Evidence for B+-->J/psip(-)Lambda; and search for B0-->J/psip(-)p.

Area of Science:

• Particle Physics
• High-Energy Physics
• Experimental Physics

Background:

• The Standard Model of particle physics describes fundamental particles and forces.
• Rare B meson decays provide sensitive probes for new physics beyond the Standard Model.
• Previous searches for B+ --> J/psi phi(-) Lambda and B0 --> J/psi phi(-) p have yielded limited results.

Purpose of the Study:

• To search for the rare decays B+ --> J/psi phi(-) Lambda and B0 --> J/psi phi(-) p.
• To set limits on the branching fractions of these decays using BABAR data.
• To constrain theoretical models and search for evidence of new physics phenomena.

Main Methods:

• Analysis of a data set of approximately 88.9 million Upsilon(4S) decays collected by the BABAR experiment.
• Reconstruction of B+ and B0 meson candidates decaying into J/psi, phi(-), Lambda, and p.
• Statistical analysis to determine the significance of observed candidates and set upper limits on branching fractions.

Main Results:

• Four candidates for the decay B+ --> J/psi phi(-) Lambda were observed, with an expected background of 0.21 events.
• A branching fraction of (12(+9)(-6)) x 10^-6 was measured, with a 90% confidence level upper limit of 26 x 10^-6.
• One candidate for the decay B0 --> J/psi phi(-) p was observed, with an expected background of 0.64 events, yielding a 90% confidence level upper limit of 1.9 x 10^-6.

Conclusions:

• The study sets stringent upper limits on the branching fractions for B+ --> J/psi phi(-) Lambda and B0 --> J/psi phi(-) p decays.
• These results contribute to the understanding of rare B meson decays and provide constraints for theoretical predictions.
• The findings help to limit the parameter space for potential new physics contributions to these processes.