272 research outputs found
Charm meson resonances in decays
Motivated by recent experimental results we reconsider semileptonic decays within a model which combines heavy quark symmetry and
properties of the chiral Lagrangian. We include excited charm meson states,
some of them recently observed, in our Lagrangian and determine their impact on
the charm meson semileptonic form factors. We find that the inclusion of
excited charm meson states in the model leads to a rather good agreement with
the experimental results on the shape of the form factor. We
also calculate branching ratios for all decays.Comment: 9 pages, 4 figures; minor corrections, added some discussion, version
as publishe
Exclusive Decays and CP Violation in the General two-Higgs-doublet Model
We calculate all the branching ratios and direct CP violations of
decays in a most general two-Higgs-doublet model with spontaneous CP violation.
As the model has rich CP-violating sources, it is shown that the new physics
effects to direct CP violations and branching ratios in some channels can be
significant when adopting the generalized factorization approach to evaluate
the hadronic matrix elements, which provides good signals for probing new
physics beyond the SM in the future B experiments.Comment: 21 page
Stokes Vector of Photon in the Decays B^0 -> rho^0 gamma and B^0 -> K^* gamma
We consider a model for the decay Bbar^0 -> rho^0 gamma in which the
short-distance amplitude determined by the Hamiltonian describing b -> d gamma
is combined with a typical long-distance contribution Bbar^0 -> D^+ D^- ->
rho^0 gamma. The latter possesses a significant dynamical phase which induces a
CP-violating asymmetry A_CP, as well as an important modification of the Stokes
vector of the photon. The components S_1 and S_3 of the Stokes vector S = (S_1,
S_2, S_3) can be measured in the decay Bbar^0 -> rho^0 gamma^* -> pi^+ pi^- e^+
e^- where they produce a characteristic effect in the angular distribution d
Gamma / d phi, phi being the angle between the pi^+ pi^- and e^+ e^- planes. A
similar analysis is carried out for the decays Bbar^0 -> Kbar^* gamma and
Bbar^0 -> Kbar^* gamma^* -> pi^+ K^- e^+ e^-Comment: 13 pages, 8 figures; v2: Some clarifying remarks added, together with
additional references. Minor typos corrected. No change in result
Chondrosarcoma of the Pelvis: Oncologic and Functional Outcome
Purpose. Chondrosarcoma (CS) most commonly involves the pelvis.
The factors that influence local and systemic control of pelvic CS and the functional outcome
should be evaluated
Semileptonic and Exclusive Rare B Decays
The exclusive rare decay B \ra K^\ast \gamma takes place in a region of
maximum recoil, , posing a problem for nonrelativistic quark models
which are usually thought to be most reliable at zero recoil. The
Bauer--Stech--Wirbel (BSW) model, formulated in the infinite--momentum--frame
(IMF) formalism, is designed to work at . We show in this model that the
ratio relating the decay B \ra K^\ast \gamma and the --spectrum of the
semileptonic decay B\ra \rho e {\bar \nu}, becomes independent of the wave
function in the SU(3) flavor symmetry limit. We show that this feature is also
true in relativistic quark models formulated in the IMF or light--cone
formalism, if the quark is infinitely heavy. In fact, these relativistic
models, which have a different spin structure from the BSW case, reduce to the
BSW model in the heavy --quark limit. A direct measurement of the
--spectrum of the semileptonic decay can therefore provide accurate
information for the exclusive rare decay.Comment: 13 pages, Latex, no figure, UTPT--94--0
Final State Interactions in
It is believed that the production rate of is almost
solely determined by final state interactions (FSI) and hence provides an ideal
place to test FSI models. Here we examine model calculations of the
contributions from s-channel resonance and t-channel exchange to
the FSI effects in . The contribution from s-channel
is sma The results from
two methods are roughly consistent with each other and can reproduce the large
rate of reasonably well$Comment: Latex, 16 pages, with 2 figure
Selection rules in three-body B decay from factorization
Extending the dynamics underlying the factorization calculation of two-body
decays, we propose simple selection rules for nonresonant three-body B decays.
We predict, for instance, that in the Dalitz plot of B^0-->D^0-bar\pi^+\pi^-,
practically no events should be found in the corner of E(\pi^+) < \Lambda_{QCD}
as compared with the corner of E(\pi^-) < \Lambda_{QCD}. We also predict that
there should be very few three-body decay events with a soft meson resonance
and two energetic mesons or meson resonances. The selection rules are quite
different from the soft pion theorem, since they apply to different kinematical
regions. For B^0 -->D^0-bar\pi^+\pi^-, the latter predicts that the decay
matrix element vanishes in the zero-four-momentum limit of \pi^+ instead of
\pi^-. Since this marked difference from the soft pion theorem is directly
related to the issue of short-distance QCD dominance in the FSI of two-body B
decays, experimental test of the selection rules will shed light on strong
interaction dynamics of B decay.Comment: 12 pages in REVTEX including 3 eps figure
A Model for the decay of the meson into three pions,
We propose a phenomenological two component model describing the decay
amplitude of the process D_s^{+} \ra 3 \pi, whose rate has been found
surprisingly large. The first component is a constant background , and
the second one is a Breit-Wigner type amplitude associated to a quasi two body
state. We show that it is possible to reproduce the
observed rate for D_s^{+} \ra \pi^{+}\pi^{+}\pi^{-} as well as the two other
measured branching ratios for the non resonant part and the resonant
one, with a common parameter . Predictions are given for
the D_s^{+} \ra \pi^{0}\pi^{0}\pi^{+} rates, as well as for the various
and , or and energy distributions for
the two possible final states.Comment: 23 pages (Latex) including 7 figures (Postscript file)
Final state rescattering as a contribution to
We provide a new estimate of the long-distance component to the radiative
transition . Our mechanism involves the soft-scattering of
on-shell hadronic products of nonleptonic decay, as in the chain . We employ a phenomenological fit to scattering data
to estimate the effect. The specific intermediate states considered here modify
the decay rate at roughly the level, although
the underlying effect has the potential to be larger. Contrary to other
mechanisms of long distance physics which have been discussed in the
literature, this yields a non-negligible modification of the channel and hence will provide an uncertainty in the extraction of
. This mechanism also affects the isospin relation between the rates
for and and may generate CP
asymmetries at experimentally observable levels.Comment: 15 pages, RevTex, 3 figure
B-physics constraints on baryon number violating couplings: grand unification or R-parity violation
We investigate the role that baryon number violating interactions may play in
phenomenology. Present in various grand unified theories, supersymmetric
theories with R-parity violation and composite models, a diquark state could be
quite light. Using the data on B decays as well as mixing, we
find strong constraints on the couplings that such a light diquark state may
have with the Standard Model quarks.Comment: 19 pages, latex, no figures, 13 tables include
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