Search for Feebly Interacting Particles in B Decays with Missing Energy at Belle

Area of Science:

• Particle Physics
• High Energy Physics
• Beyond Standard Model Physics

Background:

• Searches for new particles are crucial for understanding fundamental physics.
• Invisible particles could explain dark matter and other phenomena.
• B meson decays offer a sensitive probe for new physics.

Purpose of the Study:

• To search for an invisible hidden-sector particle, X_{inv}.
• To set limits on the branching fractions of B meson decays involving X_{inv}.
• To explore new regions of parameter space for new physics models.

Main Methods:

• Analysis of e^{+}e^{-} collision data from the Belle detector.
• Searched for X_{inv} produced in B^{0}→D[over ¯]^{0}X_{inv} and B^{±}→hX_{inv} decays (h=π^{±}, K^{±}, D_{s}^{±}, p^{±}).
• Set 90% confidence level upper limits on branching fractions and related parameters.

Main Results:

• No significant signal for X_{inv} was observed.
• Established upper limits on B(B→hX_{inv}) between 10^{-4} and 10^{-6}.
• Set limits on B(B→hX)×B(X→γγ) for various lifetimes of X.

Conclusions:

• The study provides the most stringent exclusion limits to date on the branching fractions for the searched channels.
• These results exclude previously unexplored parameter space relevant to several new physics models.
• This search contributes to the ongoing quest for physics beyond the Standard Model.