The K^{+}--->\pi^{+}\nu\bar{nu} Rare Decay in Two Higgs Doublet Model

The rare k+--->pi+ \nu \bar{\nu} decay is investigated in the context of type II two-Higgs-doublet model (2HDM). By using the existing experimental data of the branching ratio, restrictions on the free parameters of the model m_H, and tan\beta are obtained: tan\beta belong to the range 0.7- o.8, and m_H belong to the range 500- 700 GeV.Comment: 12 pages, latex file, 3 figures, postscript file

Backward K∗0K^{*0} production in the reaction π−p→Λ0K+π−\pi^{-}p \rightarrow \Lambda^{0}K^{+}\pi^{-} at 9 and 12 GeV/ c

The authors have analysed about 85000 fast Lambda /sup 0/ events, obtained in a fast proton triggered experiment performed at the CERN- Omega spectrometer at 9 and 12 GeV/c incident pi /sup -/ beam. Nearly 2500 Lambda /sup 0/K/sup +/ pi /sup -/ events have been isolated. They find strong production of quasi-two-body processes Lambda /sup 0/K* /sup 0/ and Sigma */sup -/K/sup +/ consistent with u-channel hyperon exchange. Results on Lambda /sup 0/ polarization, K*/sup 0/ decay parameters and differential cross sections are given for Lambda /sup 0 /K*/sup 0/(892) and Lambda /sup 0/K*/sup 0/(1430) final states. A comparison is made with the associated backward Lambda /sup 0/(1520)K* /sup 0/ production seen in the four-prong reaction pi /sup -/p to pK /sup -/K/sup +/ pi /sup -/ obtained in the same experiment. (13 refs)

Results on pi /sup -/p backward elastic scattering and search for pi /sup -/p to dp at 9 and 12 GeV/c

From an experiment done with the CERN Omega spectrometer, triggered by a fast forward proton device, results on the differential cross section d sigma /du for pi /sup -/p backward elastic scattering are presented. The d sigma /du distribution agrees with an Ae/sup BU/ law. The compilation of existing results shows a discrepancy between results but the (d sigma /du)/sub u=0/ data fit perfectly on s/sup 2 alpha 0-2/ dependence, as predicted by a single Delta /sub delta / Regge trajectory exchange. A search for the reaction pi /sup -/p to dp, with a fast forward deuteron, which can be produced by a double- baryon exchange mechanism, gives cross-section upper limits of approximately 1% of the backward elastic cross section. (10 refs)