3,973 research outputs found
Tests of Factorization and SU(3) Relations in B Decays into Heavy-Light Final States
Using data from the B factories and the Tevatron, we perform tests of how
well non-leptonic B decays of the kind B -> D^{(*)}_{(s)} P, where P is a pion
or kaon, are described within the factorization framework. We find that
factorization works well - as is theoretically expected - for color-allowed,
tree-diagram-like topologies. Moreover, also exchange topologies, which have a
non-factorizable character, do not show any anomalous behavior. We discuss also
isospin triangles between the B -> D^{(*)} pi decay amplitudes, and determine
the corresponding amplitudes in the complex plane, which show a significant
enhancement of the color-suppressed tree contribution with respect to the
factorization picture. Using data for B -> D^{(*)} K decays, we determine
SU(3)-breaking effects and cannot resolve any non-factorizable SU(3)-breaking
corrections larger than \sim 5%. In view of these results, we point out that a
comparison between the \bar B^0_d -> D^+\pi^- and \bar B^0_s -> D_s^+\pi^-
decays offers an interesting new determination of f_d/f_s. Using CDF data, we
obtain the most precise value of this ratio at CDF, and discuss the prospects
for a corresponding measurement at LHCb.Comment: 12 pages, 6 figures, matches published version in Physical Review
Towards Automatic Analytic Evaluation of Diagrams with Masses
A method to calculate two-loop self-energy diagrams of the Standard Model is
demonstrated. A direct physical application is the calculation of the two-loop
electroweak contribution to the anomalous magnetic moment of the muon
. Presently, we confine ourselves to a ``toy'' model with
only , and a heavy neutral scalar particle (Higgs). The algorithm
is implemented as a FORM-based program package. For generating and
automatically evaluating any number of two-loop self-energy diagrams, a special
C-program has been written. This program creates the initial FORM-expression
for every diagram generated by QGRAF, executes the corresponding subroutines
and sums up the final results.Comment: LaTeX, 20 pages, 7 eps-figures included; extended version of talk
given at AIHEN96, Lausanne, 1-6 Sept. 1996; detailed description of C-program
is given; accepted for publication in Comp.Phys.Com
Adiabatic theorem for non-hermitian time-dependent open systems
In the conventional quantum mechanics (i.e., hermitian QM) the adia- batic
theorem for systems subjected to time periodic fields holds only for bound
systems and not for open ones (where ionization and dissociation take place)
[D. W. Hone, R. Ketzmerik, and W. Kohn, Phys. Rev. A 56, 4045 (1997)]. Here
with the help of the (t,t') formalism combined with the complex scaling method
we derive an adiabatic theorem for open systems and provide an analytical
criteria for the validity of the adiabatic limit. The use of the complex
scaling transformation plays a key role in our derivation. As a numerical
example we apply the adiabatic theorem we derived to a 1D model Hamiltonian of
Xe atom which interacts with strong, monochromatic sine-square laser pulses. We
show that the gener- ation of odd-order harmonics and the absence of
hyper-Raman lines, even when the pulses are extremely short, can be explained
with the help of the adiabatic theorem we derived
Amplification of High Harmonics Using Weak Perturbative High Frequency Radiation
The mechanism underlying the substantial amplification of the high-order
harmonics q \pm 2K (K integer) upon the addition of a weak seed XUV field of
harmonic frequency q\omega to a strong IR field of frequency \omega is analyzed
in the framework of the quantum-mechanical Floquet formalism and the
semiclassical re-collision model. According to the Floquet analysis, the
high-frequency field induces transitions between several Floquet states and
leads to the appearance of new dipole cross terms. The semiclassical
re-collision model suggests that the origin of the enhancement lies in the
time-dependent modulation of the ground electronic state induced by the XUV
field.Comment: 8 pages, 2 figure
Long-range two-body final-state interactions and direct CP asymmetry in {B}^{+}\to{\pi}^{+} {K}^{0} decay
We present a calculation of the direct CP asymmetry, , for the
process including the effects of long-range inelastic
final-state interactions (FSI). We admit three channels in our calculation:
, and . The strong
scattering is described in terms of Pomeron and Regge exchanges. We find that
the direct CP asymmetry is enhanced by a factor of as a result of FSI,
but remains well short of the claims of (10 - 20)% in recent literature. A
critical assessment of papers claiming large CP asymmetries is also presented.Comment: 21 pages, latex, no figures. Added the charge-exchange channel
{B}^{+}\to {\pi}^{0} {K}^{+}. Expanded the discussion section. To be
published in Phys. Rev.
Effects of R-parity violation on direct CP violation in B decays and extraction of
In the standard model, direct CP-violating asymmetries for are roughly 2% based on perturbative calculation. Rescattering effects might
enhance it to at most (20-25)%. We show that lepton-number-violating couplings
in supersymmetric models without R-parity are capable of inducing as large as
100% CP asymmetry in this channel. Such effects drastically modify the allowed
range of the CKM parameter arising from the combinations of the
observed charged and neutral B decays in the modes. With a multichannel
analysis in B decays, one can either discover this exciting new physics, or
significantly improve the existing constraints on it.Comment: Latex, 5 pages; minor changes, to appear in Phys Rev Let
Using B_s^0 Decays to Determine the CP Angles \alpha and \gamma
Dighe, Gronau and Rosner have shown that, by assuming SU(3) flavor symmetry
and first-order SU(3) breaking, it is possible to extract the CP angles \alpha
and \gamma from measurements of the decay rates of B_d^0(t) --> \pi^+\pi^-,
B_d^0 --> \pi^- K^+ and B^+ --> \pi^+ K^0, along with their charge-conjugate
processes. We extend their analysis to include the SU(3)-related decays B_s^0
--> \pi^+ K^-, B_s^0(t) --> K^+ K^- and B_s^0 --> K^0 {\bar K^0}. There are
several advantages to this extension: discrete ambiguities are removed, fewer
assumptions are necessary, and the method works even if all strong phases
vanish. In addition, we show that \gamma can be obtained cleanly, with no
penguin contamination, by using the two decays B_s^0(t) --> K^+ K^- and B_s^0
--> K^0 {\bar K^0}.Comment: 28 pages, LaTe
Weak Phase From Ratio of Rates
The ratio of partial decay rates for charged and neutral mesons to final states provides information on the weak phase when augmented with information on the CP-violating asymmetry
in the mode. The requirements for a useful determination of
are examined in the light of present information about the decays , , and the corresponding charge-conjugate
modes. The effects of electroweak penguins and rescattering corrections are
noted, and proposals are made for estimating and measuring their importance.Comment: 16 pages, latex, 3 figures, revised version sent to Phys. Rev.
Constraints on the phase and new physics from Decays
Recent results from CLEO on indicate that the phase may
be substantially different from that obtained from other fit to the KM matrix
elements in the Standard Model. We show that extracted using is sensitive to new physics occurring at loop level. It provides
a powerful method to probe new physics in electroweak penguin interactions.
Using effects due to anomalous gauge couplings as an example, we show that
within the allowed ranges for these couplings information about
obtained from can be very different from the Standard
Model prediction.Comment: Revised version with analysis done using new data from CLEO. RevTex,
11 Pages with two figure
A Critical Study of B Decays to Light Pseudoscalar
Motivated by the large branching ratios observed for the process
, we examine critically all the ingredients that go into
estimates of B decays into two light pseudoscalars. Within factorization
approximation, we examine several assumptions on the input parameters that
could have a strong bearing on the predictions. Among these are (i) the QCD
scale (ii) value of the form factors (iii) value of the light quark
masses, and in particular (iv) the value , (v) charm content
of . It is possible to account for all the data without invoking
new physics, though future experiments will provide tighter constraints on the
parameter space. We fin that CP violating asymmetries are in the observable
range for some modes.Comment: 29 pages(Latex), 17 figures, a few changes have been made, version to
appear in Phys.Rev.
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