A new sorbent was synthesized by anchoring 7-amino-4-azaheptyltrimetoxisilane, freshly prepared, to silica gel, producing 7-amino-4-azaheptyl anchored silica gel (AAHSG). This material was ...characterized by infrared spectroscopy (IR), elemental analysis (CHN), and nitrogen adsorption-desorption isotherms. Isotherms of the adsorption of Fe3+, Fe2+ and Cu2+ on AAHSG were recorded, which indicated that Fe3+ presents a higher affinity by the sorbent. Therefore, AAHSG was successfully employed as a sorbent in a simple flow system for the preconcentration of Fe3+ in natural water samples, such as, river water, lagoonwater, springwater, stream water, well water and two water reference materials (NIST-SRM 1640, NIST-SRM 1643d). The obtained preconcentration factor was 82.2, and the detection limit achieved was 5.9 ng ml-1. The recovery of spiked water samples ranged from 95.0 - 103.1%.
One of the most time consuming process simulating pp interactions in the ATLAS detector at LHC is the simulation of electromagnetic showers in the calorimeter. In order to speed up the event ...simulation several parametrisation methods are available in ATLAS. In this paper we present a short description of a frozen shower technique, together with some recent benchmarks and comparison with full simulation.
The time-of-flight detector of the DIRAC experiment Adeva, B; Gallas, M.V; Gómez, F ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2002, Letnik:
491, Številka:
1-2
Journal Article
Recenzirano
The construction and performance of a large area time-of-flight detector for the DIRAC experiment at CERN is reported. With an average time resolution of 123ps per counter at rates up to 1MHz, it ...allows excellent separation of pπ− from π+π− pairs up to 4.6GeV/c momentum, as well as of Coulomb-correlated pion pairs from accidentals. The optimization of scintillator material, photomultiplier performance and readout electronics is described.
A search for charge-parity (CP) violation in D^{0}→K^{-}K^{+} and D^{0}→π^{-}π^{+} decays is reported, using pp collision data corresponding to an integrated luminosity of 5.9 fb^{-1} collected at a ...center-of-mass energy of 13 TeV with the LHCb detector. The flavor of the charm meson is inferred from the charge of the pion in D^{*}(2010)^{+}→D^{0}π^{+} decays or from the charge of the muon in Bover ¯→D^{0}μ^{-}νover ¯_{μ}X decays. The difference between the CP asymmetries in D^{0}→K^{-}K^{+} and D^{0}→π^{-}π^{+} decays is measured to be ΔA_{CP}=-18.2±3.2(stat)±0.9(syst)×10^{-4} for π-tagged and ΔA_{CP}=-9±8(stat)±5(syst)×10^{-4} for μ-tagged D^{0} mesons. Combining these with previous LHCb results leads to ΔA_{CP}=(-15.4±2.9)×10^{-4}, where the uncertainty includes both statistical and systematic contributions. The measured value differs from zero by more than 5 standard deviations. This is the first observation of CP violation in the decay of charm hadrons.
A measurement is reported of the ratio of branching fractions R(J/ψ)=B(B_{c}^{+}→J/ψτ^{+}ν_{τ})/B(B_{c}^{+}→J/ψμ^{+}ν_{μ}), where the τ^{+} lepton is identified in the decay mode ...τ^{+}→μ^{+}ν_{μ}νover ¯_{τ}. This analysis uses a sample of proton-proton collision data corresponding to 3.0 fb^{-1} of integrated luminosity recorded with the LHCb experiment at center-of-mass energies of 7 and 8 TeV. A signal is found for the decay B_{c}^{+}→J/ψτ^{+}ν_{τ} at a significance of 3 standard deviations corrected for systematic uncertainty, and the ratio of the branching fractions is measured to be R(J/ψ)=0.71±0.17(stat)±0.18(syst). This result lies within 2 standard deviations above the range of central values currently predicted by the standard model.
A measurement of the ratio of branching fractions of the decays B^{+}→K^{+}μ^{+}μ^{-} and B^{+}→K^{+}e^{+}e^{-} is presented. The proton-proton collision data used correspond to an integrated ...luminosity of 5.0 fb^{-1} recorded with the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV. For the dilepton mass-squared range 1.1<q^{2}<6.0 GeV^{2}/c^{4} the ratio of branching fractions is measured to be R_{K}=0.846_{-0.054}^{+0.060}_{-0.014}^{+0.016}, where the first uncertainty is statistical and the second systematic. This is the most precise measurement of R_{K} to date and is compatible with the standard model at the level of 2.5 standard deviations.
The time to simulate pp collisions in the ATLAS detector is largely dominated by the showering of electromagnetic particles in the heavy parts of the detector, especially the electromagnetic barrel ...and endcap calorimeters. Two procedures have been developed to accelerate the processing time of electromagnetic particles in these regions: (1) a fast shower parameterisation and (2) a frozen shower library. Both work by generating the response of the calorimeter to electrons and positrons with Geant 4, and then reintroduce the response into the simulation at runtime. In the fast shower parameterisation technique, a parameterisation is tuned to single electrons and used later by simulation. In the frozen shower technique, actual showers from low-energy particles are used in the simulation. Full Geant 4 simulation is used to develop showers down to ∼ 1GeV, at which point the shower is terminated by substituting a frozen shower. Judicious use of both techniques over the entire electromagnetic portion of the ATLAS calorimeter produces an important improvement of CPU time. We discuss the algorithms and their performance in this paper.
A search for a long-lived scalar particle χ is performed, looking for the decay B+→K+χ with χ→μ+μ− in pp collision data corresponding to an integrated luminosity of 3 fb−1, collected by the LHCb ...experiment at center-of-mass energies of s=7 and 8 TeV. This new scalar particle, predicted by hidden sector models, is assumed to have a narrow width. The signal would manifest itself as an excess in the dimuon invariant mass distribution over the Standard Model background. No significant excess is observed in the accessible ranges of mass 250<m(χ)<4700 MeV/c2 and lifetime 0.1<τ(χ)<1000 ps. Upper limits on the branching fraction B(B+→K+χ(μ+μ−)) at 95% confidence level are set as a function of m(χ) and τ(χ), varying between 2×10−10 and 10−7. These are the most stringent limits to date. The limits are interpreted in the context of a model with a light inflaton particle.
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