746 research outputs found
RHIC polarimetry
Polarimeters were developed to measure the polarization of the proton beam at RHIC in relative scale through the asymmetry measurement of the elastic proton-carbon scattering. Recoil carbon ions with kinetic energy of 400 ≤ E ≤ 900 keV were detected by silicon strip detectors installed at 90° with respect to the beam. The absolute polarization is given by normalizing against another polarimeter implemented at RHIC, namely a polarized hydrogen gas jet polarimeter. In this report, the details of polarization measurements, data analysis, and systematic uncertainties are discussed based on the data taken during ∫s = 200 GeV operation of Run 05 at RHIC
Measurement of Spin Correlation Parameters A, A, and A_ at 2.1 GeV in Proton-Proton Elastic Scattering
At the Cooler Synchrotron COSY/J\"ulich spin correlation parameters in
elastic proton-proton (pp) scattering have been measured with a 2.11 GeV
polarized proton beam and a polarized hydrogen atomic beam target. We report
results for A, A, and A_ for c.m. scattering angles between
30 and 90. Our data on A -- the first measurement of this
observable above 800 MeV -- clearly disagrees with predictions of available of
pp scattering phase shift solutions while A and A_ are reproduced
reasonably well. We show that in the direct reconstruction of the scattering
amplitudes from the body of available pp elastic scattering data at 2.1 GeV the
number of possible solutions is considerably reduced.Comment: 4 pages, 4 figure
Modelling nucleon-nucleon scattering above 1 GeV
Motivated by the recent measurement of proton-proton spin-correlation
parameters up to 2.5 GeV laboratory energy, we investigate models for
nucleon-nucleon (NN) scattering above 1 GeV. Signatures for a gradual failure
of the traditional meson model with increasing energy can be clearly
identified. Since spin effects are large up to tens of GeV, perturbative QCD
cannot be invoked to fix the problems. We discuss various theoretical scenarios
and come to the conclusion that we do not have a clear phenomenological
understanding of the spin-dependence of the NN interaction above 1 GeV.Comment: 36 pages, 8 figure
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
The RHIC Spin Program: Achievements and Future Opportunities
This document summarizes recent achievements of the RHIC spin program and
their impact on our understanding of the nucleon's spin structure, i.e. the
individual parton (quark and gluon) contributions to the helicity structure of
the nucleon and to understand the origin of the transverse spin phenomena. Open
questions are identified and a suite of future measurements with polarized
beams at RHIC to address them is laid out. Machine and detector requirements
and upgrades are briefly discussed
Spin observables of the reactions NN -> DeltaN and pd -> Delta (pp)(1S0) in collinear kinematics
A general formalism for double and triple spin-correlations of the reaction
NN -> DeltaN is developed for the case of collinear kinematics. A complete
polarization experiment allowing to reconstruct all of the four amplitudes
describing this process is suggested. Furthermore, the spin observables of the
inelastic charge-exchange reaction pd -> Delta^0(pp)(1S0) are analyzed in
collinear kinematics within the single pN scattering mechanism involving the
subprocess pn -> Delta^0p. The full set of spin observables related to the
polarization of one or two initial particles and one final particle is obtained
in terms of three invariant amplitudes of the reaction pd -> Delta (pp)(1S0)
and the transition form factor d->(pp)(1S0). A complete polarization experiment
for the reaction pd -> Delta^0(pp)(1S0) is suggested which allows one to
determine three independent combinations of the four amplitudes of the
elementary subprocess NN -> DeltaN.Comment: 12 pages, 1 figur
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