444 research outputs found
Meson Decay Constants from Isospin Mass Splittings in the Quark Model
Decay constants of and mesons are estimated within the framework of a
heavy-quark approach using measured isospin mass splittings in the , ,
and states to isolate the electromagnetic hyperfine interaction between
quarks. The values MeV and MeV are
obtained. Only experimental errors are given; possible theoretical ambiguities,
and suggestions for reducing them, are noted.Comment: 7 pages, LaTeX, EFI-92-3
Parametrisations of the D -> K l nu form factor and the determination of \hat{g}
The vector form factor f_+(t) of the semileptonic decay D -> K l nu, measured
recently with a high accuracy, can be used to determine the strong coupling
constant g_{D_s^* D K}. The latter is related to the normalised coupling
\hat{g} releveant in heavy-meson chiral perturbation theory. This determination
relies on the estimation of the residue of the form factor at the D_s^* pole
and thus on an extrapolation of the form factor in the unphysical region
(m_D-m_K)^2<t<(m_D+m_K)^2. We test this extrapolation for several
parametrisations of the form factors by determining the value of \hat{g}, whose
value can be compared to other (experimental and theoretical) estimates.
Several unsophisticated parametrisations, differing by the amount of physical
information that they embed, are shown to pass this test. An apparently more
elaborated parametrisation of form factors, the so-called z-expansion, is at
variance with the other models, and we point out some significant shortcomings
of this parametrisation for the problem under consideration.Comment: 16 pages, 2 figures. A few references added. Accepted for publication
in JoP
Semileptonic decays of pseudoscalar mesons to scalar "f_0" meson
The transition form factors of (D_s -> f_0 l nu), (D -> f_0 l nu) and (B_u ->
f_0 l nu) decays are calculated in 3-point QCD sum rule method, assuming that
"f_0" is a quark-antiquark state with a mixture of strange and light quarks.
The branching ratios of these decays are calculated in terms of the mixing
angle.Comment: 12 pages, 4 figures, LaTeX formatte
Model-independent analysis of \bbox{B}-\bbox{\bar B} mixing and \bbox{CP} violation in \bbox{B} decays
We present a framework to analyze effects of new physics beyond the standard
model on - mixing and violation in decays in a
model-independent manner. Assuming that tree level decay amplitudes are
dominated by the standard model ones, new physics contribution to the - mixing can be extracted from several measurements at factories. Using
this framework, we show the present constraint on new physics contribution to
the - mixing, and illustrate constraints expected to be given by
future experiments at factories. We also point out a possibility that
asymmetries in , , and modes look consistent with the standard model, even if a large new physics
contribution is present in the - mixing.Comment: 11 pages, 3 Postscript figures, also available via anonymous ftp at
ftp://ftp.kek.jp/kek/preprints/TH/TH-44
Framework for Identification of Neutral B Mesons
We introduce a method for the study of CP-violating asymmetries in tagged
states of neutral mesons with arbitrary coherence properties. A set of
time-dependent measurements is identified which completely specifies the
density matrix of the initial state in a two-component space with basis vectors
and , and permits a determination of phases in the
Cabibbo-Kobayashi-Maskawa matrix. For a given tagging configuration, the
measurement of decays both to flavor eigenstates and to CP eigenstates provides
the necessary information.Comment: Submitted to Phys. Rev. Letters. 8 pages, LaTeX, Technion-PH-93-31 /
EFI 93-3
Identification of Neutral B Mesons Using Correlated Hadrons
The identification of the flavor of a neutral meson can make use of
hadrons produced nearby in phase space. Examples include the decay of
``'' resonances or the production of hadrons as a result of the
fragmentation process. Some aspects of this method are discussed, including
time-dependent effects in neutral decays to flavor states, to eigenstates
of CP and to other states, and the effects of possible coherence between
and in the initial state. We study the behavior of the leading
hadrons in -quark jets and the expected properties of resonances.
These are extrapolated from the corresponding resonances, of whose
properties we suggest further studies.Comment: To be submitted to Phys. Rev. D. 26 pages, LaTeX, figures not
included (available upon request). Technion-PH-93-32 / EFI 93-4
Decay constants and form factors of s-wave and p-wave mesons in the covariant light-front quark model
We reanalyze the decay constants of s-wave and p-wave mesons and D, B ->M
form factors, where M represents a pseudoscalar meson, a vector meson, a scalar
meson, or an axial vector meson within a covariant light-front quark model. The
parameter \beta for wave-functions of most of s-wave mesons and of a few
axial-vector mesons are fixed with latest experimental information, wherever
available or using the lattice calculations. The treatment of masses and mixing
angles for strange axial vector mesons is improved for the purpose. We extend
our analysis to determine the form factors appearing in the transition of D_s,
B_s->M transitions, and to the isoscalar final state mesons. Numerical results
of the form factors for transitions between a heavy pseudoscalar meson and an
s-wave or p-wave light meson and their momentum dependence are presented in
detail. Further, their sensitivity to uncertainties of beta parameters of the
initial as well as the final mesons is investigated. Some experimental
measurements of the charmed and bottom meson decays are employed to compare the
decay constants and transition form factors obtained in this and other works.Comment: 36 pages, 2 figure
Heavy Quark Symmetry Violation in Semileptonic Decays of D Mesons
The decays of mesons to and final states exhibit
significant deviations from the predictions of heavy-quark symmetry, as one
might expect since the strange quark's mass is of the same order as the QCD
scale. Nonetheless, in order to understand where the most significant effects
might lie for heavier systems (such as and ),
the pattern of these deviations is analyzed from the standpoint of perturbative
QCD and corrections. Two main effects are noted. First, the
perturbative QCD corrections lead to an overall decrease of predicted rates,
which can be understood in terms of production of excited kaonic states.
Second, effects tend to cancel the perturbative QCD
corrections in the case of decay, while they have minimal effect in
decay.Comment: 25 pages (LaTeX) + 7 pages of Postscript figures (included at end),
EFI-92-3
Resonant Two-body D Decays
The contribution of a resonance to is
calculated by applying the soft pion theorem to , and is
found to be about 30% of the measured amplitude and to be larger than the
component of this amplitude. We estimate a 70% contribution to
the total amplitude from a higher resonance. This implies large
deviations from factorization in D decay amplitudes, a lifetime difference
between D^0 and D^+, and an enhancement of mixing due to SU(3)
breaking.Comment: To be published in Physical Review Letters, some corrections,
references update
Model of the Quark Mixing Matrix
The structure of the Cabibbo-Kobayashi-Maskawa (CKM) matrix is analyzed from
the standpoint of a composite model. A model is constructed with three families
of quarks, by taking tensor products of sufficient numbers of spin-1/2
representations and imagining the dominant terms in the mass matrix to arise
from spin-spin interactions. Generic results then obtained include the familiar
relation , and a less frequently
seen relation . The magnitudes of
and come out naturally to be of the right order. The phase in
the CKM matrix can be put in by hand, but its origin remains obscure.Comment: Presented by Mihir P. Worah at DPF 92 Meeting, Fermilab, November,
1992. 3 pages, LaTeX fil
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