Initial Beam Polarization Research Articles

Multiple photon Monte Carlo simulation for polarized Mo-slashller scattering with Yennie-Fraustchi-Suura exponentiation at high energies.

We present the theoretical basis and sample Monte Carlo data for the YFS exponentiated O~a! calculation of polarized Moiller scattering at c.m.s. energies large compared to 2 me . Both longitudinal and transverse polarizations are discussed. Possible applications to Moiller polarimetry at the SLD are thus illustrated. @S0556-2821~96!05713-X# ization utilizes the polarization dependence of the Moiller scattering cross section for polarized electrons in the SLC beam on a stationary polarized foil of known polarization- so-called Moiller polarimetry. While this method of measure- ment is not the primary method of measuring the SLC e 2 polarization, it is used @4# as an important cross check on the more accurate Compton polarimetry employed by the SLD Collaboration in their high precision ALR studies. Accord- ingly, radiative corrections to polarized Moiller scattering at the below 1% precision level are now of some interest. In this paper, we present the first results on the Yennis- Fraustchi-Suura ~YFS !@ 5 #exponentiated exact O~a! Monte Carlo approach @6# to these corrections in analogy with the results on the crossed Bhabha process presented in @7,8#, for example. Specifically, we extend the BHLUMI 1.xx Monte Carlo event generator in Ref. @7# to the crossed reaction of interest here. The extension involves introducing a new polarized matrix element into BHLUMI which is exact to O~a! for arbi- trarily polarized incoming e 2 beams. To this end, we follow the work of Ref. @9# for polarized Bhabha scattering and obtain the required exact O~a! matrix elements by crossing transformations on the virtual and soft corrections in this latter reference. For the corresponding O~a! hard brems- strahlung matrix element for Moiller scattering, we find it convenient to calculate it directly. These exact O~a! results are then combined with our standard YFS Monte Carlo methods as they pertain to Moiller scattering ~the respective YFS form factors are obtained via crossing from those al- ready in BHLUMI 1.xx! to yield the first ever realistic multiple photon Monte Carlo event generator for Moiller scattering with arbitrary initial beam polarizations. We call this new event generator BMOLLR. In what follows, we first review the relevant aspects of BHLUMI 1.xx insofar as our crossing transformations to the Moiller process are concerned. This is done in the next sec- tion. In Sec. III, we present the respective crossed virtual and soft corrections derived from Ref. @9#. In Sec. IV, we calcu- late the desired hard bremsstrahlung correction. In Sec. V, we combine our results to create BMOLLR and we present sample Monte Carlo data to illustrate the corresponding mul- tiple photon corrections. Comparisons with earlier analytic work in Refs. @10-12# as well as with recent SLD results @3# are also discussed in this section. Section VI contains some summary remarks.

The neutron interferometer as a macroscopic quantum device

Neutron interferometry is a unique tool for investigations in the field of particle-wave dualism because massive elementary particles behave like waves within the interferometer. The invention of perfect crystal neutron interferometers providing widely separated coherent beams stimulated a great variety of experiments with matter waves in the field of basic quantum mechanics. The phase of the spatial and spinor wave function become a measurable quantity and can be influenced individually. High degrees of coherence and high order interferences have been observed by this technique. The 4π-symmetry of a spinor wave function and the mutual modulation of nuclear and magnetic phase shifts have been measured in the past. Recent experiments dealt with polarized neutron beams, which are handled to realize the spin-superposition of two oppositionally polarized subbeams resulting in a final polarization perpendicular to both initial beam polarizations. The different actions on the coherent beams of static (DC) and dynamic (HF) flippers have been visualized.

Intermediate-mass Higgs-boson production in polarized e+e- colliders.

Production of the standard Higgs boson ${H}^{0}$ in the mass range of 40 to 150 GeV/${c}^{2}$ in e\ifmmode \bar{e}\else \={e}\fi{} annihilations into ${H}^{0}$ll\ifmmode\bar\else\textasciimacron\fi{} where l=e,\ensuremath{\mu},\ensuremath{\nu} is calculated for longitudinally polarized incoming beams. It is found that the ${H}^{0}$\ensuremath{\nu}\ensuremath{\nu}\ifmmode\bar\else\textasciimacron\fi{} is best for the ${H}^{0}$ searches if accurate determination of missing energies is available. Initial beam polarizations are useful for filtering the signals from backgrounds as well as for distinguishing them from other interesting processes, such as ${Z}^{0}$\ensuremath{\nu}\ensuremath{\nu}\ifmmode\bar\else\textasciimacron\fi{}.

Direct observation of fermion spin superposition by neutron interferometry

The coherent superposition of oppositely polarized neutron beams of equal amplitude results in a final beam polarization perpendicular to the polarization of both initial beams. This polarization can be rotated by purely scalar interaction applied to the beams before superposition, which is equivalent to an additional Larmor precession applied to the beam after superposition. We have directly observed these effects in an experiment performed using the perfect-crystal neutron interferometer at the high-flux reactor at Grenoble. This paper gives the experimental results and discusses their theoretical foundation.

Relativistic theory of electron scattering from hydrogenic systems

The electron-hydrogen scattering problem is formulated using the Dirac equation. A set of coupled equations is obtained for the radial wavefunctions for the various states of the incident electron, analogous to the coupled equations in the non-relativistic theory. A set of scattering amplitudes is obtained from which excitation cross sections, elastic and inelastic differential cross sections, and data on final electron and target polarizations can be obtained for any initial electron beam or target polarizations. Explicit formulae for the differential cross section and final electron polarization are given for certain special cases. Inclusion of magnetic and retardation effects in the interaction between the two electrons is discussed.