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K Decay efficiency. Event selection: tag on one hemisphere with identified clusters 3 cluster with: E>50 MeV T0 + 6 ns < t <T0 + 35 ns 85% of the K pp 0 tagged decay are selected by these cuts. Partial kinematic fit.
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K Decay efficiency Event selection: • tag on one hemisphere with identified clusters • 3 cluster with: E>50 MeV T0 + 6 ns < t <T0 + 35 ns 85% of the Kpp0 tagged decay are selected by these cuts
Partial kinematic fit Starting from the Tag I fit the p0 ( using 2 out of the 3 cluster I select) and K section to obtain p momentum, tof and Ecal impact point: compare with info of the 3rd cluster… Ep,xp,tp • The goals are: • Find the K decay vertex • Measure the p momentum • Measure the K momentum • Get rid of 3 body decay p± xK pK lK Kmn tag Eg,tg,xg tm t0 pK p0 The fit is almos simple…. Eg,tg,xg
Resolution tested of double tagged events with associated clusters The resolutions obtained mildly depend from the fit 2 !!!!!! Difficult to select clean sample Resolution on K momentum
Charged pion momentum resolution
Resolution on K vertex
Resolution on the Charged cluster Position on ecal
It’s a long way…. • The full event must be fit kinematically.. But • The fit is quite complex (15 variables and 6 constraint) • The fit get less stable and takes a lot of CPU • On the other hand much better resolution should be achieved • ………. Let’s go on