2,910 research outputs found
Theory of Heavy Baryon Decay
We discuss various topics in the theory of heavy baryon decays. Among these
are recent applications of the Relativistic Three Quark Model to semileptonic,
nonleptonic, one-pion and one-photon transitions among heavy baryons, new
higher order perturbative results on the correlator of two heavy baryon
currents and on the semi-inclusive decay .Comment: 10 pages, invited talk given by J.G. K\"orner at the 3rd
International Conference on B Physics and CP Violation (BCONF99), Taipei,
Taiwan, 3-7 Dec 1999, to appear in the Proceedings, edited by H.Y. Cheng and
W.S. Hou (World Scientific, 2000
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
On the rigidity of back-to-back top quark pairs in e^+e^- annihilation
We consider the effect of gluon radiation on the energy of top/antitop quarks
and on the anticollinearity of top-antitop quark pairs produced in
annihilation. Our results are presented in terms of the -dependence of the
cross section and the dependence on the cosine of the opening angle
between top and antitop for a center of mass energy of
. We then go on to determine mean values for the top
quark's energy as well as its longitudinal and transverse projections, and for
the deviation of and from the
anticollinearity limits and . For a
center of mass energy of we obtain , and . Thus, at this energy gluon radiation causes a total
average energy loss of 0.71% of the top quark's energy. The average energy loss
in the longitudinal direction is 1.06% and the average energy gain in the
transverse direction is 1.88%. These percentage figures go up to 3.77%, 5.19%
and 6.06%, respectively, at 1000\GeV. For the mean of the acollinearity angle
we obtain at
, the value of which goes up to at . From an
analysis of the transverse momentum of the top we find that the mean transverse
momentum of the top stays close to the mean total momentum of the gluon in the
energy range from threshold to showing that the gluon momentum has a
large mean transverse component in this energy range.Comment: 17 pages, 7 postscript figures, to appear in Nucl. Phys.
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