98 research outputs found
Parity Violation in Proton-Proton Scattering at 221 MeV
TRIUMF experiment 497 has measured the parity violating longitudinal
analyzing power, A_z, in pp elastic scattering at 221.3 MeV incident proton
energy. This paper includes details of the corrections, some of magnitude
comparable to A_z itself, required to arrive at the final result. The largest
correction was for the effects of first moments of transverse polarization. The
addition of the result, A_z=(0.84 \pm 0.29 (stat.) \pm 0.17 (syst.)) \times
10^{-7}, to the pp parity violation experimental data base greatly improves the
experimental constraints on the weak meson-nucleon coupling constants
h^{pp}_\rho and h^{pp}_\omega, and has implications for the interpretation of
electron parity violation experiments.Comment: 17 pages RevTeX, 14 PostScript figures. Revised version with
additions suggested by Phys. Rev.
Parity Violation in Proton-Proton Scattering at 221 MeV
The parity-violating longitudinal analyzing power, Az, has been measured in
pp elastic scattering at an incident proton energy of 221 MeV. The result
obtained is Az =(0.84 +/- 0.29 (stat.) +/- 0.17 (syst.)) x 10^{-7}. This
experiment is unique in that it selects a single parity violating transition
amplitude, 3P2-1D2, and consequently directly constrains the weak meson-nucleon
coupling constant h^pp_rho When this result is taken together with the existing
pp parity violation data, the weak meson-nucleon coupling constants h^pp_rho
and h^pp_omega can, for the first time, both be determined.Comment: 8 pages RevTeX4, 3 PostScript figures. Conclusion revised. New
information about weak coupling constants adde
Measurement of the Total Cross Section for the Reaction p + p → p + p + pio
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Experimental determination of the complete spin structure for anti-proton + proton -> anti-\Lambda + \Lambda at anti-proton beam momentum of 1.637 GeV/c
The reaction anti-proton + proton -> anti-\Lambda + \Lambda -> anti-proton +
\pi^+ + proton + \pi^- has been measured with high statistics at anti-proton
beam momentum of 1.637 GeV/c. The use of a transversely-polarized frozen-spin
target combined with the self-analyzing property of \Lambda/anti-\Lambda decay
allows access to unprecedented information on the spin structure of the
interaction. The most general spin-scattering matrix can be written in terms of
eleven real parameters for each bin of scattering angle, each of these
parameters is determined with reasonable precision. From these results all
conceivable spin-correlations are determined with inherent self-consistency.
Good agreement is found with the few previously existing measurements of spin
observables in anti-proton + proton -> anti-\Lambda + \Lambda near this energy.
Existing theoretical models do not give good predictions for those
spin-observables that had not been previously measured.Comment: To be published in Phys. Rev. C. Tables of results (i.e. Ref. 24) are
available at http://www-meg.phys.cmu.edu/~bquinn/ps185_pub/results.tab 24
pages, 16 figure
Measurement of Spin Transfer Observables in Antiproton-Proton -> Antilambda-Lambda at 1.637 GeV/c
Spin transfer observables for the strangeness-production reaction
Antiproton-Proton -> Antilambda-Lambda have been measured by the PS185
collaboration using a transversely-polarized frozen-spin target with an
antiproton beam momentum of 1.637 GeV/c at the Low Energy Antiproton Ring at
CERN. This measurement investigates observables for which current models of the
reaction near threshold make significantly differing predictions. Those models
are in good agreement with existing measurements performed with unpolarized
particles in the initial state. Theoretical attention has focused on the fact
that these models produce conflicting predictions for the spin-transfer
observables D_{nn} and K_{nn}, which are measurable only with polarized target
or beam. Results presented here for D_{nn} and K_{nn} are found to be in
disagreement with predictions from existing models. These results also
underscore the importance of singlet-state production at backward angles, while
current models predict complete or near-complete triplet-state dominance.Comment: 5 pages, 3 figure
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Search for strangelets and other rare objects in Au + Pt collisions at the AGS using a fixed-angle focusing spectrometer
During the 1993 AGS heavy ion run, experiment E886 conducted a strangelet search in Au + Pt reactions, with beam momentum of 10.8 GeV/c per nucleon. Presented here are the upper limit for strangelet production, invariant cross sections for p, t, d, {sup 3}He, {sup 4}He, {sup 6}He, {sup 8}He, {sup 6}Li, {sup 7}Li, {sup 8}Li and {sup 7}Be, along with a demonstration of their agreement with a coalescence model fit to data collected by E886 during the 1992 engineering run, and upper limits for production cross sections for other rare objects, such as (H dibaryon)-nucleus systems. All results reported are preliminary
Cooler Experiment Preparation
This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440
Nuclear Anapole Moments
Nuclear anapole moments are parity-odd, time-reversal-even E1 moments of the
electromagnetic current operator. Although the existence of this moment was
recognized theoretically soon after the discovery of parity nonconservation
(PNC), its experimental isolation was achieved only recently, when a new level
of precision was reached in a measurement of the hyperfine dependence of atomic
PNC in 133Cs. An important anapole moment bound in 205Tl also exists. In this
paper, we present the details of the first calculation of these anapole moments
in the framework commonly used in other studies of hadronic PNC, a meson
exchange potential that includes long-range pion exchange and enough degrees of
freedom to describe the five independent amplitudes induced by
short-range interactions. The resulting contributions of pi-, rho-, and
omega-exchange to the single-nucleon anapole moment, to parity admixtures in
the nuclear ground state, and to PNC exchange currents are evaluated, using
configuration-mixed shell-model wave functions. The experimental anapole moment
constraints on the PNC meson-nucleon coupling constants are derived and
compared with those from other tests of the hadronic weak interaction. While
the bounds obtained from the anapole moment results are consistent with the
broad ``reasonable ranges'' defined by theory, they are not in good agreement
with the constraints from the other experiments. We explore possible
explanations for the discrepancy and comment on the potential importance of new
experiments.Comment: 53 pages; 10 figures; revtex; submitted to Phys Rev
Cooler Experiment Preparation
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
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