6,982 research outputs found
Test beam Characterizations of 3D Silicon Pixel detectors
3D silicon detectors are characterized by cylindrical electrodes
perpendicular to the surface and penetrating into the bulk material in contrast
to standard Si detectors with planar electrodes on its top and bottom. This
geometry renders them particularly interesting to be used in environments where
standard silicon detectors have limitations, such as for example the radiation
environment expected in an LHC upgrade. For the first time, several 3D sensors
were assembled as hybrid pixel detectors using the ATLAS-pixel front-end chip
and readout electronics. Devices with different electrode configurations have
been characterized in a 100 GeV pion beam at the CERN SPS. Here we report
results on unirradiated devices with three 3D electrodes per 50 x 400 um2 pixel
area. Full charge collection is obtained already with comparatively low bias
voltages around 10 V. Spatial resolution with binary readout is obtained as
expected from the cell dimensions. Efficiencies of 95.9% +- 0.1 % for tracks
parallel to the electrodes and of 99.9% +- 0.1 % at 15 degrees are measured.
The homogeneity of the efficiency over the pixel area and charge sharing are
characterized.Comment: 5 pages, 7 figure
From phonetics to phonology : The emergence of first words in Italian
This study assesses the extent of phonetic continuity between babble and words in four Italian children followed longitudinally from 0; 9 or 0; 10 to 2;0-two with relatively rapid and two with slower lexical growth. Prelinguistic phonetic characteristics, including both (a) consistent use of specific consonants and (b) age of onset and extent of consonant variegation in babble, are found to predict rate of lexical advance and to relate to the form of the early words. In addition, each child's lexical profile is analyzed to test the hypothesis of non-linearity in phonological development. All of the children show the expected pattern of phonological advance: 'Relatively accurate first word production is followed by lexical expansion, characterized by a decrease in accuracy and an increase of similarity between word forms. We interpret such a profile as reflecting the emergence of word templates, a first step in phonological organization
Combined measurement of the inclusive diffractive cross section at HERA
A combination is presented of the inclusive diffractive cross sections measured by the H1 and ZEUS Collaborations at HERA. The analysis concentrates on deep inelastic scattering data selected with the Large Rapidity Gap
technique. The data span three orders of magnitude in negative four-momentum transfer squared, Q2. Correlations of systematic uncertainties are taken into account by the combination method, resulting in improved precision
Suppression factors in diffractive photoproduction of dijets
After new publications of H1 data for the diffractive photoproduction of
dijets, which overlap with the earlier published H1 data and the recently
published data of the ZEUS collaboration, have appeared, we have recalculated
the cross sections for this process in next-to-leading order (NLO) of
perturbative QCD to see whether they can be interpreted consistently. The
results of these calculations are compared to the data of both collaborations.
We find that the NLO cross sections disagree with the data, showing that
factorization breaking occurs at that order. If direct and resolved
contributions are both suppressed by the same amount, the global suppression
factor depends on the transverse-energy cut. However, by suppressing only the
resolved contribution, also reasonably good agreement with all the data is
found with a suppression factor independent of the transverse-energy cut.Comment: 28 pages, 11 figures, 3 table
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Measurement of WZ and ZZ production in pp collisions at [Formula: see text] in final states with b-tagged jets.
Measurements are reported of the WZ and ZZ production cross sections in proton-proton collisions at [Formula: see text][Formula: see text] in final states where one Z boson decays to b-tagged jets. The other gauge boson, either W or Z, is detected through its leptonic decay (either [Formula: see text], [Formula: see text] or [Formula: see text], [Formula: see text], or [Formula: see text]). The results are based on data corresponding to an integrated luminosity of 18.9 fb[Formula: see text] collected with the CMS detector at the Large Hadron Collider. The measured cross sections, [Formula: see text] and [Formula: see text], are consistent with next-to-leading order quantum chromodynamics calculations
Diffraction for non-believers
Diffractive reactions involving a hard scale can be understood in terms of
quarks and gluons. These reactions have become a valuable tool for
investigating the low-x structure of the proton and the behavior of QCD in the
high-density regime, and they may provide a clean environment to study or even
discover the Higgs boson at the LHC. In this paper we give a brief introduction
to the description of diffraction in QCD. We focus on key features studied in
ep collisions at HERA and outline challenges for understanding diffractive
interactions at the LHC.Comment: 23 pages, 26 figures. Contributed to the Proceedings of the Workshop
on HERA and the LHC, DESY and CERN, 2004-200
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Probing color coherence effects in pp collisions at [Formula: see text].
A study of color coherence effects in pp collisions at a center-of-mass energy of 7[Formula: see text] is presented. The data used in the analysis were collected in 2010 with the CMS detector at the LHC and correspond to an integrated luminosity of 36 pb[Formula: see text]. Events are selected that contain at least three jets and where the two jets with the largest transverse momentum exhibit a back-to-back topology. The measured angular correlation between the second- and third-leading jet is shown to be sensitive to color coherence effects, and is compared to the predictions of Monte Carlo models with various implementations of color coherence. None of the models describe the data satisfactorily
A global analysis of diffractive events at HERA
We extract diffractive parton distribution functions (DPDFs) and diffractive
structure functions from the most recent H1 and ZEUS diffractive DIS data
obtained by various methods. We consider Pomeron as an object with parton
distribution function, evolving according to the next-to-leading order (NLO)
DGLAP equations within the framework of the `Fixed Flavour Number Scheme'
(FFNS). Having performed a global fit analysis, we achieve a very good
description of all available measurements by introducing a new set of quark
distribution form for the Pomeron. We predict longitudinal and charm proton
diffractive structure function as well. Our results are compared with other
analysis from the literature.Comment: 28 Pages, 15 Figures, 3 Table
Observation of isolated high-E_T photons in deep inelastic scattering
First measurements of cross sections for isolated prompt photon production in
deep inelastic ep scattering have been made using the ZEUS detector at the HERA
electron-proton collider using an integrated luminosity of 121 pb^-1. A signal
for isolated photons in the transverse energy and rapidity ranges 5 < E_T^gamma
< 10 GeV and -0.7 < eta^gamma < 0.9 was observed for virtualities of the
exchanged photon of Q^2 > 35 GeV^2. Cross sections are presented for inclusive
prompt photons and for those accompanied by a single jet in the range E_T^jet
\geq 6 GeV and -1.5 \leq eta^jet < 1.8. Calculations at order alpha^3alpha_s
describe the data reasonably well.Comment: 16 pages, 5 figure
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