Resource
2018 EN
STAR Collaboration · STAR Collaboration J. Adam · STAR Collaboration L. Adamczyk
+341 more
Flow harmonics ($v_n$) in the Fourier expansion of the azimuthal distributionof particles are widely used to quantify the anisotropy in particle emission inhigh-energy heavy-ion collisions. The symmetric cumulants, $SC(m,n)$, are usedto measure the correlations between different orders of flow harmonics. Thesecorrelations are used to constrain the initial conditions and the transportproperties of the medium in theoretical models. In this Letter, we present thefirst measurements of the four-particle symmetric cumulants in Au+Au collisionsat $\sqrt{s_{NN}}$ = 39 and 200 GeV from data collected by the STAR experimentat RHIC. We observe that $v_{2}$ and $v_{3}$ are anti-correlated in allcentrality intervals with similar correlation strengths from 39 GeV Au+Au to2.76 TeV Pb+Pb (measured by the ALICE experiment). The $v_{2}$-$v_{4}$correlation seems to be stronger at 39 GeV than at higher collision energies.The initial-stage anti-correlations between second and third ordereccentricities are sufficient to describe the measured correlations between$v_{2}$ and $v_{3}$. The best description of $v_{2}$-$v_{4}$ correlations at$\sqrt{s_{NN}}$ = 200 GeV is obtained with inclusion of the system's nonlinearresponse to initial eccentricities accompanied by the viscous effect with$\eta/s$ $>$ 0.08. Theoretical calculations using different initial conditions,equations of state and viscous coefficients need to be further explored toextract $\eta/s$ of the medium created at RHIC.
Resource
2018 EN
L. N. Oveshnikov · E. I. Nekhaeva · A. V. Kochura
+8 more
We have studied the properties of relatively thick (about 120 nm) magneticcomposite films grown by pulsed laser deposition method using(GaSb)$_{0.59}$(MnSb)$_{0.41}$ eutectic compound as a target for sputtering.For the studied films we have observed ferromagnetism and anomalous Hall effectabove the room temperature, it manifests the presence of spin-polarizedcarriers. Electron microscopy, atomic and magnetic force microscopy resultssuggests that films under study have homogenous columnar structure in the bulkwhile MnSb inclusions accumulate near it's surface. This is in good agreementwith high mobility values of charge carriers. Based on our data we concludethat room temperature magnetic and magnetotransport properties of the films aredefined by MnSb inclusions.
Resource
2018 EN
P. V. Borisyuk · E. V. Chubunova · N. N. Kolachevsky
+3 more
The results of experimental studies of the low-energy isomeric state in the$^{229}$Th nucleus are presented. The work is consisted of several stages.During the first stage $^{229}$Th nuclei were excited with the inverse internalconversion to the low-lying isomeric level in plasma that was formed by laserpulse at the $^{229}$Th-containing target surface. Then thorium ions havingexcited nuclei were extracted from the plasma by an external electrical fieldand implanted into thin SiO$_2$ film grown on a silicon substrate (that is adielectric material with about 9 eV band-gap). Gamma decay of isomeric nucleiwas registered during the second stage by the general methods of the electronspectroscopy after the photon-electron emission from the silicon substrate.Substitution of the photon registration with the electron one allowed us toincrease the desired signal by several orders of magnitude and detect the$^{229}$Th nuclei decay. During the third stage the electron spectra fromstandard Xe VUV source was obtained that allowed determining the energy ofphotons. In order to prove that the detected signal is caused by isomeric$^{229}$Th nuclei decay a series of experiments was carried. The analysis ofelectron spectra gives the following results: the energy of the nucleartransition is $E_{\text{is}}=7.1(^{+0.1}_{-0.2})$~eV, the half-life of theisomeric level in bare nucleus in vacuum is $T_{1/2}=1880\pm170$~s, the reducedprobability of the isomeric nuclear transition is$B_{\text{W.u.}}(M1;3/2^+\rightarrow 5/2^+)=(3.3\pm0.3)\times10^{-2}$.
Resource
2018 EN
Alexander Tikhomirov · Sergey Tikhomirov · Danil Vasiliev
In this article we study the Gieseker-Maruyama moduli spaces$\mathcal{B}(e,n)$ of stable rank 2 algebraic vector bundles with Chern classes$c_1=e\in\{-1,0\},\ c_2=n\ge1$ on the projective space $\mathbb{P}^3$. Weconstruct two new infinite series $\Sigma_0$ and $\Sigma_1$ of irreduciblecomponents of the spaces $\mathcal{B}(e,n)$, for $e=0$ and $e=-1$,respectively. General bundles of these components are obtained as cohomologysheaves of monads, the middle term of which is a rank 4 symplectic instantonbundle in case $e=0$, respectively, twisted symplectic bundle in case $e=-1$.We show that the series $\Sigma_0$ contains components for all big enoughvalues of $n$ (more precisely, at least for $n\ge146$). $\Sigma_0$ yields thenext example, after the series of instanton components, of an infinite seriesof components of $\mathcal{B}(0,n)$ satisfying this property.
Resource
2018 EN
STAR Collaboration · J. Adam · L. Adamczyk
+341 more
We present a measurement of inclusive $J/\psi$ production at mid-rapidity($|y|<1$) in $p+p$ collisions at a center-of-mass energy of $\sqrt{s}$ = 200GeV with the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). Thedifferential production cross section for $J/\psi$ as a function of transversemomentum ($p_T$) for $0<p_T<14$ GeV/$c$ and the total cross section arereported and compared to calculations from the color evaporation model and thenon-relativistic Quantum Chromodynamics model. The dependence of $J/\psi$relative yields in three $p_T$ intervals on charged-particle multiplicity atmid-rapidity is measured for the first time in $p+p$ collisions at $\sqrt{s}$ =200 GeV and compared with that measured at $\sqrt{s}$ = 7 TeV, PYTHIA8 andEPOS3 Monte Carlo generators, and the Percolation model prediction.
Resource
2018 EN
R. V. Arutyunyan · A. D. Vasiliev
The excited short-lived volume-localized electron quantum levels (VLELs)existent due to Coulomb potential well inside positive ion are analyticallyinvestigated in the paper using a simplified spherical fullerene model. Hence,those electron levels appear exclusively after the ionization of neutralfullerene taking into account the unique geometrical shape of sphere. Theexistence of those levels is argued, and their basic parameters (the energylevels, the wave eigenfunctions) are approximately calculated. The wavefunctions of VLELs are basically localized inside fullerene ion sphere (with amaximum amplitude in the centre) in contrast to ordinary surface-localizedelectron levels (SLELs) having a wave functions in the vicinity of fullerenesphere formed by the cluster composed of carbon ions. Contrary to VLELs, thewave functions of SLELs are present both in charged and neutral fullerene. Theanalysis of electron beam interaction with the medium consistent of fullerenesions is conducted as the application of the methods developed. The analyticaldependencies of free electron recombination cross-sections for the capture tothe volume-localized electron levels are obtained. It is shown that theprobabilities of electron capture to these VLELs are considerably largercompared to capture to SLELs. Also, the calculational results of dipole momentsfor quantum transitions from fullerene ions VLELs to other VLELs and to SLELswith spontaneous photon emission are also presented in the paper. Thecalculated dipole moments depend on fullerene ionization extent, initial andfinal electron states, and are varied from about 0.2 to 5 in atomic system ofunits. Finally, the principal possibility of coherent radiation generation onfullerene ions VLELs is discussed.
Resource
2018 EN
V. N. Mantsevich · D. S. Smirnov · A. M. Smirnov
+5 more
We investigated the nonlinear optical properties of CdSe/CdS nanoplatelets inthe vicinity of heavy hole and light hole exciton resonances. The two colorpump-probe technique was applied. The first intense pulse creatednon-equilibrium exciton population, which was detected as a decrease of probelight absorption. We observed intense scattering of excitons between heavy- andlight-hole excitonic states. We also studied experimentally saturation ofabsorption in nanoplatelets. Theoretical description of these phenomena allowedus to determine parameters of exciton dynamics in nanoplatelets.
Resource
2018 EN
Nikolay Gorbunov · Viktor Grebenyuk · Dmitrii Karmanov
+12 more
The NUCLEON satellite experiment is designed to directly investigate theenergy spectra of cosmic-ray nuclei and the chemical composition (Z=1-30) inthe energy range of 2-500 TeV. The experimental results are presented,including the energy spectra of different abundant nuclei measured using thenew Kinematic Lightweight Energy Meter (KLEM) technique. The primary energy isreconstructed by registration of spatial density of the secondary particles.The particles are generated by the first hadronic inelastic interaction in acarbon target. Then additional particles are produced in a thin tungstenconverter, by electromagnetic and hadronic interactions.
Resource
2018 EN
and V. Grebenyuk · and D. Karmanov · and I. Kovalev
+9 more
The NUCLEON experiment is designed to measure chemical composition of cosmicrays with charges from Z=1 to 30 in an energy region from 5*10^11 to 10^15 eV.In this article the data analysis algorithm and spectra of Ni and Fe nuclei,measured in the NUCLEON experiment, are presented.
Resource
2018 EN
STAR Collaboration · J. Adam · L. Adamczyk
+346 more
In this erratum we report changes on the $D^0$ $p_T$ spectra and nuclearmodification factor ($R_{AA}$) in Au+Au collisions at$\sqrt{s_{_{\mathrm{NN}}}}$ = 200 GeV by fixing the errors in the efficiencyand selection criteria that affected the Au+Au results. The p+p referencespectrum has changed as well and is updated with new fragmentation parameters.