Pis’ma v ZhETF, vol. 118, iss. 10, pp. 723 - 724
© 2023 November 25
Linearly polarized gluon density in the rescaling model
N. A. Abdulov+, X. Chen∗×, A. V. Kotikov+1), A. V. Lipatov+◦
+Joint Institute for Nuclear Research, 141980 Dubna, Russia
∗Institute of Modern Physics, Chinese Academy of Sciences, 730000 Lanzhou, China
×School of Nuclear Science and Technology, University of Chinese Academy of Sciences, 100049 Beijing, China
◦Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, 119991 Moscow, Russia
Submitted 16 October 2023
Resubmitted 16 October 2023
Accepted 19
October 2023
DOI: 10.31857/S1234567823220044, EDN: pilnho
Determination of parton (quark and gluon) dis-
dicts that nPDFs and PDFs can be connected by simply
tribution functions (PDFs) in a proton and nuclei
scaling the argument Q2 (see also a review [21]).
is a rather important task for modern high energy
Initially, the rescaling model was proposed for the
physics. In particular, detailed knowledge on the gluon
domain of valence quarks dominance, 0.2 ≤ x ≤ 0.8,
densities is necessary for experiments planned at the
where x is the Bjorken variable. Recently it was ex-
Large Hadron Collider (LHC) and future colliders,
tended to a small x [22-24], where certain shadow-
such as Electron-Ion Collider (EIC), Future Circular
ing and antishadowing effects4) were found for the sea
hadron-electron Collider (FCC-he), Electron-Ion Col-
quark and gluon densities. Our main goal is to apply
lider in China (EicC) and Nuclotron-based Ion Col-
the rescaling model to linearly polarized gluon density
lider fAcility (NICA) [1-6]. For unpolarized cases, there
hg(x, k2t, Q2) and show its nuclear modification for small
are a distribution of unpolarized gluons, denoted as
x values.
fg(x, Q2), and a distribution of linearly polarized gluons
We found that the nuclear modification of linearly
hg(x, k2t, Q2), which corresponds to interference between
polarized gluon density is quite similar to the one of
±1 gluon helicity states2). Compared to fg(x, Q2), func-
conventional gluon density, but polarized gluons are less
tion hg(x, k2t, Q2) is currently poorly known3) in com-
affected by nuclear effects. So that, the derived expres-
parison with fg(x, Q2) and depends on the gluon trans-
sions could be useful for subsequent phenomenological
verse momentum kt (so called Transverse Momentum
applications.
Dependent, or TMD gluon density). A theoretical up-
This is an excerpt of the article “Linearly polar-
per bound for hg(x, k2t, Q2) was obtained [7, 8].
ized gluon density in the rescaling model”. Full text
Previously, we have derived an analytical expres-
of the paper is published in JETP Letters journal.
sion for linearly polarized gluon density in a proton
DOI: 10.1134/S0021364023603196
and investigated its behavior at low x [9]. Our analy-
sis was based on the small-x asymptotics for sea quark
1. D. P. Anderle, V. Bertone, X. Cao et al. (Collaboration),
and gluon densities calculated in the generalized double
Front. Phys. (Beijing) 16, 64701 (2021).
asymptotic scale (DAS) approach [10-14] (see also [15])
2. X. Chen, F. K. Guo, C. D. Roberts, and R. Wang, Few
and was done with leading order (LO) accuracy. In the
Body Syst. 61(4), 43 (2020).
present note we extend the consideration [9] for nuclei.
3. R. Abir, I. Akushevich, T. Altinoluk et al. (Collabora-
We follow the rescaling model [16-18] based on the
tion), arXiv:2305.14572 [hep-ph].
assumption [19, 20] that the effective size of gluon and
4. A. Arbuzov, A. Bacchetta, M. Butenschoen et al.
quark confinement in the nucleus is greater than in
(Collaboration), Prog. Part. Nucl. Phys. 119, 103858
the free nucleon. Within the perturbative QCD, it was
(2021).
pointed out [16-20] that this confinement rescaling pre-
5. V. M. Abazov, V. Abramov, L. G. Afanasyev et al.
(Collaboration), arXiv:2102.00442 [hep-ex].
1)e-mail: kotikov@theor.jinr.ru
4)The investigations of shadowing and antishadowing effects
2)In the literature, other notations fg1 (x, Q2) and hg1(x, k2t, Q2)
(see [25-28] and [27, 28], respectively) have been started even
or h⊥g1(x, k2t, Q2) are also widely used.
before experimental data [29, 30] were appeared (see [31-33] for
3)See also recent review [6].
an overview).
7
Письма в ЖЭТФ том 118 вып. 9 - 10
2023
723
