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The distribution of the spin of the nucleon among its constituents can be parametrized in the form of polarized parton distribution functions for quarks and gluons. Using all available data on the polarized structure function $g_1(x,Q^2)$,…

High Energy Physics - Phenomenology · Physics 2014-11-17 T. Gehrmann , W. J. Stirling

We discuss perturbative evolution of the polarized structure function g_1 in the (x,Q^2) plane, with special regard to the small-x region. We determine g_1 in terms of polarized quark and gluon distributions using coefficient functions to…

High Energy Physics - Phenomenology · Physics 2009-10-28 R. D. Ball , S. Forte , G. Ridolfi

We present a field theoretical proof of the conjectured KLT relation which states that the full tree-level scattering amplitude of gluons can be written as a product of color-ordered amplitude of gluons and color-ordered amplitude of…

High Energy Physics - Theory · Physics 2015-05-28 Yi-Jian Du , Bo Feng , Chih-Hao Fu

The AGL equation includes all multiple pomeron exchanges in the double logarithmic approximation (DLA) limit, leading to an unitarized gluon distribution in the small $x$ regime. This equation was originally obtained using the…

High Energy Physics - Phenomenology · Physics 2009-10-31 M. B. Gay Ducati , V. P. Gonçalves

We compute the gluon transverse-momentum-dependent fragmentation function (TMDFF) at next-to-leading order (NLO) into heavy quarkonium in the color-octet $^3S_1^{[8]}$ channel, based on the NRQCD factorization approach. The spurious…

High Energy Physics - Phenomenology · Physics 2024-01-02 Miguel G. Echevarria , Samuel F. Romera , Ignazio Scimemi

We present for first time the computation at large $q_T$ (or small $b_T$) matching coefficients of Transverse Momentum Dependent Parton Distribution Function (TMDPDF) for linearly polarised to the integrated gluon distribution at…

High Energy Physics - Phenomenology · Physics 2019-08-19 Daniel Gutierrez-Reyes , Sergio Leal Gómez , Ignazio Scimemi , Alexey Vladimirov

We consider Higgs production in gluon fusion and in particular the prediction of the Higgs transverse momentum distribution. We discuss the ambiguities affecting the matching procedure between fixed order matrix elements and the resummation…

High Energy Physics - Phenomenology · Physics 2016-02-10 Emanuele Bagnaschi , Alessandro Vicini

The recently proposed nonlinear evolution equation \cite{Kutak:2013hda} for unintegrated gluon densities valid for large values of the QCD coupling constant $\bar{\alpha} _s$ is presented. In particular we outline its derivation, numerical…

High Energy Physics - Phenomenology · Physics 2014-06-24 Krzysztof Kutak

We study the gluon Wigner distributions of the proton which are the phase-space distributions containing the most general one-parton information. Using the proton wave functions deduced from a light-cone spectator model that contains the…

High Energy Physics - Phenomenology · Physics 2023-12-14 Chentao Tan , Zhun Lu

We derive gauge invariant operators entering definitions of the Transverse Momentum Dependent (TMD) gluon distributions, for all five and six parton processes. Our calculations utilize color decomposition of amplitudes in the color flow…

High Energy Physics - Phenomenology · Physics 2020-07-22 Marcin Bury , Piotr Kotko , Krzysztof Kutak

Using the colour dipole picture for photon-nucleus interactions at small $x$ together with the Color Glass Condensate (CGC) effective theory, we demonstrate that the next-to-leading (NLO) order corrections to the cross-section for the…

High Energy Physics - Phenomenology · Physics 2025-05-05 Paul Caucal , Edmond Iancu

We analyze the general nonlinear evolution equations for multi gluon correlators derived in hep-ph/9709432 by restricting ourselves to a double logarithmic region. In this region our evolution equation becomes local in transverse momentum…

High Energy Physics - Phenomenology · Physics 2014-11-17 Jamal Jalilian-Marian , Alex Kovner , Andrei Leonidov , Heribert Weigert

We revisit the calculation of the next-to-leading order (NLO) corrections to dijet production in electron-ion collisions at small $x$. We focus on the back-to-back configuration where the relative transverse momentum $P_\perp$ of the…

High Energy Physics - Phenomenology · Physics 2025-10-10 Paul Caucal , Edmond Iancu , Farid Salazar , Feng Yuan

We propose exclusive diffractive dijet photoproduction as an ideal measure of the off-diagonal gluon distribution at high scales. We solve the off-diagonal evolution equations for the gluon and quark singlet over the full kinematic domain.…

High Energy Physics - Phenomenology · Physics 2010-03-25 K. Golec-Biernat , J. Kwiecinski , A. D. Martin

We outline an approach to calculate the transverse-momentum-dependent distribution of linearly polarized gluons inside an unpolarized hadron on the lattice with the help of large momentum effective theory. To achieve this purpose, we…

High Energy Physics - Phenomenology · Physics 2024-02-02 Shuai Zhao

The $k_{\perp}$ dependent gluon distribution is calculated accounting for the resummation of small~$x$ effects due to the Lipatov equation. It is represented by a convolution of a gluon density in the collinear limit and a universal…

High Energy Physics - Phenomenology · Physics 2007-05-23 J. Blümlein

We present an analysis of the current methods of approximate determination of the gluon density $G(x,Q^2)$ at low-$x$ from the scaling violations of the proton structure function $F_2(x,Q^2)$. The gluon density is obtained from DGLAP…

High Energy Physics - Phenomenology · Physics 2014-11-17 M. B. Gay Ducati , Victor P. B. Gonçalves

The transverse nucleon spin can be transferred to the quarks and gluons in several ways. In the factorizing, hard scattering processes to be considered, these are parameterized at leading twist by the transversity distribution function and…

High Energy Physics - Phenomenology · Physics 2009-11-07 Daniel Boer

We calculate the cross section of a pion diffraction dissociation in two jets with large transverse momenta originating from a hard gluon exchange between the pion constituents. To the leading logarithmic accuracy (in energy), the…

High Energy Physics - Phenomenology · Physics 2009-11-07 V. M. Braun , D. Yu. Ivanov , A. Schaefer , L. Szymanowski

An approximated solution for gluon distribution from DGLAP evolution equations with NLO splitting function in the small-$x$ limit is presented. We first obtain the simplified forms of LO and NLO splitting functions in the small-$x$ limit.…

High Energy Physics - Phenomenology · Physics 2024-01-29 Jingxuan Chen , Xiaopeng Wang , Yanbing Cai , Xurong Chen , Qian Wang