Heavy Flavour Production at HERA

Recent results from H1 and ZEUS on heavy flavour production at HERA are reviewe

Charge Transfer and Charge Broadening of GEM Structures in High Magnetic Fields

We report on measurements of charge transfer in GEM structures in high magnetic fields. These were performed in the framework of the R&D work for a Time Projection Chamber at a future Linear Collider. A small test chamber has been installed into the aperture of a superconducting magnet with the GEM structures mounted perpendicular to the B field direction. The charge transfer is derived from the electrical currents monitored during irradiation with an ${}^{55}$Fe source. No severe loss of primary ionisation charge is observed, but an improved ion feedback suppression is achieved for high magnetic fields. Additionally, the width of the charge cloud released by individual ${}^{55}$Fe photons is measured using a finely segmented strip readout after the triple GEM structure. Charge widths between 0.3 and 0.5 mm RMS are observed, which originate from the charge broadening inside the GEM readout. This charge broadening is only partly suppressed at high magnetic fields.Comment: 11 pages, 9 figure

Open Heavy Flavor Production in QCD -- Conceptual Framework and Implementation Issues

Heavy flavor production is an important QCD process both in its own right and as a key component of precision global QCD analysis. Apparent disagreements between fixed-flavor scheme calculations of b-production rate with experimental measurements in hadro-, lepto-, and photo-production provide new impetus to a thorough examination of the theory and phenomenology of this process. We review existing methods of calculation, and place them in the context of the general PQCD framework of Collins. A distinction is drawn between scheme dependence and implementation issues related to quark mass effects near threshold. We point out a so far overlooked kinematic constraint on the threshold behavior, which greatly simplifies the variable flavor number scheme. It obviates the need for the elaborate existing prescriptions, and leads to robust predictions. It can facilitate the study of current issues on heavy flavor production as well as precision global QCD analysis.Comment: 13 pages, 10 figures, Proceedings of Ringberg Workshop: New Trends in HERA Physics 2001, Munich, German

Heavy Quark Photoproduction in k_T Factorization Approach

We investigate the heavy quark photoproduction based on the k_T factorization approach, focusing on the results from the saturation model. The deviations in the results using the unintegrated gluon distribution considering the saturation model and the derivative of the collinear gluon distribution are analysed. Total cross sections and p_T distributions are analysed in detail, setting the deviations between the color dipole approximation and the complete semihard approach.Comment: 18 pages, 7 figures, minor changes, references added. Accepted for publication in Phys. Rev.

Pion and proton showers in the CALICE scintillator-steel analogue hadron calorimeter

Showers produced by positive hadrons in the highly granular CALICE scintillator-steel analogue hadron calorimeter were studied. The experimental data were collected at CERN and FNAL for single particles with initial momenta from 10 to 80 GeV/c. The calorimeter response and resolution and spatial characteristics of shower development for proton- and pion-induced showers for test beam data and simulations using Geant4 version 9.6 are compared.Comment: 26 pages, 16 figures, JINST style, changes in the author list, typos corrected, new section added, figures regrouped. Accepted for publication in JINS

Infrastructure for Detector Research and Development towards the International Linear Collider

The EUDET-project was launched to create an infrastructure for developing and testing new and advanced detector technologies to be used at a future linear collider. The aim was to make possible experimentation and analysis of data for institutes, which otherwise could not be realized due to lack of resources. The infrastructure comprised an analysis and software network, and instrumentation infrastructures for tracking detectors as well as for calorimetry.Comment: 54 pages, 48 picture