Higgs boson pair production in non-linear Effective Field Theory with full mtm_t-dependence at NLO QCD

We present a calculation of the NLO QCD corrections to Higgs boson pair production within the framework of a non-linearly realised Effective Field Theory in the Higgs sector, described by the electroweak chiral Lagrangian. We analyse how the NLO corrections affect distributions in the Higgs boson pair invariant mass and the transverse momentum of one of the Higgs bosons. We find that these corrections lead to significant and non-homogeneous K-factors in certain regions of the parameter space. We also provide an analytical parametrisation for the total cross-section and the $m_{hh}$ distribution as a function of the anomalous Higgs couplings that includes NLO corrections. Such a parametrisation can be useful for phenomenological studies.Comment: 40 pages, 26 figures, v2: published version; v3: ancillary files for 13, 14 and 27 TeV for LO and NLO differential cross sections and usage example adde

Real examples of surface reconstructions determined by direct methods

In this work the modulus sum function is briefly introduced and its applicability to the automated interpretation of projections of reconstructed surfaces shown. The selected real examples have been arranged according to the interpretation complexity of the respective two-dimensional Patterson maps and correspond to the most common types of surface reconstructions represented by: (i) a shift of the surface atoms from their ideal positions. This type of reconstruction is often found on (001) semiconductor surfaces and its most characteristic structural feature is the pairing of neighbouring surface atoms forming dimers, e.g., the In0.04Ga0.96As(001)-p(4 × 2) reconstructed surface. (ii) Different atom types occupying the surface sites. This type of reconstruction can be induced by both the adsorption of deposited atoms onto the surface, e.g. Sb/Ge(113)-c(2 × 2), or a new structural arrangement of the substrate caused by the adsorption of external molecules onto the surface, e.g. C60/Au(110)-p(6 × 5) reconstructed surface

Feasibility tests of transmission x-ray photoelectron emission microscopy of wet samples

We performed feasibility tests of photoelectron emission spectromicroscopy of wet samples in the water window (285-532 eV) soft x-ray spectral region. Water was successfully confined in an ultrahigh vacuum compatible compartment with x-ray transparent sides. This water cell was placed in the MEPHISTO spectromicroscope in a transmission geometry, and complete x-ray absorption spectra of the water window region were acquired. We also show micrographs of test samples, mounted outside of the compartment, and imaged through the water. This technique can be used to study liquid chemistry and, at least to the micron level, the microstructure of wet samples. Possibilities include cells in water or buffer, proteins in solution, oils of tribological interest, liquid crystals, and other samples not presently accessible to the powerful x-ray photoelectron emission spectromicroscopy technique

Theory of neutral and charged exciton scattering with electrons in semiconductor quantum wells

Electron scattering on both neutral ($X$) and charged ($X^-$) excitons in quantum wells is studied theoretically. A microscopic model is presented, taking into account both elastic and dissociating scattering. The model is based on calculating the exciton-electron direct and exchange interaction matrix elements, from which we derive the exciton scattering rates. We find that for an electron density of $10^9 {\rm cm}^{-2}$ in a GaAs QW at $T=5K$, the $X^-$ linewidth due to electron scattering is roughly twice as large as that of the neutral exciton. This reflects both the $X^-$ larger interaction matrix elements compared with those of $X$, and their different dependence on the transferred momentum. Calculated reflection spectra can then be obtained by considering the three electronic excitations of the system, namely, the heavy-hole and light-hole 1S neutral excitons, and the heavy-hole 1S charged exciton, with the appropriate oscillator strengths.Comment: 18 pages, 12 figure

X-ray-diffraction characterization of Pt(111) surface nanopatterning induced by C-60 adsorption

Understanding the adsorption mechanisms of large molecules on metal surfaces is a demanding task. Theoretical predictions are difficult because of the large number of atoms that have to be considered in the calculations, and experiments aiming to solve the molecule–substrate interaction geometry are almost impossible with standard laboratory techniques. Here, we show that the adsorption of complex organic molecules can induce perfectly ordered nanostructuring of metal surfaces. We use surface X-ray diffraction to investigate in detail the bonding geometry of C60 with the Pt(111) surface, and to elucidate the interaction mechanism leading to the restructuring of the Pt(111) surface. The chemical interaction between one monolayer of C60 molecules and the clean Pt(111) surface results in the formation of an ordered reconstruction based on the creation of a surface vacancy lattice. The C60 molecules are located on top of the vacancies, and 12 covalent bonds are formed between the carbon atoms and the 6 platinum surface atoms around the vacancies. In-plane displacements induced on the platinum substrate are of the order of a few picometres in the top layer, and are undetectable in the deeper layers

Study of C60/Au(110)-p(6 × 5) Reconstruction from In-Plane X-Ray Diffraction Data

Fullerene molecules absorbed on the highly anisotropic Au(110)-p(1 × 2) surface induce an ordered p(6 × 5) superstructure that has been solved by applying the 2D “direct methods” difference sum function to the surface x-ray diffraction data set. We found that the C60-gold interface is structurally much more complex than the one previously suggested by scanning tunneling microscopy data. Indeed a large fraction of Au surface atoms are displaced from their original positions producing microscopic pits that may accommodate the fullerene molecules.