Production of a Beam of Tensor-Polarized Deuterons Using a Carbon Target

Abstract

An initially unpolarized beam of deuterons is found to acquire tensor polarization after traversing a foil of spin-zero target nuclei. The effect, called nuclear spin dichroism, has been predicted theoretically, albeit resulting in small values of p zz of the order of 0.01 for energies around 10 MeV. The experiment was carried out at the Köln tandem accelerator using carbon targets bombarded by deuterons. The observed polarization is as large as p zz ¼ À0:28 AE 0:03 for a beam of 14.8 MeV and a 129 mg=cm 2 target. The results allow one to produce tensor-polarized deuterons with p zz around À0:30 (or þ0:25) from an initially unpolarized beam using a carbon target of appropriate thickness. DOI: 10.1103/PhysRevLett.104.222501 PACS numbers: 13.88.+e, 24.70.+s, 25.45.De, 29.27.Hj Nuclear spin dichroism leads to the appearance of tensor polarization in an initially unpolarized, forwardtransmitted beam of (spin 1) deuterons behind a target composed of spin-zero nuclei, like carbon [1]. The direction of primary and transmitted beam defines the quantization axis, and because of azimuthal symmetry, the beam behind the target is described by the tensor polarizationwhere is the number density of nuclei in the target (per unit of volume) and d its thickness (in units of length). The n m denote the normalized occupation numbers of deuterons in the magnetic substates m ¼ þ1, À1, and 0. The interaction of deuterons of energy E with spin-zero target nuclei is characterized by the total cross sections AE1 ðEÞ and 0 ðEÞ. Using the initial occupation numbers in the beam, n in þ1 ¼ n in À1 ¼ n in 0 ¼ 1 3 , the tensor polarization behind the target readswhere AE m ¼ R d 0 m ½EðxÞ dx, and EðxÞ is the deuteron energy at a penetration depth x into the target. When AE m ( 1, Eq. (2) reduces to p zz ð dÞ ¼ 2 3A nonzero cross-section difference is produced, for instance, by the nonspherical shape of the deuteron ground-state wave function. Recently, the deuteron-carbon interaction at deuteron energies of 5 to 20 MeV has been investigated theoretically [1]. The optical theorem relates the cross-section difference in Eq. (3) to the imaginary part of the coherent forward scattering amplitudes, When Eq. (3) is integrated over the range E in ¼ Eðx ¼ 0Þ to E out ¼ Eðx ¼ dÞ, deuterons decelerated from 20 to 11 MeV (or from 11 to 5.5 MeV) in a carbon target of areal density 180 ðor 70Þ mg=cm 2 are expected to acquire p zz ¼ þ0:014 (or p zz ¼ À0:0035) [1]. These predictions are to be compared with the experimental data obtained in this work.The measurements, presented here, were performed in two runs, in

Birefringence (spin rotation and spin dichroism) of high-energy deuterons

“…The analysis of the deuteron birefringence effect in the eikonal approximation shows that the contribution from the interaction between the deuteron electric quadrupole moment and the electric field of a nucleus is significantly smaller than the contributions pro duced by the nuclear interaction and the interference of nuclear and Coulomb interactions [10] at energies in the region of 20 MeV in which the first experiments focused on the detection of deuteron spin dichroism were carried out [5].…”

“…Hamiltonian , which char acterizes the interaction of a deuteron with a nucleus, is written as (5) where is the deuteron Hamiltonian, r p (r n ) is the coordinate of a proton (neutron) within a deuteron with respect to the center of a target nucleus, is the nucleus Hamiltonian, are the coordinates of nucleons with respect to the nucleus center, and is the deuteron-nucleus interaction potential that incorporates nuclear and Coulomb interactions.…”

“…One may neglect the deuteron binding energy (i.e., term in Hamiltonian (6)) in this approximation. As a result, Hamiltonian (6) is transformed into the follow ing form [5]: (7) where is the potential energy of interaction of a deuteron with a nucleus, and are the potential energies of nuclear interaction of a proton and a neutron with a nucleus, and is the potential energy of Coulomb interaction of a deuteron with a nucleus.…”

“…The effect of spin dichroism of deuterons was first observed for a beam with an energy of 5-20 MeV that passed through car bon targets [5]. The effect was later observed at Nuclo tron M (Joint Institute for Nuclear Research) for deu terons with a momentum of 5 GeV/c [6,7].…”

”Optical” spin rotation phenomenon and spin-filtering of antiproton beams in a nuclear pseudomagnetic field

“…In such experiments, the deuteron spin PoS(STORI11)028 "Optical" spin rotation phenomenon in a nuclear pseudomagnetic field V.Baryshevsky, A. Rouba dichroism brings about tensor polarization of the transmitted deuteron beam [2]. The experiments [8,9] were carried out this way. The main advantage of this method is its technical simplicity, because only an unpolarized deuteron beam, an unpolarized solid target, and a polarimeter are required.…”