###
This figure shows the analyzing power differences in elastic np scattering
measured at TRIUMF [1,2] and IUCF [3].
The solid error bars reflect the statistical
uncertainty and the dashed extensions the statistical and systematic
uncertainties added in quadrature.

The calculations are by Iqbal and Niskanen [4] and Holzenkamp, Holinde,
and Thomas [5]. The short dashed lines () are when only the
electromagnetic contribution due to one photon exchange is considered;
when the contribution due to the np mass difference in one boson exchange is
included these calculations give values shown by the long dashed lines
(, , and ). Including the contribution due to the
exchange of a
mixed meson are gives the solid lines
(, , , and ). Clearly these models
require the inclusion of mixing to describe the data at 183
MeV.

**[1]**- R. Abegg,
* et al.* , Phys. Rev. Let. ** 56**, 2571 (1986);
Phys. Rev. D ** 39**, 2464 (1989).

**[2]**- R. Abegg,
* et al.* , Phys. Rev. Let. ** 75**, 1711 (1995).

**[3]**- S.E. Vigdor,
* et al.* , Phys. Rev. C ** 46**, 410 (1992).

**[4]**- M.J. Iqbal and J.A. Niskanen, Phys. Rev. C
** 38**, 2259
(1988).

**[5]**- B. Holzenkamp, K. Holinde, and G.A. Miller, Phys. Lett. B
** 195**, 121 (1987).

E704 index

Allena K. Opper's research page

Allena K. Opper's homepage

Ohio University Physics Department

*Richard T. Waters*

28 August 1996