2,379 research outputs found
Fully analytical O(\alpha_s) results for on-shell and off-shell polarized W-boson decays into massive quark pairs
We provide analytical results for the three polarized decay
structure functions and that describe the decay of a
polarized boson into massive quark--antiquark pairs. As an application we
consider the decay involving the helicity fractions of
the boson followed by the polarized decay \hbox{W^+(\uparrow)}\to
q_1\bar{q}_2 described by the polarized decay structure functions . We
thereby determine the polar angle decay distribution of the
cascade decay process . As a second example we
analyze quark mass and off-shell effects in the cascade decays and . For
the decays and we find substantial deviations from the mass-zero approximation in
particular in the vicinity of the threshold region.Comment: 56 pages, 15 figures and 2 table
Quark and Pole Models of Nonleptonic Decays of Charmed Baryons
Quark and pole models of nonleptonic decays of charmed baryons are analysed
from the point of view of their symmetry properties. The symmetry structure of
the parity conserving amplitudes that corresponds to the contribution of the
ground-state intermediate baryons is shown to differ from the one hitherto
employed in the symmetry approach. It is pointed out that the "subtraction" of
sea quark effects in hyperon decays leads to an estimate of -exchange
contributions in charmed baryon decays that is significantly smaller than
naively expected on the basis of . An constraint questioning
the reliability of the factorization technique is exhibited. Finally, a
successful fit to the available data is presented.Comment: 25 pages, LATEX, 1643/PH IFJ Krako
Inclusive Semileptonic Decays in QCD Including Lepton Mass Effects
Starting from an Operator Product Expansion in the Heavy Quark Effective
Theory up to order 1/m_b^2 we calculate the inclusive semileptonic decays of
unpolarized bottom hadrons including lepton mass effects. We calculate the
differential decay spectra d\Gamma/(dE_\tau ), and the total decay rate for B
meson decays to final states containing a \tau lepton.Comment: 16 pages + 4 figs. appended in uuencoded form, LaTeX, MZ-TH/93-3
Effects of QCD Resummation on Distributions of Leptons from the Decay of Electroweak Vector Bosons
We study the distributions of leptons from the decay of electroweak vector
bosons produced in hadron collisions. The effects of the initial state multiple
soft-gluon emission, using the Collins--Soper resummation formalism, are
included. The resummed results are compared with the next-to-leading-order
results for the distributions of the transverse momentum, rapidity asymmetry,
and azimuthal angle of the decay leptons.Comment: 12 pages, 3 figures uuencoded, LaTeX, uses epsf.tex for figures. (Was
replaced on 5/2/95 because of mailer problems.
Infinite Momentum Frame Calculation of Semileptonic Heavy \Lambda_b\to\Lambda_c Transitions Including HQET Improvements
We calculate the transition form factors that occur in heavy -type
baryon semileptonic decays as e.g. in . We use Bauer-Stech-Wirbel type infinite momentum frame wave
functions for the heavy -type baryons which we assume to consist of a
heavy quark and a light spin-isospin zero diquark system. The form factors at are calculated from the overlap integrals of the initial and final
-type baryon states. To leading order in the heavy mass scale the
structure of the form factors agrees with the HQET predictions including the
normalization at zero recoil. The leading order -dependence of the form
factors is extracted by scaling arguments. By comparing the model form factors
with the HQET predictions at we obtain a consistent set of
model form factors up to . With our preferred choice of
parameter values we find that the contribution of the non-leading form factor
is practically negligible. We use our form factor predictions to compute rates,
spectra and various asymmetry parameters for the semi-leptonic decay
.Comment: 24 pages, LaTeX, 6 figures are included in PostScript format. Final
version of paper to appear in Phys.Rev.
Helicity Analysis of Semileptonic Hyperon Decays Including Lepton Mass Effects
Using the helicity method we derive complete formulas for the joint angular
decay distributions occurring in semileptonic hyperon decays including lepton
mass and polarization effects. Compared to the traditional covariant
calculation the helicity method allows one to organize the calculation of the
angular decay distributions in a very compact and efficient way. In the
helicity method the angular analysis is of cascade type, i.e. each decay in the
decay chain is analyzed in the respective rest system of that particle. Such an
approach is ideally suited as input for a Monte Carlo event generation program.
As a specific example we take the decay () followed by the nonleptonic decay for which we show a few examples of decay distributions which are
generated from a Monte Carlo program based on the formulas presented in this
paper. All the results of this paper are also applicable to the semileptonic
and nonleptonic decays of ground state charm and bottom baryons, and to the
decays of the top quark.Comment: Published version. 40 pages, 11 figures included in the text. Typos
corrected, comments added, references added and update
SU(3)_flavor analysis of two-body weak decays of charmed baryons
We study two-body weak decays of charmed baryons \Lambda_c and \Xi_c into an
octet or decuplet baryon and a pseudoscalar meson employing the SU(3) flavor
symmetry. Using certain measured Cabibbo-favored modes, we fix the reduced
amplitudes and predict the branching ratios of various decays of charmed
baryons in the Cabibbo-enhanced, -suppressed and -doubly suppressed modes.Comment: 25 pages, No figure, Phys. Rev. D (to appear
Analysis of Two-Body Decays of Charmed Baryons Using the Quark-Diagram Scheme
We give a general formulation of the quark-diagram scheme for the nonleptonic
weak decays of baryons. We apply it to all the decays of the antitriplet and
sextet charmed baryons and express their decay amplitudes in terms of the
quark-diagram amplitudes. We have also given parametrizations for the effects
of final-state interactions. For SU(3) violation effects, we only parametrize
those in the horizontal -loop quark diagrams whose contributions are solely
due to SU(3)-violation effects. In the absence of all these effects, there are
many relations among various decay modes. Some of the relations are valid even
in the presence of final-state interactions when each decay amplitude in the
relation contains only a single phase shift. All these relations provide useful
frameworks to compare with future experiments and to find out the effects of
final-state interactions and SU(3) symmetry violations.Comment: 28 pages, 20 Tables in landscape form, 4 figures. Main changes are:
(i) some errors in the Tables and in the relations between the quark-diagram
amplitudes of this paper and those of Ref.[10] are corrected, (ii)
improvements are made in the presentation so that comparisons with previous
works and what have been done to include SU(3) breaking and final-state
interactions are more clearly stated; to appear in the Physical Review
Diagnostik bei Glomerulonephritis: Rationaler Abklärungsgang
Zusammenfassung: Glomerulonephritiden sind eine wichtige und häufige Ursache der fortgeschrittenen Niereninsuffizienz. Hinsichtlich Therapierbarkeit und Prognose sind eine frühzeitige Abklärung und Diagnosestellung von entscheidender Bedeutsamkeit. Die wichtigsten klinischen Zeichen der Glomerulonephritis per se sind arterielle Hypertonie, Ödeme, Proteinurie, Hämaturie und Niereninsuffizienz. Dazu kommen Symptome allfälliger Systemerkrankungen. Der Abklärungsgang umfasst Erhebung der Anamnese, klinische Untersuchung, Laboruntersuchungen im Blut und Urin, bildgebende Verfahren wie Sonographie und Magnetresonanzuntersuchung und in den meisten Fällen die perkutane Nierenbiopsie. Bei der Diagnostik ist es besonders wichtig, eine behandelbare Ursache - wie Medikamentennebenwirkung, Infekt, Tumor oder entzündliche Systemerkrankung - zu erkennen. Glomerulonephritiden können einerseits aufgrund ihrer klinischen Präsentation und andererseits basierend auf den histologischen Veränderungen genauer klassifiziert werde
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