Search results for "QC"
showing 10 items of 3477 documents
Monitoring and data quality assessment of the ATLAS liquid argon calorimeter
2014
The liquid argon calorimeter is a key component of the ATLAS detector installed at the CERN Large Hadron Collider. The primary purpose of this calorimeter is the measurement of electron and photon kinematic properties. It also provides a crucial input for measuring jets and missing transverse momentum. An advanced data monitoring procedure was designed to quickly identify issues that would affect detector performance and ensure that only the best quality data are used for physics analysis. This article presents the validation procedure developed during the 2011 and 2012 LHC data-taking periods, in which more than 98% of the proton-proton luminosity recorded by ATLAS at a centre-of-mass ener…
Exclusive measurement of quasi-free η-photoproduction from deuterium
2003
Quasi-free photoproduction of eta-mesons from the deuteron has been measured at the tagged photon facility of the Mainz microtron MAMI with the photon spectrometer TAPS for incident photon energies from the production threshold at 630 MeV up to 820 MeV. In a fully exclusive measurement eta-mesons and recoil nucleons were detected in coincidence. At incident photon energies above the production threshold on the free nucleon, where final state interaction effects are negligible, an almost constant ratio of sigma(n)/sigma(p)=0.66+/-0.10 was found. At lower incident photon energies the ratio rises due to re-scattering effects. The average ratio agrees with the value extracted from a comparison …
Eco-friendly cavity-containing iron oxides prepared by mild routes as very efficient catalysts for the total oxidation of VOCs
2018
Iron oxides (FeOx) are non-toxic, non-expensive and environmentally friendly compounds, which makes them good candidates for many industrial applications, among them catalysis. In the present article five catalysts based on FeOx were synthesized by mild routes: hydrothermal in subcritical and supercritical conditions (Fe-HT, Few200, Few450) and solvothermal (Fe-ST1 and Fe-ST2). The catalytic activity of these catalysts was studied for the total oxidation of toluene using very demanding conditions with high space velocities and including water and CO2 in the feed. The samples were characterized by X-ray diffraction (XRD), scanning and high-resolution transmission electron microscopy (SEM and…
Jet mass and substructure of inclusive jets in $ \sqrt {s} = 7\;{\text{TeV}} $ pp collisions with the ATLAS experiment
2012
Recent studies have highlighted the potential of jet substructure techniques to identify the hadronic decays of boosted heavy particles. These studies all rely upon the assumption that the internal substructure of jets generated by QCD radiation is well understood. In this article, this assumption is tested on an inclusive sample of jets recorded with the ATLAS detector in 2010, which corresponds to 35 pb-1 of pp collisions delivered by the LHC at √s = 7TeV. In a subsample of events with single pp collisions, measurements corrected for detector efficiency and resolution are presented with full systematic uncertainties. Jet invariant mass, kt splitting scales and N-subjettiness variables are…
Exploration of jet substructure using iterative declustering in pp and Pb–Pb collisions at LHC energies
2020
The ALICE collaboration at the CERN LHC reports novel measurements of jet substructure in pp collisions at $\sqrt{s}$= 7 TeV and central Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 TeV. Jet substructure of track-based jets is explored via iterative declustering and grooming techniques. We present the measurement of the momentum sharing of two-prong substructure exposed via grooming, the $z_{\rm{g}}$, and its dependence on the opening angle, in both pp and Pb-Pb collisions. We also present the first measurement of the distribution of the number of branches obtained in the iterative declustering of the jet, which is interpreted as the number of its hard splittings. In Pb-Pb collisions, we…
High-energy resummation effects in the production of Mueller-Navelet dijet at the LHC
2016
We study the production of two forward jets with a large interval of rapidity at hadron colliders, which was proposed by Mueller and Navelet as a possible test of the high energy dynamics of QCD, within a complete next-to-leading logarithm framework. We show that using the Brodsky-Lepage-Mackenzie procedure to fix the renormalization scale leads to a very good description of the recent CMS data at the LHC for the azimuthal correlations of the jets. We show that the inclusion of next-to-leading order corrections to the jet vertex significantly reduces the importance of energy-momentum non-conservation which is inherent to the BFKL approach, for an asymmetric jet configuration. Finally, we ar…
Uncertainties on the determination of the strong coupling αs from the energy evolution of jet fragmentation functions at low z
2014
The QCD coupling alpha_s is determined at NLO*+NMLLA accuracy from the comparison of experimental jet data to theoretical predictions of the energy-evolution of the parton-to-hadron fragmentation function moments (multiplicity, peak, width, skewness) at low fractional hadron momentum z. From the existing e+e- and e-p jet data, we obtain alpha_s(m_Z^2) = 0.1195 +/- 0.0021 (exp.) {+0.0015}_{-0.0} (scale) at the Z mass. The uncertainties of the extracted alpha_s value are discussed.
Collimation of energy in medium-modified QCD jets
2012
The collimation of energy inside medium-modified jets is investigated in the leading logarithmic approximation of QCD. The Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution equations are slightly modified by introducing splitting functions enhanced in the infrared sector. As compared to elementary collisions in the vacuum, the angular distribution of the jet energy is found to broaden in QCD media.
Julkishallinnon IT-kehityshankkeiden epäonnistuminen ja siihen johtavat syyt : tapaustutkimus
2010
Tässä tutkielmassa tarkastellaan julkishallinnon sähköistämistä edistävien IT-kehityshankkeiden epäonnistumista ja siihen johtavia tekijöitä. Hankkeiden epäonnistumisella tarkoitetaan tämän tutkielman yhteydessä niiden toteutuksessa havaittujen merkittävien ongelmien realisoitumista. Tutkielman tavoitteena on tapaustutkimuksen avulla saada selville mitä ongelmia voidaan pitää kuuden tutkimuksessa analysoidun IT-kehityshankkeen perusteella merkityksellisimpinä suurten ja kompleksisten kokonaisarkkitehtuurinomaisten hankkeiden ongelmatekijöinä ja kuinka FEAR-ohjausmalli vastaa havaittuihin haasteisiin. Lukuisissa tutkimuksissa on todettu, että projektilähtöiseen työhön keskittyneen tieto- ja …
Freeze-out radii extracted from three-pion cumulants in pp, p–Pb and Pb–Pb collisions at the LHC
2014
In high-energy collisions, the spatio-temporal size of the particle production region can be measured using the Bose-Einstein correlations of identical bosons at low relative momentum. The source radii are typically extracted using two-pion correlations, and characterize the system at the last stage of interaction, called kinetic freeze-out. In low-multiplicity collisions, unlike in high-multiplicity collisions, two-pion correlations are substantially altered by background correlations, e.g. mini-jets. Such correlations can be suppressed using three-pion cumulant correlations. We present the first measurements of the size of the system at freeze-out extracted from three-pion cumulant correl…