabilize excited states, and improve thermal stability, which form key factors for tunable laser applications. The inclusion of advanced dispersion correction methods proves essential for accurately capturing many-body interactions that govern electronic behavior. By elucidating the interplay between structural features, substitution patterns, and computational modeling, the work provides valuable insights into structure-property relationships critical for designing borane-based materials with tailored optoelectronic and thermal characteristics. In addition to doping and dispersion effects, functionals' effects were examined through comparison amidst various ones with different asymptotic exchange on excitation and gap energies. In summary, the computational methodology combined good DFT/Basis/dispersion set to accurately predict geometries, IR/UV spectra, NMR chemical shifts, dipole moments, polarizability and excited-state properties, thereby offering a comprehensive theoretical understanding of syn-, anti- isomers of B18H22 and its sulfur doped variants.

physics.atm-clus↗
arXiv2026

Theoretical Study of C36 and O@C36 Fullerene Isomers with (C1, C2, Cs, D2, D3h) symmetries: Geometry Optimization, Electrical Properties and Spectroscopic Analysis

In this study, we conducted a theoretical analysis of specific C36 and O@C36 Fullerene isomers, namely those with (D3h, C1, Cs, C2, D2) symmetries, in the gaseous phase using the DFT method at B3LYP/6-31G* level. We studied geometry optimizations, relative stability, atomization energies, Fermi energy, energy gap, electronic properties, electric dipole moment, polarizabilities, and thermodynamic analysis, along with IR and NMR spectra. Consistently, our findings revealed distinct properties and characteristics among different C36 fullerene isomers. The energetic order of C36 fullerene isomers was established as C36-D3h < C36-C1 < C36-Cs < C36-C2 < C36-D2, a trend unaffected by the encapsulation of oxygen. Notably, the D2 isomer displayed the smallest energy gap, indicating higher electrical conductivity compared to other isomers, while it exhibited the largest gap after encapsulation. Furthermore, we observed that the C1 (D2) isomer exhibited the largest (smallest) Electric dipole moment among the studied C36 isomers, whereas the C2 (D2) isomer demonstrated the largest Electric dipole moment among the O@C36 isomers studied. The encapsulation of oxygen in C36 isomers influenced their properties, including alterations in electronic properties, IR, and NMR chemical shifts. A detailed analysis of BSSE corrections showed the tininess of their impact on the analyzed observables, such that uncorrected and BSSE-corrected calculations led to nearly identical results, confirming the robustness and reliability of the B3LYP/6-31G* approach used in this work and, eventually, in other large and rigid fullerenes systems.

physics.chem-ph↗
arXiv2026

Quantum Study of Halogen Substituted anti-B18H22 Borane Clusters for Optoelectronics

We offer a quantum chemical analysis of mono-halogenated borane molecules using DFT and TD-DFT theories, applying the PBE0/def2-SVPD and B3LYP/6-311+G(d) methods as implemented in ORCA, and explore how solvent effects influence electronic transition properties. The comparable benchmarks are the archetype anti-\ce{B18H22} denoted as (1) against hypothetical halogenated derivatives: 7-F-anti-\ce{B18H21} (2), 4-F-anti-\ce{B18H21} (3), and the recently synthesized 4-Br-anti-\ce{B18H21} (4). The analysis includes an optimization of the ground and first singlet excited states, vibrational frequency analysis, and a comprehensive spectroscopic profile covering IR, Raman, UV-Vis absorption, and emission spectra. The IR spectra of the fluorinated compounds feature a characteristic B-F stretching peak, while the Raman spectra closely resemble the parent molecule. UV-Vis spectral analysis shows a redshift and oscillator strength enhancement for F at position B7, indicating altered electronic properties due to substitution with lighter halogen. Furthermore, solvent effects enhance the probability of electronic transitions. Halogene presence led to a decrease of the energy gap EG(LUMO-HOMO) due to the stabilization of LUMO, which implied a redshift in the emission/absorption wavelength spectra, with the largest EG change at around 14\% occurring for the (4)$^{th}$ benchmark compound.. Notably, all compounds emit light within the visible spectrum, underscoring their potential for optoelectronic applications.

physics.atm-clus↗
arXiv2025

Cosmological Constraints on $f(T,B)$ Gravity from Observations of Early and Late Universe

This study proposes a unified framework comprising two complementary approaches to constrain three functional forms of $f(T,B)$ gravity, namely the linear, quadratic, and general power law models, by jointly utilizing early and late Universe observations. First, we impose bounds on deviations in the weak interaction freeze-out temperature, informed by the latest measurements of the primordial helium-4 mass fraction. Second, we incorporate direct Hubble parameter data, $H(\mathcal{z})$, obtained from Cosmic Chronometers in the redshift range $0.07\le\mathcal{z}\le2.0$, to trace the expansion history of the Universe. By minimizing a combined chi-square statistic across both datasets, we derive the best-fit values and confidence intervals for each model parameter. The joint analysis significantly refines the parameter constraints compared to methods based solely on Big Bang Nucleosynthesis, thereby offering a more robust test of $f(T,B)$ gravity across cosmic epochs. The results support the viability of torsion-based modifications to General Relativity and provide a consistent methodology for future evaluation using upcoming observational data.

astro-ph.CO↗
arXiv2025

Comparison between PBE-D3, B3LYP, B3LYP-D3 and MP2 Methods for quantum mechanical calculations of polarizability and IR-NMR spectra in C24 isomers, including a novel isomer with D2d symmetry

We perform a comprehensive theoretical analysis of C24 isomers in the gaseous phase using the PBE-D3-cc-pVTZ,B3LYP-cc-pVTZ,B3LYP-D3-cc-pVTZ , MP2-6-31G methods.We consider the basis set cc-pVTZ for the MP2 method , carry out optimized (single point) calculations in three isomers (remaining two isomers when convergence was too time consuming) in order to reveal the potentiality of the method.We covered many properties,including geometry optimizations,chemical stability,polarizabilities,nuclear screening constants,Fermi(FE),gap(GE) , atomization energies(AE),thermodynamic analysis,reactivity index,IR, NMR.Calculations were performed for ring (D12h), sheet (D6h) , two cage (D6d,Oh) configurations. We proposed a new structure, the bracelet (D2d) arrangement, stable according to the PBE, B3LYP,B3LYPD3 methods, but a transition state by the MP2 method. Results consistently indicated the D6h isomer is the most stable one among the C24 isomers studied, while the D2d isomer was found to be the least stable.For the gap energy(GE), the B3LYP,B3LYP-D3 methods yielded higher values compared to the PBEs,with an average DFT (PBE, B3LYP) GE of 1.89eV,whereas the MP2 method showed a substantially higher GE value of 7.6 eV, representing an increase of approximately 0.75.The polarizabilities of the C24 isomers were found to be overestimated by the PBE,B3LYP,B3LYP-D3 methods when compared to the corresponding MP2 values.The PBE-D3 method produced higher polarizabilities for the C24 isomers in comparison to the B3LYP, B3LYP-D3, MP2 methods.The investigation confirms that the Oh (D12h) isomer has the smallest (largest) polarizability.The polarizability of D12h is notably affected by the selected DFT method, while that of Oh displays lower sensitivity but shares similarities with D6d.

physics.chem-ph↗
arXiv2025

Relativistic effects on properties of halogen group elements/ions

This srudy investigates the influence of relativistic effects on some properties of the halogen group and gold atoms, including their ions. The analysis covers radii, orbital's energy, first and second ionization energies, electron affinity, and polarizability. The study confirms that the p1/2 orbitals contract under relativistic effects, whereas for the p3/2 orbitals, the mass-velocity and spin-orbit effects do not appear to cancel each other out completely. This may indicate that the spion-orbit effect grows, when increasing the atomic number, slightly faster than the mass-velocity effect. In addition, expansion of the np3/2 orbitals may lead to dilation of the bond length in the related molecules. We found that the non-relativistic Hartree-Fock method gave, for atoms from fluorine to iodine, first ionization energy values with smaller deviations from their experimental ones than other methods involving relativistic and correlation effects. In particular, the method accurately, up to three significative digits, predicts the experimental value for chlorine, and thus can be adopted, discarding other sophisticated methods considering the huge computational effort required by them while not improving much on the agreement with experiment, when evaluating physical-chemical properties of large systems containing light halogen elements. It also predicts an electron affinity of $2.4 eV$ for the tennessine atom, where it shows also that the relativistic effects play a more important role than in gold atoms.

physics.atom-ph↗
arXiv2024

Exploring $Z'$ and Right-Handed Neutrinos in the BLSM at the Large Hadron Collider

We study the collider phenomenology of the $B$-$L$ extension of the Standard Model (BLSM), focusing on the production and decay of a heavy neutral gauge boson (\( Z' \)) at the Large Hadron Collider (LHC). In this framework, the \( Z' \) can decay into pairs of heavy right-handed neutrinos (\( \nu_R \)), which subsequently decay into charged leptons and \( W \) bosons. These processes give rise to three distinctive final states: (i) two leptons plus four jets (\( 2\ell + 4j \)), (ii) four leptons plus missing transverse energy (\( 4\ell + \text{MET} \)), and (iii) three leptons plus two jets and MET (\( 3\ell + 2j + \text{MET} \)). % To enhance signal sensitivity and suppress Standard Model backgrounds, we employ multivariate analysis techniques based on Boosted Decision Trees (BDTs), as well as selection optimizations using the \texttt{XGBOOST} framework. The classifiers are trained on kinematic observables sensitive to the masses of the \( Z' \) and \( \nu_R \). We demonstrate that all three final states offer significant discovery potential for both the \( Z' \) and heavy \( \nu_R \) at the High-Luminosity LHC. Our results highlight the testability of the BLSM at current and future collider experiments, and provide a promising avenue for probing the origin of neutrino masses and the baryon asymmetry of the Universe.

hep-ph↗
arXiv2023

On Warm Natural Inflation and Planck 2018 constraints

We investigate Natural Inflation with non-minimal coupling to gravity, characterized either by a quadratic or a periodic term, within the Warm Inflation paradigm during the slow roll stage, in both strong and weak dissipation limits, and show that, in the case of $T$-linearly dependent dissipative term, it can accommodate the spectral index $n_s$ and tensor-to-scalar ratio $r$ observables given by Planck 2018 constraints, albeit with a too small value of the e-folding number to solve the horizon problem, providing thus only a partial solution to Natural Inflation issues. Assuming a $T$-cubically dependent dissipative term can provide a solution to this e-folding number issue.

gr-qc↗
arXiv2023

Dynamics and stability of the two-body problem with Yukawa correction to Newton's gravity, revisited and applied numerically to the solar system

In this manuscript, we review the motion of two-body celestial system (planet-sun) for a Yukawa-type correction on Newton's gravitational potential using Hamilton's formulation. We reexamine the stability using the corresponding linearization Jacobian matrix, and verify that the Bertrand's theorem conditions are met for radii $\ll 10^{15} m$, and so bound closed orbits are expected. Applied to the solar system, we present the equation of motion of the planet, then solve it both analytically and numerically. Making use of the analytical expression of the orbit, we estimate the Yukawa strength $α$, and find it larger than the nominal value ($10^{-8}$) adopted in previous studies, in that it is of order ($α= 10^{-4}-10^{-5}$) for terrestrial planets (Mercury, Venus, earth, Mars and Pluto) whereas it is even larger ($α= 10^{-3}$) for the Giant planets (Jupiter, Saturn, Uranus and Neptune). Taking as inputs ($r_{min}, v_{max}, e$) observed by NASA, we analyze the orbits analytically and numerically for both the estimated and nominal values of $α$, and determine the corresponding trajectories. For each obtained orbit we recalculate the characterizing parameters ($r_{min}, r_{max}, a, b, e $) and compare their values according to the used potential (Newton with/without Yukawa correction) and to the method used (analytical and/or numerical). When compared to the observational data, we conclude that the correction on the path due to Yukawa correction is of order of and up to 80 million km (20 million km) as a maximum deviation occurring for Neptune (Pluto) for nominal (estimated) value of $α$.

astro-ph.EP↗
arXiv2020

Nucleon decay in the R-parity violating MSSM

We present a reanalysis of nucleon decay in the context of the R-parity violating MSSM, updating bounds on R-parity violating parameters against recent experimental and lattice results. We pay particular attention to the derivation of these constraints and specifically to the hadronic matrix elements, which usually stand as the limiting factor in order to derive reliable bounds, except for these few channels that have been studied on the lattice.

hep-ph↗
arXiv2017

Six Higgs Doublets Model for Dark Matter

We consider an extension of the Higgs sector in the standard model (SM) with six Higgs doublets. The gauge couplings are unified without supersymmetry in this model. The lightest of the extra Higgs particles, being stabilized by a discrete symmetry imposed from the outset, presents a plausible candidate for dark matter. For a specific acceptable benchmark point, we show that the model is viable regarding the constraints of relic density, direct detection and invisible Higgs decay. We comment on the mean free path of the dark matter candidate.

hep-ph↗
arXiv2006

Helium and Deuterium Abundances as a Test for the Time Variation of the Fine Structure Constant and the Higgs Vacuum Expectation Value

We use the semi-analytic method of \citet{Esma91} to calculate the abundances of Helium and Deuterium produced during Big Bang nucleosynthesis assuming the fine structure constant and the Higgs vacuum expectation value may vary in time. We analyze the dependence on the fundamental constants of the nucleon mass, nuclear binding energies and cross sections involved in the calculation of the abundances. Unlike previous works, we do not assume the chiral limit of QCD. Rather, we take into account the quark masses and consider the one-pion exchange potential, within perturbation theory, for the proton-neutron scattering. However, we do not consider the time variation of the strong interactions scale but attribute the changes in the quark masses to the temporal variation of the Higgs vacuum expectation value. Using the observational data of the helium and deuterium, we put constraints on the variation of the fundamental constants between the time of nucleosynthesis and the present time.

astro-ph↗
arXiv2002

Non-Universal Gaugino Masses in Supersymmetric SO(10)

We consider SUSY SO(10) models in which SUSY breaking occurs via an F-term which does not transform as an SO(10) singlet. This results in non-universal GUT-scale gaugino masses leading to a different pattern of sparticle masses from what is expected in the minimal supergravity model (mSUGRA). We study three breaking chains of SO(10) down to the standard model through SU(4)$\timesSU(2)\times$SU(2), SU(2)$\times$SO(7) and `flipped' SU(5) achieved by the representations 54 and 210 which appear in the symmetric product of two SO(10) adjoints. We examine the phenomenological implications of the different boundary conditions corresponding to the different breaking chains and present the sparticle spectrum.

hep-ph↗