Low energy chaos in the Fermi-Pasta-Ulam problem

A possibility that in the FPU problem the critical energy for chaos goes to zero with the increase of the number of particles in the chain is discussed. The distribution for long linear waves in this regime is found and an estimate for new border of transition to energy equipartition is given.Comment: revtex, 12 pages, 5 figures, submitted to Nonlinearit

Asymptotic Statistics of Poincar\'e Recurrences in Hamiltonian Systems with Divided Phase Space

By different methods we show that for dynamical chaos in the standard map with critical golden curve the Poincar\'e recurrences P(\tau) and correlations C(\tau) asymptotically decay in time as P ~ C/\tau ~ 1/\tau^3. It is also explained why this asymptotic behavior starts only at very large times. We argue that the same exponent p=3 should be also valid for a general chaos border.Comment: revtex, 4 pages, 3 ps-figure

An Exact Formula to Describe the Amplification Process in a Photomultiplier Tube

An analytical function is derived that exactly describes the amplification process due to a series of discrete, Poisson-like amplifications like those in a photo multiplier tube (PMT). A numerical recipe is provided that implements this function as a computer program. It is shown how the program can be used as the core-element of a faster, simplified routine to fit PMT spectra with high efficiency. The functionality of the method is demonstrated by fitting both, Monte Carlo generated and measured PMT spectra.Comment: 12 pages, 5 figures, with cut-and-paste FORTRAN implementatio

Multianode Photo Multiplier Tubes as Photo Detectors for Ring Imaging Cherenkov Detectors

The 64-channel Multianode Photo Multiplier (MaPMT) has been evaluated as a candidate for the LHCb Ring Imaging Cherenkov (RICH) photo detectors. We present result from data taken with a 3x3 array of closely packed MaPMTs mounted onto the RICH 1 prototype vessel, exposed to charged particle beams at CERN, and read out at LHC speed. Using a LED light source, we have performed spatial light scans to study the light collection efficiency of the MaPMTs We have also measured the performance of the MaPMTs as a function of the applied high voltage. Different dynode resistor chains have been used to study the tubes at low gains. In addition, we have studied the behaviour of the MaPMT in magnetic fields.Comment: 5 pages, 6 figures, 8 .eps files, RICH2002 conference, Pylo