Status of KLOE real data analysis by the AMADEUS group

Oton Vázquez Doce, 4 Maggio 2007

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

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)

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

Strategy of search

K- + 4He -> n + (K-

ppn) n ~ 510 MeV/c

K- + 4He -> p + (K-

pnn) p ~ 550 MeV/c

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)

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

Protons identification•Implementation of cuts to remove K- 3

body decay background ( K- π-π-π+)

E (MeV)

charge * p (MeV/c)

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)

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)

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)

Final Selection:pions protons

p (MeV/c) p (MeV/c)

p (MeV/c) p (MeV/c)ADCADC

ADC ADC

Final Selection:

Λ invariantMass (MeV/c2)

θ (deg) proton-pion

pΛ (MeV/c)

Mpπ (MeV/c2)

σ~0.5 MeV/c2

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)

Final Selection:

Λ invariantMass (MeV/c2)

θ (deg) proton-pion

pΛ (MeV/c)

Cut in Λ invariant mass

1114 < MΛ < 1115 (MeV/c)

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

Search for Λ “partners”•Particles in the same vertex of the p and

π-

p (MeV/c)

Search for Λ “partners”

?

π

p

Λ

ADC

charge * p (MeV/c)

# negative tracks # positive tracks

ADC

charge * p (MeV/c)

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)

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