Preliminary Investigation of a Waveform Analysis with the WASA and the ACQIRIS Readout Electronics

The Group for the development of neutron and gamma detectors in the Central Institute of Engineering, Electronics and Analytics (ZEA-2) at Forschungszentrum J\"ulich (FZJ) is developing a fast Anger Camera prototype for improving the rejection of the gamma contamination during the detection of neutrons. The prototype is based on a scintillating plate for neutron capture and on the subsequent generation of scintillating light collected by a matrix of 4x4 vacuum Photomultipliers R268 by Hamamatsu. According to the impinging point position of the incoming neutrons the light is collected by different PMTs, and via dedicated algorithms the x and y coordinates can be calculated. In this note the WASA and ACQIRIS readout electronics are compared while performing a waveform analysis of the signals generated by using both an analogue pulse generator and an LED+PMT system. Different options of pre-amplifiers and amplifiers are considered, and the results are here presented and commented. At this stage of the prototype development, systematical studies were not performed while the scope of this work was only to validate the principle of operations by using both readout systems.Comment: 36 Pages. The current version V1.1 has minor typos correcte

Peak statistics on COBE maps

We perform the stastistics of temperature maxima and minima in COBE-DMR 2-year maps. For power-law spectra the surface distribution of peaks implies an amplitude consistent with more conventional analyses of COBE data (for instance, we get $Q_{{\rm rms-PS}}=17\pm 3\ \mu$K for a spectral index $n=1),$ but not with the measured quadrupole $Q_{{\rm rms}}=6\pm 3\ \mu$K. This provides further support for the existence an infrared cutoff in the cosmic spectrum.Comment: Latex file, Astronomy & Astrophysics L-aa style. Hardcopy figures available separately, send requests to [email protected]

Hard Exclusive Electroproduction of Two Pions off Proton and Deuteron at HERMES

Exclusive electroproduction of $\pi^+\pi^-$ pairs off hydrogen and deuterium targets has been studied with the HERMES experiment. The angular distribution of the $\pi^+$ in the $\pi^+\pi^-$ rest system has been studied in the invariant mass range $0.3 < m_{\pi\pi} <1.5$ GeV. Theoretical models derived in the framework of the Generalized Parton Distributions show that this angular distribution receives only contributions from the interference between the isoscalar channel I=0 and the isovector channel I=1.Comment: 5 pages, LaTex, 9 EPS figures. Talk given by R.Fabbri at SPIN 2002, BNL. References modifie

Low frequency gray-body factors and infrared divergences: rigorous results

Formal solutions to the mode equations for both spherically symmetric black holes and Bose-Einstein condensate acoustic black holes are obtained by writing the spatial part of the mode equation as a linear Volterra integral equation of the second kind. The solutions work for a massless minimally coupled scalar field in the s-wave or zero angular momentum sector for a spherically symmetric black hole and in the longitudinal sector of a 1D Bose-Einstein condensate acoustic black hole. These solutions are used to obtain in a rigorous way analytic expressions for the scattering coefficients and gray-body factors in the zero frequency limit. They are also used to study the infrared behaviors of the symmetric two-point function and two functions derived from it: the point-split stress-energy tensor for the massless minimally coupled scalar field in Schwarzschild-de Sitter spacetime and the density-density correlation function for a Bose-Einstein condensate acoustic black hole.Comment: 41 pages, 5 figure

Scattering coefficients and gray-body factor for 1D BEC acoustic black holes: exact results

A complete set of exact analytic solutions to the mode equation is found in the region exterior to the acoustic horizon for a class of 1D Bose-Einstein condensate (BEC) acoustic black holes. From these, analytic expressions for the scattering coefficients and gray-body factor are obtained. The results are used to verify previous predictions regarding the behaviors of the scattering coefficients and gray-body factor in the low frequency limit.Comment: 13 pages, 1 figure, Final version, to appear in Phys. Rev.