Single-spin asymmetries for semi-inclusive electroproduction of charged pions in deep-inelastic scattering of positrons are measured for the first time with transverse target polarization. The ...asymmetry depends on the azimuthal angles of both the pion (phi) and the target spin axis (phi(S)) about the virtual-photon direction and relative to the lepton scattering plane. The extracted Fourier component sin((phi+phi(S))(pi)(UT) is a signal of the previously unmeasured quark transversity distribution, in conjunction with the Collins fragmentation function, also unknown. The component sin((phi-phi(S)(pi)(UT) arises from a correlation between the transverse polarization of the target nucleon and the intrinsic transverse momentum of quarks, as represented by the previously unmeasured Sivers distribution function. Evidence for both signals is observed, but the Sivers asymmetry may be affected by exclusive vector meson production.
The Hermes experiment has investigated the tensor spin structure of the deuteron using the 27.6 GeV/c positron beam of DESY HERA. The use of a tensor-polarized deuteron gas target with only a ...negligible residual vector polarization enabled the first measurement of the tensor asymmetry A{sub zz}{sup d} and the tensor structure function b{sub 1}{sup d} for average values of the Bjorken variable 0.01< <0.45 and of the negative of the squared four-momentum transfer 0.5 GeV{sup 2}<<Q{sup 2}><5 GeV{sup 2}. The quantities A{sub zz}{sup d} and b{sub 1}{sup d} are found to be nonzero. The rise of b{sub 1}{sup d} for decreasing values of x can be interpreted to originate from the same mechanism that leads to nuclear shadowing in unpolarized scattering.
Acta Phys.Hung. A25 (2006) 347-353 For the first time single-spin asymmetries in semi-inclusive pion production
are measured by the HERMES experiment with a transversely polarised hydrogen
target. ...Two different sine-modulations are extracted which can be related to
the transversity \delta q(x) and Sivers f_{1T}^{\perp q}(x) quark distribution
functions. The extracted sine-moments still contain small sub-leading twist
contributions which can be extracted from HERMES data combining the results
from the transversely polarised hydrogen target with previously measured
results from a longitudinally polarised hydrogen target.
Single-spin asymmetries in semi-inclusive pion production are measured by the
HERMES experiment for the first time, with a transversely polarised hydrogen
target. Two different sine-dependencies are ...extracted which can be related to
the quark distributions transversity h_1(x) and the Sivers function
f_1T^perp(x).
For the first time single-spin asymmetries in semi-inclusive pion production are measured by the HERMES experiment with a transversely polarised hydrogen target. Two different sine-modulations are ...extracted which can be related to the transversity \delta q(x) and Sivers f_{1T}^{\perp q}(x) quark distribution functions. The extracted sine-moments still contain small sub-leading twist contributions which can be extracted from HERMES data combining the results from the transversely polarised hydrogen target with previously measured results from a longitudinally polarised hydrogen target.
Single-spin asymmetries in semi-inclusive pion production are measured by the HERMES experiment for the first time, with a transversely polarised hydrogen target. Two different sine-dependencies are ...extracted which can be related to the quark distributions transversity h_1(x) and the Sivers function f_1T^perp(x).
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