Some Rare Decays in Interactions ofπandKMesons with Carbon and Iron

Abstract

An experiment on the leptonic decay of vector mesons produced by K~-and ir~~-meson bombardment of carbon and iron has previously been reported. 1 ' 2 In this Letter we report some other interesting features of the data, namely, (1) a value for the cp branching ratio;(2) an upper limit for the process ?]-* JLL+JLL~";(3) upper limits for 77-77 0 JU, + JU~ and w-+ ir°ii + i±~; and (4) a comparison of the decays p°-~ JLL + JLL~ and p°-~e + e-. In Ref. 2 we reported a peak containing 12 events in the invariant-mass spectrum of muon pairs produced by K~~ mesons, which we attributed to leptonic decay of cp mesons. Unfortunately, we had, at that time, no information about cp production by K mesons. Some information is now available. 3 The cross section for Kp production of cp mesons is 56 ± 15 (ib at 5.5 GeV/c. We expect this to vary as l/p 2 as do other AS=1 cross sections. We then get 12 jUb for the production cross section of cp mesons. At 12 BeV, a cross section of 7 ±3 jub is found 4 for cp production in four-prong events by Kp interactions in a bubble chamber. Allowing for further events in the same ratio as at low energies, we also find 12 jub. In order to compare this with our cross section 2 of 33 nb for the production of lepton pairs from carbon, we need an optical model calculation. This may be done in the same way as was done for the absorption of p mesons. However, the cpN cross section is expected on the quark model 5 to be 10 jLtb which is smaller than the 30 748 jLib we used for the nucleon cross section. This is confirmed by cp photoproduction data. 6 Therefore, the absorption becomes quite small and we derive a branching ratio r -all 33X10 12~ -3

Leptonic Decays of Neutral Vector Mesons andρ−ωInterference

“…We note that while a value of, say, 9&0 would increase the predicted value of T(p -, u , this quantity has not yet been measured. A value of 0 = 0 would produce no disagreement with the present upper limits on ^(p-~ll' 11 ' 12 One must note, however, that the total cross sections for photoproduction of the p and the co appear to be in agreement with unbroken SU(3) in the diffraction region, 13 i.e., a D :or » 9:1. The agreement of the bubble-chamber data on photoproduction of p and co with the 9:1 rule and the violation of this rule in leptonic decay may be patched up by assuming that the co-nucleon cross section is larger than the p-nucleon cross section.…”

“…12 ? 14 If an experiment on p° -JU + + ju " is compared with an experiment on p° -+e + + e~, one must know the magnitude of oo production in the two experiments and the magnitude of r^"" 2 (which is not known experimentally).…”

“…14 If an experiment on p° -JU + + ju " is compared with an experiment on p° -+e + + e~, one must know the magnitude of oo production in the two experiments and the magnitude of r^"" 2 (which is not known experimentally). Alternatively, in order to have equal p-co interference effects for the muon and electron experiments, two experiments may be compared using the same incident beam and target particles at the same energy, as was done by Weinstein 14 the decay of 7r-produced p's to y-produced p's as was recently done by Wehmann et al, 12 discrepancies of up to 60% can result from the differences of the interference terms in the two experiments.…”