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Register a new user$phi$ and $omega$ Meson Production in pp Reactions at $p_{lab}$=3.67 GeV/c
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The exclusive production cross sections for $omega$ and $phi$ mesons have been measured in proton-proton reactions at $p_{lab}=3.67$ GeV/c. The observed $phi/omega$ cross section ratio is $(3.8pm0.2^{+1.2}_{-0.9})times 10^{-3}$. After phase space corrections, this ratio is enhanced by about an order of magnitude relative to naive predictions based upon the Okubo-Zweig-Iizuka (OZI) rule, in comparison to an enhancement by a factor $sim 3$ previously observed at higher beam momenta. The modest increase of this enhancement near the production threshold is compared to the much larger increase of the $phi/omega$ ratio observed in specific channels of $bar pp$ annihilation experiments. Furthermore, differential cross section results are also presented which indicate that although the $phi$ meson is predominantly produced from a $^3P_1$ proton-proton entrance channel, other partial waves contribute significantly to the production mechanism at this beam momentum.
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The total cross section of the reaction $ppto ppK^+K^-$ has been determined for proton--proton reactions with $p_{beam}=3.67 GeV/c$. This represents the first cross section measurement of the $pp to ppK^-K^+$ channel near threshold, and is equivalent to the inclusive $ppto ppK^-X$ cross section at this beam momentum. The cross section determined at this beam momentum is about a factor 20 lower than that for inclusive $ppto ppK^+X$ meson production at the same CM energy above the corresponding threshold. This large difference in the $K^+$ and $K^-$ meson inclusive production cross sections in proton-proton reactions is in strong contrast to cross sections measured in sub-threshold heavy ion collisions, which are similar in magnitude at the same energy per nucleon below the respective thresholds.
We report the first polarization transfer measurements for exclusive hyperon production reactions. The normal spin transfer coefficient DNN for pp -> p K+ Lambda is large and negative for forward Lambda production at a beam momentum of 3.67 GeV/c, a result qualitatively consistent with expectations for a mechanism dominated by kaon-exchange and rescattering. The sign of DNN is opposite to that observed in the fragmentation regime for inclusive Lambda production at much higher energies.
The ratio of the total exclusive production cross sections for $etaprime$ and $eta$ mesons has been measured in the $pp$ reaction at $p_{beam}=3.67$ GeV/c. The observed $etaprime/eta$ ratio is $(0.83pm{0.11}^{+0.23}_{-0.18})times 10^{-2}$ from which the exclusive $etaprime$ meson production cross section is determined to be $(1.12pm{0.15}^{+0.42}_{-0.31})mu b$. Differential cross section distributions have been measured. Their shape is consistent with isotropic $etaprime$ meson production.
The production of omega-mesons in the pp->pp omega reaction has been investigated with the COSY-ANKE spectrometer for excess energies of 60 and 92MeV by detecting the two final protons and reconstructing their missing mass. The large multipion background was subtracted using an event-by-event transformation of the proton momenta between the two energies. Differential distributions and total cross sections were obtained after careful studies of possible systematic uncertainties in the overall ANKE acceptance. The results are compared with the predictions of theoretical models. Combined with data on the phi-meson, a more refined estimate is made of the Okubo-Zweig-Iizuka rule violation in the phi/omega production ratio.
Using a relativistic effective Lagrangian at the hadronic level, near-threshold $omega$ and $phi$ meson productions in proton proton ($pp$) collisions, $p p to p p omega/phi$, are studied within the distorted wave Born approximation. Both initial and final state $pp$ interactions are included. In addition to total cross section data, both $omega$ and $phi$ angular distribution data are used to constrain further the model parameters. For the $p p to p p omega$ reaction we consider two different possibilities: with and without the inclusion of nucleon resonances. The nucleon resonances are included in a way to be consistent with the $pi^- p to omega n$ reaction. It is shown that the inclusion of nucleon resonances can describe the data better overall than without their inclusion. However, the SATURNE data in the range of excess energies $Q < 31$ MeV are still underestimated by about a factor of two. As for the $p p to p p phi$ reaction it is found that the presently limited available data from DISTO can be reproduced by four sets of values for the vector and tensor $phi NN$ coupling constants. Further measurements of the energy dependence of the total cross section near threshold energies should help to constrain better the $phi NN$ coupling constant.
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