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)

This paper reports a measurement of the photoproduction of charged-kaon pairs from hydrogen which was carried out to search for high-mass resonances in the mass range from 1.4 to 2.4 GeV. The only structure observed in the mass spectrum was a dip near 1.83 GeV. An analysis of the data indicates that this structure could be produced by a high-mass meson with a mass of about 1.83 GeV and a width of roughly 120 MeV which interfers with the kaon Soeding amplitude.

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 the electroproduction of single charged pions hydrogen and deuterium targets carried out at the Wilson Synchrotron at Cornell University are reported. 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, 3.4), and (3.11, 1.7) with only hydrogen. The deuterium data were used to determine the ratio of the cross sections for the reactions $gamma$/subV/d $Yields$ $pi$$sup +$nn/subs/ and $gamma$/subV/d $Yields$ $pi$$sup -$pp/subs/ and thus to measure the isoscalar contribution to the reaction $gamma$/subV/p $Yields$ $pi$$sup +$n. The data are consistent with the hypothesis that this ratio is a universal function of the momentum transfer. The measured ratio was used to determine from the hydrogen data and the data taken in earlier experiments the isovector component of the cross section. The dispersion theory formulated by Berends was then used to determine from the isovector component the pion form factor in the Q$sup 2$ range from 0.2 to 4.0 GeV$sup 2$. A simple pole expression of the form 1 + Q$sup 2$/(0.471 +- 0.010)$sup -1$ gives a good fit to the data. (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.