B. Mueller

Measurement of the Proton's Neutral Weak Magnetic Form Factor

We report the first measurement of the parity-violating asymmetry in elastic electron scattering from the proton. The asymmetry depends on the neutral weak magnetic form factor of the proton which contains new information on the contribution of strange quark-antiquark pairs to the magnetic moment of the proton. We obtain the value GMZ = 0.34±0.09±0.04±0.05 n.m. at Q^2 = 0.1 (GeV/c)^2.

A high power liquid hydrogen target for parity violation experiments

Parity-violating electron scattering measurements on hydrogen and deuterium, such as those underway at the Bates and CEBAF laboratories, require luminosities exceeding 10{sup 38} cm{sup -2} s{sup -1}, resulting in large beam power deposition into cryogenic liquid. Such targets must be able to absorb 500 watts or more with minimal change in target density. A 40 cm long liquid hydrogen target, designed to absorb 500 watts of beam power without boiling, has been developed for the SAMPLE experiment at Bates. In recent tests with 40 {micro}A of incident beam, no evidence was seen for density fluctuations in the target, at a sensitivity level of better than 1%. A summary of the target design and operational experience will be presented.

An energy feedback system for the MIT/Bates linear accelerator

Abstract We report the development and implementation of an energy feedback system for the MIT/Bates Linear Accelerator Center. General requirements of the system are described, as are the specific requirements, features, and components of the system unique to its implementation at the Bates laboratory. We demonstrate that with the system in operation, energy fluctuations correlated with the 60 Hz line voltage and with drifts of thermal origin are reduced by an order of magnitude.

Inclusive Electron Scattering from Nuclei at x ≃ 1

The inclusive A(e, e{prime}) cross section for x {approx_equal} 1 was measured on {sup 2}H, C, Fe, and Au for momentum transfers Q{sup 2} from 1-7 (GeV/c){sup 2}. The scaling behavior of the data was examined in the region of transition from y-scaling to x-scaling. Throughout this transitional region, the data exhibit {zeta}-scaling, reminiscent of the Bloom-Gilman duality seen in free nucleon scattering.

The SAMPLE experiment: Parity‐violating electron scattering from the proton and deuteron

Recent experimental evidence on nucleon structure has provided indications that some strange quark matrix elements can be comparable to those involving up and down quarks. The SAMPLE experiment will determine the strange magnetic form factor GsM at Q2=0.1 (GeV/c)2 from a measurement of the asymmetry in the scattering of polarized electrons from the proton. The error on the extraction of GsM is ultimately limited by a theoretical uncertainty—the uncertain electroweak hadronic radiative correction to the axial form factor, RT=1A. To address this issue, the collaboration is also approved to measure the asymmetry in parity‐violating quasielastic electron scattering from the deuteron. The combination of the proton and deuteron measurements will yield a value of GsM that is almost completely free of the uncertainty in RT=1A.