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Fundamental Physical Constants

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Mission and objectives 

The purpose of the CODATA Task Group on Fundamental Physical Constants (TGFC) is to periodically provide the scientific and technological communities with a self-consistent set of internationally recommended values of the basic constants and conversion factors of physics and chemistry based on all relevant data available at a given point in time.

Significance

The TGFC’s commitment to producing a new least squares adjustment (LSA) of the fundamental constants on a four-year cycle incorporates all relevant data from diverse scientific interests and fields of research.   This function primarily provides the scientific and metrological communities the most consistent set of the values of the fundamental constants and conversion factors used in physics and chemistry.  Moreover, performing an analysis over a broad spectrum of experimental and theoretical information relevant to the constants has important value.  In general, such an analysis may uncover errors in theoretical calculations or experiments; it reevaluates uncertainties so that all are expressed in a consistent manner (i.e. standard uncertainties); it identifies inconsistencies among results and weaknesses in certain areas of research; it stimulates new experimental and theoretical work due to inconsistencies; and it summarizes a large amount of rather diverse information in one place.  These values contribute to the high profile of the TGFC’s LSA and the TGFC’s continued reputation as the authoritative source for the best determination of the fundamental constants.  The review articles of each LSA are very highly cited and contribute significantly to CODATA’s international reputation.

Task Group websites

Impact

The last regular CODATA-TGFC four-year cycle adjustment of the fundamental constants was the 2022 adjustment with a closing date of 31 December, 2022 for input data to be available for consideration.  Relevant data were collected and reviewed for possible impact on the determination of the values of the fundamental constants. The results of the 2022 CODATA-TGFC adjustment will be made available early 2024 with the accepted input data and analysis published in a review article.

Planned (and later on actual) activities and outputs for 2023-2025

  • The 2023 TGFC meeting was hosted by the BIPM in a hybrid form 12 – 13 September 2023.  Preliminary results of the 2022 CODATA-TGFC adjustment of the fundamental constants were discussed at length, focusing on the publication, possible help from TGFC members of specific sections, and the posting of the results.  The 2022 TGFC meeting minutes were accepted and are posted on the BIPM website:  https://www.bipm.org/en/hosting/codata-tgfc
  • The results of the 2022 CODATA-TGFC adjustment of the fundamental constants will be made available in 2024 at https://pml.nist.gov/cuu/Constants/ with the accepted input data and analysis published in review articles.
  • The next CODATA-TGFC meeting will be held 10-11 September 2024 as a hybrid meeting at the BIPM, Paris with virtual attendance as an option. The meeting will last for two days with several scientific presentations on subjects of interest to the Task Group.

Past Achievements 

The 2021 TGFC meeting was hosted by the BIPM virtually 14-15 September 2021 in conjunction with the 25th meeting of the CCU.  Topics of discussion centered on new relevant input data, input data discrepancies that may lead to better understanding of fundamental theories, and preparations for the 2022 CODATA adjustment of the fundamental constants.  The 2020 TGFC meeting minutes were accepted and are posted on the BIPM website:  https://www.bipm.org/en/hosting/codata-tgfc

The International Committee for Weights and Measures (CIPM) has agreed on a Memorandum of Understanding (MoU) between the BIPM and CODATA. It was signed by Dr Martin Milton, Director of the BIPM and by Dr Simon Hodson, Executive Director of CODATA on 11 October 2021:  https://www.bipm.org/en/-/2021-10-11-mou-bipm-codata

The 2022 TGFC meeting was also hosted by the BIPM in a hybrid form 12 – 14 September 2022. In preparation for the upcoming 2022 adjustment of the fundamental constants, the three day meeting included special scientific sessions with invited experts in the fields of proton form factor analysis, HD+ spectroscopic measurements, and measurements on the gravitational constant G. Additional discussions were held on the inclusion of HD+ data and theoretical data for the muon magnetic moment anomaly in the 2022 adjustment of the fundamental constants.  Change in membership to reflect the needs for experts in precision atomic systems and fundamental particles was also discussed.  The 2021 TGFC meeting minutes were accepted and are posted on the BIPM website:  https://www.bipm.org/en/hosting/codata-tgfc

Contacts

  • Chair: Prof. Krzysztof Pachucki , Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, POLAND
  • Co-Chair: Dr Eite Tiesinga, NIST, Bldg. 220, Rm. B342, 100 Bureau Drive, Stop 8423, Gaithersburg, MD 20899, USA

TGFC Membership

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