A new search for conversion of muonium to antimuonium

Technical Report · Tue Oct 01 04:00:00 EDT 1991

DOI:https://doi.org/10.2172/5131986· OSTI ID:5131986

Matthias, B E

To search for conversion of muonium (M {identical to} {mu}{sup +}e{sup {minus}}) to antimuonium ({anti M} {identical to} {mu}{sup {minus}}e{sup +}) with very low background, a new signature was implemented that required the time-coincident detection of the decay e{sup {minus}}({le} 53 MeV) with the atomic e{sup +}({approximately} 13 eV) from decay of an {anti M} atom. A 20 MeV/c {mu}{sup +} beam was stopped in a 9 mg/cm{sup 2} SiO{sub 2} powder target. Muonium, formed in the powder, diffused into a vacuum region at thermal velocities and was observed for a coincidence of {anti M} decay products. Any decay e{sup {minus}} was charge and momentum analyzed in a dipole magnet and tracked by an array of MWPCs; any atomic e{sup +} was electrostatically collected, accelerated to 5.7 keV, and magnetically transported to a microchannel plate detector. To calibrate the signature, M was observed for the first time by coincidence of its decay e{sup +} and its atomic e{sup {minus}}. A maximum likelihood analysis of the position distribution of decay origins finds no {anti M} events and less than 2 at 90% confidence. This places an upper limit on the conversion probability per atom of S{anti M} < 6.5 {times} 10{sup {minus}7} (90% C.L.), which corresponds to an upper limit of G{sub M}{anti M} < 0.16 G{sub F} (90% C.L.) on the effective coupling constant for a (V - A) conversion coupling. In a class of left-right symmetric models, the value of G{sub M}{anti M} may be in this range. 116 refs., 45 figs., 10 tabs.

• Research Organization: Los Alamos National Lab., NM (United States)
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 5131986
• Report Number(s): LA-12202-T; ON: DE92002129
• Country of Publication: United States
• Language: English

Related Subjects

640302* -- Atomic
Molecular &amp; Chemical Physics-- Atomic &amp; Molecular Properties &amp; Theory
645102 -- High Energy Physics-- Particle Interactions &amp; Properties-Experimental-- Weak Interactions &amp; Properties
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
74 ATOMIC AND MOLECULAR PHYSICS
ANTIMATTER
BASIC INTERACTIONS
CONVERSION
DATA
DECAY
DETECTION
EXPERIMENTAL DATA
INFORMATION
INTERACTIONS
LEPTONIC DECAY
MAGNETIC FIELDS
MAGNETIC SPECTROMETERS
MATTER
MEASURING INSTRUMENTS
MEASURING METHODS
MUONIUM
NUMERICAL DATA
PARTICLE DECAY
SPECTROMETERS
WEAK INTERACTIONS
WEAK PARTICLE DECAY