7,303 research outputs found
Bounds on Heavy-to-Heavy Weak Decay Form Factors
We provide upper and lower bounds on the semileptonic weak decay form factors
for and decays by utilizing inclusive
heavy quark effective theory sum rules. These bounds are calculated to second
order in and first order in . The corrections to the bounds at zero recoil are also presented.Comment: 3 pages, talk given at DPF 2000, Columbus, OH, August 9, 2000;
reference adde
Partially Strong WW Scattering
What if only a light Higgs boson is discovered at the CERN LHC?
Conventional wisdom tells us that the scattering of longitudinal weak gauge
bosons would not grow strong at high energies. We show that this is not always
true. In some composite models, two-Higgs-doublet models, or even
supersymmetric models, the presence of a light Higgs boson does not guarantee
the complete unitarization of the scattering. After the partial
unitarization by the light Higgs boson, the scattering becomes strongly
interacting until it hits one or more heavier Higgs bosons or other strong
dynamics. We analyze how the LHC experiments can reveal this interesting
possibility of partially strong scattering.Comment: 4 pages, 3 figures; updated reference information and added a
referenc
SU(3) symmetry breaking and CP violation in D -> PP decays
Evidence of CP violation in the charm sector has been observed recently by
the LHCb and CDF Collaborations. Adopting the topological diagram approach, we
study flavor SU(3) symmetry breaking effects in the weak decay tree amplitudes
of singly Cabibbo-suppressed decays. The symmetry breaking in the
color-allowed and color-suppressed amplitudes is estimated with the help of the
factorization ansatz, while that in the -exchange amplitude is done by
fitting to related branching fraction data. We find that the -exchange
amplitudes stay in the second quadrant relative to the color-allowed tree
amplitude, albeit there are two possibilities for one type of -exchange
amplitude. The weak decay penguin amplitudes, on the other hand, are evaluated
within the framework of QCD factorization. Using the input of topological tree
amplitudes extracted from the Cabibbo-favored decay modes and the perturbative
results for QCD penguin amplitudes, we make predictions for the branching
fractions and CP asymmetries of singly Cabibbo-suppressed modes. The
predictions of branching fractions are generally improved from those in the
SU(3) limit. We conclude that the direct CP asymmetry difference between and is about and
for the two solutions of -exchange amplitudes,
respectively. We also find that the CP asymmetry of D^0\to K^0\ov K^0
dominated by the interference between -exchange amplitudes ranges from
to . We study phenomenological
implications of two new physics scenarios for explaining the observed CP
asymmetry in the charm sector, one with large penguin amplitudes and the other
with a large chromomagnetic dipole operator. We find that the two scenarios can
be discriminated by the measurements of CP asymmetries of a set of decay modes.Comment: 23 pages, three new paragraphs added in the beginning of Sec. III.
Version to appear in PRD. arXiv admin note: substantial text overlap with
arXiv:1201.078
- β¦