^{208}Pb Nuclear Charge Radius Revisited: Closing the Fine-Structure-Anomaly Gap

Area of Science:

• Nuclear Physics
• Atomic Physics
• Quantum Electrodynamics

Background:

• The nuclear charge radius of heavy nuclei is crucial for understanding nuclear structure.
• Previous measurements for lead-208 using muonic spectroscopy had associated anomalies.

Purpose of the Study:

• To reevaluate the root-mean-square nuclear charge radius of doubly magic ^{208}Pb.
• To reduce the long-standing muonic fine-structure anomaly and improve data analysis.
• To provide a more accurate and reliable value for the nuclear charge radius.

Main Methods:

• Utilized muonic spectroscopy measurements for ^{208}Pb.
• Integrated rigorous theoretical quantum electrodynamics calculations.
• Employed state-of-the-art numerical methods and systematic reanalysis of uncertainties.

Main Results:

• Reduced the muonic fine-structure anomaly by a factor of 20.
• Obtained a Fermi distribution charge radius of 5.5062(5) fm.
• The new value is 3 standard deviations larger than commonly used compilation data, suggesting underestimation.

Conclusions:

• The reevaluated ^{208}Pb rms charge radius is 5.5062(17) fm with reduced model dependence.
• This work establishes an improved benchmark for charge radius extraction in heavy nuclei.
• Paves the way for systematic reevaluations of nuclear charge radii across the nuclear chart.