Showing papers by "W. Meyer published in 2001"

First measurement of the Gerasimov-Drell-Hearn integral for 1 H from 200 to 800 MeV

Abstract: A direct measurement of the helicity dependence of the total photoabsorption cross section on the proton was carried out at MAMI (Mainz) in the energy range $200l{E}_{\ensuremath{\gamma}}l800\mathrm{MeV}$. The experiment used a $4\ensuremath{\pi}$ detection system, a circularly polarized tagged photon beam, and a frozen spin target. The contributions to the Gerasimov-Drell-Hearn sum rule and to the forward spin polarizability ${\ensuremath{\gamma}}_{0}$ determined from the data are $226\ifmmode\pm\else\textpm\fi{}5(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}12(\mathrm{syst})\ensuremath{\mu}\mathrm{b}$ and $\ensuremath{-}187\ifmmode\pm\else\textpm\fi{}8(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}10(\mathrm{syst})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}{\mathrm{fm}}^{4}$, respectively, for $200l{E}_{\ensuremath{\gamma}}l800\mathrm{MeV}$.