The New G 2mu Experiment At Fermilab

We present a proposal to measure the anomalous magnetic moment of the muon to 0.14 ppm precision. This new g-2 experiment will be hosted by Fermilab making use of minor modifications to the existing accelerator complex. The experiment will recycle several components from the previous g-2 experiment E821 hosted at Brookhaven. In particular, the entire storage ring and magnet will be shipped to Fermilab. We cover the motivation for the experiment and review the measurement technique. We then focus on a new in-vacuo straw tracking system planned for the new experiment and its impact on searching for a permanent electric dipole moment of the muon.

Precision measurements of fundamental quantities have played a key role in pointing the way forward in developing our understanding of the universe. Though the enormously successful Standard Model (SM) describes the breadth of both historical and modern experimental particle physics data, it is necessarily incomplete. The muon $g-2$ experiment executed at Brookhaven concluded in 2001 and measured a discrepancy of more than three standard deviations compared to the Standard Model calculation. Arguably, this remains the strongest hint of physics beyond the SM. A new initiative at Fermilab is under construction to improve the experimental accuracy four-fold. The current status is presented here.

The measurement of the anomalous magnetic moment of muon provides a precision test of the Standard Model. The Brookhaven muon g-2 experiment (E821) measured the muon magnetic moment anomaly with 0.54 ppm precision, a more than 3 deviation from the Standard Model predictions, spurring speculation about the possibility of new physics. The new g-2 experiment at Fermilab (E989) will reduce the combined statistical and systematic error of the BNL experiment by a factor of 4. An overview of the new experiment is described in this article.

The New Muon (g-2) Collaboration at Fermilab has proposed to measure the anomalous magnetic moment of the muon, a{sub {mu}}, a factor of four better than was done in E821 at the Brookhaven AGS, which obtained a{sub {mu}} = [116592089(63)] x 10−11 ± 0.54 ppm. The last digit of a{sub {mu}} is changed from the published value owing to a new value of the ratio of the muon-to-proton magnetic moment that has become available. At present there appears to be a difference between the Standard-Model value and the measured value, at the ≈= 3 standard deviation level when electron-positron annihilation data are used to determine the lowest-order hadronic piece of the Standard Model contribution. The improved experiment, along with further advances in the determination of the hadronic contribution, should clarify this difference. Because of its ability to constrain the interpretation of discoveries made at the LHC, the improved measurement will be of significant value, whatever discoveries may come from the LHC.

The D0 experiment at Fermilab is described. The detector is complete and presently taking physics data. Results from beam tests of the calorimeter and an outline of the physics agenda for the present run are also given.