On the measurement of the proton-air cross section using cosmic ray data

Cosmic ray data may allow the determination of the proton-air cross section at ultra-high energy. For example, the distribution of the first interaction point in air showers reflects the particle production cross section. As it is not possible to observe the point of the first interaction $X_{\rm 1}$ of a cosmic ray primary particle directly, other air shower observables must be linked to $X_{\rm 1}$. This introduces an inherent dependence of the derived cross section on the general understanding and modeling of air showers and, therfore, on the hadronic interaction model used for the Monte Carlo simulation. We quantify the uncertainties arising from the model dependence by varying some characteristic features of high-energy hadron production.Comment: Conference proceedings for the Blois07/EDS07 (12th International Conference on Elastic and Diffractive Scattering) Workshop DESY Hambur

Remote Sensing Analyses of Neotectonic Active Regions in East-Kamchatka

The tectonic history of the Kamchatka Peninsula is dominated by continuous accumulation and amalgamation of terranes with different origins, which were delivered by convergence between the Pacific plate and in former times, the Kula plate against Eurasia (Freitag, 2002). The Kronotsky and Cape Kamchatka Peninsulas show that the collision of terranes and the resulting tectonics are still important for major parts of East-Kamchatka. While the collision of the Kronotsky Peninsula is sorely influenced by the convergence of the Pacific plate, the Cape Kamchatka Peninsula is affected by the collision of the Aleutian Arc with Kamchatka, what gives the opportunity to compare two different processes that resulted in the amalgamation of terranes to Kamchatka.conferenc

Alkyne-Functionalized Cyclooctyne on Si(001): Reactivity Studies and Surface Bonding from an Energy Decomposition Analysis Perspective

The reactivity and bonding of an ethinyl-functionalized cyclooctyne on Si(001) is studied by means of density functional theory. This system is promising for the organic functionalization of semiconductors. Singly bonded adsorption structures are obtained by [2 + 2] cycloaddition reactions of the cyclooctyne or ethinyl group with the Si(001) surface. A thermodynamic preference for adsorption with the cyclooctyne group in the on-top position is found and traced back to minimal structural deformation of the adsorbate and surface with the help of energy decomposition analysis for extended systems (pEDA). Starting from singly bonded structures, a plethora of reaction paths describing conformer changes and consecutive reactions with the surface are discussed. Strongly exothermic and exergonic reactions to doubly bonded structures are presented, while small reaction barriers highlight the high reactivity of the studied organic molecule on the Si(001) surface. Dynamic aspects of the competitive bonding of the functional groups are addressed by ab initio molecular dynamics calculations. Several trajectories for the doubly bonded structures are obtained in agreement with calculations using the nudged elastic band approach. However, our findings disagree with the experimental observations of selective adsorption by the cyclooctyne moiety, which is critically discussed

In-Medium Spectral Functions of Vector- and Axial-Vector Mesons from the Functional Renormalization Group

In this work we present first results on vector and axial-vector meson spectral functions as obtained by applying the non-perturbative functional renormalization group approach to an effective low-energy theory motivated by the gauged linear sigma model. By using a recently proposed analytic continuation method, we study the in-medium behavior of the spectral functions of the $\rho$ and $a_1$ mesons in different regimes of the phase diagram. In particular, we demonstrate explicitly how these spectral functions degenerate at high temperatures as well as at large chemical potentials, as a consequence of the restoration of chiral symmetry. In addition, we also compute the momentum dependence of the $\rho$ and $a_1$ spectral functions and discuss the various time-like and space-like processes that can occur.Comment: 18 pages, 13 figures, 1 tabl

Spectral Functions from the Functional Renormalization Group

We present results for in-medium spectral functions obtained within the Functional Renormalization Group framework. The analytic continuation from imaginary to real time is performed in a well-defined way on the level of the flow equations. Based on this recently developed method, results for the sigma and the pion spectral function for the quark-meson model are shown at finite temperature, finite quark-chemical potential and finite spatial momentum. It is shown how these spectral function become degenreate at high temperatures due to the restoration of chiral symmetry. In addition, results for vector- and axial-vector meson spectral functions are shown using a gauged linear sigma model with quarks. The degeneration of the $\rho$ and the $a_1$ spectral function as well as the behavior of their pole masses is discussed.Comment: CPOD 2017 Proceeding