We present a new measurement of the positive muon magnetic anomaly, a_{μ}≡(g_{μ}-2)/2, from the Fermilab Muon g-2 Experiment using data collected in 2019 and 2020. We have analyzed more than 4 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 2 due to better running conditions, a more stable beam, and improved knowledge of the magnetic field weighted by the muon distribution, ωover ˜_{p}^{'}, and of the anomalous precession frequency corrected for beam dynamics effects, ω_{a}. From the ratio ω_{a}/ωover ˜_{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 a_{μ}(exp)=116 592 059(22)×10^{-11} (0.19 ppm), which represents a factor of 2 improvement in precision.
We present the first results of the Fermilab National Accelerator Laboratory (FNAL) Muon g-2 Experiment for the positive muon magnetic anomaly a_{μ}≡(g_{μ}-2)/2. The anomaly is determined from the ...precision measurements of two angular frequencies. Intensity variation of high-energy positrons from muon decays directly encodes the difference frequency ω_{a} between the spin-precession and cyclotron frequencies for polarized muons in a magnetic storage ring. The storage ring magnetic field is measured using nuclear magnetic resonance probes calibrated in terms of the equivalent proton spin precession frequency ωover ˜_{p}^{'} in a spherical water sample at 34.7 °C. The ratio ω_{a}/ωover ˜_{p}^{'}, together with known fundamental constants, determines a_{μ}(FNAL)=116 592 040(54)×10^{-11} (0.46 ppm). The result is 3.3 standard deviations greater than the standard model prediction and is in excellent agreement with the previous Brookhaven National Laboratory (BNL) E821 measurement. After combination with previous measurements of both μ^{+} and μ^{-}, the new experimental average of a_{μ}(Exp)=116 592 061(41)×10^{-11} (0.35 ppm) increases the tension between experiment and theory to 4.2 standard deviations.
The Muon g − 2 Experiment at Fermi National Accelerator Laboratory (FNAL) has measured the muon anomalous precession frequency ωam to an uncertainty of 434 parts per billion (ppb), statistical, and ...56 ppb, systematic, with data collected in four storage ring configurations during its first physics run in 2018. When combined with a precision measurement of the magnetic field of the experiment's muon storage ring, the precession frequency measurement determines a muon magnetic anomaly of aμ ( FNAL ) = 116 592 040 ( 54 ) × 10−11 (0.46 ppm). This article describes the multiple techniques employed in the reconstruction, analysis, and fitting of the data to measure the precession frequency. It also presents the averaging of the results from the 11 separate determinations of ωam, and the systematic uncertainties on the result.
The medium spiny neurons of the nucleus accumbens receive both an excitatory glutamatergic input from forebrain and a dopaminergic input from the ventral tegmental area. This integration point may ...constitute a locus whereby the N-methyl-D-aspartate (NMDA)-subtype of glutamate receptors promotes drug reinforcement. Here we investigate how dopaminergic inputs alter the ethanol sensitivity of NMDA receptors in rats and mice and report that previous dopamine receptor-1 (D1) activation, culminating in dopamine and cAMP-regulated phosphoprotein-32 kD (DARPP-32) and NMDA receptor subunit-1 (NR1)-NMDA receptor phosphorylation, strongly decreases ethanol inhibition of NMDA responses. The regulation of ethanol sensitivity of NMDA receptors by D1 receptors was absent in DARPP-32 knockout mice. We propose that DARPP-32 mediated blunting of the response to ethanol subsequent to activation of ventral tegmental area dopaminergic neurons initiates molecular alterations that influence synaptic plasticity in this circuit, thereby promoting the development of ethanol reinforcement.
The IceCube Neutrino Observatory has established the existence of a high-energy all-sky neutrino flux of astrophysical origin. This discovery was made using events interacting within a fiducial ...region of the detector surrounded by an active veto and with reconstructed energy above 60 TeV, commonly known as the high-energy starting event sample (HESE). We revisit the analysis of the HESE sample with an additional 4.5 years of data, newer glacial ice models, and improved systematics treatment. This paper describes the sample in detail, reports on the latest astrophysical neutrino flux measurements, and presents a source search for astrophysical neutrinos. We give the compatibility of these observations with specific isotropic flux models proposed in the literature as well as generic power-law-like scenarios. Assuming νe: νμ: ντ= 1 : 1 : 1 , and an equal flux of neutrinos and antineutrinos, we find that the astrophysical neutrino spectrum is compatible with an unbroken power law, with a preferred spectral index of 2.87−0.19+0.20 for the 68% confidence interval.
A single calorimeter station for the Muon g−2 experiment at Fermilab includes the following subsystems: a 54-element array of PbF2 Cherenkov crystals read out by large-area SiPMs, bias and ...slow-control electronics, a suite of 800MSPS waveform digitizers, a clock and control distribution network, a gain calibration and monitoring system, and a GPU-based front-end which is read out through a MIDAS data acquisition environment. The entire system performance was evaluated using 2.5–5GeV electrons at the End Station Test Beam at SLAC. This paper includes a description of the individual subsystems and the results of measurements of the energy response and resolution, energy-scale stability, timing resolution, and spatial uniformity. All measured performances meet or exceed the g−2 experimental requirements. Based on the success of the tests, the complete production of the required 24 calorimeter stations has been made and installation into the main experiment is complete. Furthermore, the calorimeter response measurements reported here informed the design of the reconstruction algorithms that are now employed in the running g−2 experiment.
The results of a 3 + 1 sterile neutrino search using eight years of data from the IceCube Neutrino Observatory are presented. A total of 305 735 muon neutrino events are analyzed in reconstructed ...energy-zenith space to test for signatures of a matter-enhanced oscillation that would occur given a sterile neutrino state with a mass-squared differences between 0.01 and 100 eV2. The best-fit point is found to be at sin2(2θ24) = 0.10 and Δm412 = 4.5 eV2, which is consistent with the no sterile neutrino hypothesis with a p value of 8.0%.
The electromagnetic calorimeter for the new muon (g−2) experiment at Fermilab will consist of arrays of PbF2 Cherenkov crystals read out by large-area silicon photo-multiplier (SiPM) sensors. We ...report here on measurements and simulations using 2.0–4.5GeV electrons with a 28-element prototype array. All data were obtained using fast waveform digitizers to accurately capture signal pulse shapes vs. energy, impact position, angle, and crystal wrapping. The SiPMs were gain matched using a laser-based calibration system, which also provided a stabilization procedure that allowed gain correction to a level of 10−4 per hour. After accounting for longitudinal fluctuation losses, those crystals wrapped in a white, diffusive wrapping exhibited an energy resolution σ/E of (3.4±0.1)%/E/GeV, while those wrapped in a black, absorptive wrapping had (4.6±0.3)%/E/GeV. The white-wrapped crystals—having nearly twice the total light collection—display a generally wider and impact-position-dependent pulse shape owing to the dynamics of the light propagation, in comparison to the black-wrapped crystals, which have a narrower pulse shape that is insensitive to impact position.
We report the test of many of the key elements of the laser-based calibration system for muon g - 2 experiment E989 at Fermilab. The test was performed at the Laboratori Nazionali di Frascati's Beam ...Test Facility using a 450MeV electron beam impinging on a small subset of the final g - 2 lead-fluoride crystal calorimeter system. The calibration system was configured as planned for the E989 experiment and uses the same type of laser and most of the final optical elements. We show results regarding the calorimeter's response calibration, the maximum equivalent electron energy which can be provided by the laser and the stability of the calibration system components.
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