References - Bogoliubov Laboratory of Theoretical Physics - JINR

kinematic range to low values of Bjorken x, alow0.1 GeV 2 threshold is used for Q 2 .The
structure function F2(x, Q 2 ) of the proton is presented in Fig. 1. The overall normalization
uncertainty, which is mainly due to the luminosity normalization, is estimated to be 6.4%.
Results of other experiments performed at DESY, CERN, and SLAC are presented as well
for comparison. A previously unexplored region in the plane x-Q 2 is covered by this new
measurement. At the same time there is a good agreement with world data in the overlap
region. The structure function F2(x) of the deuteron is measured as well but not shown.
p F2 ⋅ c
10 7
10 6
10 5
10 4
10 3
10 2
SLAC
JLAB
HERMES
PRELIMINARY
GD07 fit
SMC fit
BCDMS
NMC
E665
H1
ZEUS
1 10
〈x〉 c
0.008 1.6 36
0.011 1.6 35
0.015 1.6 34
0.019 1.6 33
0.025 1.6 32
0.134 1.6 24
0.108 1.6 25
0.089 1.6 26
0.073 1.6 27
0.060 1.6 28
0.049 1.6 29
0.040 1.6 30
0.033 1.6 31
0.166 1.6 23
0.211 1.6 22
0.273 1.6 21
0.366 1.6 20
0.509 1.6 19
0.679 1.6 18
Q 2 [GeV 2 ]
Figure 1: Structure function F2(x, Q 2 ) of the proton as a function of Q 2 , for different bins in x. Inner
error bars are total minus the normalization uncertainty, shown as an outer error bar. The HERMES data
are compared to measurements from NMC, BCDMS, JLab, HERA and SLAC. The phenomenological parameterizations
of world data by the SMC [4] and GD07 [5] are shown by curves. Both parameterizations
do not include the HERMES data points.
Structure function g2(x). The spin-dependent nucleon structure function g2(x) has
no probabilistic interpretation in simple quark parton model. It has contributions from
quark-gluon correlations and can be written as a sum of two terms, g2(x, Q2 )=gWW 2 (x, Q2 )
+¯g2(x, Q2 ), where gWW 2 (x, Q2 )=−g1(x, Q2 )+ � 1
x g1(y, Q2 )dy/y is the twist-2 Wandzura-
Wilczek part, while ¯g2(x, Q2 ) is the unknown twist-3 part. A measurement of the structure
function g2(x) requires a longitudinally polarized beam and a transversely polarized
target. The polarization-dependent part of the cross-section is given by:
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