Self-organizing maps have been used to explore physical variables capable to separate hadronic W-decays from QCD-background events. The separation power of the variables, which are used in the usual ...selection process, could be confirmed and a new variable, which improved the quality of the separation, has been constructed.
Data from electron positron annihilations at different center of mass
energies are collected by the four LEP experiments. Direct tests of hard QCD
are performed by measuring and analysing event shape ...observables.
Data from electron positron annihilations at different center of mass energies are collected by the four LEP experiments. Direct tests of hard QCD are performed by measuring and analysing event shape ...observables.
The activities of the QCD working group concentrated on improving the
understanding and Monte Carlo simulation of multi-jet final states due to hard
QCD processes at LEP, i.e. quark-antiquark plus ...multi-gluon and/or secondary
quark production, with particular emphasis on four-jet final states and b-quark
mass effects. Specific topics covered are: relevant developments in the main
event generators PYTHIA, HERWIG and ARIADNE; the new multi-jet generator
APACIC++; description and tuning of inclusive (all-flavour) jet rates; quark
mass effects in the three- and four-jet rates; mass, higher-order and
hadronization effects in four-jet angular and shape distributions; b-quark
fragmentation and gluon splitting into b-quarks.
The activities of the QCD working group concentrated on improving the understanding and Monte Carlo simulation of multi-jet final states due to hard QCD processes at LEP, i.e. quark-antiquark plus ...multi-gluon and/or secondary quark production, with particular emphasis on four-jet final states and b-quark mass effects. Specific topics covered are: relevant developments in the main event generators PYTHIA, HERWIG and ARIADNE; the new multi-jet generator APACIC++; description and tuning of inclusive (all-flavour) jet rates; quark mass effects in the three- and four-jet rates; mass, higher-order and hadronization effects in four-jet angular and shape distributions; b-quark fragmentation and gluon splitting into b-quarks.
The high-energy ion nanoprobe LIPSION at the University of Leipzig has been operational since October 1998. Its magnetic quadrupole lens system, arranged as a separated Russian quadruplet, has been ...developed by the Microanalytical Research Centre (MARC), Melbourne. The ultrastable single-ended 3.5 MV SINGLETRON™ accelerator (High Voltage Engineering Europa) supplies H
+ and He
+ ion beams with a beam brightness in the range of 10–20
A
rad
−2
m
−2
eV
−1
D.J.W. Mous, R.G. Haitsma, T. Butz, R.-H. Flagmeyer, D. Lehmann, J. Vogt, Nucl. Instr. and Meth. B 130 (1997) 31. Due to this high brightness, the excellent optical properties of the focusing system of the nanoprobe and the suppression of mechanical vibrations, lateral resolutions of 100 nm for the low current mode (STIM) and 340 nm at a current of 10 pA (PIXE, RBS, SEI modes) were achieved. Further improvements are expected.
