Search

We report measurements of the electroproduction of phi mesons from hydrogen at Q/sup 2/ values of 0.23, 0.43, and 0.97 GeV/sup 2/ with t varying from 0.125 to 1.3 GeV/sup 2/ at each Q/sup 2/ point. The data show no evidence for a Q/sup 2/ dependence of the slope of the t distribution; the forward cross section falls with increasing Q/sup 2/ as the square of the phi propagator; the decay angular distributions agree with the predictions of s-channel helicity conservation; and the ratio of the longitudinal to the transverse component increases linearly with Q/sup 2/.

We report measurements of kaon electroproduction from hydrogen and deuterium targets carried out at the Wilson Synchrotron Laboratory at Cornell University. The reactions ..gamma../sub V/p ..-->.. K/sup +/X/sup 0/, K/sup +/..lambda.., and K/sup +/..sigma../sup 0/ were studied in the kinematic region 2.15 .. 0 as Q/sup 2/ increases.

We report measurements of the electroproduction of phi mesons from hydrogen at Q/sup 2/ values of 0.23, 0.43, and 0.97 GeV/sup 2/ with vertical-bartvertical-bar varying from 0.125 to 1.3 GeV/sup 2/ at each Q/sup 2/ point. The data show no evidence for a Q/sup 2/ dependence of the slope of the t distribution, the forward cross section falls with increasing Q/sup 2/ as the square of the phi propagator, the decay angular distributions agree with the predictions of s-channel helicity conservation, and the ratio of the longitudinal to the transverse component increases linearly with Q/sup 2/.

Measurements are reported of the ratio of positively charged to negatively charged pions electroproduced at 0degree and 90degree in the virtual photon-nucleon center-of-mass system. The ..pi../sup +//..pi../sup -/ ratio is studied as a function of W, Q/sup 2/, ..omega.., x/sub T/, and x in the range 2.1 GeV< or =W< or =3.2 GeV and 1.2 GeV/sup 2/< or =Q/sup 2/< or =9.5 GeV/sup 2/. (AIP)

We report measurements of the exclusive electroproduction reaction $e+p\ensuremath{\rightarrow}e+{\ensuremath{\pi}}^{+}+n$ for pions produced near 0\ifmmode^\circ\else\textdegree\fi{} in the virtual-photon-proton center-of-mass system with values of $\ensuremath{\epsilon}$ in the range $0.35l\ensuremath{\epsilon}l0.45$. Combination with data taken at $\ensuremath{\epsilon}$ near 1 allows us to separate the contributions from transversely polarized and scalar photons in the range $1.2 {\mathrm{GeV}}^{2}l{Q}^{2}l3.3 {\mathrm{GeV}}^{2}$.

We report measurements of semi-inclusive pion electroproduction from both hydrogen and deuterium targets carried out at the Wilson Synchrotron Laboratory at Cornell University. Measurements were made at the (W,Q/sup 2/) points (2.15 GeV, 1.2 GeV/sup 2/), (2.15, 4.0), and (3.11, 1.2) with hydrogen and deuterium, and at (2.15, 2.0), (2.67, 3.3), and (3.11, 1.7) with hydrogen only. The invariant virtual-photoproduction cross section for pions scaled by the total cross section is studied as a function of x', P/sub T/ /sup 2/, W, and Q/sup 2/. The invariant structure function shows no Q/sup 2/ dependence and a weak W dependence. The ratio of ..pi../sup +/ to ..pi../sup -/ production is also presented, but a distinction between a universal ..omega.. or W dependence cannot be made.

We report measurements of the inclusive electroproduction reaction ep..-->..e..pi../sup +/X for pions produced at 90degree in the virtual-photon-proton center-of-mass system. Data are presented at the (W,Q/sup 2/) points (2.2 GeV, 1.2 GeV/sup 2/), (2.2, 3.6), (2.65, 1.2), (2.65, 2.0), (2.65, 2.8), (2.65, 3.6), (3.1, 1.2), and (3.1, 2.0). The invariant structure function is studied as a function of W, Q/sup 2/, x/sub T/, p/sub T//sup 2/, and the square of the invariant undetected mass. (AIP)

New measurements of inclusive pion electroproduction are reported. Data were taken with a hydrogen target at the (W,Q/sup 2/) points (2.2 GeV, 1.2 GeV/sup 2/), (2.7,2.0), (2.7,3.3), (2.7,6.2), (2.7,9.5), and (3.1,4.5). The invariant structure function is studied as a function of W, Q/sup 2/, ..omega.., and x'. (AIP)

We report measurements of the electroproduction of single charged pions from hydrogen and deuterium targets for values of $\ensuremath{\epsilon}$ in the range $0.35l\ensuremath{\epsilon}l0.45$. Data were taken with a hydrogen target at the ($W, {Q}^{2}$) points (2.15 GeV, 1.2 ${\mathrm{GeV}}^{2}$), (2.65, 2.0), (2.65, 3.4), (2.65, 6.0), and (2.65, 10.0). Data were taken with a deuterium target at the ($W, {Q}^{2}$) points (2.15, 1.2) and (2.65, 2.0). The transverse cross section obtained by using these data in conjunction with earlier data at high $\ensuremath{\epsilon}$ to separate the longitudinal and transverse components is used in conjunction with the new data and the $t$-channel Born term to determine the pion form factor and to re-evaluate previously reported measurements. In the range $0.15 \mathrm{Ge}{\mathrm{V}}^{2}l{Q}^{2}l10.0 \mathrm{Ge}{\mathrm{V}}^{2}$ the pion form factor can be described by the simple pole form ${[1+\frac{{Q}^{2}}{(0.462\ifmmode\pm\else\textpm\fi{}0.024)}]}^{\ensuremath{-}1}$.

We present evidence for a large scalar contribution to the cross section for the reaction $\mathrm{ep}\ensuremath{\rightarrow}e{K}^{+}\ensuremath{\Lambda}$. No evidence for a scalar contribution is found for the reaction $\mathrm{ep}\ensuremath{\rightarrow}e{K}^{+}{\ensuremath{\Sigma}}^{0}$. This is reminiscent of the results for the ${\ensuremath{\pi}}^{+}n$ and ${\ensuremath{\pi}}^{+}{\ensuremath{\Delta}}^{0}$ final states.

We use new measurements of the inclusive electroproduction reactions eN ..-->.. e'..pi../sup plus-or-minus/X and eN ..-->.. e'pX with epsilon values in the range 0.35 < epsilon < 0.45 together with earlier measurements with 0.85 < epsilon < 0.95 to determine the contributions to the cross section due to transversely and longitudinally polarized photons in the range 1.2 GeV/sup 2/ < Q/sup 2/ < 3.3GeV/sup 2/. The longitudinal component is small and consistent with that observed in the total virtual-photoproduction cross section.