Spin-dependent DGLAP evolution equations andtdistribution of longitudinally polarized structure functions in leading order and next-to-leading order at lowx

2008 ◽  
Vol 77 (7) ◽  
Author(s):  
Nazir Hussain Shah ◽  
J K Sarma
Keyword(s):  
Evolution Equations ◽  
Structure Functions ◽  
Dglap Evolution ◽  
Leading Order

scholarly journals SUSY-like relation of the splitting functions in evolution of gluon and quark jet multiplicities

2018 ◽  
Vol 191 ◽  
pp. 04006
Author(s):  
Anatoly Kotikov
Keyword(s):  
Evolution Equations ◽  
Dglap Evolution ◽  
Leading Order ◽  
Logarithmic Order ◽  
World Data ◽  
Charged Hadrons ◽  
Anomalous Dimensions ◽  
The World ◽  
Fragmentation Functions ◽  
Gluon Fragmentation

We show the new relationship [1] between the anomalous dimensions, resummed through next-to-next-to-leading-logarithmic order, in the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution equations for the first Mellin moments Dq,g(μ2) of the quark and gluon fragmentation functions, which correspond to the average hadron multiplicities in jets initiated by quarks and gluons, respectively. So far, such relationships have only been known from supersymmetric (SUSY) QCD. Exploiting available next-to-nextto- next-to-leading-order (NNNLO) information on the ratio D+g (μ2)=D+q (μ2) of the dominant plus components, the fit of the world data of Dq,g(μ2) for charged hadrons measured in e+e- annihilation leads to α(5)s (MZ) = 0:1205 +0:0016 -0:0020.

scholarly journals Vector meson fragmentation using a model with broken SU(3) at the next-to-leading order

2014 ◽  
Vol 29 (07) ◽  
pp. 1450049 ◽  
Author(s):  
H. Saveetha ◽  
D. Indumathi ◽  
Subhadip Mitra
Keyword(s):  
Vector Meson ◽  
Cross Section ◽  
Evolution Equations ◽  
Light Quark ◽  
Energy Scale ◽  
Dglap Evolution ◽  
Leading Order ◽  
Quark Fragmentation ◽  
Fragmentation Functions ◽  
The Cross

A detailed study of fragmentation of vector mesons at the next-to-leading order (NLO) in QCD is given for e+e- scattering. A model with broken SU(3) symmetry using three input fragmentation functions α(x, Q2), β(x, Q2) and γ(x, Q2) and a strangeness suppression parameter λ describes all the light quark fragmentation functions for the entire vector meson octet. At a starting low energy scale of [Formula: see text] for three light quarks (u, d, s) along with initial parametrization, the fragmentation functions are evolved through DGLAP evolution equations at NLO and the cross-section is calculated. The heavy quarks contribution are added in appropriate thresholds during evolution. The results obtained are fitted at the momentum scale of [Formula: see text] for LEP and SLD data. Good-quality fits are obtained for ρ, K*, ω and ϕ mesons, implying the consistency and efficiency of this model. Strangeness suppression in this model is understood both in terms of ratios of quark fragmentation functions alone as well as in terms of observables; the latter yield a suppression through the K*/ρ multiplicity ratio of about 0.23 while the x dependence of this suppression is also parametrized through the cross-section ratios.

EVOLUTION OF UNDERSTANDING POLARIZED DIS: FROM LARGE TO SMALL x

2009 ◽  
Vol 24 (35n37) ◽  
pp. 2924-2930
Author(s):  
B. I. ERMOLAEV ◽  
M. GRECO ◽  
S. I. TROYAN
Keyword(s):  
Structure Function ◽  
Spin Structure ◽  
Evolution Equations ◽  
Structure Functions ◽  
Theoretical Description ◽  
Dglap Evolution ◽  
Spin Structure Function ◽  
Logarithmic Approximation ◽  
Small X

The standard theoretical description of Polarized DIS is based on the use of the DGLAP evolution equations. This approach controls the Q2 -evolution of the DIS structure functions but cannot describe the x -evolution and therefore should not be used at small x. We complement this approach, accounting for the x-evolution of the spin structure function g1 in the leading logarithmic approximation.

scholarly journals Decoupling the NLO-coupled QED⊗QCD, DGLAP evolution equations, using Laplace transform method

2017 ◽  
Vol 32 (14) ◽  
pp. 1750065 ◽  
Author(s):  
Marzieh Mottaghizadeh ◽  
Parvin Eslami ◽  
Fatemeh Taghavi-Shahri
Keyword(s):  
Laplace Transform ◽  
Structure Function ◽  
Evolution Equations ◽  
Distribution Functions ◽  
Proton Structure Function ◽  
Dglap Evolution ◽  
Leading Order ◽  
Laplace Transform Method ◽  
Transform Method ◽  
Proton Structure

We analytically solved the QED[Formula: see text]QCD-coupled DGLAP evolution equations at leading order (LO) quantum electrodynamics (QED) and next-to-leading order (NLO) quantum chromodynamics (QCD) approximations, using the Laplace transform method and then computed the proton structure function in terms of the unpolarized parton distribution functions. Our analytical solutions for parton densities are in good agreement with those from CT14QED [Formula: see text] (Ref. 6) global parametrizations and APFEL (A PDF Evolution Library) [Formula: see text] (Ref. 4). We also compared the proton structure function, [Formula: see text], with the experimental data released by the ZEUS and H1 collaborations at HERA. There is a nice agreement between them in the range of low and high [Formula: see text] and [Formula: see text].

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.

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