arXiv subjects

S. Albino

Publications and source records attributed to S. Albino.

25 records · Page 2Linked to original sources

arXiv2005

Resummation of Soft Gluon Logarithms in the DGLAP Evolution of Fragmentation Functions

We define a general scheme for the evolution of fragmentation functions which resums both soft gluon logarithms and mass singularities in a consistent manner and to any order, and requires no additional theoretical assumptions. Using the Double Logarithmic Approximation and the known perturbative results for the splitting functions, we present our scheme with the complete contribution from the double logarithms, being the largest soft gluon logarithms. We show that the resulting approximation is more complete than the Modified Leading Logarithm Approximation even with the fixed order contribution calculated to leading order only, and find, after using it to fit quark and gluon fragmentation functions to experimental data, that this approximation in our scheme gives a good description of the data from the largest x_p values to the peak region in xi=ln (1/x_p), in contrast to other approximations. In addition, we develop a treatment of hadron mass effects which gives additional improvements at large xi.

hep-ph↗

arXiv2005

Fragmentation Functions for K0short and Lambda with Complete Quark Flavour Separation

We present new sets of next-to-leading order fragmentation functions for the production of K0short and Lambda particles from the gluon and from each of the quarks, obtained by fitting to all relevant data sets from e+e- annihilation. The individual light quark flavour fragmentation functions are constrained phenomenologically for the first time by including in the data the light quark tagging probabilities measured by the OPAL Collaboration.

hep-ph↗

arXiv2005

Fragmentation Functions for Light Charged Hadrons with Complete Quark Flavour Separation

We present new sets of next-to-leading order fragmentation functions describing the production of charged pions, kaons and protons from the gluon and from each of the quarks, obtained by fitting to all relevant data sets from e+ e- annihilation. The individual light quark flavour fragmentation functions are obtained phenomenologically for the first time by including in the data the light quark tagging probabilities obtained by the OPAL Collaboration.

hep-ph↗

arXiv2005

Generalizing the DGLAP Evolution of Fragmentation Functions to the Smallest x Values

An approach which unifies the Double Logarithmic Approximation at small x and the leading order DGLAP evolution of fragmentation functions at large x is presented. This approach reproduces exactly the Modified Leading Logarithm Approximation, but is more complete due to the degrees of freedom given to the quark sector and the inclusion of the fixed order terms. We find that data from the largest x values to the peak region can be better fitted than with other approaches.

hep-ph↗

arXiv2004

Low x particle spectra in the Modified Leading Logarithm Approximation

We show that the higher moments of the evolution obtained from the Modified Leading Logarithm Approximation may be regarded as spurious higher order terms in perturbation theory, and that neglecting them leads to a good description of the data around and above the peak in $ξ=\ln (1/x)$. Furthermore, we use this study of the moments to show that at high energy the Limiting Spectrum with Local Parton-Hadron Duality may also be derived from the Modified Leading Logarithm Approximation without any non-perturbative assumptions.

hep-ph↗

arXiv2004

The Evolution of Hadron Spectra in the Modified Leading Logarithm Approximation

We perform fits of $Λ_{\rm QCD}$ and the gluon fragmentation function $D(x,Q)$ at initial scale $Q_0 \ggΛ_{\rm QCD}$ to charged light hadron momentum spectra data by evolving in the Modified Leading Logarithm Approximation. Without additional assumptions, we achieve a good description of the available data for $ξ=\ln(1/x)$ up to and around the Gaussian peak, and values of $Λ_{\rm QCD}$ acceptably close to those in the literature. In particular, we find that this procedure describes the position of the peak, and, in contrast to the Limiting Spectrum, also the normalization.

hep-ph↗

arXiv2002

Strong Coupling Constant from the Photon Structure Function

We extract the value of the strong coupling constant alpha_s from a single-parameter pointlike fit to the photon structure function F_2^gamma at large x and Q^2 and from a first five-parameter full (pointlike and hadronic) fit to the complete F_2^gamma data set taken at PETRA, TRISTAN, and LEP. In next-to-leading order and the MSbar renormalization and factorization schemes, we obtain alpha_s(m_Z)=0.1183 +/- 0.0050(exp.)^+0.0029_-0.0028(theor.) [pointlike] and alpha_s(m_Z)=0.1198 +/- 0.0028(exp.)^+0.0034_-0.0046(theor.) [pointlike and hadronic]. We demonstrate that the data taken at LEP have reduced the experimental error by about a factor of two, so that a competitive determination of alpha_s from F_2^gamma is now possible.

hep-ph↗