High-precision measurement of the proton's atomic mass (1706.06780v1)

Abstract: We report on the precise measurement of the atomic mass of a single proton with a purpose-built Penning-trap system. With a precision of 32 parts-per-trillion our result not only improves on the current CODATA literature value by a factor of three, but also disagrees with it at a level of about 3 standard deviations.

High-Precision Measurement of the Proton's Atomic Mass

The paper, authored by Heiße et al., presents a detailed account of the high-precision measurement of the atomic mass of a single proton using a Penning-trap system. This research offers a significant enhancement in the precision of the proton mass, achieving a value at 32 parts-per-trillion (ppt), which improves upon the existing CODATA literature by a factor of three. This newly measured value of the proton mass not only provides a more precise estimation but also presents a discrepancy of about three standard deviations from the current CODATA value, thereby challenging the accepted norms.

The methodology leveraged a purpose-built cryogenic Penning-trap setup for the measurement, designed to mitigate systematic errors and enhance precision. The fundamental technique involves comparing cyclotron frequencies of the proton and a highly charged $^{12}\text{C}^{6+}$ ion, capitalizing on the precise measurement capabilities of the specific charge-to-mass ratios in a controlled magnetic field environment. The paper meticulously addresses various potential sources of error, including finite kinetic energy of the ions, image charge effects, and alignment of magnetic trapping fields.

One of the primary challenges addressed was the disparity in the charge-to-mass ratio between the proton and the $^{12}\text{C}^{6+}$ ion, which required fine-tuned adjustments in the trapping configuration to ensure that both ions were measured under identical conditions. Two independent tank circuits were employed, allowing precise control over the axial frequencies and enabling identical electrostatic field configurations for both measurements.

The authors provide a comprehensive account of the systematic uncertainties involved in the measurement, offering a detailed analysis of contributions from magnetic field inhomogeneities, ion kinetic energy, and relativistic mass effects. The reported systematic uncertainty stands at 2.89 parts-per-trillion, and combined with statistical uncertainties, underpins the robustness of the final measurement outcome.

The corrected cyclotron frequency ratio, $R_{\text{final}}$, was determined as $0.503\,776\,367\,662\,4$ with statistical and systematic precisions reported separately. From these frequencies, the mass of the proton in atomic mass units was computed as $1.007\,276\,466\,583(15)(29)~\text{u}$.

The implications of these findings are significant for the broader domain of precision atomic physics. With this enhanced precision, the proton-electron mass ratio is determined with greater accuracy, impacting calculations across atomic and subatomic physics contexts. This measurement contributes valuable data toward resolving discrepancies such as the $^3\text{He}$ mass puzzle, highlighting the scope for further investigation and verification in related measurements.

Future developments outlined by the authors include planned advancements to reduce systematic limitations. These include improvements in magnetic field homogeneity and the leveraging of simultaneous phase-sensitive measurements to further refine precision. Such enhancements hold promise for cascading benefits across multiple fields, including molecular mass spectrometry and fundamental particle research.

In conclusion, this high-precision measurement represents a structured and meticulous approach to proton mass determination. The discordance with established values invites further exploration and potential recalibration of related physical constants, marking a noteworthy development in the field of precision measurement. This work sets a cornerstone for subsequent investigations aiming to achieve even finer accuracies in the essentials of atomic mass measurements.