12 research outputs found
Radiation Damage in Polarized Ammonia Solids
Solid NH3 and ND3 provide a highly polarizable, radiation resistant source of
polarized protons and deuterons and have been used extensively in high
luminosity experiments investigating the spin structure of the nucleon. Over
the past twenty years, the UVA polarized target group has been instrumental in
producing and polarizing much of the material used in these studies, and many
practical considerations have been learned in this time. In this discussion, we
analyze the polarization performance of the solid ammonia targets used during
the recent JLab Eg4 run. Topics include the rate of polarization decay with
accumulated charge, the annealing procedure for radiation damaged targets to
recover polarization, and the radiation induced change in optimum microwave
frequency used to polarize the sample. We also discuss the success we have had
in implementing frequency modulation of the polarizing microwave frequency.Comment: 5 pages, 6 figures. XIIth International Workshop on Polarized
Sources, Targets and Polarimetr
Absolute polarimetry at RHIC
Precise and absolute beam polarization measurements are critical for the RHIC
spin physics program. Because all experimental spin-dependent results are
normalized by beam polarization, the normalization uncertainty contributes
directly to final physics uncertainties. We aimed to perform the beam
polarization measurement to an accuracy of .
The absolute polarimeter consists of Polarized Atomic Hydrogen Gas Jet Target
and left-right pairs of silicon strip detectors and was installed in the
RHIC-ring in 2004. This system features \textit{proton-proton} elastic
scattering in the Coulomb nuclear interference (CNI) region. Precise
measurements of the analyzing power of this process has allowed us to
achieve in 2005 for the first long
spin-physics run.
In this report, we describe the entire set up and performance of the system.
The procedure of beam polarization measurement and analysis results from
2004-2005 are described. Physics topics of in the CNI region
(four-momentum transfer squared ) are
also discussed. We point out the current issues and expected optimum accuracy
in 2006 and the future.Comment: 10 pages, PSTP07 proceedings contributio
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Measurement of the ratio of [Sigma]0 to [Lambda]0 inclusive production by 28.5 GeV/c protons on beryllium
The ratio of the cross section for [Sigma]0 inclusive production to the cross section for [Lambda]0 inclusive production has been measured with 28.5 GeV/c protons incident on a beryllium target at an average laboratory production angle of 4[deg]. This ratio was measured to be 0.278+/-0.011+/-0.05 where the uncertainties are statistical and systematic in that order. The ratio does not depend strongly on the momentum of the produced particle between 10 and 24 GeV/c. The effect of [Sigma]0 contamination on previous determinations of the polarization of inclusively produced [Lambda]0's is discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24727/1/0000149.pd
Polarization of [Sigma]0 hyperons in inclusive production from 28.5 GeV/c protons on beryllium
The polarization of [Sigma]0 hyperons produced in an inclusive reactons hasbeen measured for the first time. From a sample of 11 000 events produced by 28.5 GeV/c ptorons in the reaction p+Be-->[Sigma]0+X, the [Sigma]0 polarization has a value of +0.28+/-0.13 at pt=1.01 GeV/c and xf=0.60. The polarization of 53 000 [Lambda] hyperons produced from 28.5 Gev/c protons inthe reaction p+Be-->[Lambda]+X has been measured in the kinematic range 0.64ptc and 0.42xf<0.62. The average [Lambda] polarization is found to be -0.188+/-0.024, consistent with previous results.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26640/1/0000182.pd
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A study of inclusive [Lambda] polarization from hydrogen and other targets at 28 GeV
We report measurements of inclusive [Lambda] polarization, produced by unpolarized protons incident at several momenta (20, 24, and 28.5 GeV/c) onto hydrogen, deuterium, and beryllium targets. A large polarization from hydrogen, P = -0.34 +/- 0.06 at pT = 1.2 GeV/c, establishes the fact that inclusive [Lambda] polarization arises from p-p collisions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23313/1/0000252.pd