Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userAnomalous dimensions and splitting functions beyond the next-to-next-to-leading order
117
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We report on recent progress on the splitting functions for the evolution of parton distributions and related quantities, the (lightlike) cusp anomalous dimensions, in perturbative QCD. New results are presented for the four-loop (next-to-next-to-next-to-leading order, N^3LO) contributions to the flavour-singlet splitting functions and the gluon cusp anomalous dimension. We present first results, the moments N=2 and N=3, for the five-loop (N^4LO) non-singlet splitting functions.
rate research
Read More
We present a first analysis of parton-to-pion fragmentation functions at next-to-next-to-leading order accuracy in QCD based on single-inclusive pion production in electron-positron annihilation. Special emphasis is put on the technical details necessary to perform the QCD scale evolution and cross section calculation in Mellin moment space. We demonstrate how the description of the data and the theoretical uncertainties are improved when next-to-next-to-leading order QCD corrections are included.
We determine an approximate expression for the O(alpha_s^3) contribution chi_2 to the kernel of the BFKL equation, which includes all collinear and anticollinear singular contributions. This is derived using recent results on the relation between the GLAP and BFKL kernels (including running-coupling effects to all orders) and on small-x factorization schemes. We present the result in various schemes, relevant both for applications to the BFKL equation and to small-x evolution of parton distributions.
We present the results of our QCD analysis for non-singlet unpolarized quark distributions and structure function $F_2(x,Q^2)$ up to N$^3$LO. In this regards 4-loop anomalous dimension can be obtain from the Pade approximations. The analysis is based on the Jacobi polynomials expansion of the structure function. New parameterizations are derived for the non-singlet quark distributions for the kinematic wide range of $x$ and $Q^2$. Our calculations for non-singlet unpolarized quark distribution functions up to N$^3$LO are in good agreement with available theoretical models. The higher twist contributions of $F_2^{p,d}(x,Q^2)$ are extracted in the large $x$ region in N$^3$LO analysis. The values of $Lambda_{QCD}$ and $alpha_s(M_z^2)$ are determined.
On the basis of a renormalization group analysis of the kernel and of the solutions of the BFKL equation with subleading corrections, we propose and calculate a novel expansion of a properly defined effective eigenvalue function. We argue that in this formulation the collinear properties of the kernel are taken into account to all orders, and that the ensuing next-to-leading truncation provides a much more stable estimate of hard Pomeron and of resummed anomalous dimensions.
We present new sets of fragmentation functions in next-to-leading order QCD that are determined from e+e- annihilation data of inclusive particle production. In addition to the O(alpha_s) unpolarized cross section the longitudinal cross section is also used to extract the gluon fragmentation function from e+e- annihilation data. As the O(alpha_s) vanishes for longitudinal polarized photons (or Z bosons), the O(alpha_s^2) corrections are required to reduce the scale ambiguities. Recently, P.J. Rijken and W.L. van Neerven presented the longitudinal coefficient functions to next-to-leading order. We confirm part of their results in this thesis and complete the calculation by the results for the color class C_F*T_R that must be included for a consistent comparison with LEP1 data. The complete set of coefficient functions is then used together with novel data from ALEPH to determine the fragmentation functions for charged hadrons. This set, and also sets for charged pions, kaons, and D^* mesons as well as neutral kaons published previously, can then be employed to test QCD in e+e- annihilation, photoproduction, gamma-gamma collisions, p-p_bar scattering and DIS. Finally, we suggest how the improved knowledge on the fragmentation in particular of the gluon could be used to determine the gluon and charm content of the photon.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
