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In the absence and presence of a circularly polarized monochromatic electromagnetic pulse, we have analyzed the electron–nucleon scattering process, where the nucleon is assumed to be spinless with a spherical shape. We have provided the theoretical calculation of the differential cross section (DCS) by using the Dirac–Volkov formalism. This research paper aims to provide two comparisons: We first compare the DCS in the absence of the laser field with its corresponding laser-assisted DCS. A second comparison is made between the electron–proton and electron–neutron scattering processes to study the effect of the laser on both processes. The results obtained about the effect of the laser field on the DCS and the electric form factor have been discussed for both scattering processes. We have found that the DCS is reduced when the laser field is applied for both processes. In addition, the form factor is also decreased by raising the incident electron energy in electron–proton scattering, but it increases in electron–neutron scattering. Moreover, the form factors for both scattering situations are unchanged by raising the laser field strength up to 1 0 8 V/cm. [ABSTRACT FROM AUTHOR]

This study employs a first-principles approach to comprehensively examine the structural, electronic, optical, and magnetic properties of the thermodynamically stable scintillating double perovskite halides A 2 N a T a X 6 ( A = C s , R b ; X = C l , B r , I ). The dynamic stability of these materials were explained based on deduced phonon properties. Our analysis reveals that these compounds exhibit intriguing electronic behavior with spin polarization, demonstrating half-metallicity. In spin-up, the band gap is found to be zero, while in spin-down, it falls within the range of 3 to 4 eV with the incorporation of DFT+U corrections. Notably, the optical properties assessment highlights the exceptional UV and high-energy absorption capabilities of A 2 N a T a I 6 , making it a promising candidate for scintillation applications in particle detection. This research sheds light on the unique and versatile properties of these materials, with implications for various technological and scientific applications. [ABSTRACT FROM AUTHOR]

This research work investigates the structural, electronic, optical, and thermoelectric characteristics of VFeZ (Z = N and P) half‐Heusler compounds. The study employs the full‐potential linearized augmented plane wave (FP‐LAPW) method integrated into the WIEN2K algorithm, serving as the underpinning framework for density functional theory (DFT) analysis. In the study, we use the PBE generalized gradient approximation (PBE‐GGA) to identify numerous parameters associated with structural and elastic properties. Lattice parameter results are in agreement with previous outcomes. Moreover, computed elastic parameters satisfy the criterion for stability. In the cubic structure VFeZ (Z = N and P) is ductile, to enhance the computations of electronic characteristics, Tran and Blaha's modified Becke‐Johnson potential (TB‐mBJ) is used. Our simulations demonstrate that the materials exhibit semiconductor behavior, with a direct band gap for VFeZ (Z = N and P). Strong UV absorption is found via optical experiments suggest compounds are suitable for optical application. Furthermore, study of the thermoelectric properties suggests its application in the thermoelectric generators. [ABSTRACT FROM AUTHOR]

In the center of mass frame, we have investigated the process of Higgs-strahlung production in association with a pair of fermions, e + e - → f f ¯ H , at the leading order in the presence of an intense electromagnetic field with circular polarization. Our analytical calculations are based on the narrow width approximation, which is valid in the leading order as Γ Z / M Z = 2 % . We have considered only the initial particles inside the laser field as a first step. In the second part, we have embedded both initial and final particles in the laser field. We have analyzed the angular distribution of the produced Higgs boson as a function of the laser parameters in both cases. We have found that the order of magnitude of the differential cross section of both processes e + e - → μ + μ - H and e + e - → b b ¯ H is reduced more significantly in the case where both initial and final particles are embedded in the laser field. [ABSTRACT FROM AUTHOR]

In a previous paper, we showed theoretically that the total cross-section of the top-quark pair production by electron–positron annihilation is strongly reduced by the presence of a circularly polarized laser field. In this paper, we present the result for the case of a linearly polarized laser field. This time, the total cross-section is significantly enhanced by the laser field. [ABSTRACT FROM AUTHOR]

In this research paper, we consider the process of neutral Higgs production from e+e– annihilation in Inert Higgs Doublet Model (IHDM) in the absence and presence of an external field. The latter is assumed to be a plane and monochromatic wave with linear polarization. In the theoretical framework, we present the analytic calculation of the lowest order differential cross section by using the scattering matrix approach and Dirac–Volkov formalism for charged incident particles. The total cross section is computed by performing a numerical integration of the differential cross section over the solid angle. The results obtained are analyzed and discussed for different centre of mass energies and laser parameters. We found that inserting a laser wave with linear polarization is a suitable mechanism to enhance the total cross section of the process. Indeed, the probability of the process to occur increases with the presence of a linearly polarized laser field, especially with low frequency and high strength. [ABSTRACT FROM AUTHOR]

A theoretical treatment, using the first Born approximation, is presented to analyse the results of relativistic laser-assisted Proton--hydrogen atom scattering. Specific calculations are carried out for excitation of hydrogen atoms from 1[s.sub.[1/2]] to 2[s.sub.[1/2]] states by proton impact. We work in an approximation in which the incoming proton may be described by Dirac-Volkov states in the presence of a laser field. Semi-relativistic Darwin wave functions are used to describe the hydrogen atom in its initial and final states, while relativistic, spin, and laser interaction effects are also accounted for. The results presented in this paper show that the differential cross section for this process depends not only upon the energy of the incident proton, but also upon its interaction with the laser field through intensity and frequency. Key words: laser assisted, QED calculations, Dirac equation, relativistic atomic process, Dirac algebra. Nous presentons un calcul en premiere approximation de Born, pour analyser les resultats de diffusion proton-atome d'hydrogene en regime relativiste, sous l'influence d'un champ laser. Nos calculs sont specialises fi l'excitation d'un atome d'hydrogene du 1[s.sub.[1/2]] au 2[s.sub.[1/2]] par impact de proton. Nous travaillons dans l'approximation oU le proton peut etre decrit par des etats de Dirac-Volkov en presence d'un champ laser. Des fonctions d'onde semi-relativistes de Darwin sont utilisees pour decrire l'atome d'hydrogene dans ses etats initial et final, tout en tenant compte des effets relativistes, de spin et d'interaction laser. Les resultats presentes ici montrent que la section efficace differentielle pour ce processus depend non seulement de l'energie du proton incident, mais aussi de son interaction avec le champ laser via son intensite et sa frequence. [Traduit par la Redaction] Mots-cles : processus atomique relativiste assiste par laser, calculs EDQ/QED. PACS Nos.: 34.80.Dp, 12.20.Ds., 1. Introduction Analysis of inelastic proton-atom and proton-molecule scattering at intermediate to high energies has recently attracted a considerable amount of interest. In the case of electron- or positron-impact, relativistic [...]

In the framework of the first Born approximation and using the Dirac-Volkov formalism, we investigate the relativistic model describing the laser assisted elastic differential cross sections (DCSs) for positron scattering by the hydrogen atom. Both the DCSs for electron and positron are notably modified by the circularly polarized laser field, particularly in the regime of high energies and medium intensities. Comparing the two numerical DCSs, we recover the well-known result that the elastic scattering differential cross sections with and without laser field for a hydrogen atom by electron and positron impact are the same (Greiner and Reinhardt. Quantum Electrodynamics, 2nd ed., Springer Verlag, New York, Berlin, Heidelberg. 1994). The numerical results reveal that the differential cross section for positron--hydrogen atom scattering is significantly reduced with the increase of the electric field strength. PACS Nos.: 34.80.Qb, 12.20.Ds. Dans le cadre de la premiere approximation de Born et utilisant le formalisme de Dirac-Volkov, nous etudions le modele relativiste qui decrit la section efficace differentielle elastique de la diffusion de positrons sur des atomes d'hydrogene en presence d'un champ laser (DCSs). Les DCSs pour electrons et positrons sont affectes notablement par le champ laser a polarisation circulaire, particulierement aux hautes et moyennes intensites. Comparant les resultats numeriques pour les deux DCSs, nous retrouvons le resultat bien connu que les sections efficaces differentielles de diffusion elastique avec et sans champ laser pour des electrons et des positrons sur des atomes d'hydrogene sont les memes (Greiner et Reinhardt. Quantum Electrodynamics, 2e ed., Springer Verlag, New York, Berlin, Heidelberg. 1994). Les resultats numeriques revelent que la section efficace differentielle pour la diffusion positron-hydrogene est significativement reduite avec l'augmentation du champ electrique. [Traduit par la Redaction], 1. Introduction The solutions of the Dirac equation for the fermionic particles in an external electromagnetic field, known as the Volkov wave functions [1], have been widely used as asymptotic [...]

In this work, we review and correct the first Born differential cross section for the process of Mott scattering of a Dirac-Volkov electron, namely, expression (26) derived by Szymanowski et al. (Phys. Rev. A, 56, 3846 (1997)). In particular, we disagree with the expression of (dσ/dΩ) that they obtained and we give the exact coefficients multiplying the various Bessel functions appearing in the scattering differential cross section. Comparison of our numerical calculations with those of Szymanowski et al. shows qualitative and quantitative differences when the incoming total electron energy and the electricfield strength are increased particularly in the direction of the laser propagation. Such corrections are very important since the relativistic electronic dressing of any Dirac-Volkov charged particle gives rise to these coefficients that multiply the various Bessel functions, and the relativistic study of other processes (such as excitation, ionization, etc....) depends strongly upon the correctness and reliability of the calculations for this process of Mott scattering in the presence of a laser field. Our work has been accepted, Attaourti and Manaut (Phys. Rev. A, 68, 067401 (2003)) but only as a comment. In this paper, we give full details of the calculations as well as a clear explanation of the large discrepancies that their results could cause when working in the ultra relativistic regime and using a very strong laser field corresponding to an electric field strength ζ = 5.89 au. PACS Nos.: 34.80.Qb, 12.20.Ds Nous passons ici en revue la section efficace differentielle a la premiere de Born pour le probleme de la diffusion de Mott d'un electron de Dirac-Volkov, nommement l'expression (26) obtenue par Szymanowski et al. (Phys. Rev. A, 56, 3846 (1997)). En particulier, nous sommes en desaccord avec l'expression de (ds/dU) qu'ils ont obtenue et nous donnons la valeur exacte des coefficients qui multiplient les differentes fonctions de Bessel qui apparaissent dans l'expression de la section efficace differentielle. Une comparaison de nos calculs numeriques avec ceux de Szymanowski et al montre des differences qualitatives et quantitatives quand l'energie totale de l'electron incident et l'intensite du champ electrique augmentent, en particulier dans la direction du faisceau laser. De telles corrections sont tres importantes, parce que l'habillage electronique relativiste de toute particule chargee de Dirac-Volkov donne naissance a ces coefficients qui multiplient les differentes functions de Bessel et l'etude relativiste des autres mecanismes (excitation, ionisation, ...) dependent fortement de la viabilite et de l'exactitude des calculs en presence d'un champ laser. Notre travail a ete accepte pour publication Attaourti et Manaut (Phys. Rev. A, 68, 067401 (2003)), mais seulement sous la forme d'un Commentaire. Ici, nous donnons tous les details des calculs, aussi bien qu'une explication claire des differences importantes que leurs resultats peuvent causer lorsqu'on travaille en regime ultra-relativiste utilisant un champ laser tres fort correspondant a un champ electrique de force ζ = 5,89 au. [Traduit par la Redaction], 1. Introduction In a pioneering and very often cited paper, Szymanowski et al. [1] studied the Mott-scattering process in a strong laser field. The main purpose of their work was [...]

We analyse a light charged Higgs boson in the 2-Higgs Doublet Model (2HDM) Type-I, when its mass satisfies the condition MH±< Mt + Mb and the parameter space is consistent with theoretical requirements of self-consistency as well as the latest experimental constraints from Large Hadron Collider (LHC) and other data. Over such a parameter space, wherein the Standard Model (SM)-like state discovered at the LHC in 2012 is the heaviest CP-even state of the 2HDM, it is found that the decay modes of the charged Higgs boson are dominated by H±→ W±(∗)h. Furthermore, the light neutral Higgs boson h dominantly decays into two photons. Under these conditions, we find that the production and decay process pp → H±h → W±(∗)hh → ℓνℓ + 4γ (ℓ = e, μ) is essentially background free. However, since the W±(∗) could be largely off-shell and the h state is very light, so that both the lepton coming from the former and the photons coming from the latter could be rather soft, we perform here a full Monte Carlo (MC) analysis at the detector level demonstrating that such a W± + 4γ signal is very promising, as it would be yielding significant excesses at the LHC with an integrated luminosity of L = 300 fb−1 at both s = 13 and 14 TeV. [ABSTRACT FROM AUTHOR]

The theory of triple differential cross-sections, developed previously within the framework of nonrelativistic Schrödinger formalism, is extended to the relativistic treatment by using the Dirac-Volkov formalism. At high energies, the colliding particles lose their Coulomb character and the channel of the symmetric coplanar geometry is opened. In the first Born approximation, we have studied theoretically the laser-assisted relativistic ionization of hydrogen atoms by positron impact in this geometry. Triple differential cross-sections are calculated by using two approaches: (i) RPWSG to describe relativistic plane wave in the symmetric geometry, (ii) DVPWSG (Dirac- Volkov plane wave in the symmetric geometry) in which we take full account of the relativistic dressing effects, has been proposed to study the influence of laser field on the colliding particles. To check the consistency of our model, we have used, for comparison, the nonrelativistic approach: nonrelativistic plane wave in the symmetric geometry. Numerical results for the variation of relativistic triple differential cross-sections and their dependences on laser field parameters (intensity, frequency) and incident positron energy are also presented. As for the laser modifications, by summing over a very large number of exchanged photons, the laser-assisted triple differential cross-sections usually tends to approach the laser-free triple differential cross-sections, obeying the famous Kroll-Watson sum rule for positron projectile. In the absence, of any experimental data at high energies for this particular ionization process, we are not in a position to compare the present results with the experimental findings. [ABSTRACT FROM AUTHOR]

In the framework of the first Born approximation, we present a semirelativistic theoretical study of the inelastic excitation (1s1/2 → 2s1/2) of hydrogen atom by electronic impact. The incident and scattered electrons are described by a free Dirac spinor and the hydrogen atom target is described by the Darwin wave function. Relativistic and spin effects are examined in the relativistic regime. A detailed study has been devoted to the nonrelativistic regime as well as the moderate relativistic regime. Some aspects of this dependence as well as the dynamic behavior of the differential cross-section in the relativistic regime have been addressed. [ABSTRACT FROM AUTHOR]