V. W. Hughes

Measurement of the ratios of deep inelastic muon-nucleus cross sections on various nuclei compared to deuterium

Measurement of the ratios of deep inelastic muon-nucleus cross sections on various nuclei compared to deuterium

Development of a low-momentum “surface” muon beam for LAMPF☆

Abstract A low momentum positive muon beam has been developed at LAMPF, utilizing muons which originate from pion decays at rest near the surface of the pion production target and are transported by the LAMPF stopped muon channel. The muon beam has a total flux of 2.5 × 104μ+ per s per μA of a proton beam (8 × 106μ+ s−1 for the present operating current at LAMPF of 300 μA), an extremely narrow range spread of 50 mg/cm2 in CH2, and a positron contamination (e+/gm+) of 60%.

Improved upper limit on muonium to antimuonium conversion

A new experiment has been set up at the Paul Scherrer Institut to search for muonium to antimuonium conversion. No event was found to fulfil the requested signature which consists of the coincident detection of both constituents of the antiatom in its decay. Assuming an effective (V - A) x (V - A) type interaction an improved upper limit is established for the conversion probability of P() less than or equal to 8 x 10(-9) (90% C.L.), which is almost 2 orders of magnitude lower compared to previous results and provides a sensitive test for theoretical extensions of the standard model.

Operating Experience with the Polarized Electron Gun at SLAC

During the two years of operation of the SLAC Polarized Electron Gun (PEGGY), the electron intensity delivered to the target has increased from 7 x 10/sup 7/ e/sup -//pulse to 1 x 10/sup 9/ e/sup -//pulse. The polarization is 0.85 with no measurable degradation caused by acceleration through the linear accelerator. The predominant cause of downtime is replenishment of lithium, which now averages 43 hours. The lifetime of a lithium load is about 175 hours.

Measurement of the muonium 1S‐2S transition frequency

Resonant ionization spectroscopy has been employed for measuring the 12S1/2−22S1/2 frequency difference in the hydrogen‐like muonium atom to 2 455 529 002(33)(46) MHz. The 1S‐2S two‐photon transition was induced Doppler‐free using two counter‐propagating laser beams. The 2S state was photo‐ionized by a third photon from the same laser field. The measurement agrees with QED theory within two standard deviations. The mass of the positive muon can be extracted from the isotope shifts in this transition to hydrogen and deuterium to 105.658 80(29)(43) MeV/c2.

Measurement of the internal spin structure of the proton

Our final results of measurements at SLAC of the spin dependent asymmetry in the deep inelastic scattering of longitudinally polarized electrons by longitudinally polarized protons are presented. Data were obtained at a scattering angle of 10° and for incident energies of 16.2 and 22.7 GeV, which cover the kinematic range 0.18<x<0.70 and 3.5<Q2<10.0 (GeV/c)2. We compare our results with various models of proton spin structure and with the Bjorken and Ellis‐Jaffe sum rules.