Measurement of the Neutron Radius of Pb-208 through Parity Violation in Electron Scattering

We report the first measurement of the parity-violating asymmetry A(PV) in the elastic scattering of polarized electrons from Pb-208. APV is sensitive to the radius of the neutron distribution (R-n). The result A(PV) = 0.656 +/- 0.060(stat) +/- 0.014(syst) ppm corresponds to a difference between the radii of the neutron and proton distributions R-n - R-p = 0.33(-0.18)(+0.16) fm and provides the first electroweak observation of the neutron skin which is expected in a heavy, neutron-rich nucleus

Cleaning and sputtering using planar acoustoplasma magnetron

The paper describes the obtained experimental results for a planar acoustoplasma magnetron. The small radius of the anode loopallows focusing and accelerating the ionic component of the sprayed material.Argon was used as a buffer gas. The characteristics of the magnetron in case of direct current supply and in acoustoplasma mode(AP) (with modulated current containing constant and variable components) are compared. The sputtering speed in AP modeincreases. For the copper cathode, the gas pressure made < 1 Pa and current density of the order of 100 mA/cm2with increasingdistance from the anode to the deposited substrate from 2 to 4 cm in case of DC supply, the deposition speed drops 3.3 times (from17 to 5 nm/s), in the acoustoplasma mode – 2 times (from 13 to 6.4 nm/s).For the anode-substrate distance 4 cm, the gain in the deposition speed in the AP mode, compared with DC is 1.2–1.5 times. Thedependences of ion and electron currents on the substrate for different discharge parameters were measured. The study was basedon a scheme with two potential grids with fixed and variable potentials. The possibility of forming an annular vapor-plasma flowof fast particles is shown

Nematode fauna of fish in Armenia

The purpose of the research is to study the species composition of nematodes dwelling in fish in natural reservoirs and on artificial pond fish farms in Armenia.Materials and methods. The studies were performed at the Research Center for Veterinary Medicine and Veterinary and Sanitary Expertise of the Armenian National Agrarian University and at the Laboratory of Molecular Parasitology of the Scientific Center of Zoology and Hydroecology from March 2020 to December 2022. Traditional ichthyo-parasitological methods were used to study 246 fish of 10 species from fish farms in the Ararat and Armavir Regions, from Lake Sevan and the Sevjur, Hrazdan, Marmarik, Akhuryan and Debed Rivers, as well as the Yerevan, Aparan and Akhuryan reservoirs. The study results were statistically processed (descriptive statistics) using the BioStat software.Results and discussion. The fish were found to have four types of nematodes: Contracaecum microcephalum Rudolphi, 1819, Philometroides sanguineus Rudolphi, 1819, Rhabdochona fortunatowi Dinnik, 1933 and Cystidicola farionis Fischer, 1798. Parasites were found in the body, on the serosa, in the air bladder walls, the intestinal lumen and the caudal fin thickness. The total nematode infection rate in fish was 9.76%. The nematode infection rate in fish was characterized by low values of prevalence and intensity other than the infection by the species Rh. fortunatowi (up to 24 specimens per fish). Among the found nematodes, the species C. microcephalum posed a potential threat to human health

New Measurements of the Transverse Beam Asymmetry for Elastic Electron Scattering from Selected Nuclei

We have measured the beam-normal single-spin asymmetry An in the elastic scattering of 1-3 GeV transversely polarized electrons from H-1 and for the first time from He-4, C-12, and Pb-208. For H-1, He-4, and C-12, the measurements are in agreement with calculations that relate A(n) to the imaginary part of the two-photon exchange amplitude including inelastic intermediate states. Surprisingly, the Pb-208 result is significantly smaller than the corresponding prediction using the same formalism. These results suggest that a systematic set of new A(n) measurements might emerge as a new and sensitive probe of the structure of heavy nuclei

Physics Opportunities with the 12 GeV Upgrade at Jefferson Lab

This white paper summarizes the scientific opportunities for utilization of the upgraded 12 GeV Continuous Electron Beam Accelerator Facility (CEBAF) and associated experimental equipment at Jefferson Lab. It is based on the 52 proposals recommended for approval by the Jefferson Lab Program Advisory Committee.The upgraded facility will enable a new experimental program with substantial discovery potential to address important topics in nuclear, hadronic, and electroweak physics.Comment: 64 page

Secluded Dark Matter Coupled to a Hidden CFT

Models of secluded dark matter offer a variant on the standard WIMP picture and can modify our expectations for hidden sector phenomenology and detection. In this work we extend a minimal model of secluded dark matter, comprised of a U(1)'-charged dark matter candidate, to include a confining hidden-sector CFT. This provides a technically natural explanation for the hierarchically small mediator-scale, with hidden-sector confinement generating m_{gamma'}>0. Furthermore, the thermal history of the universe can differ markedly from the WIMP picture due to (i) new annihilation channels, (ii) a (potentially) large number of hidden-sector degrees of freedom, and (iii) a hidden-sector phase transition at temperatures T << M_{dm} after freeze out. The mediator allows both the dark matter and the Standard Model to communicate with the CFT, thus modifying the low-energy phenomenology and cosmic-ray signals from the secluded sector.Comment: ~50p, 8 figs; v2 JHEP versio

Measurements of the Electric Form Factor of the Neutron up to Q2=3.4 GeV2 using the Reaction He3(e,e'n)pp

The electric form factor of the neutron was determined from studies of the reaction He3(e,e'n)pp in quasi-elastic kinematics in Hall A at Jefferson Lab. Longitudinally polarized electrons were scattered off a polarized target in which the nuclear polarization was oriented perpendicular to the momentum transfer. The scattered electrons were detected in a magnetic spectrometer in coincidence with neutrons that were registered in a large-solid-angle detector. More than doubling the Q2-range over which it is known, we find GEn = 0.0225 +/- 0.0017 (stat) +/- 0.0024 (syst), 0.0200 +/- 0.0023 +/- 0.0018, and 0.0142 +/- 0.0019 +/- 0.0013 for Q2 = 1.72, 2.48, and 3.41 GeV2, respectively.Comment: submitted to PR

Measurement of the Neutron Radius of 208Pb Through Parity-Violation in Electron Scattering

We report the first measurement of the parity-violating asymmetry A_PV in the elastic scattering of polarized electrons from 208Pb. A_PV is sensitive to the radius of the neutron distribution (Rn). The result A_PV = 0.656 \pm 0.060 (stat) \pm 0.014 (syst) ppm corresponds to a difference between the radii of the neutron and proton distributions Rn - Rp = 0.33 +0.16 -0.18 fm and provides the first electroweak observation of the neutron skin which is expected in a heavy, neutron-rich nucleus.Comment: 6 pages, 1 figur