W. Earle

Improved measurement of the positive muon anomalous magnetic moment

A new measurement of the positive muons anomalous magnetic moment has been made at the Brookhaven Alternating Gradient Synchrotron using the direct injection of polarized muons into the superferric storage ring. The angular frequency difference omega (a) between the angular spin precession frequency omega (s) and the angular orbital frequency omega (c) is measured as well as the free proton MMR frequency omega (p). These determine R = omega (a)/omega (p) = 3.707 201(19) x 10(-3). With mu (mu)/mu (p) = 3.183 345 39(10) this gives a(mu+) = 11 659 191(59) x 10-(10) (+/-5 ppm), in good agreement with the previous CERN and BNL measurements for mu (+) and mu (-), and with the standard model prediction.

Improved measurement of the positive-muon lifetime and determination of the fermi constant

The mean life of the positive muon has been measured to a precision of 11 ppm using a low-energy, pulsed muon beam stopped in a ferromagnetic target, which was surrounded by a scintillator detector array. The result, tau(micro)=2.197 013(24) micros, is in excellent agreement with the previous world average. The new world average tau(micro)=2.197 019(21) micros determines the Fermi constant G(F)=1.166 371(6)x10(-5) GeV-2 (5 ppm). Additionally, the precision measurement of the positive-muon lifetime is needed to determine the nucleon pseudoscalar coupling g(P).

The Brookhaven muon storage ring magnet

Abstract The muon g-2 experiment at Brookhaven National Laboratory has the goal of determining the muon anomalous g-value a μ (=(g−2)/2) to the very high precision of 0.35 parts per million and thus requires a storage ring magnet with great stability and homogeniety. A superferric storage ring with a radius of 7.11 m and a magnetic field of 1.45 T has been constructed in which the field quality is largely determined by the iron, and the excitation is provided by superconducting coils operating at a current of 5200 A. The storage ring has been constructed with maximum attention to azimuthal symmetry and to tight mechanical tolerances and with many features to allow obtaining a homogenous magnetic field. The fabrication of the storage ring, its cryogenics and quench protection systems, and its initial testing and operation are described.

Detailed Report of the MuLan Measurement of the Positive Muon Lifetime and Determination of the Fermi Constant

We report results from the MuLan measurement of the positive muon lifetime. The experiment was conducted at the Paul Scherrer Institute using a time-structured surface muon beam and a segmented plastic scintillator array. Two different in-vacuum muon stopping targets were used: a ferromagnetic foil with a large internal magnetic field and a quartz crystal in a moderate external magnetic field. From a total of 1.6 x 10^{12} decays, we obtained the muon lifetime tau_mu = 2196980.3(2.2) ps (1.0 ppm) and Fermi constant G_F = 1.1663787(6) x 10^{-5} GeV^{-2} (0.5 ppm).

A high voltage RF oscillator for driving multipole ion guides

A high voltage RF oscillator circuit has been designed and constructed for driving multipole ion guides. The circuit is tunable from 500 kHz to 1.5 MHz by changing a capacitor and provides 0–1000 Vp-p that is controlled by a 0–10 V input using a negative feedback circuit. This inexpensive circuit uses a set of high voltage transistors oscillating in tandem and does not require tuning of the resonance drive frequency as the oscillator automatically resonates at the (LC)−1/2 frequency. Matrix-assisted laser desorption/ionization-Fourier transform mass spectrometry (MALDI-FTMS) mass spectra were acquired using this tunable RF oscillator circuit to allow transmission of protein ions in the 8.5–39 kDa range through the quadrupole ion guide from the ion source to the mass analyzer.

A fast TDC for the CPLEAR experiment at CERN

Abstract A fast time-to-digital converter, FTDC, based on a time-to-voltage converter and a fast successive-approximation ADC, is described. Results of tests of 64 FTDC cards within the experiments data acquisition system are presented. Circuit design techniques useful to future applications are discussed.

The muon anomalous magnetic moment

The muon g-2 experiment at the Brookhaven National Laboratory is described, including its motivation, goal and present status. The latest result based on 1998 data is aμ+=g−2/2=11 659 191(59)×10−10 (5 ppm), where the error is primarily statistical. This value agrees with the present theoretical value. Data obtained thus far and now being analyzed should have a statistical error of about 0.5 ppm.

Muon g-2 experiment at Brookhaven National Laboratory

By the end of an excellent data taking in 1999, we collected ≈ 1 billion decay positrons with energy greater than 2 GeV and 30 μs after injection. The analysis of the 1999 data set were performed in parallel by various teams in the collaboration and each team provides a different approach to the analysis. The projected errors are expected to be of order 1.3 ppm statistical and below 0.5 ppm systematic. The data obtained in the 2000 run contains ≈ 4 times more decay positrons compared to 1999.

Rate and pileup studies for photomultiplier tubes/bases and some electronics

Abstract The shift in the electron transit time of a reference pulse due to preceding the pulse with a 100 pulse burst at a rate up to 20 MHz was found to be less than a couple of picoseconds for the two types of photomultiplier tubes and bases intended for use in the new muon (g−2) experiment. Timing shifts of the photomultiplier tubes due to bringing two pulses to within 10 ns of each other were found to be purely from a tail effect. The change in pulse area from the photomultiplier tubes from high rate and pileup was found to be less than a few parts per thousand. The performance of some commonly used electronics was also tested under high rate conditions.

Recent results on the muon anomalous magnetic moment from BNL E821

The new muon (g−2) experiment at BNL aims at a final precision of 0.35 ppm on the muon anomaly. The experiment has completed four runs beginning in 1997 and has sub-ppm data on tape. Analyzed data include a published 13 ppm result from our initial commissioning run and a recently completed 5 ppm result from our 1998 initial muon injection run. We are actively working on the remainder of the data analysis and on systematic studies.