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Area of Science:

  • Particle Physics
  • High-Energy Physics
  • Hadron Spectroscopy

Background:

  • The Lambda_c+ (car{u}) charmed baryon is a key subject in studying the weak interaction of heavy quarks.
  • Precise measurements of its semileptonic decays are crucial for testing theoretical models and understanding quark dynamics.
  • Previous determinations of the Lambda_c+ -> Lambda e+ nu_e branching fraction relied on indirect methods, limiting precision.

Purpose of the Study:

  • To report the first direct measurement of the absolute branching fraction for the decay Lambda_c+ -> Lambda e+ nu_e.
  • To provide a benchmark value for other Lambda_c+ semileptonic decay channels.
  • To offer a stringent test for theoretical models describing heavy baryon decays.

Main Methods:

  • Analysis of 567 pb^-1 of e+e- annihilation data collected at sqrt(s) = 4.599 GeV using the BESIII detector.
  • The collision energy was chosen to be just above the Lambda_c+ Lambda_c- pair production threshold.
  • Determination of the branching fraction B(Lambda_c+ -> Lambda e+ nu_e) through direct observation and reconstruction of the decay products.

Main Results:

  • The absolute branching fraction for Lambda_c+ -> Lambda e+ nu_e was measured to be [3.63 +/- 0.38 (stat) +/- 0.20 (syst)]%.
  • This result represents a significant improvement in precision compared to previous indirect determinations.
  • The measured value provides a crucial data point for theoretical calculations and comparisons.

Conclusions:

  • The precise measurement of the Lambda_c+ -> Lambda e+ nu_e branching fraction is a significant advancement in the study of charmed baryon decays.
  • This result serves as a benchmark for other semileptonic Lambda_c+ decays and offers a stringent test for theoretical models.
  • The findings from BESIII enhance our understanding of weak interactions involving heavy quarks.