Simulation of free-electron lasers seeded with broadband radiation
Physical Review Special Topics - Accelerators and Beams 14:6 (2011)
Abstract:
The longitudinal coherence of free-electron laser (FEL) radiation can be enhanced by seeding the FEL with high harmonics of an optical laser pulse. The radiation produced by high-harmonic generation (HHG), however, has a fast-varying temporal profile that can violate the slowly varying envelope approximation and limited frequency window that is employed in conventional free-electron laser simulation codes. Here we investigate the implications of violating this approximation on the accuracy of simulations. On the basis of both analytical considerations and 1D numerical studies, it is concluded that, for most realistic scenarios, conventional FEL codes are capable of accurately simulating the FEL process even when the seed radiation violates the slowly varying envelope approximation. We additionally discuss the significance of filtering the harmonic content of broadband HHG seeds. © 2011 American Physical Society.Measurement of heavy-quark jet photoproduction at HERA
(2011)
Measurement of the energy dependence of the total photon-proton cross section at HERA
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 697:3 (2011) 184-193
Abstract:
The energy dependence of the photon-proton total cross section, σtotγp, was determined from e+p scattering data collected with the ZEUS detector at HERA at three values of the center-of-mass energy, W, of the γp system in the range 194Study of tau-pair production at HERA
Journal of High Energy Physics 2011:2 (2011)
Abstract:
A study of events containing two tau leptons with high transverse momentum has been performed with the ZEUS detector at HERA, using a data sample corresponding to an integrated luminosity of 0.33 fb-1. The tau candidates were identified from their decays into electrons, muons or hadronic jets. The number of tau-pair candidates has been compared with the prediction from the Standard Model, where the largest contribution is expected from Bethe-Heitler processes. The total visible cross section was extracted. Standard Model expectations agree well with the measured distributions, also at high invariant mass of the tau pair.Measurement of beauty production in deep inelastic scattering at HERA using decays into electrons
(2011)