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Pitonyak, Daniel

Publications and source records attributed to Pitonyak, Daniel.

16 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

TMD Handbook

This handbook provides a comprehensive review of transverse-momentum-dependent parton distribution functions and fragmentation functions, commonly referred to as transverse momentum distributions (TMDs). TMDs describe the distribution of partons inside the proton and other hadrons with respect to both their longitudinal and transverse momenta. They provide unique insight into the internal momentum and spin structure of hadrons, and are a key ingredient in the description of many collider physics cross sections. Understanding TMDs requires a combination of theoretical techniques from quantum field theory, nonperturbative calculations using lattice QCD, and phenomenological analysis of experimental data. The handbook covers a wide range of topics, from theoretical foundations to experimental analyses, as well as recent developments and future directions. It is intended to provide an essential reference for researchers and graduate students interested in understanding the structure of hadrons and the dynamics of partons in high energy collisions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

First Global Extraction of the Worm-gear TMD g 1 T

In these proceedings, we report on the first simultaneous extraction of the worm-gear function g 1 T , one of the eight leading-twist TMDs. The study analyzes COMPASS, HERMES and JLab semi-inclusive deep-inelastic scattering data using Monte Carlotechniques. We also provide a comparison of g 1 T obtained from this experimental data with a large N c analysis, the Wandzura–Wilczek-type approximation, and lattice QCD.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Extraction of the worm-gear TMD g1t from COMPASS , HERMES and JLab data on semi-inclusive DIS

Transverse momentum dependent parton distributions (TMDs) are an important class of functions required to understand the 3D structure of hadrons in terms of their underlying partons. One of the least known TMDs in terms of a global QCD analysis is the worm-gear TMD g1t . It carries the probabilistic interpretation of finding longitudinally polarized quarks inside transversely polarized hadrons. In this proceedings, we present the first-ever global QCD analysis of the semi-inclusive DIS $A^ {cos(φ_h-φ_S)}_{LT}$ data using Monte Carlo techniques to extract the worm-gear TMD g1T . The relevant data are available from COMPASS, HERMES and JLab. We compare our results for g1T with different theoretical approaches, including the large-N c approximation, the Wandzura Wilczek-type approximation, and lattice QCD.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Origin of single transverse-spin asymmetries in high-energy collisions

In this paper, we perform the first simultaneous QCD global analysis of data from semi-inclusive deep inelastic scattering, Drell-Yan, e + e - annihilation into hadron pairs, and proton-proton collisions. Consequently, we are able to extract a universal set of nonperturbative functions that describes the observed asymmetries in these reactions. The outcome of our analysis indicates single transverse-spin asymmetries in high-energy collisions have a common origin. Furthermore, we achieve the first phenomenological agreement with lattice QCD on the up and down quark tensor charges.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Polarized hyperon production in single-inclusive electron-positron annihilation at next-to-leading order

We study the production of polarized Λ-hyperons in electron-positron annihilation. We are particularly interested in the transverse-spin dependence of the cross section for unpolarized incident electron-positron pairs. At high energies this process may be described in the collinear twist-3 framework, where the hadronization transition of partons into a transversely polarized Λ-hyperon can be written in terms of collinear twist-3 fragmentation matrix elements. We calculate the hard partonic cross sections and interference terms in perturbative QCD to next-to-leading order accuracy. We find that the QCD equation of motion plays a crucial role in our analysis. As a byproduct, assuming the validity of QCD factorization for twist-3 observables at next-to-leading order, we derive the evolution equation for the relevant twist-3 fragmentation matrix element.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Connections between collinear and transverse-momentum-dependent polarized observables within the Collins–Soper–Sterman formalism

We extend the improved Collins–Soper–Sterman (iCSS) W+Y construction recently presented in [1] to the case of polarized observables, where we focus in particular on the Sivers effect in semi-inclusive deep-inelastic scattering. We further show how one recovers the expected leading-order collinear twist-3 result from a (weighted) q T -integral of the differential cross section. We are also able to demonstrate the validity of the well-known relation between the (TMD) Sivers function and the (collinear twist-3) Qiu–Sterman function within the iCSS framework. This relation allows for their interpretation as functions yielding the average transverse momentum of unpolarized quarks in a transversely polarized spin-$\frac{1}{2}$ target. We further outline how this study can be generalized to other polarized quantities.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Small-x asymptotics of the gluon helicity distribution

Here, we determine the small-x asymptotics of the gluon helicity distribution in a proton at leading order in perturbative QCD at large N c . To achieve this, we begin by evaluating the dipole gluon helicity TMD at small x. In the process we obtain an interesting new result: in contrast to the unpolarized dipole gluon TMD case, the operator governing the small-x behavior of the dipole gluon helicity TMD is different from the operator corresponding to the polarized dipole scattering amplitude (used in our previous work to determine the small-x asymptotics of the quark helicity distribution).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Phenomenological constraints on A N in p ↑ p→πX from Lorentz invariance relations

We present a new analysis of A N in p ↑ p→πX within the collinear twist-3 factorization formalism. We incorporate recently derived Lorentz invariance relations into our calculation and focus on input from the kinematical twist-3 functions, which are weighted integrals of transverse momentum dependent (TMD) functions. In particular, we use the latest extractions of the Sivers and Collins functions with TMD evolution to compute certain terms in A N . Consequently, we are able to constrain the remaining contributions from the lesser known dynamical twist-3 correlators.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Helicity evolution at small x : Flavor singlet and nonsinglet observables

We extend our earlier results for the quark helicity evolution at small x to derive the small-x asymptotics of the flavor singlet and flavor nonsinglet quark helicity TMDs and PDFs and of the g 1 structure function. In the flavor singlet case we rederive the evolution equations obtained in our previous paper on the subject, performing additional cross-checks of our results. In the flavor nonsinglet case we construct new small-x evolution equations by employing the large-N c limit. Here, all evolution equations resum double-logarithmic powers of α s ln 2 (1/x) in the polarization-dependent evolution along with the single-logarithmic powers of α s ln(1/x) in the unpolarized evolution which includes saturation effects.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Small- x asymptotics of the quark helicity distribution

We construct a numerical solution of the small-x evolution equations derived in our recent work for the (anti)quark transverse momentum dependent helicity TMDs and parton distribution functions (PDFs) as well as the g 1 structure function. We focus on the case of large N c , where one finds a closed set of equations. Employing the extracted intercept, we are able to predict directly from theory the behavior of the quark helicity PDFs at small x, which should have important phenomenological consequences. Finally, we also give an estimate of how much of the proton’s spin carried by the quarks may be at small x and what impact this has on the spin puzzle.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Operator constraints for twist-3 functions and Lorentz invariance properties of twist-3 observables

We investigate the behavior under Lorentz transformations of perturbative coefficient functions in a collinear twist-3 formalism relevant for high-energy observables including transverse polarization of hadrons. We argue that those perturbative coefficient functions can, a priori , acquire quite different yet Lorentz-invariant forms in various frames. This somewhat surprising difference can be traced back to a general dependence of the perturbative coefficient functions on light cone vectors which are introduced by the twist-3 factorization formulas and which are frame-dependent. One can remove this spurious frame dependence by invoking so-called Lorentz invariance relations (LIRs) between twist-3 parton correlation functions. Some of those relations for twist-3 distribution functions were discussed in the literature before. In this paper we derive the corresponding LIRs for twist-3 fragmentation functions. We explicitly demonstrate that these LIRs remove the light cone vector dependence by considering transverse spin observables in the single-inclusive production of hadrons in lepton-nucleon collisions, ℓN→hX. Furthermore, with the LIRs in hand, we also show that twist-3 observables in general can be written solely in terms of three-parton correlation functions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Helicity evolution at small x

Here, 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 α s ln 2 (1/x) in the polarization-dependent evolution along with the powers of α s ln(1/x) in the unpolarized evolution which includes saturation effects. Moreover, the equations are written in an operator form in terms of polarization-dependent Wilson line-like operators. While the equations do not close in general, they become closed and self-contained systems of non-linear equations in the large-N c and large-N c & N f limits. Finally, as a cross-check, in the ladder approximation, our equations map onto the same ladder limit of the infrared evolution equations for the g 1 structure function derived previously by Bartels, Ermolaev and Ryskin.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗