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We computed the longitudinal proton structure function $F_{L}$, using the nonlinear Dokshitzer-Gribov-Lipatov-Altarelli-parisi (NLDGLAP) evolution equation approach at small $x$. For the gluon distribution, the nonlinear effects are related…

High Energy Physics - Phenomenology · Physics 2014-02-07 G. R. Boroun

In the high-energy limit of QCD, scattering off nucleons and nuclei can be described in terms of Wilson-line correlators whose energy dependence is perturbative. The energy dependence of the two-point correlator, called the dipole…

High Energy Physics - Phenomenology · Physics 2026-03-13 Meisen Gao , Zhong-Bo Kang , Jani Penttala , Ding Yu Shao

The modified evolution equation for parton distributions of Dokshitzer, Marchesini and Salam is extended to non-singlet Deep Inelastic Scattering coefficient functions and the physical evolution kernels which govern their scaling violation.…

High Energy Physics - Phenomenology · Physics 2014-11-20 Georges Grunberg

When computed to next-to-leading order in perturbative QCD, the non-linear Balitsky-Kovchegov (BK) equation for the high-energy evolution of the dipole-hadron scattering appears to be unstable. We show that this instability can be avoided…

High Energy Physics - Phenomenology · Physics 2021-02-03 B. Ducloué , E. Iancu , A. H. Mueller , G. Soyez , D. N. Triantafyllopoulos

Important corrections to BFKL evolution are obtained from non-leading contributions and from non-linear effects due to unitarisation or saturation. It has been difficult to estimate the relative importance of these effects, as NLO effects…

High Energy Physics - Phenomenology · Physics 2009-11-11 Emil Avsar , Gosta Gustafson , Leif Lonnblad

We construct small-x evolution equations which can be used to calculate quark and anti-quark helicity TMDs and PDFs, along with the $g_1$ structure function. These evolution equations resum powers of $\alpha_s \, \ln^2 (1/x)$ in the…

High Energy Physics - Phenomenology · Physics 2016-07-15 Yuri V. Kovchegov , Daniel Pitonyak , Matthew D. Sievert

Phenomenological models of the dipole cross section that enters in the description of for instance deep inelastic scattering at very high energies have had considerable success in describing the available small-x data in both the saturation…

High Energy Physics - Phenomenology · Physics 2008-11-26 Daniel Boer , Andre Utermann , Erik Wessels

We suggest a modified form of a unitarized BFKL equation imposing the so-called kinematic constraint on the gluon evolution in multi-Regge kinematics. The underlying nonlinear effects on the gluon evolution are investigated by solving the…

High Energy Physics - Phenomenology · Physics 2019-06-14 P. Phukan , M. Lalung , J. K. Sarma

We consider a nonlinear evolution equation recently proposed to describe the small-$x$ hadronic physics in the regime of very high gluon density. This is a functional Fokker-Planck equation in terms of a classical random color source, which…

High Energy Physics - Phenomenology · Physics 2009-10-31 Edmond Iancu , Andrei Leonidov , Larry McLerran

Within the Color Glass Condensate effective field theory, we assess the importance of including a finite size for the target on observables sensitive to small-$x$ evolution. To this end, we study the Balitsky-Kovchegov (BK) equation with…

High Energy Physics - Phenomenology · Physics 2025-04-03 Heikki Mäntysaari , Jani Penttala , Farid Salazar , Björn Schenke

We perform a global fit to the structure function F_2 measured in lepton-proton experiments at small values of Bjorken-x, x\le 0.01, for all experimentally available values of Q^2, 0.045 GeV^2\le Q^2 \le 800 GeV^2. We show that the recent…

High Energy Physics - Phenomenology · Physics 2009-09-01 J. L. Albacete , N. Armesto , J. G. Milhano , C. A. Salgado

We review small $x$ contributions to perturbative evolution equations for parton distributions, and their resummation. We emphasize in particular the resummation technique recently developed in order to deal with the apparent instability of…

High Energy Physics - Phenomenology · Physics 2007-05-23 Guido Altarelli , Richard D. Ball , Stefano Forte

We present a detailed description of the Q^2 and x dependence of the structure functions F2 and FL as extracted from the Deep Inelastic Scattering data at HERA in the small Bjorken x region. Making use of a collinearly-improved BFKL…

High Energy Physics - Phenomenology · Physics 2013-04-10 Martin Hentschinski , Agustin Sabio Vera , Clara Salas

After a brief introduction to Deep Inelastic Scattering in the Bjorken limit and in the Regge Limit we discuss the operator product expansion in terms of non local string operator and in terms of Wilson lines. We will show how the…

High Energy Physics - Phenomenology · Physics 2010-02-25 Giovanni Antonio Chirilli

Inclusive as well as exclusive emissions in forward and central directions of rapidity are widely recognized as excellent channels to access the proton structure at small-x. In this regime, to describe nucleons structure, it is necessary to…

We present posterior distributions of parameters that characterize the nonperturbative initial input for the Balitsky-Kovchegov evolution equation. The BK equation evolves an initial dipole-target scattering amplitude at moderate…

High Energy Physics - Phenomenology · Physics 2024-07-16 Carlisle Casuga , Mikko Karhunen , Heikki Mäntysaari

We construct an anomalous dimension for small x evolution which goes beyond standard fixed order perturbative evolution by including resummed small x logarithms deduced from the leading order BFKL equation with running coupling.…

High Energy Physics - Phenomenology · Physics 2008-11-26 Guido Altarelli , Richard D. Ball , Stefano Forte

We present a Monte Carlo based analysis of the combined world data on polarized lepton-nucleon deep-inelastic scattering at small Bjorken $x$ within the polarized quark dipole formalism. We show for the first time that double-spin…

High Energy Physics - Phenomenology · Physics 2021-08-11 Daniel Adamiak , Yuri V. Kovchegov , W. Melnitchouk , Daniel Pitonyak , Nobuo Sato , Matthew D. Sievert

We explore the subleading-N_c corrections to the large-N_c Balitsky-Kovchegov (BK) evolution equation by comparing its solution to that of the all-N_c Jalilian-Marian-Iancu-McLerran-Weigert-Leonidov-Kovner (JIMWLK) equation. In earlier…

High Energy Physics - Phenomenology · Physics 2009-11-19 Yuri V. Kovchegov , Janne Kuokkanen , Kari Rummukainen , Heribert Weigert

We investigate the recently proposed nonlinear equation for the unintegrated gluon distribution function which includes the subleading effects at small $x$. We obtained numerically the solution to this equation in $(x,k)$ space, and also…

High Energy Physics - Phenomenology · Physics 2008-11-26 K. Kutak , A. M. Stasto