Hadronic final states in deep-inelastic scattering with Sherpa

We extend the multi-purpose Monte-Carlo event generator Sherpa to include processes in deeply inelastic lepton-nucleon scattering. Hadronic final states in this kinematical setting are characterised by the presence of multiple kinematical scales, which were up to now accounted for only by specific resummations in individual kinematical regions. Using an extension of the recently introduced method for merging truncated parton showers with higher-order tree-level matrix elements, it is possible to obtain predictions which are reliable in all kinematical limits. Different hadronic final states, defined by jets or individual hadrons, in deep-inelastic scattering are analysed and the corresponding results are compared to HERA data. The various sources of theoretical uncertainties of the approach are discussed and quantified. The extension to deeply inelastic processes provides the opportunity to validate the merging of matrix elements and parton showers in multi-scale kinematics inaccessible in other collider environments. It also allows to use HERA data on hadronic final states in the tuning of hadronisation models.Comment: 32 pages, 22 figure

Measurements of the Lattice Modifications for the Cryogenic Undulator CPMU17

A 2 mrad canted double undulator system is in preparation as the wide energy range light source for the Energy Material in situ Laboratory EMIL at the HZB storage ring BESSY II. The cryogenic undulator CPMU 17 is the hard X ray device of the double undulator system. The soft X ray undulator UE 48 is of the APPLE II type. It was installed and commissioned a few months ago, whereas the CPMU 17 is under fabrication. The CPMU 17 will employ a minimum magnetic gap of 5.5mm. Including a CuNi foil for RF shielding and geometric tolerances the free aperture is planned to be 5.0 mm. The BESSY II lattice has been modified locally in order to cope with the small gap device. The adapted betatron functions with a shifted vertical beam waist were measured and fitted with LOCO. The new optics agrees with the predicted performance. The free aperture at the installation place of the CPMU 17 was measured with four vertical scrapers. It is compatible with the projected minimum undulator gap. Finally, the measured injection efficiency with the new EMIL optics switched on is compatible with top up operation injection efficiency amp; 8805; 9

Status of the BESSY VSR Project

BESSY VSR is set out to provide a variable pulse pattern to the BESSY II users. This project is now fully funded and heading into its implementation phase. The pulse pattern, consisting of long and short pulses, require inserting cavities providing a 3rd and a 3.5th harmonic of the fundamental harmonic of the ring. Therefore 1.5 and 1.75 GHz cavities are developed with appropriate higher order mode damping spectrum. Similarly the BESSY II ring and injector chain has to be upgraded to provide appropriate diagnostics and increase the injection eiciency. In this paper we give the current status of the project and give an overview of scienti amp; 260;c challenges currently being tackle

Renewal of Bessy II Rf System Solid State Amplifiers and Hom Damped Cavities

The BESSY II storage ring is a synchrotron light source in user operation since 1999. Due to the aging of the cavities and due to the fact that the klystron tubes run out of production a renewal of the BESSY II RF system was necessary. The old hardware has been replaced by solid state amplifiers SSA and HOM damped normal conducting nc single cell cavities. The parameters of the components, the installation phase and the impact on the beam are presente