Pion interferometry in Au+Au collisions at sqrt[sNN]=200GeV

We present a systematic analysis of two-pion interferometry in Au+Au collisions at sqrt[sNN]=200GeV using the STAR detector at Relativistic Heavy Ion Collider. We extract the Hanbury-Brown and Twiss radii and study their multiplicity, transverse momentum, and azimuthal angle dependence. The Gaussianness of the correlation function is studied. Estimates of the geometrical and dynamical structure of the freeze-out source are extracted by fits with blast-wave parametrizations. The expansion of the source and its relation with the initial energy density distribution is studied

Dead layer on silicon p–i–n diode charged-particle detectors

Semiconductor detectors in general have a dead layer at their surfaces that is either a result of natural or induced passivation, or is formed during the process of making a contact. Charged particles passing through this region produce ionization that is incompletely collected and recorded, which leads to departures from the ideal in both energy deposition and resolution. The silicon p-i-n diode used in the KATRIN neutrinomass experiment has such a dead layer. We have constructed a detailed Monte Carlo model for the passage of electrons from vacuum into a silicon detector, and compared the measured energy spectra to the predicted ones for a range of energies from 12 to 20 keV. The comparison provides experimental evidence that a substantial fraction of the ionization produced in the "dead" layer evidently escapes by diffusion, with 46% being collected in the depletion zone and the balance being neutralized at the contact or by bulk recombination. The most elementary model of a thinner dead layer from which no charge is collected is strongly disfavored

Study of the neutron response of a G-M counter.

The use of a commercial G-M counter as a neutron insensitive device in mixed neutron/photon fields was explored experimentally. The counter was operated in the proportional region, and the event size spectra were measured and analysed. Pulse height spectra were collected over a dynamic range of 104. Considerable experimental difficulties were encountered because of the steep slope of the relationship between pulse height and collection voltage in the proportional region. Values of k(u) for monoenergetic neutrons of 0.57 and 1.5 MeV were obtained from an analysis of the pulse height spectra. They are compared with data available from other techniques. Theoretical considerations are given to explain qualitatively the spectra caused by the nuclear reactions of the neutrons in the counter gas and wall