The p 1 p ! p 1 1 d reaction is studied at excess energies between 0.275 and 3.86 MeV. Differential and total cross section were measured employing a magnetic spectrometer with nearly 4p acceptance in the center of mass system. The measured anisotropies between 0.008 and 0.29 indicate that the p wave is not negligible even so close to threshold. The data are compared to other data offering no evidence for charge symmetry breaking or time reversal violation. The s-wave and p-wave contributions at threshold are deduced.[S0031-9007 (96)00602-3] PACS numbers: 13.75.Cs, 25.40.Ve, 21.30.Cb, 25.40.QaThreshold meson production reactions are characterized by large momentum transfer 2370 MeV͞c for p 1 p ! p 1 1 d 2 and dominant s wave in the exit channel with strong overlap at short distance. Both favor heavy meson exchange. Recently, this reaction close to threshold has again attracted theoretical interest. Horowitz [1] claims that the s-wave production should be increased by heavy meson exchange in addition to pion rescattering only. The need for such an additional cross section results from the use of a modern value of the p-NN coupling constant which reduces the fraction of the cross section due to the pion rescattering. His work is along similar paths as for p 1 p ! p 1 p 1 p 0 [2,3]. In contrast, Niskanen [4] claims that inclusion of the D isobar will produce a larger s-wave cross section. However, these findings are not based on data for the reaction of interest but on data from n 1 p ! p 0 1 d [5] and from time reversed p 1 1 d ! 2p [6]. Moreover, inconsistencies were recently found between these two reactions at small pion momenta [5]. As the Coulomb force does not affect the first reaction either in the entrance or in the exit channel, the data from the second reaction were corrected for some Coulomb effects. The validity of these correction procedures is questionable [5]. Usually the data were expressed in terms of the Gell-Mann and Watson model [7] s͑p 1 p°! p 1 1 d͒ Xwhich was derived from barrier penetration for the reversed reaction. In Eq. (1) h p p ͞m p and p p denotes the pion momentum in the center of mass system and ᐉ its angular momentum. The charged and neutral particle induced reactions yield a 0 0.24 and 0.184 mb, respectively. A part of this discrepancy was cured by new data [8] for p 1 1 d ! 2p in the range 0.215 # h # 0.518. However, if we fit the existing world data body (published after 1967) of charged particle reactions including the data of Ref.[8] with Eq. (1) for h # 0.8, a value of a 0 0.22 mb is obtained. In this analysis all data (including the ones of Rose [6]) were corrected for Coulomb effects by commonly applying Reitan's results [9]. A part of the discrepancy may result from the fact that the momenta ranges of the two data sets are different. The neutron induced reactions cover only the pion momentum range up to h 0.32 which is dominated by s-wave production while the other data are mostly dominated by p-wave contributions. The aim of the present study is, therefore, to measure cro...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.