scholarly journals EVOLUTION EQUATIONS OF TWIST-THREE PARTON DISTRIBUTIONS

2011 ◽  
Vol 04 ◽  
pp. 157-167
Author(s):  
BJÖRN PIRNAY
Keyword(s):  
Recent Work ◽  
Correlation Functions ◽  
Evolution Equations ◽  
Spin Asymmetry ◽  
Scale Dependence ◽  
Transverse Spin ◽  
Collinear Factorization ◽  
Parton Distributions ◽  
Gluon Momentum

We report on a recent work concerning the scale dependence of twist-three correlation functions relevant for the single transverse spin asymmetry in the framework of collinear factorization. Evolution equations are presented for both the flavor–nonsinglet and flavor–singlet distributions. Our results do not agree with previous calculations of the evolution in the limit of vanishing gluon momentum. Possible sources for this discrepancy are identified.

SCALE DEPENDENCE OF TWIST-3 CORRELATION FUNCTIONS

2011 ◽  
Vol 04 ◽  
pp. 146-156
Author(s):  
Zhong-Bo Kang ◽  
Jian-Wei Qiu
Keyword(s):  
Correlation Functions ◽  
Evolution Equations ◽  
Scale Dependence ◽  
Leading Order ◽  
Coupling Constant ◽  
Parton Distributions ◽  
Spin Asymmetries ◽  
Single Spin ◽  
Single Spin Asymmetries ◽  
Similarities And Differences

In this talk, we introduce two sets of twist-3 quark-gluon correlation functions that are relevant to transverse single spin asymmetries, and present corresponding evolution equations at the leading order in strong coupling constant, αs. The similarities and differences between the evolution of the leading power parton distributions and that of the twist-3 multiparton correlation functions are also discussed.

scholarly journals QCD Evolution Equations from Conformal Symmetry

2015 ◽  
Vol 37 ◽  
pp. 1560048
Author(s):  
V. M. Braun ◽  
A. N. Manashov
Keyword(s):  
Perturbation Theory ◽  
Conformal Invariance ◽  
Evolution Equations ◽  
Conformal Symmetry ◽  
Scale Dependence ◽  
Conformal Anomaly ◽  
Parton Distributions ◽  
Anomalous Dimensions ◽  
The Given ◽  
Modified Theory

QCD evolution equations in MS-like schemes can be recovered from the same equations in a modified theory, QCD in non-integer d = 4 - 2ϵ dimensions, which enjoys exact scale and conformal invariance at the critical point. Restrictions imposed by the conformal symmetry of the modified theory allow one to obtain complete evolution kernels in integer (physical) dimensions at the given order of perturbation theory from the spectrum of anomalous dimensions added by the calculation of the special conformal anomaly at one order less. We use this technique to derive two-loop evolution equations for flavor-nonsinglet quark-antiquark light-ray operators that encode the scale dependence of generalized hadron parton distributions.

BESSEL-WEIGHTED ASYMMETRIES AND TRANSVERSE SPIN EFFECTS

2012 ◽  
Vol 20 ◽  
pp. 168-176
Author(s):  
LEONARD GAMBERG
Keyword(s):  
Transverse Momentum ◽  
Cross Section ◽  
Parton Distribution ◽  
Evolution Equations ◽  
Distribution Functions ◽  
Transverse Spin ◽  
High Transverse Momentum ◽  
Transverse Momentum Dependent ◽  
Fragmentation Functions ◽  
The Cross

We consider the cross section for semi-inclusive deep inelastic scattering in Fourier space, conjugate to the outgoing hadron's transverse momentum, where convolutions of transverse momentum dependent parton distribution functions and fragmentation functions become simple products. Individual asymmetric terms in the cross section can be projected out by means of a generalized set of weights involving Bessel functions. Advantages of employing these Bessel weights are that they suppress (divergent) contributions from high transverse momentum and that soft factors cancel in (Bessel-) weighted asymmetries. Also, the resulting compact expressions immediately connect to previous work on evolution equations for transverse momentum dependent parton distribution and fragmentation functions and to quantities accessible in lattice QCD. Bessel-weighted asymmetries are thus model independent observables that augment the description and our understanding of correlations of spin and momentum in nucleon structure.

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