Journals
2017 EN
Y. A. Ovchenkov · D. A. Chareev · V. A. Kulbachinskii
+5 more
Magnetotransport properties of the high-quality FeSe crystal, measured in awide temperature range and in magnetic fields up to 50 T, show the symmetry ofthe main holelike and electronlike bands in this compound. In addition to themain two bands, there is also a tiny, highly mobile, electronlike band which isresponsible for the non-linear behavior of $\rho_{xy}$(B) at low temperaturesand some other peculiarities of FeSe. We observe the inversion of the$\rho_{xx}$ temperature coeficient at a magnetic field higher than about 20 Twhich is an implicit conformation of the electron-hole symmetry in the mainbands.
Journals
2017 EN
D. Rochman · O. Leray · Mathieu Hursin
+16 more
International audienceThe impact of the current nuclear data library covariances such as in ENDF/B-VII.1, JEFF-3.2, JENDL-4.0, SCALE and TENDL, for relevant current reactors is presented in this work. The uncertainties due to nuclear data are calculated for existing PWR and BWR fuel assemblies (with burn-up up to 40 GWd/tHM, followed by 10 years of cooling time) and for a simplified PWR full core model (without burn-up) for quantities such as k∞ , macroscopic cross sections, pin power or isotope inventory. In this work, the method of propagation of uncertainties is based on random sampling of nuclear data, either from covariance files or directly from basic parameters. Additionally, possible biases on calculated quantities are investigated such as the self-shielding treatment. Different calculation schemes are used, based on CASMO, SCALE, DRAGON, MCNP or FISPACT-II, thus simulating real-life assignments for technical-support organizations. The outcome of such a study is a comparison of uncertainties with two consequences. One: although this study is not expected to lead to similar results between the involved calculation schemes, it provides an insight on what can happen when calculating uncertainties and allows to give some perspectives on the range of validity on these uncertainties. Two: it allows to dress a picture of the state of the knowledge as of today, using existing nuclear data library covariances and current methods
Journals
2017 EN
M. Korjik · В. В. Аленков · A. Borisevich
+12 more
This report presents results on the significant improvement of GAGG:Ce based scintillation detector performance with temperature decrease. When temperature of a PMT based detector is lowered to −45 °C, its amplitude response at registration of γ -quanta is improved by 30%; FHHM was found to be better up to factor of 0.85, whereas scintillation kinetics become even faster in crystals co-doped with magnesium and magnesium and titanium. All this opens an opportunity for a wide application of GAGG scintillation detectors, particularly in a combination with SiPM photo-sensors, which signal-to-noise ratio would also improve with temperature decrease.
Journals
2017 EN
J. D. Maxwell · W. R. Armstrong · S. Choi
+102 more
The Spin Asymmetries of the Nucleon Experiment (SANE) performed inclusive,double-polarized electron scattering measurements of the proton at theContinuous Electron Beam Accelerator Facility at Jefferson Lab. A noveldetector array observed scattered electrons of four-momentum transfer $2.5 <Q^2< 6.5$ GeV$^2$ and Bjorken scaling $0.3<x<0.8$ from initial beam energies of4.7 and 5.9 GeV. Employing a polarized proton target whose magnetic fielddirection could be rotated with respect to the incident electron beam, bothparallel and near perpendicular spin asymmetries were measured, allowingmodel-independent access to transverse polarization observables $A_1$, $A_2$,$g_1$, $g_2$ and moment $d_2$ of the proton. This document summarizes theoperation and performance of the polarized target, polarized electron beam, andnovel detector systems used during the course of the experiment, and describesanalysis techniques utilized to access the physics observables of interest.
Journals
2017 EN
M. A. Vasiliev
A new construction for gauge invariant functionals in the nonlinear higher-spin theory is proposed. Being supported by differential forms closed by virtue of the higher-spin equations, invariant functionals are associated with central elements of the higher-spin algebra. In the on-shell AdS4 higher-spin theory we identify a four-form conjectured to represent the generating functional for 3d boundary correlators and a two-form argued to support charges for black hole solutions. Two actions for 3d boundary conformal higher-spin theory are associated with the two parity-invariant higher-spin models in AdS4. The peculiarity of the spinorial formulation of the on-shell AdS3 higher-spin theory, where the invariant functional is supported by a two-form, is conjectured to be related to the holomorphic factorization at the boundary. The nonlinear part of the star-product function F⁎(B(x)) in the higher-spin equations is argued to lead to divergencies in the boundary limit representing singularities at coinciding boundary space–time points of the factors of B(x), which can be regularized by the point splitting. An interpretation of the RG flow in terms of proposed construction is briefly discussed
Journals
2017 EN
A. A. Sharapov · E. D. Skvortsov
The formal algebraic structures that govern higher-spin theories within theunfolded approach turn out to be related to an extension of the KontsevichFormality, namely, the Shoikhet-Tsygan Formality. Effectively, this allows oneto construct the Hochschild cocycles of higher-spin algebras that make theinteraction vertices. As an application of these results we construct a familyof Vasiliev-like equations that generate the Hochschild cocycles with $sp(2n)$symmetry from the corresponding cycles. A particular case of $sp(4)$ may berelevant for the on-shell action of the $4d$ theory. We also give the exactequations that describe propagation of higher-spin fields on a background oftheir own. The consistency of formal higher-spin theories turns out to have apurely geometric interpretation: there exists a certain symplectic invariantassociated to cutting a polytope into simplices, namely, the Alexander-Spaniercocycle.
Journals
2017 EN
Iuliana Vasiliev · Eveline M. Mezger · Stefano Lugli
+3 more
The Messinian salinity crisis (MSC; 5.97–5.33 Ma) is an enigmatic episode of paleoceanographic change, when kilometers-thick evaporite units were deposited in the Mediterranean basin. It is generally accepted that during the MSC interval there was a dry climate in the Mediterranean region. It is difficult to assess how dry the climate was during the MSC because a modern analogue, in size and duration, is absent. Here we reconstruct hydrological changes in the Mediterranean basin during the three main MSC stages using excellently preserved biomarkers. We used the hydrogen isotopic composition of the long chain n-alkanes (δDn-alkanes) to reconstruct the hydrological changes on the land adjacent to the Mediterranean Sea. Additionally, the δD of long-chain alkenones (δDalkenones) is used to observe changes in the Mediterranean Sea water source. The δDn-alkanes recorded during the deposition of Primary Lower Gypsum (stage 1) in Monte Tondo indicate a δD of the precipitation comparable to the present-day Mediterranean implying a similar hydrologic regime (indicated by experiments modelling the Miocene-Pliocene transition). Elevated δDalkenones values from halite unit (stage 2) of the Realmonte mine are associated with kainite and giant polygons, consistent with presumably high evaporative conditions during halite deposition. The δDn-alkanes recorded during the deposition of Upper Gypsum (stage 3) in Eraclea Minoa indicate a δDprecipitation typical for much drier settings, similar to the Red Sea region. The relative contribution of the different alkenones from Eraclea Minoa is similar to the one observed in present-day marine settings suggesting that, during stage 3, connections to the open Ocean were likely maintained. However, the δDalkenones records during deposition of the evaporites in Eraclea Minoa are similar to those synchronously registered in the Black Sea implying that a similar hydrologic regime, characterized by extended drought, covered large areas of southeastern Europe. Based on the δDalkenones similarity and the Paratethys type of ´Lago Mare´ fauna in the Mediterranean we speculate that the surface water during stage 3 was, at times, derived from the Black Sea
Journals
2017 EN
L. Adamczyk · J. K. Adkins · G. Agakishiev
+336 more
We report the direct virtual photon invariant yields in the transverse momentum ranges 16 GeV/c the production follows TAA scaling. Model calculations with contributions from thermal radiation and initial hard parton scattering are consistent within uncertainties with the direct virtual photon invariant yield
Journals
2017 EN
V. E. Didenko · M. A. Vasiliev
The local form of higher-spin equations found recently to the second order[1] is shown to properly reproduce the anticipated $AdS/CFT$ correlators forappropriate boundary conditions. It is argued that consistent $AdS/CFT$holography for the parity-broken boundary models needs a nontrivialmodification of the bosonic truncation of the original higher-spin theory withthe doubled number of fields, as well as a nonlinear deformation of theboundary conditions in the higher orders.
Journals
2017 EN
J. Adamczewski-Musch · G. Agakishiev · O. Arnold
+100 more
The production of $\Sigma^{0}$ baryons in the nuclear reaction p (3.5 GeV) +Nb (corresponding to $\sqrt{s_{NN}}=3.18$ GeV) is studied with the detectorset-up HADES at GSI, Darmstadt. $\Sigma^{0}$s were identified via the decay$\Sigma^{0} \rightarrow \Lambda \gamma$ with subsequent decays $\Lambda\rightarrow p \pi^{-}$ in coincidence with a $e^{+}e^{-}$ pair from eitherexternal ($\gamma \rightarrow e^{+} e^{-}$) or internal (Dalitz decay$\gamma^{*}\rightarrow e^{+} e^{-}$) gamma conversions. The differential$\Sigma^0$ cross section integrated over the detector acceptance, i.e. therapidity interval $0.5 < y < 1.1$, has been extracted as$\Delta\sigma_{\Sigma^{0}} = 2.3 \pm (0.2)^{stat} \pm\left(^{+0.6}_{-0.6}\right)^{sys} \pm (0.2)^{norm}$ mb, yielding the inclusiveproduction cross section in full phase space $\sigma^{total}_{\Sigma^{0}} = 5.8\pm (0.5)^{stat} \pm \left(^{+1.4}_{-1.4}\right)^{sys} \pm (0.6)^{norm} \pm(1.7)^{extrapol}$ mb by averaging over different extrapolation methods. The$\Lambda_{all}$/$\Sigma^{0}$ ratio within the HADES acceptance is equal to 2.3$\pm$ $(0.2)^{stat}$ $\pm$ $(^{+0.6}_{-0.6})^{sys}$. The obtained rapidity andmomentum distributions are compared to transport model calculations. The$\Sigma^{0}$ yield agrees with the statistical model of particle production innuclear reactions.