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Advanced Kinematic Fitting for K Decay Efficiency and Vertex Measurement

This study focuses on the advanced techniques for selecting K decay events using specific tagging and clustering criteria. By employing a partial kinematic fit that incorporates two clusters per event, we aim to accurately measure crucial parameters such as K momentum and decay vertex. Despite the complexity of fitting with numerous variables and constraints, our methodology emphasizes the importance of clean sample selection and aims to improve resolution for charged pion momentum and vertex accuracy. The analysis presents challenges but promises significant insight into K decay processes.

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Advanced Kinematic Fitting for K Decay Efficiency and Vertex Measurement

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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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