This paper reports the first measurement of the tensor polarization t 2 o ine-d elastic scattering. The polarization of the recoil deuterons was measured for two values of momentum transfer, # = 1.74 and 2.03 fm" 1 , with a high-efficiency polarimeter. The results are in good agreement with reasonable models for the deuteron.PACS numbers: 25.30.Bf, 24.70,+ s, 25.10.+ S A complete experimental determination 1 ' 2 of the electromagnetic current of the deuteron requires the measurement of at least one polarization observable, in addition to the differential cross section. Here we report the first measurement of t 20 in elastic e-d scattering. Measurements of t 20 have previously not been feasible because of the absence of high-efficiency deuteron tensor polarimeters or tensor-polarized targets, and the lack of high-intensity electron beams and large-acceptance magnetic spectrometers. The results are found to be in good agreement with the predictions of t 20 for "reasonable" models of the deuteron, but in disagreement with those of separable-potential models.Electron elastic scattering from the deuteron can be described by three form factors: charge (F c ), quadrupole (FQ), and magnetic (F M ). Thus far, only F M has been isolated 3 in measurements of the cross section. The form factors F c and F Q have not been isolated previously from measurements of the structure function. 4 A determination of these form factors separately would discriminate further among different deuteron wave functions. The sensitivity of t 20 to the deuteron wave function arises from the fact that the leading term in t 2Q is proportional to the ratio of F Q to F c . in this ratio, the poorly known isoscalar electric nucleon form factor drops out. The expression for t 2Q is given 2 by t 20 2 , and/(6>) = i + (l+77)tan 2 (6i/2). Here, q is the four-momentum transfer, M d is the rest mass of the deuteron, and 6 is the angle of the scattered electron. The terms involving powers of X in the numerator are dominant in the momentum transfer region of 1-5 fm" 1 . Thus, t 20 is sensitive to the ratio of F Q to F c . The quantity F Q is sensitive to the tensor part of the N-N interaction, while F c is dominated by the S-wave part of the deuteron wave function at these values of low momentum transfer. Additionally, recent work 1 ' 2 has shown that t 2Q is also sensitive to the isoscalar meson exchange current (MEC) and relativistic corrections, about which there is much controversy. 5 The experiment was performed at the South Experimental Hall of the Massachusetts Institute of Technology-Bates Linear Accelerator Center. A schematic diagram of the experimental arrangement is given in Fig. 1. The electrons from the linac were focused on a windowless D 2 0 target which consisted of a 0.38-or 0.64-mm-thick laminar flow of heavy water. The incident electron energies were 371 ±2 MeVfor ^r=2.03fm" 1 , and 310± 1.8 MeVfor #=1.74 fm" 1 . During the experiment the average current and duty factor of the electron beam varied from 15 to 50 /iA and 0.3% to 0.4%, respec...

No abstract

No abstract

The shortcomings of conventional scintillation cameras are analysed theoretically with a view towards improving performance at gamma ray energies above 140 keV. A camera design is proposed which incorporates several new features to obtain good spatial resolution from thicker crystals of sodium iodide. Computer simulations show that in addition to having good efficiency and spatial resolution, the new design allows parallax error correction and (possibly) Compton scattering correction at gamma energies up to 511 keV.

We propose calculations and measurements of N+ d breakup cross sections as a function of a new set of kinematic variables. When carried out as a function of these variables, separable-potential calculations predict cross sections which exhibit a very deep destructive interference minimum over a wide range of bombarding energies. We proposed a procedure for isolating the effect of the crucial M d2 amplitude on the cross section.A basic difficulty in attempting to extract new information about the NN force from measured three-body observables is that the observables are largely determined by what is already known about the NN force from the nucleon-nucleon data. The purpose of this article is to suggest a method of selecting the kinematical situations under which to perform N+d breakup measurements to facilitate the observation of short-range effects. (These we take to include both the off-energy-shell behavior of the NN force and explicit three-body forces.) We shall also present estimates of the variation in the cross section which might be caused by these short-range effects.Since three-body breakup amplitudes depend sensitively on the three final-state NN relative energies, we suggest that the relative energies be used to parametrize the kinematics and that comparisons of data and calculations should be done for fixed values of these relative energies. If in addition the direction of one of the finalstate nucleon momenta is held fixed, the cross section can depend only on the cm. rotation angle of a momentum triangle of fixed shape about the direction of the fixed nucleon momentum. This rotation angle, or an equivalent kinematic variable, is the continuous variable against which the cross section is to be measured and calculated in this scheme. The above specification fixes four independent kinematic variables, thus defining a one-dimensional kinematic locus in three-body phase space. We have computed the breakup cross section along a particular one of these constant-relative-energy loci using the YY model, 1 where the Watson-Faddeev integral equations are solved with separable spin-dependent s-wave NN interactions. 2 The model cross section is given bywhere F K is a kinematic factor, M q is the amplitude for breakup in the quartet state {S = • §-), and M dl and M d2 are the doublet-state (S= ?) amplitudes in which the two identical nucleons are coupled to spin 1 or 0, respectively. Results from model calculations of elastic N-d scattering phase parameters 3 with different NN forces lead us to expect that M d2 is much more sensitive to the details of the NN force used in the calculations than the other amplitudes. This can be understood because wave-function antisymmetry makes a state contributing to M d2 the only one in which there is a significant probability of finding the three nucleons simultaneously close together. 3 ' 4The advantage of the above procedure is that the s-wave parts of M q , M dU and M d2 are all constant along such a locus. If we assume that the deviation between the model-predicted M d2 a...