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Status of KLOE real data analysis by the AMADEUS group
Oton Vázquez Doce, 4 Maggio 2007
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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
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K- “stopped” Monte Carlo
Nuclear Interactions: K- + N
0.1% stoppedinside the DC's | z | < 140 cm 40 < ρ < 150 cm
ρ vs z (cm)
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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
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Strategy of search
K- + 4He -> n + (K-
ppn) n ~ 510 MeV/c
K- + 4He -> p + (K-
pnn) p ~ 550 MeV/c
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Signature for ppnK- Decay
decay: + p + n
p + -
4He + K- ppnK- + n
n
n
p p
-
-
•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)
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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
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Protons identification•Implementation of cuts to remove K- 3
body decay background ( K- π-π-π+)
E (MeV)
charge * p (MeV/c)
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Protons identification•Implementation of cuts to remove K- 3
body decay background ( K- π-π-π+)
charge * p (MeV/c)
E (MeV)
proton p (MeV/c)pion p (MeV/c)
Lambda inv. Mass (Mev/c2) Lambda p (Mev/c)
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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 wiresADC counts
p (MeV/c)
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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 wiresADC counts
p (MeV/c)
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Final Selection:pions protons
p (MeV/c) p (MeV/c)
p (MeV/c) p (MeV/c)ADCADC
ADC ADC
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Final Selection:
Λ invariantMass (MeV/c2)
θ (deg) proton-pion
pΛ (MeV/c)
Mpπ (MeV/c2)
σ~0.5 MeV/c2
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Final Selection:
Λ invariantMass (MeV/c2)
θ (deg) proton-pion
pΛ (MeV/c)
Cut in momentum in the Λ c.m.s.
91 < pp,π- < 111 (MeV/c)
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Final Selection:
Λ invariantMass (MeV/c2)
θ (deg) proton-pion
pΛ (MeV/c)
Cut in Λ invariant mass
1114 < MΛ < 1115 (MeV/c)
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Λ vertices
ρ vs Z (cm)
Z (cm)ρ (cm)
x vs y (cm)
ρ (cm)
Interactions in the DC entrance wall (Carbon)
8500 events
Interactions in 4He
1500 events
search for Σ(1385) Λ π
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Search for Λ “partners”•Particles in the same vertex of the p and
π-
p (MeV/c)
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Search for Λ “partners”
?
π
p
Λ
ADC
charge * p (MeV/c)
# negative tracks # positive tracks
ADC
charge * p (MeV/c)
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Search for Λ “partners”
?
π
p
Λ
ADC
charge * p (MeV/c)
# negative tracks # positive tracks
ADC
charge * p (MeV/c)
Invariant mass Λ d (MeV/c2)
angle Λ d (deg)
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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