New structures in the proton-antiproton system

In the most recent measurements of the reaction $e^+e^- \rightarrow p\bar{p}$ by the BABAR collaboration, new structures have been found with unknown origin. We examine a possible relation of the most distinct peak to the recently observed $\Phi(2170)$. Alternatively, we analyse possible explanations due to the nucleon$\,\bar{\Delta}$ and $\Delta\bar{\Delta}$ thresholds. The latter could explain a periodicity found in the data

Theoretical study of electronic damage in single particle imaging experiments at XFELs for pulse durations 0.1 - 10 fs

X-ray free-electron lasers (XFELs) may allow to employ the single particle imaging (SPI) method to determine the structure of macromolecules that do not form stable crystals. Ultrashort pulses of 10 fs and less allow to outrun complete disintegration by Coulomb explosion and minimize radiation damage due to nuclear motion, but electronic damage is still present. The major contribution to the electronic damage comes from the plasma generated in the sample that is strongly dependent on the amount of Auger ionization. Since the Auger process has a characteristic time scale on the order of femtoseconds, one may expect that its contribution will be significantly reduced for attosecond pulses. Here, we study the effect of electronic damage on the SPI at pulse durations from 0.1 fs to 10 fs and in a large range of XFEL fluences to determine optimal conditions for imaging of biological samples. We analyzed the contribution of different electronic excitation processes and found that at fluences higher than $10^{13}$-$10^{15}$ photons/$\mu$m$^2$ (depending on the photon energy and pulse duration) the diffracted signal saturates and does not increase further. A significant gain in the signal is obtained by reducing the pulse duration from 10 fs to 1 fs. Pulses below 1 fs duration do not give a significant gain in the scattering signal in comparison with 1 fs pulses. We also study the limits imposed on SPI by Compton scattering.Comment: 35 pages, 9 figures, 1 table, 2 appendixes, 45 reference

Strong interference effects in the resonant Auger decay of atoms induced by intense X-Ray fields

The theory of resonant Auger decay of atoms in a high intensity coherent X-ray pulse is presented. The theory includes the coupling between the ground state and the resonance due to an intense X-ray pulse, taking into account the decay of the resonance and the direct photoionization of the ground state, both populating the final ionic states coherently. The theory also considers the impact of the direct photoionization of the resonance state itself which typically populates highly-excited ionic states. The combined action of the resonant decay and of the direct ionization of the ground state in the field induces a non-hermitian time-dependent coupling between the ground and the 'dressed' resonance stats. The impact of these competing processes on the total electron yield and on the 2s$^2$2p$^{4}(^1\mathrm{D})$3p $^2$P spectator and 2s$^1$2p$^{6}$ $^2$S participator Auger decay spectra of the Ne 1s$\to$3p resonance is investigated. The role of the direct photoionization of the ground state and of the resonance increases dramatically with the field intensity. This results in strong interference effects with distinct patterns in the electron spectra, different for the participator and spectator final states.Comment: 31 pages, 6 figure

Breaking the resilience of a two-dimensional Bose-Einstein condensate to fragmentation

A two-dimensional Bose-Einstein condensate (BEC) split by a radial potential barrier is investigated. We determine on an accurate many-body level the system's ground-state phase diagram as well as a time-dependent phase diagram of the splitting process. Whereas the ground state is condensed for a wide range of parameters, the time-dependent splitting process leads to substantial fragmentation. We demonstrate for the first time the dynamical fragmentation of a BEC despite its ground state being condensed. The results are analyzed by a mean-field model and suggest that a large manifold of low-lying fragmented excited states can significantly impact the dynamics of trapped two-dimensional BECs.Comment: 5+eps pages, 4 figure

The role of noise and initial conditions in the asymptotic solution of a bounded confidence, continuous-opinion model

We study a model for continuous-opinion dynamics under bounded confidence. In particular, we analyze the importance of the initial distribution of opinions in determining the asymptotic configuration. Thus, we sketch the structure of attractors of the dynamical system, by means of the numerical computation of the time evolution of the agents density. We show that, for a given bound of confidence, a consensus can be encouraged or prevented by certain initial conditions. Furthermore, a noisy perturbation is added to the system with the purpose of modeling the free will of the agents. As a consequence, the importance of the initial condition is partially replaced by that of the statistical distribution of the noise. Nevertheless, we still find evidence of the influence of the initial state upon the final configuration for a short range of the bound of confidence parameter

Reduction of Guided Acoustic Wave Brillouin Scattering in Photonic Crystal Fibers

Guided Acoustic Wave Brillouin Scattering (GAWBS) generates phase and polarization noise of light propagating in glass fibers. This excess noise affects the performance of various experiments operating at the quantum noise limit. We experimentally demonstrate the reduction of GAWBS noise in a photonic crystal fiber in a broad frequency range using cavity sound dynamics. We compare the noise spectrum to the one of a standard fiber and observe a 10-fold noise reduction in the frequency range up to 200 MHz. Based on our measurement results as well as on numerical simulations we establish a model for the reduction of GAWBS noise in photonic crystal fibers.Comment: 4 pages, 7 figures; added numerical simulations, added reference

Off-resonance field enhancement by spherical nanoshells

We study light scattering by spherical nanoshells consistent of metal/dielectric composites. We consider two geometries of metallic nanoshell with dielectric core, and dielectric coated metallic nanoparticle. We demonstrate that for both geometries the local field enhancement takes place out of resonance regions ("dark states"), which, nevertheless, can be understood in terms of the Fano resonance. At optimal conditions the light is stronger enhanced inside the dielectric material. By using nonlinear dielectric materials it will lead to a variety nonlinear phenomena applicable for photonics applications

Reduction of the proton radius discrepancy by 3 sigma

We show that in previous analyses of electron-proton scattering, the uncertainties in the statistical procedure to extract the proton charge radius are underestimated. Using a fit function based on a conformal mapping, we can describe the scattering data with high precision and extract a radius value in agreement with the one obtained from muonic hydrogen.Comment: minor changes, matches the accepted versio