Electrical properties of low-threshold field emission cathodes produced by growth nanocluster graphene films on the pointed surface of heavily doped
n
+
SiC by sublimation epitaxy have been ...considered. The quality of the graphene coating has been assessed based on the morphological studies and Raman spectroscopy. Using the volt–ampere characteristics the work function from a pointed cathode with graphene coating was calculated (∼ 0.76 eV). Such a low value of the work function is explained on the assumptions that the graphene film has the nanocluster nature and the sources of the field emission are graphene nanoclusters.
Metal and hybrid TimePix detectors imaging beams of particles Pugatch, V.; Campbell, M.; Chaus, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2011, Letnik:
650, Številka:
1
Journal Article
Recenzirano
Timepix chips were evaluated for imaging low energy ion beams and as candidates for building an ‘electronic focal plane’ of a laser mass-spectrometer. The uniformity of response of the pixel matrix ...with respect to ion mass, energy and detection position has been studied. Two samples each of hybrid silicon pixel detectors and metal micro-pixel detectors (using bare readout chip input electrodes) were used. The results obtained illustrate that both detector types can be used as an ‘electronic focal plane’ of a mass-spectrometer. Two-dimensional imaging of the charge/mass distribution of ion beams accordingly to their charge/mass distribution can improve the mass-spectrometer resolution.
The branching fraction ratio R(D^{*})≡B(Bover ¯^{0}→D^{*+}τ^{-}νover ¯_{τ})/B(Bover ¯^{0}→D^{*+}μ^{-}νover ¯_{μ}) is measured using a sample of proton-proton collision data corresponding to 3.0 ...fb^{-1} of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode τ^{-}→μ^{-}νover ¯_{μ}ν_{τ}. The semitauonic decay is sensitive to contributions from non-standard-model particles that preferentially couple to the third generation of fermions, in particular, Higgs-like charged scalars. A multidimensional fit to kinematic distributions of the candidate Bover ¯^{0} decays gives R(D^{*})=0.336±0.027(stat)±0.030(syst). This result, which is the first measurement of this quantity at a hadron collider, is 2.1 standard deviations larger than the value expected from lepton universality in the standard model.
A measurement of the ratio of the branching fractions of the B(+) → K(+)μ(+)μ(-) and B(+) → K(+)e(+)e(-) decays is presented using proton-proton collision data, corresponding to an integrated ...luminosity of 3.0 fb(-1), recorded with the LHCb experiment at center-of-mass energies of 7 and 8 TeV. The value of the ratio of branching fractions for the dilepton invariant mass squared range 1 < q(2) < 6 GeV(2)/c(4) is measured to be 0.745(-0.074)(+0.090)(stat) ± 0.036(syst). This value is the most precise measurement of the ratio of branching fractions to date and is compatible with the standard model prediction within 2.6 standard deviations.
Observations of exotic structures in the J/ψp channel, which we refer to as charmonium-pentaquark states, in Λ_{b}^{0}→J/ψK^{-}p decays are presented. The data sample corresponds to an integrated ...luminosity of 3 fb^{-1} acquired with the LHCb detector from 7 and 8 TeV pp collisions. An amplitude analysis of the three-body final state reproduces the two-body mass and angular distributions. To obtain a satisfactory fit of the structures seen in the J/ψp mass spectrum, it is necessary to include two Breit-Wigner amplitudes that each describe a resonant state. The significance of each of these resonances is more than 9 standard deviations. One has a mass of 4380±8±29 MeV and a width of 205±18±86 MeV, while the second is narrower, with a mass of 4449.8±1.7±2.5 MeV and a width of 39±5±19 MeV. The preferred J^{P} assignments are of opposite parity, with one state having spin 3/2 and the other 5/2.
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