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K Decay efficiency

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

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  1. 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pp0 tagged decay are selected by these cuts

  2. 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

  3. 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

  4. Charged pion momentum resolution

  5. Resolution on K vertex

  6. Resolution on the Charged cluster Position on ecal

  7. 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

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