1,644 research outputs found
Testing factorization in B -> D(*)X decays
In QCD the amplitude for B0 -> D(*)+pi- factorizes in the large Nc limit or
in the large energy limit Q >> Lambda_QCD where Q = {m_b, m_c, m_b-m_c}. Data
also suggests factorization in exclusive processes B-> D* pi+ pi- pi- pi0 and
B-> D* omega pi-, however by themselves neither large Nc nor large Q can
account for this. Noting that the condition for large energy release in B0-> D+
pi- is enforced by the SV limit, m_b, m_c >> m_b-m_c >> Lambda, we propose that
the combined large Nc and SV limits justify factorization in B -> D(*) X. This
combined limit is tested with the inclusive decay spectrum measured by CLEO. We
also give exact large Nc relations among isospin amplitudes for B -> D(*)X and
B -> D(*) D-bar(*)X, which can be used to test factorization through exclusive
or inclusive measurements. Predictions for the modes B-> D(*) pi pi, B-> D(*)K
K-bar and B-> D(*) D-bar(*) K are discussed using available data.Comment: 15 pages, 3 included .eps figures, minor change
Can there be any new physics in b -> d penguins
We analyze the possibility of observing new physics effects in the
penguin amplitudes. For this purpose, we consider the decay mode , which has only penguin contributions. Using the QCD
factorization approach, we find very tiny CP violating effects in the standard
model for this process. Furthermore, we show that the minimal supersymmetric
standard model with mass insertion and R-parity violating supersymmetric
model can provide substantial CP violation effects. Observation of sizable CP
violation in this mode would be a clear signal of new physics.Comment: Published versio
Strong Phases and Factorization for Color Suppressed Decays
We prove a factorization theorem in QCD for the color suppressed decays B0->
D0 M0 and B0-> D*0 M0 where M is a light meson. Both the color-suppressed and
W-exchange/annihilation amplitudes contribute at lowest order in LambdaQCD/Q
where Q={mb, mc, Epi}, so no power suppression of annihilation contributions is
found. A new mechanism is given for generating non-perturbative strong phases
in the factorization framework. Model independent predictions that follow from
our results include the equality of the B0 -> D0 M0 and B0 -> D*0 M0 rates, and
equality of non-perturbative strong phases between isospin amplitudes,
delta(DM) = delta(D*M). Relations between amplitudes and phases for M=pi,rho
are also derived. These results do not follow from large Nc factorization with
heavy quark symmetry.Comment: 38 pages, 6 figs, typos correcte
B-> K photon photon via intermediate eta'
We examine our previous conjecture that the eta' intermediate resonance has
the dominant role in the long distance contributions to B decay into two
photons and a strange final state hadron. We calculate the branching ratio of
the exclusive B-> K eta'-> K photon photon decay using the nonspectator
mechanism for eta' production in charmless hadronic B decays. It is shown that
the obtained branching ratio B^eta'(B-> K\gamma\gamma)~ 8.7 X 10^{-7} is more
than twice as large as the eta_c contribution to this decay mode.Comment: 6 pages, latex, no figure
Decay of the Sinai Well in D dimensions
We study the decay law of the Sinai Well in dimensions and relate the
behavior of the decay law to internal distributions that characterize the
dynamics of the system. We show that the long time tail of the decay is
algebraic (), irrespective of the dimension .Comment: 14 pages, Figures available under request. Revtex. Submitted to Phys.
Rev. E.,e-mail: [email protected]
Exact sampling of self-avoiding paths via discrete Schramm-Loewner evolution
We present an algorithm, based on the iteration of conformal maps, that
produces independent samples of self-avoiding paths in the plane. It is a
discrete process approximating radial Schramm-Loewner evolution growing to
infinity. We focus on the problem of reproducing the parametrization
corresponding to that of lattice models, namely self-avoiding walks on the
lattice, and we propose a strategy that gives rise to discrete paths where
consecutive points lie an approximately constant distance apart from each
other. This new method allows us to tackle two non-trivial features of
self-avoiding walks that critically depend on the parametrization: the
asphericity of a portion of chain and the correction-to-scaling exponent.Comment: 18 pages, 4 figures. Some sections rewritten (including title and
abstract), numerical results added, references added. Accepted for
publication in J. Stat. Phy
The integrated density of states of the random graph Laplacian
We analyse the density of states of the random graph Laplacian in the
percolating regime. A symmetry argument and knowledge of the density of states
in the nonpercolating regime allows us to isolate the density of states of the
percolating cluster (DSPC) alone, thereby eliminating trivially localised
states due to finite subgraphs. We derive a nonlinear integral equation for the
integrated DSPC and solve it with a population dynamics algorithm. We discuss
the possible existence of a mobility edge and give strong evidence for the
existence of discrete eigenvalues in the whole range of the spectrum.Comment: 4 pages, 1 figure. Supplementary material available at
http://www.theorie.physik.uni-goettingen.de/~aspel/data/spectrum_supplement.pd
Evading the CKM Hierarchy: Intrinsic Charm in B Decays
We show that the presence of intrinsic charm in the hadrons' light-cone wave
functions, even at a few percent level, provides new, competitive decay
mechanisms for B decays which are nominally CKM-suppressed. For example, the
weak decays of the B-meson to two-body exclusive states consisting of strange
plus light hadrons, such as B\to\pi K, are expected to be dominated by penguin
contributions since the tree-level b\to s u\bar u decay is CKM suppressed.
However, higher Fock states in the B wave function containing charm quark pairs
can mediate the decay via a CKM-favored b\to s c\bar c tree-level transition.
Such intrinsic charm contributions can be phenomenologically significant. Since
they mimic the amplitude structure of ``charming'' penguin contributions,
charming penguins need not be penguins at all.Comment: 28 pages, 6 figures, published version. References added, minor
change
Factorization and Nonfactorization in B Decays
Using NLL values for Wilson coefficients and including the contributions from
the penguin diagrams, we estimate the amount of nonfactorization in two-body
hadronic B decays. Also, we investigate the model dependence of the
nonfactorization parameters by performing the calculation using different
models for the form factors. The results support the universality of
nonfactorizable contributions in both Cabibbo-favored and Cabibbo-suppressed B
decays.Comment: 17 pages, 5 figures, revte
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