CERN Accelerating science

Thesis
Report number	WUB-DIS-2002-01 ; WU-B-DIS-2002-01 ; CERN-THESIS-2002-092
Title	Messung der Helizitätskomponenten der Fragmentationsfunktion geladener Hadronen auf der Z-Resonanz
Related title	Measurement of helicity components of the fragmentation function of charged hadrons at the Z-resonance. (In German)
Translation of title	Measurement of helicity components of the fragmentation function of charged hadrons at the Z-resonance
Author(s)	Malek, Abdellah (Wuppertal U.)
Publication	2002 - 75.
Thesis note	PhD : Wuppertal U. : 2002
Subject category	Particle Physics - Experiment
Accelerator/Facility, Experiment	CERN LEP ; DELPHI
Abstract	The transverse, longitudinal and asymmetric components of the fragmentation function are measured from the inclusive charged particles in e +e − collisions at LEP. The study of the process e +e − → h + X provides a test of the QCD predictions using these fragmentation functions. The transverse σT and longitudinal σL components of the total hadronic cross section σtot are evaluated from the fragmentation functions. They are determined to be σT σtot = 0.9429 ± 0.0006(stat) ± 0.0050(syst) and σL σtot = 0.0571 ± 0.0007(stat) ± 0.0050(syst) respectively. The strong coupling constant is calculated from the longitudinal cross section σL σtot in next-to-leading order of perturbative QCD, giving αs(MZ) = 0.132 ± 0.001(stat) ± 0.008(syst). Including non-perturbative power corrections leads to αs(MZ) = 0.113 ± 0.001(stat) ± 0.008(syst). By integrating the fragmentation functions, we determine the average charged particle multiplicity to be < nch >= 20.979 ± 0.004(stat) ± 0.199(syst). From the longitudinal fragmentation function we are able to extract the gluon fragmentation function. The fragmentation functions in b ¯b and light quark events are compared.

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