The proton is one of the main building blocks of all visible matter in the Universe
. Among its intrinsic properties are its electric charge, mass and spin
. These properties emerge from the complex ...dynamics of its fundamental constituents-quarks and gluons-described by the theory of quantum chromodynamics
. The electric charge and spin of protons, which are shared among the quarks, have been investigated previously using electron scattering
. An example is the highly precise measurement of the electric charge radius of the proton
. By contrast, little is known about the inner mass density of the proton, which is dominated by the energy carried by gluons. Gluons are hard to access using electron scattering because they do not carry an electromagnetic charge. Here we investigated the gravitational density of gluons using a small colour dipole, through the threshold photoproduction of the J/ψ particle. We determined the gluonic gravitational form factors of the proton
from our measurement. We used a variety of models
and determined, in all cases, a mass radius that is notably smaller than the electric charge radius. In some, but not all cases, depending on the model, the determined radius agrees well with first-principle predictions from lattice quantum chromodynamics
. This work paves the way for a deeper understanding of the salient role of gluons in providing gravitational mass to visible matter.
We present new measurements of electron scattering from high-momentum nucleons in nuclei. These data allow an improved determination of the strength of two-nucleon correlations for several nuclei, ...including light nuclei where clustering effects can, for the first time, be examined. The data also include the kinematic region where three-nucleon correlations are expected to dominate.
Fredholm integral equations of the second kind, which describe the fields of TE and TM polarized waves in metal films with allowance for the anomalous skin effect, are formulated. The equations can ...be solved numerically by the quadrature method. The electric fields in gold and aluminum films deposited on a silicon substrate and the angular dependences of the polarization angles of light reflected from these films are investigated. It is found that the solution of the inverse problem of multiangle ellipsometry of metal films within the approximation of the normal skin effect is characterized by the instability of the reconstructed complex refractive index of the metal with a change in the thickness of the metal film.
The ejection of particles from the free surface of metal liners accelerated to velocities of 4–5 km/s using explosive energy has been investigated. It is shown experimentally that the effect of ...shock-wave dusting can be suppressed by quasi-isentropic or isentropic loading of liners during their acceleration.
Comparative experimental studies of the shock-induced particle ejection (“dusting”) from the free rough (Rz20) surface of copper and lead liners exposed to one or two successive shock waves separated ...in time by 0.2 μs have been carried out for the first time. This situation usually occurs in cumulative systems for the compression of the plasma by cylindrical or spherical liners shock or quasi-isentropically accelerated by explosion products. Using pulsed X-ray diffraction, laser optical recording, piezoelectric pressure sensors, and heterodyne interferometry, a qualitative picture has been studied and the quantitative characteristics of particle ejection from the free surface such as the velocities of the free surface and the particle flux front and the density (mass) distribution of particle flux in the direction of its motion, which are necessary for more accurate determination of features and the development of more appropriate models of the effect, have been evaluated.
The structure of deformed semifinished products (forgings) from titanium alloys of Ti–Al–Zr + 0.15% Ru, Ti–Al–V–Mo + 0.15% Ru, and Ti–Al–V–Cr–Fe–Mo + 0.15% Ru systems has been investigated. The basic ...mechanical properties, microstructure, results of local elemental and phase analyses obtained by X-ray spectral microanalysis and backscattered electron diffraction, and also a model of the effect of ruthenium on increasing corrosion resistance of titanium alloys of various classes are presented.
—This article discusses the results of corrosion tests and microstructural studies of forgings from various titanium alloys modified with ruthenium, of systems Ti–Al–Zr + 0.15% Ru, Ti–Al–V–Mo + 0.15% ...Ru, and Ti–Al–V–Cr–Fe–Mo + 0.15% Ru and similar systems of basic compositions. On the basis of the performed complex of studies, the influence of the amount of the β phase on the local content of ruthenium and, as a consequence, on the effect of cathodic protection in general is analyzed.
Two devices intended for copper cylindrical liner gasdynamic acceleration to velocities of 5–7 km/s using the chemicals explosion energy have been investigated. It has been demonstrated that the ...acceleration of quasi-isentropically and isentropically loaded liners under the conditions of high-level dynamics, symmetry of deposition, and suppression of shock-induced dusting is feasible.
The GlueX experiment at Jefferson Laboratory aims to perform quantitative tests of non-perturbative QCD by studying the spectrum of light-quark mesons and baryons. A Detector of Internally Reflected ...Cherenkov light (DIRC) was installed to enhance the particle identification (PID) capability of the GlueX experiment by providing clean
π
/K separation up to 3.7 GeV/
c
momentum in the forward region (
θ
< 11°), which will allow the study of hybrid mesons decaying into kaon final states with significantly higher efficiency and purity. The new PID system is constructed with radiators from the decommissioned BaBar DIRC counter, combined with new compact photon cameras based on the SuperB FDIRC concept. The full system was successfully installed and commissioned with beam during 2019/2020. The initial PID performance of the system was evaluated and compared to one from Geant4 simulation.
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