Search for Long-Lived Particles in e+ e- Collisions

Area of Science:

• Particle Physics
• High-Energy Physics
• Experimental Physics

Background:

• Searches for new neutral, long-lived particles are crucial for extending the Standard Model.
• Understanding particle decays and production mechanisms provides insights into fundamental forces.

Purpose of the Study:

• To search for a neutral, long-lived particle (L) produced in electron-positron collisions.
• To set upper limits on the production cross section, branching fractions, and efficiency of the particle L.
• To constrain models beyond the Standard Model by analyzing decay properties.

Main Methods:

• Analysis of a large electron-positron collision dataset (489.1 fb^-1) collected by the BABAR detector.
• Targeting data collected at the Upsilon (4S), (3S), and (2S) resonances and just below the Upsilon (4S).
• Fitting the two-track mass distribution to identify potential signal peaks from the decay of particle L.

Main Results:

• No significant signal for the neutral, long-lived particle (L) was observed.
• 90% confidence level upper limits were set on the product of production cross section, branching fraction, and reconstruction efficiency for six decay modes.
• Upper limits were also placed on the branching fraction B(B→XsL).

Conclusions:

• The absence of a signal places constraints on the existence and properties of such a particle.
• The derived upper limits are applicable to various production models, providing valuable input for theoretical physics.
• This study contributes to the ongoing search for new physics beyond the Standard Model.