1,721,376 research outputs found
The ZEUS microvertex detector
No full textA new vertex detector far the ZEUS experiment at HERA will be installed during the 1999-2000 shutdown, for the high-luminosity runs of HERA. It will allow to reconstruct secondary vertex tracks, coming from the decay of long-lived particles with a lifetime of about 10(-12) s, and improve the global momentum resolution of the tracking system. The interaction region will be surrounded with single-sided silicon strip detectors, with capacitive charge division: three double layers in the central region (600 detectors), and 4 "wheels" in the forward region (112 silicon planes). Due to the high number of readout channels, 512 readout strips per silicon plane in the barrel region and 480 in the forward part, and the large coverage of the vertex detector (almost I m long), the front-end electronics has to be placed on top of the detectors and has to be radiation tolerant since doses up to 2 kGy are expected near the interaction region. The HELIX chip has been chosen as analog chip with a low-noise, charge-sensitive amplifier/shaper. The chip integrates 128 read out channels which are sampled in an analog pipeline with the HERA bunch crossing frequency of 10.4 MHz. A review of the status of the project is presented. A test program is underway in order to gain experience in the understanding of the detectors and their performance characteristics (i.e. detection efficiency, noise, large angle track position resolution, irradiation studies). (C) 1999 Elsevier Science B.V. All rights reserved
Diffractive PDFs and factorisation tests at HERA
No full textThe HERA collider at DESY (Hamburg) has provided Deep Inelastic Scattering (DIS) of elec- trons off protons in the years 1992-2007 for the H1 and ZEUS experiments with a centre of mass energy up to 318 GeV. Diffractive dissociation of photons in the reaction γ (∗) p → X p, constitute a large fraction (∼ 10%) of the visible cross section in deep inelastic scattering (DIS), and the process can be seen as a reaction where the colliding proton emerges intact in the interaction. Different experimental methods have been developed by the H1 and ZEUS experiments to select diffractive events: by detecting the final state proton with forward proton spectrometers or thanks to to the peculiar topology of diffractive events, by requiring a large rapidity gap in the main de- tector between the leading proton (or the low-mass baryonic system) and the photon dissociation system X. The ZEUS and H1 collaborations have performed next-to-leading-order (NLO) QCD fit to the inclusive diffractive data extracting diffractive parton densities (DPDFs). As a direct test of the QCD factorisation theorem, dijet cross sections have been compared to the NLO or- der QCD predictions, based on recent DPDFs obtained by H1 and ZEUS. New sets of DPDFs are obtained through a simultaneous fit to the inclusive and dijet diffractive cross sections. The analysis allows for a precise determination of both the quark and gluon distributions over a wide z range: the precision on the gluon density at high momentum fractions is improved compared to previous extractions since data on diffractive dijets allow to constrain the gluon density. Finally, recent factorization tests on diffractive dijets in photoproduction are presented and discussed in the following
Observation of neutrino interactions in the OPERA detector
No full textOPERA is a long baseline neutrino oscillation experiment designed to observe oscillations by looking at the appearance of 's in an almost pure beam. The beam is produced at CERN and sent towards the Gran Sasso INFN laboratories where the experiment is running. OPERA started its data taking in October 2007, when the first 38 neutrino interactions where successfully located and reconstructed. This paper reviews the status of the experiment discussing its physics potential and performances for neutrino oscillation studies.OPERA is a long baseline neutrino oscillation experiment designed to observe oscillations by looking at the appearance of 's in an almost pure beam. The beam is produced at CERN and sent towards the Gran Sasso INFN laboratories where the experiment is running. OPERA started its data taking in October 2007, when the first 38 neutrino interactions where successfully located and reconstructed. This paper reviews the status of the experiment discussing its physics potential and performances for neutrino oscillation studies
A 16 channel discriminator VME board with enhanced triggering capabilities
No full textElectronics and data acquisition systems used in small and large scale laboratories often have to handle analog signals with varying polarity, amplitude and duration which have to be digitized to be used as trigger signals to validate the acquired data. In the specific case of experiments dealing with ionizing radiation, ancillary particle detectors (for instance plastic scintillators or Resistive Plate Chambers) are used to trigger and select the impinging particles for the experiment. A novel approach using commercial LVDS line receivers as discriminator devices is presented. Such devices, with a proper calibration, can handle positive and negative analog signals in a wide dynamic range (from 20mV to 800mV signal amplitude). The clear advantages, with respect to conventional discriminator devices, are reduced costs, high reliability of a mature technology and the possibility of high integration scale. Moreover, commercial discriminator boards with positive input signal and a wide threshold swing are not available on the market. The present paper describes the design and characterization of a VME board capable to handle 16 differential or single-ended input channels. The output digital signals, available independently for each input, can be combined in the board into three independent trigger logic units which provide additional outputs for the end user
ERRATUM: new results on nu (mu) -> nu (tau) appearance with the OPERA experiment in the CNGS beam (vol 11, 036, 2013)
No full textStatus of the GERDA Experiment at the Laboratori Nazionali del Gran Sasso
Full text linkThe Germanium Detector Array (Gerda) is a low background experiment at the Laboratori Nazionali del Gran Sasso (LNGS) of the INFN designed to search for the rare neutrinoless double beta decay (0νββ) of 76Ge. In its first phase, high purity germanium diodes inherited from the former Heidelberg-Moscow and Igex experiments are operated “bare” and immersed in liquid argon, with an overall background environment of 10−2 cts/(keV·kg·yr), a factor of ten better than its predecessors. Measurements on two-neutrino double beta decay (2νββ) giving T1/22ν=(1.88±0.10)×1021 yr and recently published background model and pulse shape performances of the detectors are discussed in the paper. A new result on 0νββ has been recently published with a half-life limit on 0νββ decay T1/20ν>2.1×1025 yr (90% C.L.). A second phase of the experiment is scheduled to start during the year 2014, after a major upgrade shutdown. Thanks to the increased detector mass with new designed diodes and to the introduction of liquid argon instrumentation techniques, the experiment aims to reduce further the expected background to about 10−3 cts/(keV·kg·yr) and to improve the 0νββ sensitivity to about T1/20ν>1.5×1026 yr (90% C.L.)
The assembly of the silicon modules for the ZEUS Micro Vertex Detector
No full textFor the luminosity upgrade of the HERA ep collider the ZEUS experiment is constructing a precision vertex detector. The interaction region will be surrounded with single-sided, AC-coupled, Si microstrip detectors with capacitive charge division: a 60cm long cylinder with 600 silicon detectors arranged around the beam pipe in the central part and a four circular shaped disks (112 detectors) in the forward part. After a short introduction on the detector design, the experience gained during the assembly of the silicon modules of the central part is presented
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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