Tensor polarization in elastic electron-deuteron scattering in the momentum transfer range 3.8≤Q≤4.6fm−1

Abstract

The tensor polarization of the recoil deuteron in elastic electron-deuteron scattering has been measured at the Bates Linear Accelerator Center at three values of four-momentum transfer, Q = 3.78, 4.22, and 4.62 fm-', corresponding to incident electron energies of 653, 755, and 853 MeV. The scattered electrons and the recoil deuterons were detected in coincidence. The recoil deuterons were transported to a liquid hydrogen target to undergo a second scattering. The angular distribution of the d-p scattering was measured using a polarimeter. The polarimeter was calibrated in an auxiliary experiment using a polarized deuteron beam at the Laboratoire National Saturne. A Monte Carlo procedure was used to generate interpolated calibration data because the energy spread in the deuteron energies in the Bates experiment spanned the range of deuteron energies in the calibration experiment. The extracted values of tzo are compared to predictions of different theoretical models of the electromagnetic form factors of the deuteron: nonrelativistic and relativistic nucleon-meson dynamics, Skyrme model, quark models, and perturbative quantum chromodynamics. Along with the world data on the structure functions A ( Q ) and B(Q), they are used to separate the charge monopole and charge quadrupole form factors of the deuteron. A node in the charge monopole form factor is observed at Q = 4.39 i 0.16 fm-' .

Phenomenology of the deuteron electromagnetic form factors

“…[2,4], and in a lesser extent for the t 20 measurements of Refs. [21,26]. The fits then give an average representation of the data, though biased toward experiments with a larger number of data points.…”

“…For our purpose, it is useful to define new quantities A 0 ≡ A−B/2(1+η) andt 20 [26], derived respectively from A and t 20 by eliminating the magnetic contribution:…”

“…The analyses presented in [22,26] need to be updated, because of new t 20 [21,23,25] and A [2,4] data. In particular, the parameterization of A used in [26] gave a very small weight to the then only existing high Q data [5] and is lower than the new data [2,4] around 4.5 fm −1 . Furthermore, we present here a more compact solution and a more rigorous treatment of errors.…”

“…[21][22][23]26,27] which lay partially outside the physical region − √ 2 ≤t 20 ≤ 1/ √ 2. This situation is quite probable for points with finite errors close to a physical limit [37].…”

“…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.…”