Charmed baryon decays observed in e/sup +/e/sup -/ annihilation at SPEAR

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1982

OSTI ID:5210926

Vella, E N

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
• Country of Publication: United States
• Language: English

Related Subjects

645101 -- High Energy Physics-- Particle Interactions & Properties-Experimental-- Electromagnetic Interactions & Properties
645102 -- High Energy Physics-- Particle Interactions & Properties-Experimental-- Weak Interactions & Properties
645103* -- High Energy Physics-- Particle Interactions & Properties-Experimental-- Strong Interactions & Baryon & Meson Properties
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
BARYON RESONANCES
BARYONS
BOSONS
BRANCHING RATIO
CHARM PARTICLES
CHARMED BARYON RESONANCES
CROSS SECTIONS
DATA
DECAY
ELECTRON-POSITRON INTERACTIONS
ELEMENTARY PARTICLES
EXPERIMENTAL DATA
FERMIONS
HADRONIC PARTICLE DECAY
HADRONS
INFORMATION
INTERACTIONS
KAONS
LAMBDA-1405 RESONANCES
LAMBDA-2250 RESONANCES
LEPTON-LEPTON INTERACTIONS
LEPTONS
LIFETIME
MASS
MESONS
NUCLEONS
NUMERICAL DATA
PARTICLE DECAY
PARTICLE INTERACTIONS
PARTICLE PRODUCTION
PARTICLE PROPERTIES
PARTICLE WIDTHS
PIONS
PIONS PLUS
POSITRONS
POSTULATED PARTICLES
PROTONS
PSEUDOSCALAR MESONS
RESONANCE PARTICLES
REST MASS
SEMILEPTONIC DECAY
SPEAR
STORAGE RINGS
STRANGE PARTICLES
WEAK PARTICLE DECAY
Y RESONANCES