References - Bogoliubov Laboratory of Theoretical Physics - JINR

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Figure 2: Quark densities in the kT plane for longitudinally polarized quarks in a transversely polarized
proton for up (left panel ) and down (right panel) quark.
TMDs [13] are satisfied in our model, see [5].) These model results are supported from a
recent lattice calculation [14, 15] which gives, for the density related to g1T , 〈k u
x 〉 = 67(5)
MeV, and 〈k d
x〉 = −30(5) MeV. For the density related to h⊥ 1L , they also find shifts of
〉 = −60(5) MeV, and 〈kd〉
= 15(5) MeV.
similar magnitude but opposite sign: 〈k u
x
2 Results for azimuthal SSAs
In Ref. [16] the present results for the T-even TMDs were applied to estimate azimuthal
asymmetries in SIDIS, discussing the range of applicability of the model, especially with
regard to the scale dependence of the observables and the transverse-momentum depen-
dence of the distributions. Here we review the results for the Collins asymmetry A sin(φ+φS)
UT
and for A sin(3φ−φS)
UT
TMDs h1, andh ⊥ 1T
, due to the Collins fragmentation function and to the chirally-odd
, respectively. In both cases, we use the results extracted in [17] for
the Collins function. In the denominator of the asymmetries we take f1 from [18] and the
unpolarized fragmentation function from [19], both valid at the scale Q 2 =2.5 GeV 2 .
In Fig. 2 the results for the Collins asymmetry in DIS production of charged pions off
proton and deuterium targets are shown as function of x. The model results for h1 evolved
from the low hadronic scale of the model to Q 2 =2.5 GeV 2 ideally describe the HER-
0.1
0.05
0
-0.05
A sin(φ h + φ S )
UT
π + proton
-0.1
0 0.1 0.2 0.3
(a)
x
0.05
0
-0.05
-0.1
A sin(φ h + φ S )
UT
π - proton
-0.15
0 0.1 0.2 0.3
(b)
x
0.1
0
-0.1
A sin(φ C )
UT
10 -2
10 -1
(c)
π + deuteron
x
0.1
0.05
0
-0.05
x
A sin(φ C )
UT
10 -2
10 -1
(d)
π - deuteron
Figure 3: The single-spin asymmetry A sin(φh+φS) sin φC
UT ≡−AUT in DIS production of charged pions off
proton and deuterium targets, as function of x. The theoretical curves are obtained on the basis of the
light-cone CQM predictions for h1(x, Q2 ) from Ref. [4,5]. The (preliminary) proton target data are from
HERMES [20], the deuterium target data are from COMPASS [21].
105
x