A large class of two- and three-Higgs-doublet models with discrete symmetries has been employed in the literature to address various aspects of flavor physics. We analyze how the precision measurement of the Higgs to diphoton signal strength would severely constrain these scenarios due to the nondecoupling behavior of the charged scalars, to the extent that in the presence of exact discrete symmet

We demonstrate that light charged and extra neutral scalars in the (100-200) GeV mass range pass the potentially dangerous flavor constraints in a particular class of two-Higgs-doublet model which has appropriately suppressed flavor-changing neutral currents at tree level. We study their decay branching ratios into various fermionic final states and comment on the possibility of their detection in

We investigate the scalar potential of a general S3-symmetric three-Higgs-doublet model. The outcome of our analysis does not depend on the fermionic sector of the model. We identify a decoupling limit for the scalar spectrum of this scenario. In view of the recent LHC Higgs data, we show our numerical results only in the decoupling limit. Unitarity and stability of the scalar potential demand tha

We analyze the scalar sector properties of a general class of two-Higgs-doublet models which has a global U(1) symmetry in the quartic terms. We find constraints on the parameters of the potential from the considerations of unitarity of scattering amplitudes, the global stability of the potential and the p-parameter. We concentrate on the spectrum of the non-standard scalar masses in the decouplin

Prompted by the recent observation of a Higgs-like particle at the CERN Large Hadron Collider, we investigate a quantitative correlation between possible departures of the gauge and Yukawa couplings of this particle from their Standard Model expectations and the scale of unitarity violation in the processes WW→WW and tt̄→WW.

The shortest time interval controlled by a human being is the duration of a light pulse as short as only 100 attoseconds, i.e., 10-16 s. This "attosecond" light pulse belongs to the extreme ultraviolet range (XUV) of the electromagnetic spectrum, with central photon energy typically between 20 and 200 eV. Related to its brevity, an attosecond pulse has a broad bandwidth covering tens of eV. These

We study the behavior of the multiphoton ionization rate of He+ ions as a function of the perturbation order N. By comparing the N-, (N+1)-,..., (N+S)-photon ionization processes, we prove that the absorption of photon in the continuum spectrum is increased at the largest wavelengths.

We present experimental results of harmonic generation using a 1-ps 1015-W/cm2 Nd-glass laser. We see up to the 29th harmonic in Xe, 57th in Ar, and at least up to the 135th harmonic in Ne (160 eV), being then limited by our monochromator's resolution. The conversion efficiencies in Xe, Ar, Ne, and He are compared and different ways of optimizing the number of photons by defocusing the laser beam

The authors have calculated two-photon electron detachment cross sections of the 5p shell of negative iodine in the photon energy region 0-1 Ryd. The results cover the region from the two-photon ionisation threshold of I - at 0.12 Ryd to well above the one-photon ionisation threshold of neutral iodine at about 0.8 Ryd. They demonstrate the importance of many-electron screening effects and double e

We investigate different processes which may be responsible for ejection of two electrons from the external shell of xenon through the absorption of two and three photons, namely two-photon direct double ionization and three-photon sequential double ionization via the ion in an excited state or in the ground state. We calculate the cross sections of the ionization processes involved, using many-bo

The authors present calculations of the two-photon one-electron ionisation of the 5p shell of xenon including non-linear response. Screening effects are described within the random-phase approximation (RPA). The authors use both a local-density approximation (LDA) and a Hartree-Fock average basis set. They describe a large energy region from the two-photon ionisation threshold to above the one-pho

The recent advances concerning high-order harmonic generation processes in strong laser fields are discussed. We show how the width of the plateau inherent to the production of high harmonics varies with the pulse width, the laser wavelength and the atomic medium. Phase matching effects are discussed in terms of coherence length owing to the laser focusing. Finally, we show that the idea of genera

We apply the random-phase approximation to two-photon ionization. We develop a formalism which, by means of screened electron-photon interactions, includes the nonlinear response and, in particular, double-excitation processes. The theory is illustrated by numerical calculations of the two-photon ionization cross section of the external (5p and 5s) shell of xenon, over a large energy range: from t

We present experimental results of harmonic generation at 1064 nm using a 36-ps neodymium-doped yttrium aluminum garnet laser tightly focused in a gas jet of xenon. The harmonic yields are studied as a function of the position of the focus in the jet at several laser intensities and as a function of intensity at several focus positions. These results bring information about how the high harmonics

We review the main experimental results obtained in the multielectron multiphoton ionization of rare gases. Multiple ionization is interpretated as a sequential process. We study the influence of many‐electron effects in multiphoton ionization within the framework of the random phase approximation. This is applied to a calculation of the two‐photon ionization cross section of xenon. Finally, the r