Introducing the CTA concept

The Cherenkov Telescope Array (CTA) is a new observatory for very high-energy (VHE) gamma rays. CTA has ambitions science goals, for which it is necessary to achieve full-sky coverage, to improve the sensitivity by about an order of magnitude, to span about four decades of energy, from a few tens of GeV to above 100 TeV with enhanced angular and energy resolutions over existing VHE gamma-ray observatories. An international collaboration has formed with more than 1000 members from 27 countries in Europe, Asia, Africa and North and South America. In 2010 the CTA Consortium completed a Design Study and started a three-year Preparatory Phase which leads to production readiness of CTA in 2014. In this paper we introduce the science goals and the concept of CTA, and provide an overview of the project

Bose-Einstein correlations in deep inelastic e p scattering at HERA

Two-particle correlations in invariant mass are studied separately for like-sign and unlike-sign charged particles produced in deep inelastic positron-proton scattering in a new kinematical domain. The data were taken with the H1 detector at the HERA storage ring in 1994, in which 27.5 GeV positrons collided with 820 GeV protons at a centre of mass energy sqrt{s}=300 GeV. The observed enhancement of the like-sign correlations at low invariant masses is related to the dimensions of the hadronic source. The data are compared to different QCD models where the hadronization is performed with the string-fragmentation model. Results are presented for the first time separately for diffractive and non-diffractive scattering, in domains of four-momentum transfer, Bjorken-x, and hadronic center of mass energy, and in intervals of charged particle multiplicity. The observed source radii do not differ strongly from those measured in lower energy lepton-nucleon inelastic scattering, and e^+e^- annihilation.Comment: 36 pages, 10 Figure

Photoproduction of K"0 and #LAMBDA# at HERA and a comparison with deep inelastic scattering

Inclusive K"0 and #LAMBDA# photoproduction has been investigated at HERA with the H1 detector at an average photon-proton center of mass energy of 200 GeV in the transverse momentum range 0.5 < p_t < 5 GeV. The production rates as a function of p_t and center of mass rapidity are compared to those obtained in deep inelastic scattering at left angle Q"2 right angle = 23 GeV"2. A similar comparison is made of the rapidity spectra of charged particles. The rate of strangeness photoproduction is compared with pp measurements. The observations are also compared with next-to-leading order QCD calculations and the predictions of a Monte Carlo model. (orig.)SIGLEAvailable from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Electroweak parameters of the Z0^0 resonance and the standard model

Media temporalities of the elderly : evolutions in stability This article shows the context of analysis and the first results of a research on media temporalities of the elderly. Several works have finely analysed the diversity of the media practices and studied meanings of media uses. I wish to continue these analyses by insisting on the evolutionary and dynamic aspect of the practices and temporalities of users having expanded, enhanced, so called "interactive" radio and especially television programming. A priori, the elderly, upon retirement, have a "full-time free time". Their media practices seem strongly influenced by their first experiments ; the appropriation of the various peripheral accessories which gradually came with the media, to the latest digital ones, seems to reinforce their habits of watching television. Their representations and relations with times and media are very far away from the image of television like omnipresent media or "devourer of time". Rather, their media practices are to be understood like a temporality of the occupation, according to the expression of Gerard Derèze, characterized by interest and utility. A particular glance at the users who do not carry out a systematic selection of the programs, accepting the unforeseen, highlights an approach of media and time that allow "useful encounter" which I would qualify in a first stage by : "chance and encounter" and "random and the following". The few points presented here make me assume that the global relation of the autonomous elderly persons to the media can evolve when confronted to their new temporal framework and the new program offer, whereas their representations and use of the media remain quite stable