Single-spin asymmetries for semi-inclusive pion production in deep-inelastic scattering have been measured for the first time. A significant target-spin asymmetry of the distribution in the azimuthal ...angle straight phi of the pion relative to the lepton scattering plane was formed for pi(+) electroproduction on a longitudinally polarized hydrogen target. The corresponding analyzing power in the sinstraight phi moment of the cross section is 0.022+/-0.005+/-0.003. This result can be interpreted as the effect of terms in the cross section involving chiral-odd spin distribution functions in combination with a chiral-odd fragmentation function that is sensitive to the transverse polarization of the fragmenting quark.
Spin asymmetries of semi-inclusive cross sections for the production of positively and negatively charged hadrons have been measured in deep-inelastic scattering of polarized positrons on polarized ...hydrogen and
3
He targets, in the kinematic range 0.023<
x<0.6 and 1 GeV
2<
Q
2<10 GeV
2. Polarized quark distributions are extracted as a function of
x for up
(u+
u
̄
) and down (
d+
d
̄
) flavors. The up quark polarization is positive and the down quark polarization is negative in the measured range. The polarization of the sea is compatible with zero. The first moments of the polarized quark distributions are presented. The isospin non-singlet combination
Δq
3 is consistent with the prediction based on the Bjorken sum rule. The moments of the polarized quark distributions are compared to predictions based on SU(3)
f
flavor symmetry and to a prediction from lattice QCD.
Cross section ratios for deep-inelastic scattering from
14N and
3He with respect to
2H have been measured by the HERMES experiment at DESY using a 27.5 GeV positron beam. The data cover a range in ...the Bjorken scaling variable
x between 0.013 and 0.65, while the negative squared four-momentum transfer
Q
2 varies from 0.5 to 15 GeV
2. The data are compared to measurements performed by NMC, E665, and SLAC on
4He and
12C, and are found to be different for
x<0.06 and
Q
2<1.5 GeV
2. The observed difference is attributed to an
A-dependence of the ratio
R=
σ
L
/
σ
T
of longitudinal to transverse deep-inelastic scattering cross sections at low
x and low
Q
2.
We present a measurement of the longitudinal spin asymmetry A(||) in photoproduction of pairs of hadrons with high transverse momentum p(T). Data were accumulated by the HERMES experiment using a ...27.5 GeV polarized positron beam and a polarized hydrogen target internal to the HERA storage ring. For h(+)h(-) pairs with p(h(1))(T)>1.5 GeV/c and p(h(2))(T)>1.0 GeV/c, the measured asymmetry is A(||) = -0. 28+/-0.12(stat)+/-0.02(syst). This negative value is in contrast to the positive asymmetries typically measured in deep inelastic scattering from protons, and is interpreted to arise from a positive gluon polarization.
A measurement of the proton spin structure function g1p(x,Q{sup 2}) in deep-inelastic scattering is presented. The data were taken with the 27.6 GeV longitudinally polarised positron beam at HERA ...incident on a longitudinally polarised pure hydrogen gas target internal to the storage ring. The kinematic range is 0.021<x<0.85 and 0.8 GeV{sup 2}<Q{sup 2}<20 GeV{sup 2}.
A high precision alignment system has been developed for online monitoring of the tracking detectors of HERMES. The system consists of a He–Ne laser, Fresnel zone plates, CCD cameras, and electronics ...to read out the image. It records the alignment information of each detector automatically every 30
min during the experiment. The relative detector positions can be monitored with a precision of better than
±60
μ
m (1
σ).
Mitsubishi Heavy Industries, Ltd (MHI) and Hitachi, Ltd have established a joint venture company which will handle sales and related engineering activities of metal rolling mills and their downstream ...facilities.
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