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 High-energy operator product expansion at sub-eikonal level

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Giovanni Antonio Chirilli
Keyword(s):  
Operator Product Expansion ◽  
Evolution Equations ◽  
Energy Operator ◽  
High Energy ◽  
Structure Functions ◽  
Distribution Functions ◽  
Impact Factors ◽  
Operator Product ◽  
The Impact ◽  
New Distribution

Abstract The high energy Operator Product Expansion for the product of two electromagnetic currents is extended to the sub-eikonal level in a rigorous way. I calculate the impact factors for polarized and unpolarized structure functions, define new distribution functions, and derive the evolution equations for unpolarized and polarized structure functions in the flavor singlet and non-singlet case.

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 Quark sivers function at small x: spin-dependent odderon and the sub-eikonal evolution

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
Yuri V. Kovchegov ◽  
M. Gabriel Santiago
Keyword(s):  
Evolution Equations ◽  
Wilson Line ◽  
Distribution Functions ◽  
Coupling Constant ◽  
Parton Distribution Functions ◽  
Transverse Momentum Dependent ◽  
Sivers Function ◽  
Small X ◽  
Dipole Scattering ◽  
Line Operator

Abstract We apply the formalism developed earlier [1, 2] for studying transverse momentum dependent parton distribution functions (TMDs) at small Bjorken x to construct the small-x asymptotics of the quark Sivers function. First, we explicitly construct the complete fundamental “polarized Wilson line” operator to sub-sub-eikonal order: this object can be used to study a variety of quark TMDs at small x. We then express the quark Sivers function in terms of dipole scattering amplitudes containing various components of the “polarized Wilson line” and show that the dominant (eikonal) term which contributes to the quark Sivers function at small x is the spin-dependent odderon, confirming the re- cent results of Dong, Zheng and Zhou [3]. Our conclusion is also similar to the case of the gluon Sivers function derived by Boer, Echevarria, Mulders and Zhou [4] (see also [5]). We also analyze the sub-eikonal corrections to the quark Sivers function using the constructed “polarized Wilson line” operator. We derive new small-x evolution equations re-summing double-logarithmic powers of αs ln2(1/x) with αs the strong coupling constant. We solve the corresponding novel evolution equations in the large-Nc limit, obtaining a sub-eikonal correction to the spin-dependent odderon contribution. We conclude that the quark Sivers function at small x receives contributions from two terms and is given by$$ {f}_{1T}^{\perp q}\left(x,{k}_T^2\right)={C}_O\left(x,{k}_T^2\right)\frac{1}{x}+{C}_1\left({k}_T^2\right){\left(\frac{1}{x}\right)}^0+\cdots $$ f 1 T ⊥ q x k T 2 = C O x k T 2 1 x + C 1 k T 2 1 x 0 + ⋯ with the function CO(x,$$ {k}_T^2 $$ k T 2 ) varying slowly with x and the ellipsis denoting the subasymptotic and sub-sub-eikonal (order-x) corrections.

scholarly journals Solution of the NLO BFKL Equation and γ*γ* Cross-Section at NLO

2015 ◽  
Vol 37 ◽  
pp. 1560055
Author(s):  
Giovanni Antonio Chirilli
Keyword(s):  
Cross Section ◽  
Operator Product Expansion ◽  
Scattering Amplitude ◽  
Wilson Line ◽  
Energy Operator ◽  
High Energy ◽  
Bfkl Equation ◽  
Operator Product ◽  
Scattering Process

The analytic NLO cross section of the γ*γ* scattering process at high-energy is calculated. The result is obtained factorizing the scattering amplitude in rapidity space using the high-energy Operator Product Expansion in terms of composite Wilson line operators. The next-to-leading logarithmic resummation is included employing the solution of the NLO BFKL equation which obtained from the linearization of the evolution in rapidity space of the composite Wilson line operators.

scholarly journals One-loop matching for spin-dependent quasi-TMDs

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Markus A. Ebert ◽  
Stella T. Schindler ◽  
Iain W. Stewart ◽  
Yong Zhao
Keyword(s):  
Spin Structure ◽  
Wilson Line ◽  
Three Dimensional ◽  
Distribution Functions ◽  
Longitudinal Momentum ◽  
Loop Order ◽  
Parton Distribution Functions ◽  
Transverse Momentum Dependent ◽  
Unique Probe ◽  
Transverse Position

Abstract Transverse momentum dependent parton distribution functions (TMDPDFs) provide a unique probe of the three-dimensional spin structure of hadrons. We construct spin-dependent quasi-TMDPDFs that are amenable to lattice QCD calculations and that can be used to determine spin-dependent TMDPDFs. We calculate the short-distance coefficients connecting spin-dependent TMDPDFs and quasi-TMDPDFs at one-loop order. We find that the helicity and transversity distributions have the same coefficient as the unpolarized TMDPDF. We also argue that the same is true for pretzelosity and that this spin universality of the matching will hold to all orders in αs. Thus, it is possible to calculate ratios of these distributions as a function of longitudinal momentum and transverse position utilizing simpler Wilson line paths than have previously been considered.

scholarly journals POLARIZED STRUCTURE FUNCTIONS AND SPIN PHYSICS

2002 ◽  
Vol 17 (23) ◽  
pp. 3220-3238
Author(s):  
UTA STÖSSLEIN
Keyword(s):  
Parton Distribution ◽  
Spin Structure ◽  
High Energy ◽  
Structure Functions ◽  
Distribution Functions ◽  
High Energy Particle ◽  
Particle Interactions ◽  
Parton Distribution Functions ◽  
Spin Physics ◽  
Further Development

Recent progress in the field of spin physics of high energy particle interactions is reviewed with particular emphasis on the spin structure functions as measured in polarized deep inelastic lepton-nucleon scattering (DIS). New measurements are presented to obtain more direct information on the composition of the nucleon angular momentum, with results from semi-inclusive DIS accessing flavour-separated parton distribution functions (PDF) and with first data from hard exclusive reactions which may be interpreted in terms of recently developed generalizations of parton distribution functions (GPD). Finally, experimental prospects are outlined which will lead to a further development of the virtues of QCD phenomenology of the spin structure of the nucleon.

scholarly journals QCD Factorization and PDFs from Lattice QCD Calculation

2015 ◽  
Vol 37 ◽  
pp. 1560041 ◽  
Author(s):  
Yan-Qing Ma ◽  
Jian-Wei Qiu
Keyword(s):  
Euclidean Space ◽  
Minkowski Space ◽  
Lattice Qcd ◽  
Correlation Functions ◽  
Parton Distribution ◽  
Distribution Functions ◽  
Matrix Elements ◽  
Parton Distribution Functions ◽  
Qcd Factorization ◽  
The Matrix

In this talk, we review a QCD factorization based approach to extract parton distribution and correlation functions from lattice QCD calculation of single hadron matrix elements of quark-gluon operators. We argue that although the lattice QCD calculations are done in the Euclidean space, the nonperturbative collinear behavior of the matrix elements are the same as that in the Minkowski space, and could be systematically factorized into parton distribution functions with infrared safe matching coefficients. The matching coefficients can be calculated perturbatively by applying the factorization formalism on to asymptotic partonic states.

scholarly journals QCD PRECISION MEASUREMENTS AND STRUCTURE FUNCTION EXTRACTION AT A HIGH STATISTICS, HIGH ENERGY NEUTRINO SCATTERING EXPERIMENT: NuSOnG

2010 ◽  
Vol 25 (05) ◽  
pp. 909-949 ◽  
Author(s):  
T. ADAMS ◽  
P. BATRA ◽  
L. BUGEL ◽  
L. CAMILLERI ◽  
J. M. CONRAD ◽  
...  
Keyword(s):  
Standard Model ◽  
Energy Shift ◽  
High Energy ◽  
Structure Functions ◽  
Distribution Functions ◽  
Neutrino Beam ◽  
Model Parameters ◽  
Parton Distribution Functions ◽  
Neutrino Scattering ◽  
Scattering Experiment

We extend the physics case for a new high-energy, ultra-high statistics neutrino scattering experiment, NuSOnG (Neutrino Scattering On Glass) to address a variety of issues including precision QCD measurements, extraction of structure functions, and the derived Parton Distribution Functions (PDF's). This experiment uses a Tevatron-based neutrino beam to obtain a sample of Deep Inelastic Scattering (DIS) events which is over two orders of magnitude larger than past samples. We outline an innovative method for fitting the structure functions using a parametrized energy shift which yields reduced systematic uncertainties. High statistics measurements, in combination with improved systematics, will enable NuSOnG to perform discerning tests of fundamental Standard Model parameters as we search for deviations which may hint of "Beyond the Standard Model" physics.

NLO EVOLUTION OF STRUCTURE FUNCTIONS AT SMALL x

2011 ◽  
Vol 04 ◽  
pp. 46-55
Author(s):  
GIOVANNI ANTONIO CHIRILLI
Keyword(s):  
Impact Factor ◽  
Energy Operator ◽  
High Energy ◽  
Structure Functions ◽  
Coordinate Space ◽  
Operator Product ◽  
Leading Order ◽  
Small X ◽  
Evolution Of Structure ◽  
First Time

Using the high-energy Operator Product Expansion of the T-product of two electromagnetic currents, we calculate the Photon Impact Factor for Deep Inelastic Scattering at small value of the Bjorken variable x B at the next-to-leading order (NLO) accuracy in αs. We provide for the first time an analytic expression in coordinate space and in Mellin space of the NLO impact factor for the forward unpolarized structure functions.

scholarly journals FLAVOR DEPENDENCE OF UNPOLARIZED TMDS FROM SEMI-INCLUSIVE PION PRODUCTION

2014 ◽  
Vol 25 ◽  
pp. 1460020 ◽  
Author(s):  
ANDREA SIGNORI ◽  
ALESSANDRO BACCHETTA ◽  
MARCO RADICI
Keyword(s):  
Transverse Momentum ◽  
Pion Production ◽  
Distribution Functions ◽  
Momentum Dependence ◽  
Parton Distribution Functions ◽  
Final State ◽  
Fragmentation Functions ◽  
First Time ◽  
Better Than ◽  
Independent Model

Recent data from semi-inclusive deep inelastic scattering collected by the HERMES collaboration allow for the first time to discuss how the transverse-momentum dependence of unpolarized distribution and fragmentation functions is affected by the flavor of the involved partons. A model built with flavor-dependent Gaussian transverse-momentum distributions fits data better than the same flavor-independent model. The current analysis is performed for totally unpolarized scattering of leptons off protons and deuterons, with detected pions in the final state. There are convincing indications of flavor dependence in the fragmentation functions, while for parton distribution functions the evidence is weaker.

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