RESUMO
The charge and magnetic form factors, F_{C} and F_{M}, respectively, of ^{3}He are extracted in the kinematic range 25 fm^{-2}≤Q^{2}≤61 fm^{-2} from elastic electron scattering by detecting ^{3}He recoil nuclei and scattered electrons in coincidence with the two High Resolution Spectrometers of the Hall A Facility at Jefferson Lab. The measurements find evidence for the existence of a second diffraction minimum for the magnetic form factor at Q^{2}=49.3 fm^{-2} and for the charge form factor at Q^{2}=62.0 fm^{-2}. Both minima are predicted to exist in the Q^{2} range accessible by this Jefferson Lab experiment. The data are in qualitative agreement with theoretical calculations based on realistic interactions and accurate methods to solve the three-body nuclear problem.
RESUMO
This corrects the article DOI: 10.1103/PhysRevLett.119.162501.
RESUMO
The charge form factor of 4He has been extracted in the range 29 fm(-2) ≤ Q2 ≤ 77 fm(-2) from elastic electron scattering, detecting 4He recoil nuclei and electrons in coincidence with the high resolution spectrometers of the Hall A Facility of Jefferson Lab. The measurements have uncovered a second diffraction minimum for the form factor, which was predicted in the Q2 range of this experiment. The data are in qualitative agreement with theoretical calculations based on realistic interactions and accurate methods to solve the few-body problem.
RESUMO
We present a search at the Jefferson Laboratory for new forces mediated by sub-GeV vector bosons with weak coupling α' to electrons. Such a particle A' can be produced in electron-nucleus fixed-target scattering and then decay to an e + e- pair, producing a narrow resonance in the QED trident spectrum. Using APEX test run data, we searched in the mass range 175-250 MeV, found no evidence for an A'â e+ e- reaction, and set an upper limit of α'/α ~/= 10(-6). Our findings demonstrate that fixed-target searches can explore a new, wide, and important range of masses and couplings for sub-GeV forces.
RESUMO
An experimental study of the (16)O(e,e'K(+))(Lambda)(16)N reaction has been performed at Jefferson Lab. A thin film of falling water was used as a target. This permitted a simultaneous measurement of the p(e,e'K(+))Lambda, Sigma(0) exclusive reactions and a precise calibration of the energy scale. A ground-state binding energy of 13.76+/-0.16 MeV was obtained for (Lambda)(16)N with better precision than previous measurements on the mirror hypernucleus (Lambda)(16)O. Precise energies have been determined for peaks arising from a Lambda in s and p orbits coupled to the p(1/2) and p(3/2) hole states of the (15)N core nucleus.
RESUMO
An experiment measuring electroproduction of hypernuclei has been performed in hall A at Jefferson Lab on a 12C target. In order to increase counting rates and provide unambiguous kaon identification two superconducting septum magnets and a ring imaging Cherenkov detector were added to the hall A standard equipment. An unprecedented energy resolution of less than 700 keV FWHM has been achieved. Thus, the observed (Lambda)(12)B spectrum shows for the first time identifiable strength in the core-excited region between the ground-state s-wave Lambda peak and the 11 MeV p-wave Lambda peak.
RESUMO
The 1987 amendments to the Older Americans Act mandate a special effort to serve low-income minority elderly persons. A literature review showed that "practice-oriented" research on service use has focused primarily on identifying barriers with much less attention to identification of strategies for overcoming the barriers. This paper identifies and describes strategies used throughout Texas. Strategies addressing the "lack of knowledge" barrier included use of influential groups, working with significant individuals, and the media. Strategies addressing the "lack of access" barrier included transportation, affordability, and availability. Strategies addressing the "lack of intent" barrier focused on cultural differences, making services attractive, and overcoming negative attitudes toward service use.