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Abstract

Absolute differential cross sections for the reaction $p+p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}+d$ have been measured at incident proton energies (lab system) from 310 to 338 Mev and at meson angles (c.m.) from 30\ifmmode^\circ\else\textdegree\fi{} to 90\ifmmode^\circ\else\textdegree\fi{}. The two final particles were counted in coincidence. The data are well fitted by the phenomenological theoretical expression $4\ensuremath{\pi}\frac{d\ensuremath{\sigma}}{d\ensuremath{\Omega}}(\mathrm{c}.\mathrm{m}.)={\ensuremath{\alpha}}_{10}\ensuremath{\eta}+{\ensuremath{\beta}}_{10}{\ensuremath{\eta}}^{3}\frac{(x+{cos}^{2}\ensuremath{\theta})}{x+\frac{1}{3}},$ with $x=0.082\ifmmode\pm\else\textpm\fi{}0.034$, ${\ensuremath{\alpha}}_{10}=(0.138\ifmmode\pm\else\textpm\fi{}0.015)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}27}$ ${\mathrm{cm}}^{2}$, and ${\ensuremath{\beta}}_{10}=(1.01\ifmmode\pm\else\textpm\fi{}0.08)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}27}$ ${\mathrm{cm}}^{2}$; $\ensuremath{\theta}=\mathrm{meson}$ c.m. angle and $\ensuremath{\eta}=\frac{{p}_{\ensuremath{\pi}} (\mathrm{c}.\mathrm{m}.)}{{m}_{\ensuremath{\pi}}c}$. By measuring ${\ensuremath{\alpha}}_{10}$ we have determined directly the amount of $S$-wave in this reaction.Further measurements with polarized protons of \ensuremath{\sim}315 Mev are presented. These confirm directly the presence of interfering $S$- and $P$-waves and give a result $|Q|=0.39\ifmmode\pm\else\textpm\fi{}0.05$ for the asymmetry $\frac{(R\ensuremath{-}L)}{(R+L)}$ which would be obtained at 90\ifmmode^\circ\else\textdegree\fi{} c.m. with 100 percent polarized protons. The polarized and unpolarized results are used together to determine the relative phases of the $S$- and $P$-wave mesons.Using the recent Chicago measurement of the sign of the proton polarization, the sign we observe for meson production asymmetry shows that spin up protons produce more mesons to the right than to the left. The sign of this result, according to a theoretical prediction of B. T. Feld, provides strong evidence in favor of the Fermi type meson-nucleon interaction, and against the Yang type interaction.

Reactionp+p→π++d

Abstract

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