We report on the first observation of the beauty baryon LAMBDA(b) in an exclusive decay channel at the CERN ppBAR collider. Using 4.7 pb-1 of muon data collected in the 1988/89 collider runs we reconstruct 16 +/- 5 LAMBDA(b)'s in the decay mode LAMBA(b) --> J/psi-LAMBDA above a background of 9 +/- 1 events, corresponding to a significance of about five standard deviations. We measure the LAMBDA(b) mass to be m(LAMBDA(b)) = 5640 +/- 50 +/- 30 MeV/c2. Using the beauty cross-section measured by UA1 we deduce for the product of the production fraction and branching ratio f(LAMBDA(b)) Br(LAMBDA(b) --> J/psi-LAMBDA) = (1.8 +/- 1.0) X 10(-3). Our sample contains a three-muon event in which the beauty particle opposite to the LAMBDA(b)BAR is tagged by the third muon. We also observe an indication of a signal in the decay channel B0 --> J/psi-K0* with a significance of three standard deviations.

1ST OBSERVATION OF THE BEAUTY BARYON-LAMBDA-B IN THE DECAY CHANNEL LAMBDA-B->J/PSI-LAMBDA AT THE CERN PROTON-ANTIPROTON COLLIDER

CAVANNA, FLAVIO;
1991-01-01

Abstract

We report on the first observation of the beauty baryon LAMBDA(b) in an exclusive decay channel at the CERN ppBAR collider. Using 4.7 pb-1 of muon data collected in the 1988/89 collider runs we reconstruct 16 +/- 5 LAMBDA(b)'s in the decay mode LAMBA(b) --> J/psi-LAMBDA above a background of 9 +/- 1 events, corresponding to a significance of about five standard deviations. We measure the LAMBDA(b) mass to be m(LAMBDA(b)) = 5640 +/- 50 +/- 30 MeV/c2. Using the beauty cross-section measured by UA1 we deduce for the product of the production fraction and branching ratio f(LAMBDA(b)) Br(LAMBDA(b) --> J/psi-LAMBDA) = (1.8 +/- 1.0) X 10(-3). Our sample contains a three-muon event in which the beauty particle opposite to the LAMBDA(b)BAR is tagged by the third muon. We also observe an indication of a signal in the decay channel B0 --> J/psi-K0* with a significance of three standard deviations.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11697/801
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