69 research outputs found
Renormalization of the Cabibbo-Kobayashi-Maskawa Quark Mixing Matrix
We have investigated the present renormalization prescriptions of
Cabibbo-Kobayashi-Maskawa (CKM) matrix. When considering the prescription which
is formulated with reference to the case of zero mixing we find it doesn't
satisfy the unitary condition of the bare CKM matrix. After added a delicate
patch this problem can be solved at one-loop level. In this paper We generalize
this prescription to all loop levels and keep the unitarity of the bare CKM
matrix, simultaneously make the amplitude of an arbitrary physical process
involving quark mixing convergent and gauge independent. We also find that in
order to keep the CKM counterterms gauge independent the unitarity of the bare
CKM matrix must be preserved.Comment: has been revised, 8 pages, 1 figur
Twist-3 distribution amplitudes of scalar mesons from QCD sum rules
We study the twist-3 distribution amplitudes for scalar mesons made up of two
valence quarks based on QCD sum rules.
By choosing the proper correlation functions, we derive the moments of the
scalar mesons up to the first two order. Making use of these moments, we then
calculate the first two Gegenbauer coefficients for twist-3 distribution
amplitudes of scalar mesons. It is found that the second Gegenbauer
coefficients of scalar density twist-3 distribution amplitudes for
and mesons are quite close to that for , which indicates that the
SU(3) symmetry breaking effect is tiny here. However, this effect could not be
neglected for the forth Gegenbauer coefficients of scalar twist-3 distribution
amplitudes between and . Besides, we also observe that the first two
Gegenbauer coefficients corresponding to the tensor current twist-3
distribution amplitudes for all the , and are very small.
The renormalization group evolution of condensates, quark masses, decay
constants and moments are considered in our calculations. As a byproduct, it is
found that the masses for isospin I=1, scalar mesons are around
GeV and GeV respectively, while the mass for
isospin state composed of is GeV.Comment: replaced with revised version, to be published in Phys. Rev.
Searching for new physics in decays
For any new physics possibly emerging in the future B experiments, the
problem is how to extract the signals from the SM background. We consider the
decay which is very small in the SM. In the MSSM this decay is
possibly accessible in the future experiments. In the supersymmetric models
with R-parity violating couplings, this channel is not strictly constrained,
thus being useful in obtaining bounds on the lepton-number violating couplings.
A typical candidate for the suggested search is the mode.Comment: 9 pages, one figure, late
Recalculation of QCD Corrections to Decay
We give a more complete calculation of decay, including
leading log QCD corrections from to in addition to corrections
from to . We have included the full set of dimension-6 operators
and corrected numerical mistakes of anomalous dimensions in a previous
paper\cite{Cho}. Comparing with the calculations without QCD running from
to \cite{Mis}, the inclusive decay rate is found to be enhanced.
At GeV, it results in 12\% enhancement, and for GeV, 15\% is
found. The total QCD effect makes an enhanced factor of 4.2 at GeV,
and 3.2 for GeV.Comment: 16 pages, 7 figures (uuencoded ps files), Changes of description. To
appear in Phys. Rev.
Constraints on Masses of Charged PGBs in Technicolor Model from Decay
In this paper we calculate the contributions to the branching ratio of from the charged Pseudo-Goldstone bosons appeared in one generation
Technicolor model. The current experimental results can eliminate large
part of the parameter space in the plane, and
specifically, one can put a strong lower bound on the masses of color octet
charged PGBs : at for free
.Comment: 9 pages, 3 figures(uuencoded), Minor changes(Type error), to appear
in Phys. Rev.
Branching ratio and CP asymmetry of decays in the perturbative QCD approach
In this paper, we calculate the decay rate and CP asymmetry of the decay in perturbative QCD approach with Sudakov resummation. Since
none of the quarks in final states is the same as those of the initial
meson, this decay can occur only via annihilation diagrams in the standard
model. Besides the current-current operators, the contributions from the QCD
and electroweak penguin operators are also taken into account. We find that (a)
the branching ratio is about ; (b) the penguin diagrams
dominate the total contribution; and (c) the direct CP asymmetry is small in
size: no more than ; but the mixing-induced CP asymmetry can be as large
as ten percent testable in the near future LHC-b experiments.Comment: 12 pages, 4 figures included, RevTe
Exclusive semileptonic decays of in supersymmetric theories
The weak decays of () are
investigated in Minimal Supersymmetric Standard Model (MSSM) and also in
Supersymmetric (SUSY) SO(10) Grand Unified Models. In MSSM the special
attention is paid to the Neutral Higgs Bosons (NHBs) as they make quite a large
contribution in exclusive decays at large
regions of parameter space of SUSY models, since part of SUSY
contributions is proportional to . The analysis of decay rate,
forward-backward asymmetries, lepton polarization asymmetries and the
polarization asymmetries of baryon in show that the values of these physical observables are greatly modified
by the effects of NHBs. In SUSY SO(10) GUT model, the new physics contribution
comes from the operators which are induced by the NHBs penguins and also from
the operators having chirality opposite to that of the corresponding SM
operators. SUSY SO(10) effects show up only in the decay where the longitudinal and transverse lepton polarization
asymmetries are deviate significantly from the SM value while the effects in
the decay rate, forward-backward asymmetries and polarization asymmetries of
final state baryon are very mild. The transverse lepton polarization
asymmetry in is almost zero in SM
and in MSSM model. However, it can reach to -0.1 in SUSY SO(10) GUT model and
could be seen at the future colliders; hence this asymmetry observable will
provide us useful information to probe new physics and discriminate between
different models.Comment: 26 pages, 8 figure
Branching Ratio and CP Violation of B to pi pi Decays in Perturbative QCD Approach
We calculate the branching ratios and CP asymmetries for B^0 to pi^+pi^-, B^+
to pi^+pi^0 and B^0 to pi^0pi^0 decays, in a perturbative QCD approach. In this
approach, we calculate non-factorizable and annihilation type contributions, in
addition to the usual factorizable contributions. We found that the
annihilation diagram contributions are not very small as previous argument. Our
result is in agreement with the measured branching ratio of B to pi^+pi^- by
CLEO collaboration. With a non-negligible contribution from annihilation
diagrams and a large strong phase, we predict a large direct CP asymmetry in
B^0 to pi^+pi^-, and pi^0pi^0, which can be tested by the current running B
factories.Comment: Latex, 28 pages including 11 figures; added contents and figures,
corrected typo
Decay and Right-handed Top-bottom Charged Current
We introduce an anomalous top quark coupling (right-handed current) into
Standard Model Lagrangian. Based on this, a more complete calculation of decay including leading log QCD corrections from to
in addition to corrections from to is given. The inclusive decay
rate is found to be suppressed comparing with the case without QCD running from
to except at the time of small values of . e.g. when
, it is only of the value given before. As
goes smaller, this contribution is an enhancement like standard model case.
From the newly experiment of CLEO Collaboration, strict restrictions to
parameters of this top-bottom quark coupling are found.Comment: 20 Pages, 2 figures( ps file uuencoded)
Study of pure annihilation type decays
In this work, we calculate the rare decays and in perturbative QCD approach with Sudakov resummation.
We give the branching ratio of for , which will
be tested soon in factories.
The decay has a very small branching ratio at
, due to the suppression from CKM matrix elements . It may be sensitive to new physics contributions.Comment: 14 pages, 1 figur
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