ACCOUNT OF NONLOCAL IONIZATION AND SLOW ELECTRON ENERGY BALANCE IN GLOW DISCHARGE MODELS

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The influence of depolarization field on dielectric and pyroelectric properties of ferroelectric films

Calculations of the spontaneous polarization (Ps), dielectric susceptibility (c) and pyroelectric coefficient (P) of the ferroelectric films have been performed in the thermodynamic phenomenological theory framework. The Euler-Lagrange equation determining polarization dependence on the film parameters and the external electric field was solved analytically under the boundary conditions with different extrapolation lengths at two surfaces, respectively. The depolarization field contribution was taken into account in the model of short-circuited mono-domain ferroelectric film, treated as perfect insulator. The detailed analysis of the aforementioned quantities, space distribution and their average values in two cases with and without depolarization field was carried out. It was shown that the depolarization field shifts critical temperature to smaller values and the critical thickness to bigger value in comparison to those obtained without accounting the depolarization field. Meanwhile average values of Ps, c and P dependences on the film parameters and temperature are similar to the corresponding dependences obtained without accounting the depolarization field. The depolarization field was shown to flatten Ps, c and P space distributions, which have the peculiarities otherwise (e.g. small maxima in c and P coordinate profiles near the film surfaces). It was shown that depolarization field influence in short-circuited film could be neglected when the film thickness or the extrapolation lengths in the boundary conditions are larger than the correlation length value

Modelling of pyroelectric response in inhomogeneous ferroelectric-semiconductor films

We have modified the Landau-Khalatnikov approach and shown that the pyroelectric response of inhomogeneous ferroelectric-semiconductor films can be described using six coupled equations for six order parameters: average displacement, its mean-square fluctuation and correlation with charge defect density fluctuations, average pyroelectric coefficient, its fluctuation and correlation with charge defect density fluctuations. Coupled equations demonstrate the inhomogeneous reversal of pyroelectric response in contrast to the equations of the Landau-Khalatnikov type, which describe the homogeneous reversal with the sharp pyroelectric coefficient peak near the thermodynamic coercive field value. Within the framework of our model, the pyroelectric hysteresis loop becomes much smoother, thinner and lower as well as the pyroelectric coefficient peaks near the coercive field completely disappear with increase in disordering caused by defects. This effect is similar to the well-known "square to slim transition" of the ferroelectric hysteresis loops in relaxor ferroelectrics. Also the increase of defect concentration leads to the drastic decrease of the coercive field typical for disordered ferroelectrics. Usually pyroelectric hysteresis loops of doped and inhomogeneous ferroelectrics have typical smooth shape without any pyroelectric coefficient peaks, and the coercive field values much lower than the thermodynamic one. Therefore, our approach qualitatively explains available experimental results. A rather well quantitative agreement between our modelling and typical Pb(Zr,Ti)O₃ film pyroelectric and ferroelectric loops has been obtained

Partial polarization switching in ferroelectrics-semiconductors with charged defects

We propose the phenomenological description of ferroelectric disordering caused by charged defects in ferroelectric-semiconductors. The good agreement between the obtained experimental results for PZT films and theoretical calculations has been shown. We suppose that proportional to the averaged charge density of defects improper conductivity is sufficiently high to provide the screening of charge density random fluctuations drs in the absence of external field. When external electric field is applied, inner field fluctuations and induction fluctuations dD appear in the inhomogeneously polarized system “charged fluctuation + screening cloud”. We show that the macroscopic state of ferroelectric-semiconductor with random charged defects and sufficiently high improper conductivity can be described by three coupled equations for three order parameters. Averaged over sample volume induction determines the ferroelectric ordering in the system, its square fluctuation determines disordering caused by electric field fluctuations appeared around charged fluctuations drs, and reflects the correlations between the free carriers screening cloud and charged defects drs. For the first time, we derive the following system of three coupled equations: Also the obtained system of coupled equations qualitatively describes the peculiarities of polarization switching (footprint and minor hysteresis loops) in such ferroelectric materials with charged defects as PZT films with growth imperfections, PLZT ceramics and SBN single crystals doped with cerium

Search for Doubly-Charged Higgs Boson Production at HERA

A search for the single production of doubly-charged Higgs bosons H^{\pm \pm} in ep collisions is presented. The signal is searched for via the Higgs decays into a high mass pair of same charge leptons, one of them being an electron. The analysis uses up to 118 pb^{-1} of ep data collected by the H1 experiment at HERA. No evidence for doubly-charged Higgs production is observed and mass dependent upper limits are derived on the Yukawa couplings h_{el} of the Higgs boson to an electron-lepton pair. Assuming that the doubly-charged Higgs only decays into an electron and a muon via a coupling of electromagnetic strength h_{e \mu} = \sqrt{4 \pi \alpha_{em}} = 0.3, a lower limit of 141 GeV on the H^{\pm\pm} mass is obtained at the 95% confidence level. For a doubly-charged Higgs decaying only into an electron and a tau and a coupling h_{e\tau} = 0.3, masses below 112 GeV are ruled out.Comment: 15 pages, 3 figures, 1 tabl

Measurement of prompt D0^{0} and D‾\overline{D}0^{0} meson azimuthal anisotropy and search for strong electric fields in PbPb collisions at root SNN\sqrt{S_{NN}} = 5.02 TeV

The strong Coulomb field created in ultrarelativistic heavy ion collisions is expected to produce a rapiditydependent difference (Av2) in the second Fourier coefficient of the azimuthal distribution (elliptic flow, v2) between D0 (uc) and D0 (uc) mesons. Motivated by the search for evidence of this field, the CMS detector at the LHC is used to perform the first measurement of Av2. The rapidity-averaged value is found to be (Av2) = 0.001 ? 0.001 (stat)? 0.003 (syst) in PbPb collisions at ?sNN = 5.02 TeV. In addition, the influence of the collision geometry is explored by measuring the D0 and D0mesons v2 and triangular flow coefficient (v3) as functions of rapidity, transverse momentum (pT), and event centrality (a measure of the overlap of the two Pb nuclei). A clear centrality dependence of prompt D0 meson v2 values is observed, while the v3 is largely independent of centrality. These trends are consistent with expectations of flow driven by the initial-state geometry. ? 2021 The Author. Published by Elsevier B.V. This is an open access article under the CC BY licens

Observation of electroweak production of Wγ with two jets in proton-proton collisions at √s = 13 TeV

A first observation is presented for the electroweak production of a W boson, a photon, and two jets in proton-proton collisions. The W boson decays are selected by requiring one identified electron or muon and an imbalance in transverse momentum. The two jets are required to have a high dijet mass and a large separation in pseudorapidity. The measurement is based on data collected with the CMS detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. The observed (expected) significance for this process is 4.9 (4.6) standard deviations. After combining with previously reported CMS results at 8 TeV, the observed (expected) significance is 5.3 (4.8) standard deviations. The cross section for the electroweak W$_{γjj}$ production in a restricted fiducial region is measured as 20.4 +/- 4.5 fb and the total cross section for W$_{γ}$ production in association with 2 jets in the same fiducial region is 108 +/- 16 fb. All results are in good agreement with recent theoretical predictions. Constraints are placed on anomalous quartic gauge couplings in terms of dimension-8 effective field theory operators

Jet production in ep collisions at high Q(2) and determination of alpha(s)

The production of jets is studied in deep-inelastic e(+/-) p scattering at large negative four momentum transfer squared 150 LT Q(2) LT 15000 GeV2 using HERA data taken in 1999-2007, corresponding to an integrated luminosity of 395 pb(-1). Inclusive jet, 2-jet and 3-jet cross sections, normalised to the neutral current deep-inelastic scattering cross sections, are measured as functions of Q(2), jet transverse momentum and proton momentum fraction. The measurements are well described by perturbative QCD calculations at next-to-leading order corrected for hadronisation effects. The strong coupling as determined from these measurement