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Recent KLOE results on kaon branching ratios

Speaker:  Patrizia De Simone


 
1) The measurement of the absolute BR of of the K+- -> 3pi(gamma) decay completes the KLOE program of precise and fully inclusive kaon dominant BR's measurements. The most recent result, BR(K+- --> pi+- pi+ pi- = (5.56 +- 0.20)%) (Chiang et al.), dates back to more than 30 years ago. We use as normalization sample the tags given by K->munu decays. The track of the tagged kaon is backward extrapolated to the interacion point, then the kinematics of the decay phi -> K+ K-, gives us the possibility to define the path of the signal kaon (direction and momentum). The decay products of the kaons have a very low momentum, less than 200 MeV/c, and curl up in the KLOE magnetic field (0.52 T). To optimize the quality of the track reconstruction we select kaons decaying before the Drift Chamber Inner Wall (inner radius(DC) = 25 cm), so that only their decay products cross the DC (three tracks instead of four). We require at least two reconstructed tracks (pion candidates) and we count the K>3pi(gamma) decays from the missing mass spectrum. The preliminary KLOE result on the BR will be presented.

2) The Ks --> 3pi0 decay is a pure CP violating process which, assuming CPT invariance, allows direct CP violation to be investigated. This decay has not been observed so far, and the best upper limit on the branching ratio 
BR(KS --> 3pi0)< 1.2 10-7 is two orders of magnitude larger than predictions based on the Standard Model. We present the search for the Ks --> 3pi0 decay performed with the KLOE detector at the DAFNE Phi-factory of the INFN Frascati Laboratory improving the present upper limit by a factor about 5. We describe the experimental techniques used in the background rejection and signal events selection. We also discuss briefly the perspectives for a new measurement using the KLOE-2 apparatus equipped with a new Inner Tracker and calorimeters at low
theta angle.
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Kaon13 Conference,
Apr 30, 2013, 6:56 AM
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