15,269 research outputs found
Flavor SU(3) analysis of charmless B->PP decays
We perform a global fits to charmless decays which independently
constrain the vertex of the unitarity triangle. The
fitted amplitudes and phase are used to predict the branching ratios and CP
asymmetries of all decay modes, including those of the system. Different
schemes of SU(3) breaking in decay amplitude sizes are analyzed. The
possibility of having a new physics contribution to decays is also
discussed.Comment: 3 pages, 2 figs. Talk given at EPS-HEP07 To appear in the
proceedings, Reference adde
Quasi-local energy for cosmological models
First we briefly review our covariant Hamiltonian approach to quasi-local
energy, noting that the Hamiltonian-boundary-term quasi-local energy
expressions depend on the chosen boundary conditions and reference
configuration. Then we present the quasi-local energy values resulting from the
formalism applied to homogeneous Bianchi cosmologies. Finally we consider the
quasi-local energies of the FRW cosmologies. Our results do not agree with
certain widely accepted quasi-local criteria.Comment: Contributed to International Symposium on Cosmology and Particle
Astrophysics (CosPA 2006), Taipei, Taiwan, 15-17 Nov 200
Revisiting Charmless Hadronic B_{u,d} Decays in QCD Factorization
Within the framework of QCD factorization (QCDF), we consider two different
types of power correction effects in order to resolve the CP puzzles and rate
deficit problems with penguin-dominated two-body decays of B mesons and
color-suppressed tree-dominated and modes: penguin
annihilation and soft corrections to the color-suppressed tree amplitude. We
emphasize that the electroweak penguin solution to the CP puzzle
via New Physics is irrelevant for solving the CP and rate puzzles related to
tree-dominated decays. While some channels e.g.
need penguin annihilation to
induce the correct magnitudes and signs for their CP violation, some other
decays such as and require the presence of both power corrections to
account for the measured CP asymmetries. In general, QCDF predictions for the
branching fractions and direct CP asymmetries of decays
are in good agreement with experiment. The predictions of pQCD and
soft-collinear effective theory are included for comparison.Comment: 51 pages, 1 figur
U-Spin Tests of the Standard Model and New Physics
Within the standard model, a relation involving branching ratios and direct
CP asymmetries holds for the B-decay pairs that are related by U-spin. The
violation of this relation indicates new physics (NP). In this paper, we assume
that the NP affects only the Delta S = 1 decays, and show that the NP operators
are generally the same as those appearing in B -> pi K decays. The fit to the
latest B -> pi K data shows that only one NP operator is sizeable. As a
consequence, the relation is expected to be violated for only one decay pair:
Bd -> K0 pi0 and Bs -> Kbar0 pi0.Comment: 12 pages, latex, no figures. References changed to follow MPL
guidelines; info added about U-spin breaking and small NP strong phases;
discussion added about final-state pi-K rescattering; analysis and
conclusions unaltere
Spin Information from Vector-Meson Decay in Photoproduction
For the photoproduction of vector mesons, all single and double spin
observables involving vector meson two-body decays are defined consistently in
the center of mass. These definitions yield a procedure for
extracting physically meaningful single and double spin observables that are
subject to known rules concerning their angle and energy evolution. As part of
this analysis, we show that measuring the two-meson decay of a photoproduced
or does not determine the vector meson's vector polarization, but
only its tensor polarization. The vector meson decay into lepton pairs is also
insensitive to the vector meson's vector polarization, unless one measures the
spin of one of the leptons. Similar results are found for all double spin
observables which involve observation of vector meson decay. To access the
vector meson's vector polarization, one therefore needs to either measure the
spin of the decay leptons, make an analysis of the background interference
effects or relate the vector meson's vector polarization to other accessible
spin observables.Comment: 22 pages, 3 figure
Quasi-local energy and the choice of reference
A quasi-local energy for Einstein's general relativity is defined by the
value of the preferred boundary term in the covariant Hamiltonian formalism.
The boundary term depends upon a choice of reference and a time-like
displacement vector field (which can be associated with an observer) on the
boundary of the region. Here we analyze the spherical symmetric cases. For the
obvious analytic choice of reference based on the metric components, we find
that this technique gives the same quasi-local energy values using several
standard coordinate systems and yet can give different values in some other
coordinate systems. For the homogeneous-isotropic cosmologies, the energy can
be non-positive, and one case which is actually flat space has a negative
energy. As an alternative, we introduce a way to determine the choice of both
the reference and displacement by extremizing the energy. This procedure gives
the same value for the energy in different coordinate systems for the
Schwarzschild space, and a non-negative value for the cosmological models, with
zero energy for the dynamic cosmology which is actually Minkowski space. The
timelike displacement vector comes out to be the dual mean curvature vector of
the two-boundary.Comment: 21 pages; revised version to appear in CQ
Bond Refunding In Efficient Markets: A Dynamic Analysis With Tax Effects
This paper provides a dynamic analysis of the bond refunding problem in an efficient market setting with corporate taxes and transaction costs. A new methodology is developed to analyze the optimal exercise problem in the presence of imperfections. This analysis enables prediction of the effect of changes in corporate tax laws on the refunding decision. It also explains the empirical observation that bonds are often called when the bond price is below the call price.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/108309/1/jfir00667.pd
Chiral Condensates in Quark and nuclear Matter
We present a novel treatment for calculating the in-medium quark condensates.
The advantage of this approach is that one does not need to make further
assumptions on the derivatives of model parameters with respect to the quark
current mass. The normally accepted model-independent result in nuclear matter
is naturally reproduced. The change of the quark condensate induced by
interactions depends on the incompressibility of nuclear matter. When it is
greater than 260 MeV, the density at which the condensate vanishes is higher
than that from the linear extrapolation. For the chiral condensate in quark
matter, a similar model-independent linear behavior is found at lower
densities, which means that the decreasing speed of the condensate in quark
matter is merely half of that in nuclear matter if the pion-nucleon sigma
commutator is six times the average current mass of u and d quarks. The
modification due to QCD-like interactions is found to slow the decreasing speed
of the condensate, compared with the linear extrapolation.Comment: 12 pages, 7 figures, revtex4 styl
X-ray Lags in PDS 456 Revealed by Suzaku Observations
X-ray reverberation lags from the vicinity of supermassive black holes have
been detected in almost 30 AGN. The soft lag, which is the time delay between
the hard and soft X-ray light curves, is usually interpreted as the time
difference between the direct and reflected emission, but is alternatively
suggested to arise from the direct and scattering emission from distant clouds.
By analysing the archival Suzaku observations totalling an exposure time of ~
770 ks, we discover a soft lag of ks at Hz in
the luminous quasar PDS 456, which is the longest soft lag and lowest Fourier
frequency reported to date. In this study, we use the maximum likelihood method
to deal with non-continuous nature of the Suzaku light curves. The result
follows the mass-scaling relation for soft lags, which further supports that
soft lags originate from the innermost areas of AGN and hence are best
interpreted by the reflection scenario. Spectral analysis has been performed in
this work and we find no evidence of clumpy partial-covering absorbers. The
spectrum can be explained by a self-consistent relativistic reflection model
with warm absorbers, and spectral variations over epochs can be accounted for
by the change of the continuum, and of column density and ionization states of
the warm absorbers.Comment: accepted for publication in MNRA
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