In a study of proton--antiproton collisions at a center of mass energy of 
1.8 TeV, we have observed the Lambda_b --> J/psi Lambda^0 decay and measured 
the Lambda_b mass and its production cross section times branching fraction 
relative to that of the B^0 --> J/psi K_s decay. In addition, we have 
established a limit for the production cross section times branching fraction 
for the decay Lambda_b --> J/psi Lambda(1520). Our results are:

M(Lambda_b) = 5621 +/- 4 (stat.) +/- 3 (sys.) MeV/c^2

{sigma(Lambda_b) * Br(Lambda_b --> J/psi Lambda^0)}/
{sigma(B^0) * Br(B^0 --> J/psi K_S) = 0.27 +/- 0.12 (stat.) +/- 0.05 (sys.)

(sigma(Lambda_b)/sigma(B^0)) * Br(Lambda_b --> J/psi Lambda(1520)) < 
1.38 * 10^{-4}



Posted to /cdf/pub/thesis/cdf4636_Lambda_b_thesis.ps
    http://www-cdf.fnal.gov/thesis/cdf4636_Lambda_b_thesis.ps

Posted by titov@FNALD