Equations are derived for the polarization analysis in a multidetector to separate coherent, spin incoherent, and magnetic scattering using three‐dimensional analysis or the xyz‐difference method. Then the conditions for the magnetic guide fields to rotate the polarization into the three directions x, y, and z are discussed on the basis of the existing instrument D7 at the ILL in Grenoble.

The £-deeay asymmetry of the free neutron is measured by use of a beam of polarized neutrons and a long solenoidal p spectrometer with 4-TT solid angle for electron detection. The asymmetry parameter corrected for recoil and weak magnetism is A 0 = -0.1146 ± 0.0019, implying g A l gv=-1.262 ± 0.005 for the ratio of the axial-vector to the vector weak-coupling constants.PACS numbers: 13.30.Ce, 23.40.Bw From the /3 decay of the free neutron, /?--* p +e~ +v e > one can obtain unique information on the weak interaction between quarks of the first generation. The structure of the charged weak current is believed to be described by the V -A theory. Within this theory neutron decay is determined to good approximation (the allowed approximation) by momentum-independent vector and axial-vector weak coupling constants g A and g v . The constant g v is presently most accurately determined from studies of nuclear 0 + -0 + superallowed fi decay. 1 The preservation of the vector coupling strength, despite the nuclear environment, is an important consequence of vector current conservation. The relatively small corrections, made necessary by electromagnetic isospin-symmetry breaking, are well enough understood 2 for uncertainties in them to be of no significant consequence for the analysis of our present results.Axial-vector current conservation is known to be violated and g A must be measured in free-neutron fi decay. The ratio g A /gy has already been measured in a number of neutron-decay angular-correlation measurements and neutron-lifetime measurements. 3 There are, however, serious discrepancies and, in particular, several recent neutron-lifetime measurements disagree by as much as 7% while the individual experiments claim precisions of about l°/o. 4 Meanwhile, the exact value of g A lgy has important consequences for the fundamental weak interaction as well as for astrophysics and cosmology, 5 and thus it is crucial to know it as well as possible. In this Letter we report on a sensitive measurement of the neutron-spin-electron-momentum angular correlation (the neutron (3 asymmetry) from which we obtain a precise value for g A /gy.The decay probability per unit time for emission of electrons from a polarized neutron is given bywhere vie is the electron speed in units of the speed of light, 9 is the emission angle relative to the neutron polarization P, A is the /3 asymmetry parameter which is nonzero because of parity nonconservation, and dT{E) is the decay rate into a differential solid angle for unpolarized neutrons. In the allowed approximation the asymmetry parameter iswhere k=\g A /gy\ and time-reversal invariance with the usual phase convention is assumed. 6 In fact the true asymmetry parameter, A in Eq. (1), is energy dependent but its maximum deviation from A 0 , due to recoil corrections and the effect of induced currents (weak magnetism is expected to be the only significant induced-current effect), is only 1%.In our experiment we directly measure the p asymmetry from polarized neutrons by observing the difference...

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A neutron scattering study of the structure of amorphous glucoseWe present the results of a combined experimental ͑neutron scattering͒ and theoretical ͑computer simulation͒ effort to investigate structural properties of polycarbonate melts and glasses in the wave vector regime of Qр2.2 Å Ϫ1 . The experimental part consists of advanced spin polarized scattering experiments, allowing us to extract the coherent scattering for protonated and deuterated samples. The simulations employ recently developed novel mapping procedures, which allow us to efficiently equilibrate complex polymer melts, thereby reproducing the experiment in much closer detail than earlier attempts.

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