Low momentum antiproton flux enhancement in the LESB Page: 2 of 7
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in connection with our interest in the narrow width resonance observed
in the p-p total cross section at a mass of 1932 MeV by Carroll et.al. , we
h:va I *d'i d lit p rol 'mf o1 enhic in, the low moment um p flex in t he L::NI
by uwLnLtimu degradation while maintaining good optical quality. Degraders
of sufficient material to reduce the momentum of 700 MeV/c antiprotons to
450 MeV/c were placed at 1) the mass slit, 2) 1.1 meters upstream of our
target, and 3) at the production target "C" in the slowly extracted primary
A coincidence between a timing counter, T, located directly at the
mass slit, a counter, S1, lm upstream of the final focus, and a counter,
S2, at the final focus, determined the incident particle rate. The final
focus was located 2m from the exit of the last quadrupole in the beam.
Counter S2, 2-in, wide by 1k-in. high by t-in. along the beam, was used
to require a minimum dE/dx for the incident particles: dE/dx for anti-
protons of 700 MeV/c momentum is greater than two times minimum ionizing,
and that of 450 MeV/c greater than 3.5 times minimum ionizing.
The timing of the antiproton signal was determined by increasing
the resolving time of the T-Sl-S2 coincidence and examining the time of
flight spectrum between T and S2, see Fig. 1. Antiproton plus accidental
rates were measured by gating the spectrum on the antiproton time peak,
and accidentals were determined by gating the spectrum in a region to
exclude antiprotons and pions.
1. Degrading the antiproton momentum at the mass slit is advantageous
for three reasons:
a. Degraded p's are momentum analyzed after degradation,
b. pion contamination is reduced since the momentum loss of pions is
significantly less than that of p's and the downstream half of the
beam does not pass these high momentum particles, and
c. the mass slit is a nominal double focus so that the effects of
multiple scattering are reduced.
2. Degrading near the final focus, with sufficient distance between the
degrader and the focus to permit determination of particle trajectories
has none of the above advantages; however, effects of multiple scattering
may be less if there is not a true focus at the mass slit.
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Lovett, B.; Mishina, M.; Nakano, I.; Snyder, J.; Zeller, M.E. & Lazarus, D. Low momentum antiproton flux enhancement in the LESB, report, December 28, 1974; Upton, New York. (https://digital.library.unt.edu/ark:/67531/metadc1020945/m1/2/: accessed April 25, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.