arXiv subjects

Florian Weissbach

Publications and source records attributed to Florian Weissbach.

6 recordsLinked to original sources

arXiv2009

Improved radiative corrections and proton charge form factor from the Rosenbluth separation technique

We investigate whether the apparent discrepancy between proton electric form factor from measurements using the Rosenbluth separation technique and polarization transfer method is due to the standard approximations employed in radiative correction procedures. Inaccuracies due to both the peaking approximation and the soft-photon approximation have been removed in our simulation approach. In contrast to results from (e,e'p) experiments, we find them in this case to be too small to explain the discrepancy.

hep-ph↗

arXiv2008

Improved radiative corrections for (e,e'p) experiments - A novel approach to multi-photon bremsstrahlung

Radiative processes lead to important corrections to (e,e'p) experiments. While radiative corrections can be calculated exactly in QED and to a good accuracy also including hadronic corrections, these corrections cannot be included into data analyses to arbitrary orders exactly. Nevertheless consideration of multi-photon bremsstrahlung above the low-energy cut-off is important for many (e,e'p) experiments. To date, higher-order bremsstrahlung effects concerning electron scattering experiments have been implemented approximately by employing the soft-photon approximation (SPA). In this paper we propose a novel approach to multi-photon emission which partially removes the SPA from (e,e'p) experiments. In this combined approach one hard photon is treated exactly; and additional softer bremsstrahlung photons are taken into account resorting to the soft-photon approximation. This partial removal of the soft-photon approximation is shown to be relevant for the missing-energy distribution for several kinematic settings at MAMI and TJNAF energies.

nucl-th↗

arXiv2007

Improved radiative corrections for (e,e'p) experiments: Beyond the peaking approximation and implications of the soft-photon approximation

Analysing (e,e'p) experimental data involves corrections for radiative effects which change the interaction kinematics and which have to be carefully considered in order to obtain the desired accuracy. Missing momentum and energy due to bremsstrahlung have so far always been calculated using the peaking approximation which assumes that all bremsstrahlung is emitted in the direction of the radiating particle. In this article we introduce a full angular Monte Carlo simulation method which overcomes this approximation. The angular distribution of the bremsstrahlung photons is reconstructed from H(e,e'p) data. Its width is found to be underestimated by the peaking approximation and described much better by the approach developed in this work.

nucl-th↗

arXiv2002

High-Order Variational Perturbation Theory for the Free Energy

In this paper we introduce a generalization to the algebraic Bender-Wu recursion relation for the eigenvalues and the eigenfunctions of the anharmonic oscillator. We extend this well known formalism to the time-dependent quantum statistical Schroedinger equation, thus obtaining the imaginary-time evolution amplitude by solving a recursive set of ordinary differential equations. This approach enables us to evaluate global and local quantum statistical quantities of the anharmonic oscillator to much higher orders than by evaluating Feynman diagrams. We probe our perturbative results by deriving a perturbative expression for the free energy which is then subject to variational perturbation theory as developed by Kleinert, yielding convergent results for the free energy for all values of the coupling strength.

quant-ph↗

arXiv2002

Boundary-Layer Theory, Strong-Coupling Series, and Large-Order Behavior

The introduction of a lattice converts a singular boundary-layer problem in the continuum into a regular perturbation problem. However, the continuum limit of the discrete problem is extremely nontrivial and is not completely understood. This paper examines two singular boundary-layer problems taken from mathematical physics, the instanton problem and the Blasius equation, and in each case examines two strategies, Pade resummation and variational perturbation theory, to recover the solution to the continuum problem from the solution to the associated discrete problem. Both resummation procedures produce good and interesting results for the two cases, but the results still deviate from the exact solutions. To understand the discrepancy a comprehensive large-order behavior analysis of the strong-coupling lattice expansions for each of the two problems is done.

math-ph↗

arXiv2001

Variational Perturbation Theory for the Ground-State Wave Function

We evaluate perturbatively the density matrix in the low-temperature limit and thus the ground-state wave function of the anharmonic oscillator up to second order in the coupling constant. We then employ Kleinert's variational perturbation theory to determine the ground-state wave function for all coupling strengths.

quant-ph↗