The parton distributions in the proton are evaluated dynamically using a nonlinear QCD evolution equation - the DGLAP equation with twist-4 (the GLR-MQ-ZSR) corrections - starting from a low scale $μ^2$, where the nucleon consists of valence quarks. We find that the negative nonlinear corrections can improve the perturbative stability of the QCD evolution equation at low $Q^2$. Our resulting parton distributions of the proton with four free parameters are compatible with the existing databases.
We show that the sea quark distributions exhibit a positive and flattish behavior at small $x$ and low $Q^2$. This approach provides a powerful tool to connect the quark models of the hadron and various non-perturbative effects on them at scale $μ^2$ with the measured structure functions at high scale $Q^2>> μ^2$.
In this talk we present the results of the investigation on the so called double parton distribution functions (dPDFs), accessible quantities in high energy proton-proton and proton nucleus collisions, in double parton scattering processes (DPS). These new and almost unknown distributions encode information on how partons inside a proton are correlated among each other and represent a new tool to explore the three dimensional partonic structure of hadrons. In the present contribution, results of the calculations of dPFDs are presented also including phenomenological investigations on the impac…
In this contribution we discuss the main outcomes of our studies on the so called double parton distribution functions (dPDFs), accessible quantities in high energy proton-proton and proton nucleus collisions, in double parton scattering processes (DPS). These new distributions are almost unknown, nevertheless they encode information on how partons inside a proton are correlated among each other. Double PDFs represent a new tool to explore the three dimensional partonic structure of hadrons. Here, we show results obtained from calculations of dPFDs. In particular we focus our attention on the …
We consider double parton distribution functions (dPDFs), essential quantities in double parton scattering (DPS) studies, which encode novel non perturbative insight on the partonic proton structure. We develop the formalism to extract this information from dPDFs and present results by using constituent quark model calculations within the Light-Front approach, focusing on radiatively generated gluon dPDFs. Moreover, we generalize the relation between the mean transverse partonic distance between two active partons in a DPS process and the so called effective cross section to include partonic c…
The structure function approach and the parton picture, developed for the theoretical description of the deep inelastic electron-proton scattering, also proved to be very effective for calculation of radiative corrections in Quantum Electrodynamics. We use them to calculate radiative corrections to the cross section of electron-proton scattering due to electron-photon interaction, in the experimental setup with the recoil proton detection, proposed by A.A. Vorobev to measure the proton radius. In the one-loop approximation, explicit expressions for these corrections are obtained for arbitrary …
We explore the application of a two-component model of proton structure functions in the analysis of deep-inelastic scattering (DIS) data at low $Q^2$ and small $x$. This model incorporates both vector meson dominance and the correct photo-production limit. The CJ15 parameterization is applied to the QCD component, in order to take into account effects of order $1/Q^2$ effects, such as target mass corrections and higher twist contributions. The parameters of the leading twist parton distribution functions and higher twist coefficient functions are determined by fitting deep inelastic scatterin…
In the present paper we address double parton scattering (DPS) in quasi-real photon-proton interactions. By using electromagnetic and hadronic models of the photon light cone wave functions, we compute the so-called effective cross-section, $σ_{eff}^{γp}$ which allows us to calculate the DPS contribution to these processes under dedicated assumptions. In particular, for the four-jet photoproduction in HERA kinematics we found a sizeable DPS contribution. We show that if the photon virtuality $Q^2$ could be measured and thus the dependence of $σ_{eff}^{γp}$ on such a parameter exposed, informat…
Dijet production in proton-nucleus ($p$A) collisions at the LHC provides invaluable information on the underlying parton distributions in nuclei, especially the gluon distributions. Triple-differential dijet cross sections enable a well-controlled kinematic scan (over momentum fraction $x$ and probing scale $Q^2$) of the nuclear parton distribution functions (nPDFs), i.e., $f^\textrm{A}_i(x,Q^2)$. In this work, we study several types of triple-differential cross sections for dijet production in proton-proton ($pp$) and proton-lead ($p$Pb) collisions at the LHC, to next-to-leading order within …
Forward-backward multiplicity correlations have been studied in electron-positron, proton-proton and more recently in lead-lead collisions. For the proton-proton case, comparison of experimental results to different models reveals an incomplete understanding of the physical phenomenon associated with these correlations. In this work, we present a study of forward-backward multiplicity correlations in proton-proton collisions using the PYTHIA event generator, at LHC energies. A detailed analysis is presented with and without weak decays, splitting data samples into soft and hard QCD processes, …
We study the radiative energy loss contribution to proton stopping in $AA$ collisions. The analyses is performed within the light-cone path integral approach to induced gluon emission. We have found that the radiative correction can fill in partly the midrapidity dip in the net proton rapidity distribution in $AA$ collisions at $\sqrt{s}\sim 10$ GeV. We argue that at $\sqrt{s}\sim 10$ GeV the net proton fluctuations at midrapidity may be dominated by the initial fluctuations of the proton flow, which, to a good accuracy, should be binomial.
Double parton scattering events are directly sensitive to the correlations between two partons inside a proton and can answer fundamental questions on the connections between the proton constituents. In this chapter, the different types of possible correlations, our present knowledge of them, and the processes where they are likely to be important, are introduced and explained. The increasing integrated luminosity at the LHC and the refinements of the theory of double parton scattering, lead to interesting prospects for measuring, or severely constraining, two-parton correlations in the near f…
The production process of quarkonia in proton-proton (pp) collision is a very good probe of the parton structure of the proton. Recent experimental data of the production of J/psi+vector boson or quarkonium pairs at the LHC and Tevatron suggest the relevance of double parton scatterings (DPS). We discuss here the single parton scattering (SPS) contribution to the J/psi +Z, J/psi +W, and J/psi +J/psi productions in hadron collisions. By revisiting the computations of the SPS contributions to the J/psi+Z and J/psi +W productions, we demonstrate that the ATLAS data in fact show evidence for DPS.
We study the contribution from double parton scattering (DPS) to four-jet production at the LHC, both at the leading order accuracy and after incorporating the effects of QCD radiation. Apart from DPS, we also include and discuss the contribution from single parton scattering (SPS). We find that the QCD radiation impacts theoretical predictions significantly, with DPS contributions more affected than the SPS. We also examine a number of observables in regard to their effectiveness for discrimination between DPS and SPS events and propose sets of kinematical cuts to improve the prospects of mea…
We present our studies of four-jet double parton scattering production in proton-nucleus collisions within the framework of the PYTHIA8 event generator. We demonstrate that double absorptive processes in pA generated by the Angantyr model in PYTHIA8 give an enhancement of the total double parton scattering cross section similar to the predictions by Strikman and Treleani in 2001. Additionally, we discuss how the growth of activity in a direction of a nucleus affects an A-scaling of a total double parton scattering cross section in proton-nucleus collisions.
We propose a new procedure for parton-to-hadron fragmentation in proton-proton collisions. The hadronization is considered in the parton-parton center-of-mass system and hadrons are assumed to be emitted in the direction of outgoing partons in that frame and then their four-momenta are transformed to the overall center-of-mass system using relevant Lorentz transformations and appropriate distributions are constructed. For heavy hadron production the energy-momentum condition is imposed. In many cases our procedure disagrees with the commonly used rule that rapidity of produced hadron is the sa…
We present the parton distribution functions (PDFs) for un- polarised, longitudinally polarized and transversely polarized quarks in a proton using the light-front quark diquark model. We also present the scale evolution of PDFs and calculate axial charge and tecsor charge for $u$ and $d$ quarks at a scale of experimental findings.
Lev Lipatov was a giant in the field of strong interactions and a dominant force in high-energy QCD for many decades. His work deeply influenced both how we think about QCD and how we perform calculations in the theory. Below we describe the work in two related research directions: the physics of parton saturation and proton spin at small $x$. Both developments would have been impossible without Lipatov's groundbreaking work. Saturation physics would not have happened without the Balitsky-Fadin-Kuraev-Lipatov (BFKL) equation. The recent progress in our theoretical understanding of the proton s…
