Editing Fermilab (section)

====Muon g−2====
{{main|Muon g−2}}

[[Muon g−2]]: (pronounced "gee minus two") is a [[particle physics]] experiment to measure the anomaly of the magnetic moment of a muon to a precision of 0.14&nbsp;[[Parts per million|ppm]], which will be a sensitive test of the [[Standard Model]].

[[File:Muon g-2 building at Fermilab.jpg|thumb|[[Muon g-2|Muon g−2]] building (white and orange) which hosts the magnet]]
Fermilab is continuing an experiment conducted at [[Brookhaven National Laboratory]] to measure the [[anomalous magnetic dipole moment]] of the [[muon]].

The magnetic dipole moment (''g'') of a charged lepton ([[electron]], muon, or [[tau (particle)|tau]]) is very nearly 2. The difference from 2 (the "anomalous" part) depends on the lepton, and can be computed quite exactly based on the current [[Standard Model of particle physics]]. Measurements of the electron are in excellent agreement with this computation. The Brookhaven experiment did this measurement for muons, a much more technically difficult measurement due to their short lifetime, and detected a tantalizing, but not definitive, [[statistical significance|3&nbsp;''σ'' discrepancy]] between the measured value and the computed one.

The Brookhaven experiment ended in 2001, but 10&nbsp;years later Fermilab acquired the equipment,<ref>{{Cite web |title=Physics Phoenix: Plotting the Journey of Muon&nbsp;g–2 |url=https://www.bnl.gov/newsroom/news.php?a=22567 |first=Emily |last=Ruppel |date=September 30, 2011 |publisher=Brookhaven National Laboratory |url-status=live |archive-url=https://web.archive.org/web/20151208044744/https://www.bnl.gov/newsroom/news.php?a=22567 |archive-date=December 8, 2015 }}</ref> and is working to make a more accurate measurement (smaller&nbsp;''σ'') which will either eliminate the discrepancy or, hopefully, confirm it as an experimentally observable example of [[physics beyond the Standard Model]].

[[File:Photo of the Week- An Incredible Journey -- Transporting a 600-ton Magnet (9324124048).jpg|thumb|Transportation of the 600&nbsp;ton magnet to Fermilab]]

Central to the experiment is a 50&nbsp;foot-diameter [[superconducting magnet]] with an exceptionally uniform magnetic field. This was transported, in one piece, from Brookhaven in [[Long Island]], New York, to Fermilab in the summer of 2013.  The move traversed 3,200&nbsp;miles over 35&nbsp;days, mostly on a barge down the [[East Coast of the United States|East Coast]] and up the [[Mississippi River|Mississippi]].

The magnet was refurbished and powered on in September&nbsp;2015,<ref>{{Cite news |journal=Aurora Beacon-News |via=Chicago Tribune |title=Fermilab brings super magnet to life after 10&nbsp;years |url=http://www.chicagotribune.com/suburbs/aurora-beacon-news/news/ct-abn-fermilab-st-0928-20150925-story.html |first=Steve |last=Lord |date=September 26, 2015 |url-status=live |archive-url=https://web.archive.org/web/20151208095422/http://www.chicagotribune.com/suburbs/aurora-beacon-news/news/ct-abn-fermilab-st-0928-20150925-story.html |archive-date=December 8, 2015 }}</ref> and has been confirmed to have the same {{val|1300|ul=ppm}} (0.13%) [[peak-to-peak|p-p]] basic magnetic field uniformity that it had before the move.<ref name=2015-10-26>{{Cite report |url=https://www.fnal.gov/directorate/program_planning/all_experimenters_meetings/special_reports/Kiburg-g-2-AEM-10-26-15.pdf |title=G-2 Report |date=October 26, 2015 |first=Brendan |last=Kiburg |access-date=December 5, 2015 |url-status=live |archive-url=https://web.archive.org/web/20151208080946/https://www.fnal.gov/directorate/program_planning/all_experimenters_meetings/special_reports/Kiburg-g-2-AEM-10-26-15.pdf |archive-date=December 8, 2015}}</ref>{{Rp|4}}

The project worked on [[shim (magnetism)|shim]]ming the magnet to improve its magnetic field uniformity.<ref name=2015-10-26/> This had been done at Brookhaven,<ref>{{Cite conference |chapter-url=http://accelconf.web.cern.ch/accelconf/p99/PAPERS/THP91.PDF |chapter=Magnetic Field shimming, Measurement and Control for the BNL Muon (g-2) Experiment |first=S.I. |last=Redin |title=Proceedings of the 1999 Particle Accelerator Conference (Cat. No.99CH36366) |conference=1999 Particle Accelerator Conference |location=New York |year=1999 |volume=5 |pages=3167–3169 |doi=10.1109/PAC.1999.792238 |isbn=0-7803-5573-3 |url-status=live |archive-url=http://archive.wikiwix.com/cache/20151207084923/http://accelconf.web.cern.ch/accelconf/p99/PAPERS/THP91.PDF |archive-date=December 7, 2015 }}</ref> but was disturbed by the move and had to be re-done at Fermilab.

In 2018, the experiment started taking data at Fermilab.<ref>{{cite web |last1=Martin |first1=Bruno |title=Fermilab's Muon g-2 experiment officially starts up |url=https://news.fnal.gov/2018/02/fermilabs-muon-g-2-experiment-officially-starts-up/ |website=Fermilab |date=February 6, 2018 |publisher=United States Government |access-date=February 25, 2021}}</ref> In 2021, the laboratory reported that results from initial study involving the particle challenged the [[Standard Model]], with the potential for discovery of new forces and particles.<ref name="NYT-20210407">{{cite news |last=Overbye |first=Dennis |authorlink=Dennis Overbye |title=Finding From Particle Research Could Break Known Laws of Physics - It's not the next Higgs boson — yet. But the best explanation, physicists say, involves forms of matter and energy not currently known to science. |url=https://www.nytimes.com/2021/04/07/science/particle-physics-muon-fermilab-brookhaven.html |date=April 7, 2021 |work=[[The New York Times]] |accessdate=April 7, 2021 }}</ref><ref name="FL-20210407">{{cite news |last=Marc |first=Tracy |title=First results from Fermilab's Muon g-2 experiment strengthen evidence of new physics |url=https://news.fnal.gov/2021/04/first-results-from-fermilabs-muon-g-2-experiment-strengthen-evidence-of-new-physics/ |date=April 7, 2021 |work=Fermilab |accessdate=April 7, 2021 }}</ref>

In August 2023, the Fermilab group said they may be getting closer to proving the existence of a new force of nature. They have found more evidence that sub-atomic particles, called muons, are not behaving in the way predicted by the current theory of sub-atomic physics.<ref>{{Cite news |date=August 10, 2023 |title=Scientists at Fermilab close in on fifth force of nature |language=en-GB |work=BBC News |url=https://www.bbc.com/news/science-environment-66407099 |access-date=August 11, 2023}}</ref>