339 research outputs found
Spectator Effects in the Decay B -> K \gamma \gamma
We report the results of the first computation related to the study of the
spectator effects in the rare decay mode within the
framework of Standard Model. It is found that the account of these effects
results in the enhancement factor for the short-distance reducible contribution
to the branching ratio.Comment: 5 pages, 5 figures, RevTeX
Pade-Improved Estimate of Perturbative Contributions to Inclusive Semileptonic Decays
Pade-approximant methods are used to estimate the three-loop perturbative
contributions to the inclusive semileptonic decay rate. These
improved estimates of the decay rate reduce the theoretical uncertainty in the
extraction of the CKM matrix element from the measured inclusive
semileptonic branching ratio.Comment: 3 pages, latex, write-up of talk presented at DPF 200
Improvement of Renormalization-Scale Uncertainties Within Empirical Determinations of the b-Quark Mass
Accurate determinations of the MS-bar b-quark mass from
experimental data currently contain three
comparable sources of uncertainty; the experimental uncertainty from moments of
this cross-section, the uncertainty associated with , and the
theoretical uncertainty associated with the renormalization scale. Through
resummation of all logarithmic terms explicitly determined in the perturbative
series by the renormalization-group (RG) equation, it is shown that the
renormalization-scale dependence is virtually eliminated as a source of
theoretical uncertainty in . This resummation also reduces the
estimated effect of higher-loop perturbative contributions, further reducing
the theoretical uncertainties in . Furthermore, such resummation
techniques improve the agreement between the values of the MS-bar b-quark mass
extracted from the various moments of [], obviating the need to
choose an optimummoment for determining . Resummation techniques are
also shown to reduce renormalization-scale dependence in the relation between
b-quark MS-bar and pole mass and in the relation between the pole and
mass.Comment: 19 pages, latex2e, 6 eps figures contained in latex file. Errors
corrected in equations (20)--(22
Minimal Retraction of Space-time and Their Foldings
The deformation retract of space-time onto itself and into a geodesics will be achieved. The concept of retraction and folding of zero dimension space-time will be obtained.The relation between limit of folding and retraction presented
Possible large direct CP asymmetry in hadronic B+- -> \pi+- \eta' decays
We calculate the branching ratio and direct CP asymmetry in nonleptonic two
body B decays B^+- ->\pi^+- \eta'. It is shown that the tree diagram and gluon
fusion mechanism via penguin diagram have comparable contributions to these
decays which, as a result, could provide an interesting venue for investigating
CP violation. Our estimate shows that the direct CP asymmetry in the above
decays could be as large as 75% which along with a branching ratio B(B^-
->\pi^- \eta')=3.4 X 10^{-6} should be accessible to experiment in the near
future.Comment: 13 pages, Revtex, 4 figures (included
B -> X_s l+ l- in the vectorlike quark model
We extend the standard model by adding an extra generation of isosinglet up-
and down-type quark pair which engage in weak interactions only via mixing with
the three ordinary quark families. It is shown that the generalized
quark mixing matrix, which is necessarily nonunitary, leads to nonvanishing
flavor changing neutral currents. We then proceed to investigate various
distributions and total branching ratio of the inclusive B -> X_s l+ l- (l
=e,\mu) rare B decays in the context of this model. It is shown that the shapes
of the differential branching ratio and forward-backward asymmetry distribution
are very sensitive to the value of the model parameters which are constrained
by the experimental upper bound on BR(B -> X_s \mu^+ \mu^-). We also indicate
that, for certain values of the dileptonic invariant mass, CP asymmetries up to
10% can be obtained.Comment: 10 pages, 5 figures, Talk given at 23rd Annual MRST
(Montreal-Rochester-Syracuse-Toronto) Conference on High Energy Physics (MRST
2001), London, Ontario, Canada, 16-18 May 200
Estimates of B-decays into K-Resonances and Dileptons
Short and long distance contributions to the exclusive B-decays into various
K-resonances and dileptons, i.e. B --> Ki l l ( l = e, mu , nu ), are examined.
The heavy quark effective theory has been used to calculate the hadronic matrix
elements. Substantial branching fractions are obtained for the dileptonic
B-decays into some higher excited states of K-mesons. The long distance
(resonance) contributions to these exclusive rare B-decay modes dominate the
short distance contributions mostly by two orders of magnitude. It is pointed
out that, excluding the resonance contributions, the P-wave channels are
dominant, accounting for about 50% of the inclusive B --> X_s l l branching
fraction.Comment: 11 pages, LATEX, no figure
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