Charmed baryon decays observed in e/sup +/e/sup -/ annihilation at SPEAR
Various weak decays of the charmed baryon ..lambda../sub c/ are observed in the Mark II detector at the SLAC e/sup +/e/sup -/ storage ring SPEAR. Hadronic decays ..lambda../sub c//sup +/ ..-->.. pK/sup -/..pi../sup +/ and ..lambda../sub c//sup +/ ..-->.. pK/sub s//sup 0/ and their charge conjugates are observed as peaks in invariant mass spectra at m(..lambda../sub c/) = (2286 +/- 6) MeV/c/sup 2/. An estimate of the charmed baryon production cross section, sigma(..lambda../sub c/) + sigma(..lambda..'/sub c/ = (1.7 +/- 0.4)nb, derived from Mark II measurements of the inclusive baryon cross sections R/sub p/ and R/sub ..lambda../ as functions of center-of-mass energy, is used to calculate branching ratios for these hadronic decays: BR (..lambda../sub c//sup +/ ..-->.. pK/sup -/..pi../sup +/) = (2.0 +/- 0.8)%; BR (..lambda../sub c//sup +/ ..-->.. pK/sub s//sup 0/)/BR (..lambda../sub c//sup +/ ..-->.. pK/sup -/..pi../sup +/) = (36 +/- 16)%. An attempt is also made to observe higher mass charmed baryons by reconstructing cascade decays ..sigma../sub c/ ..-->.. ..lambda../sub c/..pi... Evidence for the observation of semileptonic decays of the charmed baryon is presented. Direct electrons are observed in events containing antiprotons, lambdas and antilambdas. The number of electrons per baryon event, after background subtraction and efficiency correction, is used, together with an estimate of the charmed baryon content of proton and lambda events, to calculate inclusive and semi-inclusive semileptonic branching ratios of the ..lambda../sub c/: BR (..lambda../sub c//sup +/ ..-->.. e/sup +/X) = (4.5 +/- 1.8)%; BR (..lambda../sub c//sup +/ ..-->.. pe/sup +/X) = (1.9 +/- 0.8)%; BR (..lambda../sub c//sup +/ ..-->.. ..lambda../sup 0/e/sup +/X) = (1.2 +/- 0.6)%. The inclusive semileptonic branching ratio, combined with a theoretical calculation of the total semileptonic width, implies a lifetime tau(..lambda../sub c/) = (2.4 +/- 1.1) 10/sup -13/ sec, in good agreement with recent direct measurements.
- Research Organization:
- California Univ., Berkeley (USA)
- OSTI ID:
- 5210926
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ELECTRON-POSITRON INTERACTIONS
PARTICLE PRODUCTION
LAMBDA-2250 RESONANCES
HADRONIC PARTICLE DECAY
SEMILEPTONIC DECAY
BRANCHING RATIO
CROSS SECTIONS
EXPERIMENTAL DATA
KAONS
LAMBDA-1405 RESONANCES
LIFETIME
PARTICLE WIDTHS
PIONS PLUS
POSITRONS
PROTONS
REST MASS
SPEAR
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
BARYON RESONANCES
BARYONS
BOSONS
CHARM PARTICLES
CHARMED BARYON RESONANCES
DATA
DECAY
ELEMENTARY PARTICLES
FERMIONS
HADRONS
INFORMATION
INTERACTIONS
LEPTON-LEPTON INTERACTIONS
LEPTONS
MASS
MESONS
NUCLEONS
NUMERICAL DATA
PARTICLE DECAY
PARTICLE INTERACTIONS
PARTICLE PROPERTIES
PIONS
POSTULATED PARTICLES
PSEUDOSCALAR MESONS
RESONANCE PARTICLES
STORAGE RINGS
STRANGE PARTICLES
WEAK PARTICLE DECAY
Y RESONANCES
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645102 - High Energy Physics- Particle Interactions & Properties-Experimental- Weak Interactions & Properties
645101 - High Energy Physics- Particle Interactions & Properties-Experimental- Electromagnetic Interactions & Properties