Sub-part-per-trillion test of the Standard Model with atomic hydrogen

Area of Science:

• Fundamental physics
• Quantum electrodynamics
• Atomic spectroscopy

Background:

• Quantum electrodynamics (QED) is a cornerstone of the Standard Model (SM), enabling precise predictions of atomic energy levels.
• Discrepancies in proton charge radius (r_p) values from atomic hydrogen spectroscopy hinder rigorous testing of QED.
• Existing atomic hydrogen measurements of r_p conflict with more precise muonic hydrogen data.

Purpose of the Study:

• To perform a high-precision measurement of the 2S-6P transition in atomic hydrogen.
• To resolve discrepancies in the proton charge radius (r_p) values.
• To enable stringent tests of quantum electrodynamics (QED) and the Standard Model (SM).

Main Methods:

• High-precision laser spectroscopy of the 2S-6P transition in atomic hydrogen.
• Utilizing advanced spectroscopic techniques to achieve unprecedented accuracy.
• Extracting the proton charge radius from the measured transition frequency.

Main Results:

• The measured 2S-6P transition frequency is 730,690,248,610.79(48) kHz.
• A proton charge radius of r_p = 0.8406(15) fm was determined, significantly more precise than previous atomic hydrogen measurements.
• The result aligns perfectly with the value obtained from muonic hydrogen spectroscopy.

Conclusions:

• The new atomic hydrogen measurement resolves discrepancies in the proton charge radius.
• This work provides the most precise test of bound-state QED corrections to date.
• The findings strongly support the validity of the Standard Model and QED at high precision levels.