arXiv subjects

Krzysztof Golec-Biernat

Publications and source records attributed to Krzysztof Golec-Biernat.

At least 19 recordsLinked to original sources

arXiv2026

Partonic Entropy of the Proton from DGLAP Evolution

We investigate the concept of partonic entropy of the proton within the Dokshitzer--Gribov--Lipatov--Altarelli--Parisi (DGLAP) evolution scheme of collinear parton distributions. We show that such entropy increases monotonically with the evolution scale. The mechanism underlying this growth is illustrated using a simplified model of DGLAP evolution, highlighting the importance of including saturation effects at small x in the evolution of parton distributions, which tame the otherwise unbounded growth of partonic entropy. Based on existing literature, we present two simplified models of parton saturation at small x. In one of these models, partonic entropy is identified with entanglement entropy and proposed as an experimentally testable observable.

hep-ph↗

arXiv2023

Momentum sum rule and factorization of double parton distributions

We show that the momentum sum rule is a necessary condition for factorization of double parton distributions into a product of two single parton distributions for small values of the parton momentum fractions x and large enough values of the evolution scale Q. This is a somewhat surprising result since the momentum sum rule involves integration over all values of the momentum fraction. In essence, the momentum sum rule provides a proper relation between the double and single parton distributions, which is necessary for the small x factorization at large $Q$.

hep-ph↗

arXiv2021

Prompt photon production in proton collisions as a probe of parton scattering in high energy limit

We study the prompt photon hadroproduction at the LHC with the $k_T$-factorization approach and the $qg^* \to qγ$ and $g^*g^* \to q\bar qγ$ partonic channels, using three unintegrated gluon distributions which depend on gluon transverse momentum. They represent three different theoretical schemes which are usually considered in the $k_T$-factorization approach, known under the acronyms: KMR, CCFM and GBW gluon distributions. We find sensitivity of the calculated prompt photon transverse momentum distribution to the gluon transverse momentum distribution. The predictions obtained with the three approaches are compared to data, that allows to differentiate between them. We also discuss the significance of the two partonic channels, confronted with the expectations which are based on the applicability of the $k_T$-factorization scheme in the high energy approximation.

hep-ph↗

arXiv2020

Drell-Yan production with the CCFM-K evolution

We discuss the Drell-Yan dilepton production using the transverse momentum dependent parton distributions evolved with the Catani-Ciafaloni-Fiorani-Marchesini-Kwieciński (CCFM-K) equations in the single loop approximation. Such equations are obtained assuming angular ordering of emitted partons (coherence) for $x\sim 1$ and transverse momentum ordering for $x \ll 1$. This evolution scheme also contains the Collins-Soper-Sterman (CSS) soft gluon resummation. We make a comparison with a broad class of data on transverse momentum spectra of low mass Drell-Yan dileptons.

hep-ph↗

arXiv2019

Drell-Yan plus jet production and BFKL evolution

Production of a forward Drell-Yan lepton pair accompanied by a jet separated by a large rapidity interval is proposed to study the BFKL evolution at the LHC. Several observables to be measured are presented including the azimuthal angle dependence of the lepton pair which allows to determine Drell-Yan structure functions.

hep-ph↗

arXiv2018

Forward Drell-Yan and backward jet production as a probe of the BFKL dynamics

We propose a new process which probes the BFKL dynamics in the high energy proton-proton scattering, namely the forward Drell-Yan (DY) production accompanied by a backward jet, separated from the DY lepton pair by a large rapidity interval. The proposed process probes higher rapidity differences and smaller transverse momenta than in the Mueller-Navelet jet production. It also offers a possibility of measuring new observables like leptons angular distribution coefficients in the DY lepton pair plus jet production.

hep-ph↗

arXiv2018

Saturation model of DIS : an update

We present the results of new fits to the recently extracted data on $F_2$ at low $x$ with the GBW saturation model and its modification to cover high values of $Q^2$. We find that the model stands the test of time and gives a good description of the data with slightly modified parameters. All the essential elements of the model, especially the saturation scale, are retained.

hep-ph↗

arXiv2018

On the use of the KMR unintegrated parton distribution functions

We discuss the unintegrated parton distribution functions (UPDFs) introduced by Kimber, Martin and Ryskin (KMR), which are frequently used in phenomenological analyses of hard processes with transverse momenta of partons taken into account. We demonstrate numerically that the commonly used differential definition of the UPDFs leads to erroneous results for large transverse momenta. We identify the reason for that, being the use of the ordinary PDFs instead of the cutoff dependent distribution functions. We show that in phenomenological applications, the integral definition of the UPDFs with the ordinary PDFs can be used.

hep-ph↗

arXiv2017

Numerical analysis of the unintegrated double gluon distribution

We present detailed numerical analysis of the unintegrated double gluon distribution which includes the dependence on the transverse momenta of partons. The unintegrated double gluon distribution was obtained following the Kimber-Martin-Ryskin method as a convolution of the perturbative gluon splitting function with the collinear integrated double gluon distribution and the Sudakov form factors. We analyze the dependence on the transverse momenta, longitudinal momentum fractions and hard scales. We find that the unintegrated gluon distribution factorizes into a product of two single unintegrated gluon distributions in the region of small values of $x$, provided the splitting contribution is included and the momentum sum rule is satisfied.

hep-ph↗

arXiv2016

Unintegrated Double Parton Distributions - a Summary

We present main elements of the construction of unintegrated double parton distribution functions which depend on transverse momenta of partons. We follow the method proposed by Kimber, Martin and Ryskin for a construction of unintegrated single parton distributions from the standard parton distribution functions.

hep-ph↗

arXiv2016

The double gluon distribution from the single gluon distribution

Using momentum sum rule for evolution equations for Double Parton Distribution Functions (DPDFs) in the leading logarithmic approximation, we find that the double gluon distribution function can be uniquely constrained via the single gluon distribution function. We also study numerically its evolution with a hard scale and show that an approximately factorized ansatz into the product of two single gluon distributions performs quite well at small values of $x$ but is always violated for larger values, as expected.

hep-ph↗

arXiv2016

Generalized Valon Model for Double Parton Distributions

We show how the double parton distributions may be obtained consistently from the many-body light-cone wave functions. We illustrate the method on the example of the pion with two Fock components. The procedure, by construction, satisfies the Gaunt-Stirling sum rules. The resulting single parton distributions of valence quarks and gluons are consistent with a phenomenological parametrization at a low scale.

hep-ph↗

arXiv2015

Constraining the double gluon distribution by the single gluon distribution

We show how to consistently construct initial conditions for the QCD evolution equations for double parton distribution functions in the pure gluon case. We use to momentum sum rule for this purpose and a specific form of the known single gluon distribution function in the MSTW parameterization. The resulting double gluon distribution satisfies exactly the momentum sum rule and is parameter free. We also study numerically its evolution with a hard scale and show the approximate factorization into product of two single gluon distributions at small values of x, whereas at large values of x the factorization is always violated in agreement with the sum rule.

hep-ph↗

arXiv2014

Electroweak boson production in double parton scattering

We study the $W^+W^-$ and $Z^0Z^0$ electroweak boson production in double parton scattering using QCD evolution equations for double parton distributions. In particular, we analyze the impact of splitting terms in the evolution equations on the double parton scattering cross sections. Unlike the standard terms, the splitting terms are not suppressed for large values of the relative momentum of two partons in the double parton scattering. Thus, they play an important role which we discuss in detail for the single splitting contribution to the cross sections under the study.

hep-ph↗

arXiv2014

How to impose initial conditions for QCD evolution of double parton distributions?

Double parton distribution functions (DPDFs) are used in the QCD description of double parton scattering. The DPDFs evolve with hard scales through QCD evolution equations which obey nontrivial momentum and valence quark number sum rules. We describe an attempt to construct initial conditions for the evolution equations which exactly fulfil these sum rules and discuss its shortcomings. We also discuss the factorization of the DPDFs into a product of two single parton distribution functions at small values of the parton momentum fractions.

hep-ph↗

arXiv2013

Initial conditions for evolution of double parton distributions

Double parton distribution functions (DPDFs) are used in the QCD description of double parton scattering. The DPDFs evolve with hard scales through relatively new QCD evolution equations which obey nontrivial momentum and valence quark number sum rules. Based on the constructed numerical program, we present results on the QCD evolution of the DPDFs. In particular, we discuss the problem how to specify initial conditions for the evolution equations which exactly fulfill the sum rules.

hep-ph↗

arXiv2013

Electroweak vector boson production at the LHC as a probe of mechanisms of diffraction

We show that the double diffractive electroweak vector boson production in the $pp$ collisions at the LHC is an ideal probe of QCD based mechanisms of diffraction. Assuming the resolved Pomeron model with flavor symmetric parton distributions, the $W$ production asymmetry in rapidity equals exactly zero. In other approaches, like the soft color interaction model, in which soft gluon exchanges are responsible for diffraction, the asymmetry is non-zero and equal to that in the inclusive $W$ production. In the same way, the ratio of the $W$ to $Z$ boson production is independent of rapidity in the models with resolved Pomeron in contrast to the predictions of the soft color interaction model.

hep-ph↗

arXiv2012

Nonlinear equation for coherent gluon emission

Motivated by the regime of QCD explored nowadays at LHC, where both the total energy of collision and momenta transfers are high, we investigate evolution equations of high energy factorization. In order to study such effects like parton saturation in final states one is inevitably led to investigate how to combine physics of the BK and CCFM evolution equations. In this paper we obtain a new exclusive form of the BK equation which suggests a possible form of the nonlinear extension of the CCFM equation.

hep-ph↗