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B.E.A.CH. Vancouver, june 24-28, 2002
SERGIO P. RATTI INFN and Dipartimento di Fisica
Nucleare e Teorica PAVIA (for the FOCUS
Collaboration)
NEW RESULTS ON CHARMED BARYONS IN FOCUS
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Outline of the talk
- Lc production asymmetry (no) - Lc decays into
Ss - Lc high multiplicity decays -
double-charmed baryons - Conclusions
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Lc signals
INVESTIGATE PRODUCTION ASYMMETREY
large and clean samples make precision studies
possible
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preliminary
R(E691) 0.79 .17 R(E687) 0.93 .14 RFOCUS
0.725.021.021
A(E691) 0.110 .089 A(E687) 0.035
.076 AFOCUS 0.155.014.014
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Lc into Spp, SKp, SKK
The most aboundant final states containing the S
hyperons are S p p and SK-K and the Cabibbo
Suppressed channels S Kp
We measured the relative B.R. G(S-p
p)/G(Spp-) 0.422 ? .033
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or
2 body dominant
without FSI the same
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95 cl
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Using Spp- as refence channel we minimize
systematic errors
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or
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Conclusions - 1
FOCUS results compared to other experiments
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• CLS gt 5
• P(Lc)gt 50 GeV/c
• Picon on 4 ps gt -8
• iso2 lt 0.1
• Out of Target gt -2

Selection criteria
1 S event on PDG
N. Events 18.6 5.8
1st evidence
Mass(2.281.004) MeV
PRELIMINARY
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First attempt to reconstruct a decay containing
a neutron
5107 S-?np- candidates
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Preliminary results
1st evidence
Y24 6 s11 3 S/n5.9
M( n K-p-ppp )
B.R. might come soon Kind of nice to see the
decay!
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Wc CHARM BARYON CLEO
Y40.4 ? 9.0
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Woc CHARM BARYON FOCUS
Y6414
Y389
Y237
M2697.52.2
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It was year 2000
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The X, general topology
We searched for cc baryons in year 2000

• select charm candidates (Do,D,Lc) in golden
  modes (Kp, Kpp, kppp and pKp)
• combine either Ds or Lc momentum vectors to
  meet additional tracks
• cc candidate momentum vector to seed primary
  vertex
• CLgt1 for all 3 vertices l/sgt0 Cherenkov cut
  K,p,p.

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SAMPLES
ABOUT 1.2 MILLION EVENTS TO BEGIN WITH
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14 Xcc(Do,X) decays and 7 Xcc(LcX) decays
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Combined distribution
Selex areas in green
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Conclusions 2
No evidence of Xcc. May be sprod in SELEX is 40
to 100 times our sprod ?
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Final conclusions
With 20,000 Lc 1.2 million D,o, no evidence
for production of neither Xcc nor Xcc double
charm baryons seen by SELEX