Measurement of the Tensor Polarization in Electron-Deuteron Elastic Scattering

Abstract

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...

Phenomenology of the deuteron electromagnetic form factors

“….008 (±.004) [21] Deuteron form factors G C , G Q and G M as a function of Q. The data for G C and G Q are from Table 1, corresponding to t 20 measurements of Refs [21] (solid diamonds, and open diamonds for the second solution), [22] (star), [23] (open squares), [24,29] (triangles up), [25] (open circle), [26] (full squares), [27] (triangles down), [28] (full circles). The G M data corresponds to the B measurements of Refs.…”

“…Above 7 fm −1 , only small angle cross section data are available, preventing the separate determination of the three form factors. We have determined the three deuteron electromagnetic form factors by fitting directly the measured differential cross section [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and polarization [21][22][23][24][25][26][27][28][29] observables. This procedure eliminates the need for an intermediate determination of A and B, and results in a more realistic evaluation of errors for the form factors.…”

Spin-Momentum Correlations in Quasielastic Electron Scattering from Deuterium

“…Because of the tensor part of the NN interaction a D-state component is generated (see, e.g., [5,11]). The models predict that the S-and D-state components strongly depend on p and are sensitive to the repulsive core of the NN interaction at short distances [5].Traditionally, the spin structure of the deuteron has been studied through measurements of the tensor analyzing power T 20 [12][13][14][15][16][17][18] in elastic electron-deuteron scattering. Complementary information can be obtained by electrodisintegration studies in the region of quasielastic scattering.…”

“…Traditionally, the spin structure of the deuteron has been studied through measurements of the tensor analyzing power T 20 [12][13][14][15][16][17][18] in elastic electron-deuteron scattering. Complementary information can be obtained by electrodisintegration studies in the region of quasielastic scattering.…”

Electron Scattering from Tensor-Polarized Deuterons in the VEPP-3 Electron Storage Ring

“…The resulting values for T20 are also listed in table 1, and plotted in figure 7. Also shown are the results at lower Q from previous experiments at Novosibirsk 13 and Bates 14 , and the results at higher Q from the Bates/Ahead collaboration 15 , discussed elsewhere in these proceedings.…”