430 research outputs found
Statistical approach for unpolarized fragmentation functions for the octet baryons
A statistical model for the parton distributions in the nucleon has proven
its efficiency in the analysis of deep inelastic scattering data, so we propose
to extend this approach to the description of unpolarized fragmentation
functions for the octet baryons. The characteristics of the model are
determined by using some data on the inclusive production of proton and
in unpolarized deep inelastic scattering and a next-to-leading
analysis of the available experimental data on the production of unpolarized
octet baryons in annihilation. Our results show that both parton
distributions and fragmentation functions are compatible with the statistical
approach, in terms of a few free parameters, whose interpretation will be
discussed.Comment: 14 pages, 7 eps figures, to appear in Phys. Rev.
An SU(3) model for octet baryon and meson fragmentation
The production of the octet of baryons and mesons in e^+ e^- collisions is
analysed, based on considerations of SU(3) symmetry and a simple model for
SU(3) symmetry breaking in fragmentation functions. All fragmentation
functions, D_q^h(x, Q^2), describing the fragmentation of quarks into a member
of the baryon octet (and similarly for fragmentation into members of the meson
octet) are expressed in terms of three SU(3) symmetric functions, \alpha(x,
Q^2), \beta(x, Q^2), and \gamma(x, Q^2). With the introduction of an SU(3)
breaking parameter, \lambda, the model is successful in describing
hadroproduction data at the Z pole. The fragmentation functions are then
evolved using leading order evolution equations and good fits to currently
available data at 34 GeV and at 161 GeV are obtained.Comment: 24 pages LaTeX file including 11 postscript figure file
Association study with Wegener granulomatosis of the human phospholipase Cγ2 gene
BACKGROUND: Wegener Granulomatosis (WG) is a multifactorial disease of yet unknown aetiology characterized by granulomata of the respiratory tract and systemic necrotizing vasculitis. Analyses of candidate genes revealed several associations, e.g. with α(1)-antitrypsin, proteinase 3 and with the HLA-DPB1 locus. A mutation in the abnormal limb mutant 5 (ALI5) mouse in the region coding for the hydrophobic ridge loop 3 (HRL3) of the phospholipaseCγ2 (PLCγ-2) gene, corresponding to human PLCγ-2 exon 27, leads to acute and chronic inflammation and granulomatosis. For that reason, we screened exons 11, 12 and 13 coding for the hydrophobic ridge loop 1 and 2 (HRL1 and 2, respectively) and exon 27 of the PLCγ-2 protein by single strand conformation polymorphism (SSCP), sequencing and PCR/ restriction fragment length polymorphism (RFLP) analyses. In addition, we screened indirectly for disease association via 4 microsatellites with pooled DNA in the PLCγ-2 gene. RESULTS: Although a few polymorphisms in these distinct exons were observed, significant differences in allele frequencies were not identified between WG patients and respective controls. In addition, the microsatellite analyses did not reveal a significant difference between our patient and control cohort. CONCLUSION: This report does not reveal any hints for an involvement of the PLCγ-2 gene in the pathogenesis of WG in our case-control study
Search for Charged Higgs Bosons in Decays of Top Quark Pairs
We present a search for charged Higgs bosons in decays of pair-produced top
quarks using 109.2 +- 5.8 pb^-1 of data recorded from ppbar collisions at
sqrt{s} = 1.8 TeV by the D0 detector during 1992-96 at the Fermilab Tevatron.
No evidence is found for charged Higgs production, and most parts of the
[m(H+),tan(beta)] parameter space where the decay t -> bH+ has a branching
fraction close to or larger than that for t -> bW+ are excluded at 95%
confidence level. Assuming m(t) = 175 GeV and sigma(ppbar -> ttbar) = 5.5 pb,
for m(H+) = 60 GeV, we exclude tan(beta) 40.9.Comment: 11 pages, 3 figures, submitted to PR
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