45 research outputs found
Implications of Results from Z- and WW-Threshold Running
One year of Z- and WW-Threshold running of TESLA can provide the possibility
to measure electroweak precision observables to an extremely high accuracy. At
the Z peak O(10^9) Z bosons and about 6 10^8 b quarks can be collected. We
employ the expected uncertainties \Delta MW = 6 MeV and \Delta sin(theta_W,eff)
= 0.00001 and demonstrate in this way that very stringent consistency tests of
the Standard Model and the Minimal Supersymmetric Standard Model will be
possible. The indirect determination of the Higgs-boson mass within the
Standard Model can reach an accuracy of about 5 %. The 6 10^8 b quarks can be
used to investigate various b physics topics.Comment: 7 pages, 2 figures, talk given at LCWS99, Sitges, Spain. Two
clarifications, one reference adde
The Renormalization Group Evolution of the CKM Matrix
We compute the renormalization of the complete CKM matrix in the MSbar scheme
and perform a renormalization group analysis of the CKM parameters. The
calculation is simplified by studying only the Higgs sector, which for the
\beta-function of the CKM matrix is at one loop the same as in the full
Standard Model. The renormalization group flow including QCD corrections can be
computed analytically using the hierarchy of the CKM parameters and the large
mass differences between the quarks. While the evolution of the Cabibbo angle
is tiny V_{ub} and V_{cb} increase sizably. We compare our results with the
ones in the full Standard Model.Comment: Latex, 31 pages, extensions amsmath, epsfig required The complete
paper, including figures, is also available via anonymous ftp at
ftp://ttpux2.physik.uni-karlsruhe.de/, or via www at
http://www-ttp.physik.uni-karlsruhe.de/cgi-bin/preprints
Form Factors and Strong Couplings of Heavy Baryons from QCD Light-Cone Sum Rules
We derive QCD light-cone sum rules for the hadronic matrix elements of the
heavy baryon transitions to nucleon. In the correlation functions the
and -baryons are interpolated by three-quark
currents and the nucleon distribution amplitudes are used. To eliminate the
contributions of negative parity heavy baryons, we combine the sum rules
obtained from different kinematical structures. The results are then less
sensitive to the choice of the interpolating current. We predict the
form factor and calculate the widths of the and decays. Furthermore, we consider double
dispersion relations for the same correlation functions and derive the
light-cone sum rules for the and strong
couplings. Their predicted values can be used in the models of charm production
in collisions.Comment: 45 pages, 3 figure
Width and from QCD Light-Cone Sum Rules
We employ the form factors obtained from QCD light-cone sum rules
and calculate the width () in units of
, integrated over the region of accessible momentum transfers,
. Using the most recent BABAR-collaboration
measurements we extract . The sum rule results for the form factors, taken
as an input for a -series parameterization, yield the -shape in the
whole semileptonic region of . We also present the
charged lepton energy spectrum in this decay. Furthermore, the current
situation with is discussed from the QCD point of view. We
suggest to use the ratio of the and widths as an additional test of Standard Model. The
sensitivity of this observable to new physics is illustrated by including a
charged Higgs-boson contribution in the semileptonic decay amplitude.Comment: 22 pages, 8 figures; comments added in section 4, version to be
published in Phys. Rev.
Semileptonic charm decays D \to \pi l \nu_{\l} and from QCD Light-Cone Sum Rules
We present a new calculation of the and form factors from
QCD light-cone sum rules. The scheme for the -quark mass is
used and the input parameters are updated. The results are , and
. Combining the calculated form
factors with the latest CLEO data, we obtain and
where the first and second errors are of experimental origin and the third
error is due to the estimated uncertainties of our calculation. We also
evaluate the form factors and and predict the slope
parameters at . Furthermore, calculating the form factors from the sum
rules at , we fit them to various parameterizations. After analytic
continuation, the shape of the form factors in the whole
semileptonic region is reproduced, in a good agreement with experiment.Comment: 34 pages, 5 figure
Kaon Distribution Amplitude from QCD Sum Rules
We present a new calculation of the first Gegenbauer moment of the
kaon light-cone distribution amplitude. This moment is determined by the
difference between the average momenta of strange and nonstrange valence quarks
in the kaon. To calculate , QCD sum rule for the diagonal correlation
function of local and nonlocal axial-vector currents is used. Contributions of
condensates up to dimension six are taken into account, including
-corrections to the quark-condensate term. We obtain
, differing by the sign and magnitude from the recent
sum-rule estimate from the nondiagonal correlation function of pseudoscalar and
axial-vector currents. We argue that the nondiagonal sum rule is numerically
not reliable. Furthermore, an independent indication for a positive is
given, based on the matching of two different light-cone sum rules for the
form factor. With the new interval of we update our previous
numerical predictions for SU(3)-violating effects in form
factors and charmless (B) decays.Comment: a comment and a reference added, version to appear in Phys.Rev.D, 17
pages, 7 figure
Higher Order Power Corrections in Inclusive B Decays
We discuss order 1/m_b^4 and 1/m_b^5 corrections in inclusive semileptonic
decay of a meson. We identify relevant hadronic matrix elements of
dimension seven and eight and estimate them using the ground-state saturation
approximation. Within this approach the effects on the integrated rate and on
kinematic moments are estimated. The overall relative shift in V_{cb} turns out
about +0.4% as applied to the existing fits. Similar estimates are presented
for B -> X_s+\gamma decays.Comment: 30 pages, 16 figure