We report on a precision measurement of the neutron spin structure function g1ng^n_1g1n using deep inelastic scattering of polarized electrons by polarized ^3He. For the kinematic range 0.014<x<0.7 ...and 1 (GeV/c)^2< Q^2< 17 (GeV/c)^2, we obtain ∫0.0140.7g1n(x)dx=−0.036±0.004(stat)±0.005(syst)\int^{0.7}_{0.014} g^n_1(x)dx = -0.036 \pm 0.004 (stat) \pm 0.005 (syst)∫0.0140.7g1n(x)dx=−0.036±0.004(stat)±0.005(syst) at an average Q2=5(GeV/c)2Q^2=5 (GeV/c)^2Q2=5(GeV/c)2. We find relatively large negative values for g1ng^n_1g1n at low xxx. The results call into question the usual Regge theory method for extrapolating to x=0 to find the full neutron integral ∫01g1n(x)dx\int^1_0 g^n_1(x)dx∫01g1n(x)dx, needed for testing quark-parton model and QCD sum rules. (arXiv)
We present a next-to-leading order perturbative QCD analysis of world data on the spin dependent structure functions
g
1
p
,
g
1
n
, and
g
1
d
, including the new experimental information on the
Q
2 ...dependence of
g
1
n
. Careful attention is paid to the experimental and theoretical uncertainties. The data constrain the first moments of the polarized valence quark distributions, but only qualitatively constrain the polarized sea quark and gluon distributions. The NLO results are used to determine the
Q
2 dependence of the ratio
g
1
F
1
and evolve the experimental data to a constant
Q
2 = 5 GeV
2. We determine the first moments of the polarized structure functions of the proton and neutron and find agreement with the Bjorken sum rule.
The ratio of the nucleon F_{2} structure functions, F_{2}^{n}/F_{2}^{p}, is determined by the MARATHON experiment from measurements of deep inelastic scattering of electrons from ^{3}H and ^{3}He ...nuclei. The experiment was performed in the Hall A Facility of Jefferson Lab using two high-resolution spectrometers for electron detection, and a cryogenic target system which included a low-activity tritium cell. The data analysis used a novel technique exploiting the mirror symmetry of the two nuclei, which essentially eliminates many theoretical uncertainties in the extraction of the ratio. The results, which cover the Bjorken scaling variable range 0.19<x<0.83, represent a significant improvement compared to previous SLAC and Jefferson Lab measurements for the ratio. They are compared to recent theoretical calculations and empirical determinations of the F_{2}^{n}/F_{2}^{p} ratio.
We have measured the spin structure functions
g
2
p
and
g
2
d
and the virtual photon asymmetries
A
2
p
and
A
2
d
over the kinematic range 0.02≤
x≤0.8 and 1.0≤
Q
2≤30 (GeV/c)
2 by scattering 38.8 GeV ...longitudinally polarized electrons from transversely polarized NH
3 and
6LiD targets. The absolute value of
A
2 is significantly smaller than the
R
positivity limit over the measured range, while
g
2 is consistent with the twist-2 Wandzura-Wilczek calculation. We obtain results for the twist-3 reduced matrix elements
d
2
p
,
d
2
d
and
d
2
n
. The Burkhardt-Cottingham sum rule integral
∫
g
2(x)dx
is reported for the range 0.02≤
x≤0.8.
The charge form factor of 4He has been extracted in the range 29 fm(-2) ≤ Q2 ≤ 77 fm(-2) from elastic electron scattering, detecting 4He recoil nuclei and electrons in coincidence with the high ...resolution spectrometers of the Hall A Facility of Jefferson Lab. The measurements have uncovered a second diffraction minimum for the form factor, which was predicted in the Q2 range of this experiment. The data are in qualitative agreement with theoretical calculations based on realistic interactions and accurate methods to solve the few-body problem.
PDF
