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Status of KLOE real data analysis by the AMADEUS group

Status of KLOE real data analysis by the AMADEUS group. Oton Vázquez Doce, 4 Maggio 2007. Our firsts steps were with Monte Carlo. Production of dedicated KLOE Monte Carlo ntuples Estimation of fraction of K - stopped in the Drift Chambers volume of KLOE setup. Nuclear Interactions: K - + N.

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Status of KLOE real data analysis by the AMADEUS group

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  1. Status of KLOE real data analysis by the AMADEUS group Oton Vázquez Doce, 4 Maggio 2007

  2. Our firsts steps were withMonte Carlo... • Production of dedicated KLOE Monte Carlontuples • Estimation of fraction of K- stopped in the Drift Chambers volume of KLOE setup

  3. Nuclear Interactions: K- + N K- “stopped” Monte Carlo 0.1% stopped inside the DC's | z | < 140 cm 40 < ρ < 150 cm ρ vs z (cm)

  4. Since begginning of 2007 • February 2007 accepted to use 2005 data up to a luminosity equivalent to the 2001/2002 year (400 pb-1) • Production of KLOE real data ntuples with tag mechanisms 2BODY + DE/DX (50 pb-1 up to now) • Start analysis tunning strategy

  5. Strategy of search K- + 4He -> n + (K-ppn) n ~ 510 MeV/c K- + 4He -> p + (K-pnn) p ~ 550 MeV/c

  6. Signature for ppnK- Decay 4He + K- ppnK- + n • Many channels with Λ can be identified by their decay products: p+π- or n+π0 • Classical hadronic interactions of K- in 4He producing also Λ (69%) • P. A. Katz, et.al., Reactions of stopping K- in Helium, Phys. Rev. D1, 1267-1276, (1970) decay:  + p + n p + - n n - - p p

  7. Λp+π- search criteria: • Vertex made of two opposite charge particles inside the Drift Chamber volume • For the negative track (π-) require energy deposit in the DC wires < 95 ADC counts • For the positive track (proton) start looking for an associated cluster to in the extrapolation of the track to the calorimeter region

  8. Protons identification • Implementation of cuts to remove K- 3 body decay background ( K-π-π-π+) E (MeV) charge * p (MeV/c)

  9. Protons identification • Implementation of cuts to remove K- 3 body decay background ( K-π-π-π+) E (MeV) Lambda inv. Mass (Mev/c2) Lambda p (Mev/c) pion p (MeV/c) proton p (MeV/c) charge * p (MeV/c)

  10. Protons identification (low energy) • If no cluster associated, require: • last DC measurement for the track compatible with the particle reaching the calorimeter • Proton signature in the ADC values of DC wires ADC counts p (MeV/c)

  11. Protons identification (low energy) • If no cluster associated, require: • last DC measurement for the track compatible with the particle reaching the calorimeter • Proton signature in the ADC values of DC wires ADC counts p (MeV/c)

  12. Final Selection: pions protons ADC ADC p (MeV/c) p (MeV/c) ADC p (MeV/c) ADC p (MeV/c)

  13. Final Selection: Λ invariant Mass (MeV/c2) σ~0.5 MeV/c2 θ (deg) proton-pion pΛ (MeV/c) Mpπ(MeV/c2)

  14. Final Selection: Λ invariant Mass (MeV/c2) Cut in momentum in the Λ c.m.s. 91 < pp,π- < 111 (MeV/c) θ (deg) proton-pion pΛ (MeV/c)

  15. Final Selection: Λ invariant Mass (MeV/c2) Cut in Λ invariant mass 1114 < MΛ< 1115 (MeV/c) θ (deg) proton-pion pΛ (MeV/c)

  16. Λ vertices Interactions in the DC entrance wall (Carbon) 8500 events Interactions in 4He 1500 events ρ vs Z (cm) x vs y (cm) search for Σ(1385)  Λπ ρ (cm) ρ (cm) Z (cm)

  17. Search for Λ “partners” • Particles in the same vertex of the p and π- p (MeV/c)

  18. Search for Λ “partners” ADC • Particles “near” to the Λ vertex # negative tracks # positive tracks π p ADC ? Λ charge * p (MeV/c) charge * p (MeV/c)

  19. Search for Λ “partners” ADC • Particles “near” to the Λ vertex # negative tracks # positive tracks π p Invariant mass Λ d (MeV/c2) ADC ? Λ charge * p (MeV/c) angle Λ d (deg) charge * p (MeV/c)

  20. Next steps... • Additional checks on Λ (low momentum, vertex reconstruction, efficiencies...) • Increase statistics • Study the underlying physics of Λ (formation mechanism, deeply bound?) • Search for Λ n+π0 (started) • Strategy for neutral particle search

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