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Determination of K vertex efficiency using a kinematical fit

Determination of K vertex efficiency using a kinematical fit. F. Ambrosino, P. de Simone, P. Massarotti , V. Patera. Why a kinematical fit Fit performances: resolutions K decay vertex efficiencies. K charged meeting - 2 7 april 2004 P. Massarotti. Motivations for a kinematical fit.

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Determination of K vertex efficiency using a kinematical fit

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  1. Determination of K vertex efficiency using a kinematical fit F. Ambrosino, P. de Simone, P. Massarotti, V. Patera • Why a kinematical fit • Fit performances: resolutions • K decay vertex efficiencies K charged meeting - 27 april 2004 P. Massarotti

  2. Motivations for a kinematical fit The main aim is to improve the resolution of the neutral vertex position and the secondary charged track momentum (before actually seeing it !!), in order to have detailed vertex efficiencies plots. Other byproducts: • Improve 2 body/3 body separation • Possibly improve K momentum resolution • Improve photons timing resolution

  3. Fit strategy 11 input parameters: • E, x, y, z, t for 2 photon candidates • Delta (see next slide) 4 constraints: • abs( t - | xclu - xv |/c - TOFK) = t0 (2) • Mgg = Mp0 • Angle between K and p0 vs p0 energy from 2 body decay

  4. Fit procedure : definition of delta L.H. L.H. L.H. F.H. F.H. F.H. Vertex Len K Len track = len K – len track

  5. second gaussian sx sy  1.5 cm sz 1. cm third gaussian sx sy  9.5 cm sz 5.5 cm first gaussian sx sy  sz  3.5 mm Resolution on vertex position Xrec - Xmc (cm)

  6. second gaussian spx  spy  3. MeV/c spz  4. MeV/c first gaussian spx  spy  spz  1.5 MeV/c third gaussian spx  spy  15.5 MeV/c Resolution on Kaon momentum Pxrec - Pxmc (MeV/c)

  7. first gaussian spx  spy  spz  2.5 MeV/c second gaussian spx  spy  spz  7. MeV/c third gaussian spx  spy  spz  25.5 MeV/c Resolution on son momentum Pxrec - Pxmc (MeV/c)

  8. e vertex e vertex Vertex efficiency as a function of K decay length L kaon (cm) L kaon (cm)

  9. e vertex e vertex Vertex efficiency as a function of son momentum Pmod (MeV/c) Pmod (MeV/c) • Kfit selection

  10. •Looking for a neutral vertex using son track •Looking for a neutral vertex using K tag Informations Kaon tracking efficiency Ep,xp,tp Eg,tg,xg p± xK pK lK Kmn tag tm t0 pK p0 Eg,tg,xg

  11. e tracking e tracking tracking efficiency as a function of K decay length L kaon (cm) L kaon (cm)

  12. e tracking e tracking Using the ‘or’ condition : L kaon (cm) L kaon (cm)

  13. e decay Decay efficiency using K tag informations Working on progress L kaon (cm)

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