We present a new measurement of the positive muon magnetic anomaly, a µ ≡ (gµ − 2)/2, from the Fermilab Muon g −2 Experiment based on data collected in 2019 and 2020. We have analyzed more than four times the number of positrons from muon decay than in our previous result from 2018 data. The systematic error is reduced by more than a factor of two due to better running conditions, a more stable beam, and improved knowledge of the magnetic field weighted by the muon distribution, ω′ p , and of the anomalous precession frequency corrected for beam dynamics effects, ωa. From the ratio ωa/ω ′ p , together with precisely determined external parameters, we determine a µ = 116 592 057(25) × 10 −11 (0.21 ppm). Combining this result with our previous result from the 2018 data, we obtain a µ (FNAL) = 116 592 055(24) × 10 −11 (0.20 ppm). The new experimental world average is aµ(Exp) = 116 592 059(22) × 10 −11 (0.19 ppm), which represents a factor of two improvement in precision.

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In early 2010, the Long-Baseline Neutrino Experiment (LBNE) science collaboration initiated a study to investigate the physics potential of the experiment with a broad set of different beam, near-and far-detector configurations. Nine initial topics were identified as scientific areas that motivate construction of a long-baseline neutrino experiment with a very large far detector. We summarize the scientific justification for each topic and the estimated performance for a set of far detector reference configurations. We report also on a study of optimized beam parameters and the physics capability of proposed Near Detector configurations. This document was presented to the collaboration in fall 2010 and updated with minor modifications in early 2011.

The anomalous magnetic moment of the muon is one of the most precisely measured quantities in experimental particle physics. Its latest measurement at Brookhaven National Laboratory deviates from the Standard Model expectation by approximately 3.5 standard deviations. The goal of the new experiment, E989, now under construction at Fermilab, is a fourfold improvement in precision. Here, we discuss the details of the future measurement and its current status.

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The MuCool hydrogen-absorber R&D program is summarized. Prototype absorbers featuring thin aluminum windows and "flow-through" or "convection" cooling are under development for eventual power-handling tests in a proton beam and a cooling demonstration in a muon beam. Testing these prototypes and their components involves application of novel techniques.Cooling is based on the principle that the density of a beam can be increased only by nonconservative interactions such as ionization energy loss, as phase space is otherwise conserved by Liouville's Theorem. The evolution of transverse beam emittance  n within matter is given by [1]where s is path length, E  is beam energy in GeV,  = v/c, L R is the radiation length of the absorber material and   is the betatron function describing the focusing strength of the lattice. The second term describes beam "heating" and is minimized when absorbers are placed in a strong focusing field (low   ) and consist of material of low atomic number (high L R ), the optimal choice being hydrogen.The main absorber design issues are 1) the large amount of heat deposited by a high-intensity beam, 2) the desire to minimize beam "heating" from multiple scattering and 3) the densely-packed and high-radiation environment in which absorbers must operate in a cooling channel. Additionally, the combustive nature of hydrogen imposes safety requirements that drive aspects of the engineering design and will require extensive reviews to ensure that the system is sufficiently robust and failsafe.Minimizing multiple scattering has led to novel window designs (figure 1) that depart from the standard spherical and torispherical shells. Our first design, a torispherical shell modified with tapered thickness near the "knuckle" for additional strength, achieved a minimum thickness about half that of a standard torispherical shell. A second design incorporated a spherical cap joined to the mounting flange via an inflected, tapered toroidal section, gaining another factor 2 in thickness. A more recent design achieves the same strength with the same central thinness and less material at the edges.Testing these windows presents interesting technical challenges. Confirming that the manufactured window is consistent with design can be cumbersome, since standard coordinate measuring machines (CMM) require physical contact with the window and can only measure one

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The Central Outer Tracker (COT) is a large axial drift chamber in the Collider Detector at Fermilab operating with a gas mixture that is 50/50 argon/ethane with an admixture of 1.7% isopropanol. In its first two years of operation the COT showed unexpected aging with the worst parts of the chamber experiencing a gain loss of 50% for an accumulated charge of 35 mC/cm. By monitoring the pulse height of hits on good tracks, it was possible to determine the gain as a function of time and location in the chamber. In addition, the currents of the high voltage supplies gave another monitor of chamber gain and its dependence on the charge deposition rate. The aging was worse on the exhaust end of the chamber consistent with polymer buildup as the gas flows through the chamber. The distribution in azimuth suggests that aging is enhanced at lower temperatures, but other factors such as gas flow patterns may be involved. Elemental and molecular analysis of the sense wires found a coating that is mostly carbon and hydrogen with a small amount of oxygen; no silicon or other contaminants were identified. High resolution electron microscope pictures of the wire surface show that the coating is smooth with small sub-micron nodules. In the course of working with the chamber gas system, we discovered a small amount of O 2 is enough to reverse the aging. Operating the chamber with 100 ppm of O 2 reversed almost two years of gain loss in less than 10 days while accumulating 2 mC/cm.