scholarly journals ANALYTIC PROPERTIES OF MULTI-PARTON POLE MATRIX ELEMENTS AND UNIVERSALITY OF FRAGMENTATION FUNCTIONS

2011 ◽  
Vol 04 ◽  
pp. 115-125
Author(s):  
LEONARD GAMBERG ◽  
ASMITA MUKHERJEE ◽  
P. J. MULDERS
Keyword(s):  
High Energy ◽  
Distribution Functions ◽  
Analytic Structure ◽  
Matrix Elements ◽  
Parton Distribution Functions ◽  
Transverse Momentum Dependent ◽  
Spin Asymmetries ◽  
Single Spin ◽  
Fragmentation Functions ◽  
High Energy Scattering

Gluonic pole matrix elements explain the appearance of single spin asymmetries (SSA) in high-energy scattering processes. They involve a combination of operators which are odd under time reversal (T-odd). Such matrix elements appear in principle both for parton distribution functions and parton fragmentation functions. We show that for parton fragmentation functions these gluonic pole matrix elements vanish as a consequence of the analytic structure of scattering amplitudes in Quantum Chromodynamics. We extend this analysis to the case of multi-partonic pole matrix elements. This result is important in the study of the universality of transverse momentum dependent (TMD) fragmentation functions.

scholarly journals GENERALIZED UNIVERSALITY FOR TMD DISTRIBUTION FUNCTIONS

2012 ◽  
Vol 20 ◽  
pp. 66-74 ◽  
Author(s):  
M. G. A. BUFFING ◽  
P. J. MULDERS
Keyword(s):  
Transverse Momentum ◽  
Parton Distribution ◽  
Azimuthal Angle ◽  
High Energy ◽  
Distribution Functions ◽  
Transverse Spin ◽  
Parton Distribution Functions ◽  
Transverse Momentum Dependent ◽  
Spin Asymmetries ◽  
Azimuthal Asymmetries

Azimuthal asymmetries in high-energy processes, most pronounced showing up in combination with single or double (transverse) spin asymmetries, can be understood with the help of transverse momentum dependent (TMD) parton distribution and fragmentation functions. These appear in correlators containing expectation values of quark and gluon operators. TMDs allow access to new operators as compared to collinear (transverse momentum integrated) correlators. These operators include nontrivial process dependent Wilson lines breaking universality for TMDs. Making an angular decomposition in the azimuthal angle, we define a set of universal TMDs of definite rank, which appear with process dependent gluonic pole factors in a way similar to the sign of T-odd parton distribution functions in deep inelastic scattering or the Drell-Yan process. In particular, we show that for a spin 1/2 quark target there are three pretzelocity functions.

scholarly journals Single-spin asymmetry ATsin(2ϕ−ϕS) in π−p Drell-Yan process within TMD factorization

2022 ◽  
Vol 258 ◽  
pp. 03002
Author(s):  
Hui Li ◽  
Xiaoyu Wang ◽  
Zhun Lu
Keyword(s):  
Spin Asymmetry ◽  
Distribution Functions ◽  
Single Spin Asymmetry ◽  
Parton Distribution Functions ◽  
Sudakov Form Factor ◽  
Transverse Momentum Dependent ◽  
Single Spin ◽  
Mulders Function ◽  
Light Cone Wave Function ◽  
The Asymmetry

We study the single-spin asymmetry ATsin(2ϕ−ϕS) in the pion-induced Drell-Yan process within the transverse momentum dependent factorization (TMD factorization). The asymmetry can be expressed as the convolution of the Boer-Mulders function and the transversity function. We numerically estimate the asymmetry ATsin(2ϕ−ϕS) at the COMPASS kinematics with the model results for the pion meson distributions from the light-cone wave function approach and the available parametrization for the proton distributions. We also include the TMD evolution formalism both proton and pion parton distribution functions by using two different parametrizations on nonperturbative Sudakov form factor. We find that the asymmetry ATsin(2ϕ−ϕS) as functions of xp, xπ, xF and q⊥ is qualitatively consistent with the recent COMPASS measurement.

HADRON STRUCTURE STUDY IN FORTHCOMING DRELL–YAN EXPERIMENTS: COMPASS PROJECT AT CERN

2009 ◽  
Vol 24 (35n37) ◽  
pp. 3033-3044 ◽  
Author(s):  
◽  
OLEG DENISOV
Keyword(s):  
Transverse Momentum ◽  
Structure Study ◽  
Distribution Functions ◽  
Proton Target ◽  
Production Mechanism ◽  
Hadron Structure ◽  
Parton Distribution Functions ◽  
Transverse Momentum Dependent ◽  
Spin Asymmetries ◽  
Hadron Beam

The study of Drell–Yan (DY) processes involving the collision of an (un)polarised hadron beam on an (un)polarised proton target can result in a fundamental improvement of our knowledge on the transverse momentum dependent (TMDs) parton distribution functions (PDFs) of hadrons. The production mechanism of J/ψ and J/ψ - DY duality can also be addressed. One of the forthcoming polarised DY experiments (COMPASS (SPS, CERN)) is discussed in this context. The most important features of this project are briefly reviewed, as well as its sensitivity to the various transverse momentum dependent spin asymmetries.

scholarly journals Polarized Drell-Yan at COMPASS-II: Transverse Spin Physics Program

2016 ◽  
Vol 40 ◽  
pp. 1660109
Author(s):  
Bakur Parsamyan
Keyword(s):  
High Energy ◽  
Muon Beam ◽  
Distribution Functions ◽  
Transverse Spin ◽  
Spin Physics ◽  
Transverse Momentum Dependent ◽  
Spin Asymmetries ◽  
Compass Experiment ◽  
Physics Program ◽  
Azimuthal Asymmetries

Successful realization of polarized Drell-Yan physics program is one of the main goals of the second stage of the COMPASS experiment. Drell-Yan measurements with high energy (190 GeV/c) pion beam and transversely polarized NH3 target have been initiated by a pilot-run in the October 2014 and will be followed by 140 days of data taking in 2015. In the past twelve years COMPASS experiment performed series of SIDIS measurements with high energy muon beam and transversely polarized deuteron and proton targets. Results obtained for Sivers effect and other target transverse spin dependent and unpolarized azimuthal asymmetries in SIDIS serve as an important input for general understanding of spin-structure of the nucleon and are being used in numerous theoretical and phenomenological studies being carried out in the field of transvers-spin physics. Measurement of the Sivers and all other azimuthal effects in polarized Drell-Yan at COMPASS will reveal another side of the spin-puzzle providing a link between SIDIS and Drell-Yan branches. This will be a unique possibility to test universality and key-features of transverse momentum dependent distribution functions (TMD PDFs) using essentially same experimental setup and exploring same kinematic domain. In this review main physics aspects of future COMPASS polarized Drell-Yan measurement of azimuthal transverse spin asymmetries will be presented, giving a particular emphasis on the link with very recent COMPASS results obtained for SIDIS transverse spin asymmetries from four ”Drell-Yan” [Formula: see text]-ranges.

scholarly journals The Sivers asymmetry in hadronic dijet production

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Zhong-Bo Kang ◽  
Kyle Lee ◽  
Ding Yu Shao ◽  
John Terry
Keyword(s):  
Spin Asymmetry ◽  
Star Collaboration ◽  
Heavy Ion ◽  
Distribution Functions ◽  
Relativistic Heavy Ion Collider ◽  
Parton Distribution Functions ◽  
Dijet Production ◽  
Transverse Momentum Dependent ◽  
Spin Asymmetries ◽  
Polarized Proton

Abstract We study the single spin asymmetry in the back-to-back dijet production in transversely polarized proton-proton collisions. Such an asymmetry is generated by the Sivers functions in the incoming polarized proton. We propose a QCD formalism in terms of the transverse momentum dependent parton distribution functions, which allow us to resum the large logarithms that arise in the perturbative calculations. We make predictions for the Sivers asymmetry of hadronic dijet production at the kinematic region that is relevant to the experiment at the Relativistic Heavy Ion Collider (RHIC). We further compute the spin asymmetries in the selected positive and negative jet charge bins, to separate the contributions from u- and d-quark Sivers functions. We find that both the sign and size of our numerical results are roughly consistent with the preliminary results from the STAR collaboration at the RHIC.

scholarly journals Unpolarized quark and gluon TMD PDFs and FFs at N3LO

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Ming-xing Luo ◽  
Tong-Zhi Yang ◽  
Hua Xing Zhu ◽  
Yu Jiao Zhu
Keyword(s):  
Distribution Functions ◽  
Leading Order ◽  
Momentum Fraction ◽  
Parton Distribution Functions ◽  
Third Order ◽  
Probability Interpretation ◽  
Transverse Momentum Dependent ◽  
Precision Determination ◽  
Fragmentation Functions

Abstract In this paper we calculate analytically the perturbative matching coefficients for unpolarized quark and gluon Transverse-Momentum-Dependent (TMD) Parton Distribution Functions (PDFs) and Fragmentation Functions (FFs) through Next-to-Next-to-Next-to-Leading Order (N3LO) in QCD. The N3LO TMD PDFs are calculated by solving a system of differential equation of Feynman and phase space integrals. The TMD FFs are obtained by analytic continuation from space-like quantities to time-like quantities, taking into account the probability interpretation of TMD PDFs and FFs properly. The coefficient functions for TMD FFs exhibit double logarithmic enhancement at small momentum fraction z. We resum such logarithmic terms to the third order in the expansion of αs. Our results constitute important ingredients for precision determination of TMD PDFs and FFs in current and future experiments.

scholarly journals Spin asymmetries in electron-jet production at the future electron ion collider

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
Zhong-Bo Kang ◽  
Kyle Lee ◽  
Ding Yu Shao ◽  
Fanyi Zhao
Keyword(s):  
Distribution Functions ◽  
Parton Distribution Functions ◽  
Transverse Momentum Dependent ◽  
Spin Asymmetries ◽  
Proton Collisions ◽  
Jet Production ◽  
The Future ◽  
Jet Fragmentation ◽  
Unpolarized Electron ◽  
Azimuthal Asymmetries

Abstract We study all the possible spin asymmetries that can arise in back-to-back electron-jet production, ep → e + jet + X, as well as the associated jet fragmentation process, ep → e+jet(h)+X, in electron-proton collisions. We derive the factorization formalism for these spin asymmetries and perform the corresponding phenomenology for the kinematics relevant to the future electron ion collider. In the case of unpolarized electron-proton scattering, we also give predictions for azimuthal asymmetries for the HERA experiment. This demonstrates that electron-jet production is an outstanding process for probing unpolarized and polarized transverse momentum dependent parton distribution functions and fragmentation functions.

scholarly journals HIGH-ENERGY QCD FACTORIZATION FROM DIS TO pA COLLISIONS

2012 ◽  
Vol 20 ◽  
pp. 200-207 ◽  
Author(s):  
GIOVANNI ANTONIO CHIRILLI
Keyword(s):  
Gluon Distribution ◽  
Wilson Line ◽  
Energy Operator ◽  
High Energy ◽  
Distribution Functions ◽  
Operator Product ◽  
Parton Distribution Functions ◽  
Qcd Factorization ◽  
Fragmentation Functions ◽  
Line Operator

The high-energy QCD factorization for Deep Inelastic Scattering and for proton-nucleus collisions using Wilson line formalism and factorization in rapidity is discussed. We show that in DIS the factorization in rapidity reduces to the k T -factorization when the 2-gluon approximation is applied, provided that the composite Wilson line operator is used in the high-energy Operator Product Expansion. We then show that the inclusive forward cross-section in proton-nucleus collisions factorizes in parton distribution functions, fragmentation functions and dipole gluon distribution function at one-loop level.

scholarly journals Single-Spin Asymmetries AULsinϕh in Semi-Inclusive Pions Production

2016 ◽  
Vol 40 ◽  
pp. 1660045 ◽  
Author(s):  
Zhun Lu ◽  
Wenjuan Mao
Keyword(s):  
Pion Production ◽  
Neutral Pion ◽  
Spin Asymmetry ◽  
Distribution Functions ◽  
Proton Target ◽  
Deuteron Target ◽  
Transverse Momentum Dependent ◽  
Spin Asymmetries ◽  
Single Spin ◽  
Single Spin Asymmetries

The single-spin asymmetry [Formula: see text] of charged and neutral pion production in semi-inclusive deep-inelastic scattering on longitudinally polarized nucleon targets is studied. We particularly consider the effects of the twist-3 transverse-momentum dependent distribution functions [Formula: see text] and [Formula: see text], which are calculated in two different spectator-diquark models. We estimate the asymmetry for [Formula: see text], [Formula: see text] and [Formula: see text] produced off the proton target at HERMES and compare the results with the HERMES measurements. We also predict the same asymmetric moment for different pions at the kinematics of CLAS 5.5 GeV on a proton target, as well as at COMPASS on a deuteron target for comparison.

Predictions on the Transverse Single-Spin Asymmetries at Subleading Twist of Pion Production in Semi-Inclusive DIS

2016 ◽  
Vol 40 ◽  
pp. 1660030
Author(s):  
Wenjuan Mao ◽  
Zhun Lu ◽  
Bo-Qiang Ma
Keyword(s):  
Transverse Momentum ◽  
Pion Production ◽  
Diquark Model ◽  
Transverse Momentum Dependent ◽  
Spin Asymmetries ◽  
Single Spin ◽  
Single Spin Asymmetries ◽  
Fragmentation Functions

We estimate the single-spin asymmetries with [Formula: see text] and [Formula: see text] angular dependencies for electroproduction of pions in transversely polarized semi-inclusive DIS process. We consider the effect of the twist-3 transverse momentum dependent distributions which convoluted with twist-2 fragmentation functions. We calculate these distributions in a spectator-diquark model, and predict the corresponding single-spin asymmetries at the kinematics of HERMES, JLab and COMPASS. We find that the numerical estimates show that the asymmetries are sizable, and the T-odd twist-3 TMDs play an important role in these asymmetries.

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