Observation of B+-->LambdaLambdaK+

Area of Science:

• Particle Physics
• High-Energy Physics
• Experimental Physics

Background:

• Understanding B meson decays provides insights into fundamental particle interactions.
• Charmless hyperonic B decays are rare processes that test the Standard Model.
• Previous searches for these decays have yielded limited results.

Purpose of the Study:

• To report the first observation of the charmless hyperonic B decay B+ --> Lambda Lambda K+.
• To measure the branching fraction of this decay.
• To search for the related decay B+ --> Lambda Lambda pi+ and set an upper limit.

Main Methods:

• Analysis of a 140 fb^-1 data sample collected with the Belle detector at the KEKB e+e- collider.
• Utilizing data recorded at the Upsilon(4S) resonance.
• Applying established techniques for particle identification and event reconstruction.

Main Results:

• The charmless hyperonic B decay B+ --> Lambda Lambda K+ was observed for the first time.
• The branching fraction was measured as B(B+ --> Lambda Lambda K+) = (2.91(+0.90)(-0.70) +/- 0.38) x 10^-6.
• No significant signal was found for B+ --> Lambda Lambda pi+, with a 90% confidence-level upper limit set at B(B+ --> Lambda Lambda pi+) < 2.8 x 10^-6.

Conclusions:

• The observation of B+ --> Lambda Lambda K+ provides a new channel to study B meson physics.
• The measured branching fraction can be used to constrain theoretical models.
• The upper limit on B+ --> Lambda Lambda pi+ further restricts new physics scenarios.