Developments in spin-polarized internal targets for storage rings have permitted measurements of 197 MeV polarized protons scattering from vector polarized deuterons. This work presents measurements ...of the polarization observables A(y), iT11, and C(y,y) in proton-deuteron elastic scattering. When compared to calculations with and without three-nucleon forces, the measurements provide further evidence that three-nucleon forces make a contribution to the observables. This work indicates that three-body forces derived from static nuclear properties appear to be crucial to the description of dynamical properties.
The HERMES polarized atomic beam source Nass, A.; Baumgarten, C.; Braun, B. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2003, Letnik:
505, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The HERMES atomic beam source is used to provide nuclear polarized hydrogen or deuterium atoms for the HERMES target. The setup including the dissociator, the sextupole magnet system and the ...high-frequency transitions is described. Measurements of the hydrogen intensity of up to
6.4×10
16
atoms/
s
in two hyperfine substates and of the deuterium intensity of up to
5.8×10
16
atoms/
s
in three hyperfine substates are presented. A degree of dissociation of 92.8% for H (94.5% for D) at the entrance of the storage cell and a nuclear polarization of around 0.97 (H) and 0.92 (D) have been found constant within a couple of percent over the whole running period of the HERMES experiment.
A
bstract
A comprehensive set of azimuthal single-spin and double-spin asymmetries in semi-inclusive leptoproduction of pions, charged kaons, protons, and antiprotons from transversely polarized ...protons is presented. These asymmetries include the previously published HERMES results on Collins and Sivers asymmetries, the analysis of which has been extended to include protons and antiprotons and also to an extraction in a three-dimensional kinematic binning and enlarged phase space. They are complemented by corresponding results for the remaining four single-spin and four double-spin asymmetries allowed in the one-photon-exchange approximation of the semi-inclusive deep-inelastic scattering process for target-polarization orientation perpendicular to the direction of the incoming lepton beam. Among those results, significant non-vanishing cos (
ϕ−ϕ
S
) modulations provide evidence for a sizable worm-gear (II) distribution,
g
1
T
q
x
p
T
2
. Most of the other modulations are found to be consistent with zero with the notable exception of large sin (
ϕ
S
) modulations for charged pions and
K
+
.
Gottfried sum from the ratio F2n/F2p Amaudruz, P; Arneodo, M; Arvidson, A ...
Physical review letters,
1991-May-27, Letnik:
66, Številka:
21
Journal Article
Recenzirano
Experimental results obtained at the CERN Super Proton Synchrotron on the structure-function ratio F2n/F2p in the kinematic range 0.004 < x < 0.8 and 0.4 < Q2 < 190 GeV2, together with ...the structure function F2d determined from a fit to published data, are used to derive the difference F2p(x) - F2n(x). The value of the Gottfried sum integral (F2p - F2n) dx/x = 0.240 +/- 0.016 is below the quark-parton-model expectation of 1/3.
Single-spin asymmetries for pions and charged kaons are measured in semi-inclusive deep-inelastic scattering of positrons and electrons off a transversely nuclear-polarized hydrogen target. The ...dependence of the cross section on the azimuthal angles of the target polarization (ϕS) and the produced hadron (ϕ) is found to have a substantial sin(ϕ+ϕS) modulation for the production of π+, π− and K+. This Fourier component can be interpreted in terms of non-zero transversity distribution functions and non-zero favored and disfavored Collins fragmentation functions with opposite sign. For π0 and K− production the amplitude of this Fourier component is consistent with zero.
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