2,012 research outputs found
Implications of a DK Molecule at 2.32 GeV
We discuss the implications of a possible quasinuclear DK bound state at 2.32
GeV. Evidence for such a state was recently reported in D_s^+pi^o by the BaBar
Collaboration. We first note that a conventional quark model c-sbar assignment
is implausible, and then consider other options involving multiquark systems.
An I=0 c sbar n nbar baryonium assignment is one possibility. We instead favor
a DK meson molecule assignment, which can account for the mass and quantum
numbers of this state. The higher-mass scalar c-sbar state expected at 2.48 GeV
is predicted to have a very large DK coupling, which would encourage formation
of an I=0 DK molecule. Isospin mixing is expected in hadron molecules, and a
dominantly I=0 DK state with some I=1 admixture could explain both the narrow
total width of the 2.32 GeV state as well as the observed decay to D_s^+ pi^o.
Additional measurements that can be used to test this and related scenarios are
discussed.Comment: 6 pages, 1 figur
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
Large N Scaling Behavior of the Lipkin-Meshkov-Glick Model
We introduce a novel semiclassical approach to the Lipkin model. In this way
the well-known phase transition arising at the critical value of the coupling
is intuitively understood. New results -- showing for strong couplings the
existence of a threshold energy which separates deformed from undeformed states
as well as the divergence of the density of states at the threshold energy --
are explained straightforwardly and in quantitative terms by the appearance of
a double well structure in a classical system corresponding to the Lipkin
model. Previously unnoticed features of the eigenstates near the threshold
energy are also predicted and found to hold.Comment: 4 pages, 2 figures, to appear in PR
An interacting quark-diquark model of baryons
A simple quark-diquark model of baryons with direct and exchange interactions
is constructed. Spectrum and form factors are calculated and compared with
experimental data. Advantages and disadvantages of the model are discussed.Comment: 13 pages, 3 eps-figures, accepted by Phys.Rev. C Rapid Communication
Why is the B -> eta' X decay width so large ?
New mechanism for the observed inclusive B -> \eta'X decay is suggested. We
argue that the dominant contribution to this amplitude is due to the Cabbibo
favored b -> \bar{c}cs process followed by the transition \bar{c}c -> \eta'. A
large magnitude of the "intrinsic charm" component of \eta' is of critical
importance in our approach. Our results are consistent with an unexpectedly
large Br(B -> \eta'+X) \sim 10^{-3} recently announced by CLEO. We stress the
uniqueness of this channel for 0^{-+} gluonia search.Comment: Comments on a mixing model for intrinsic charm and pre-asymptotic
effects and some references are added. Latex, 9 page
The wavelength of neutrino and neutral kaon oscillations
Neutral kaons, and probably also neutrinos, exhibit oscillations between
flavor eigenstates, as a result of being produced in a superposition of mass
eigenstates. Several recent papers have addressed the question of the energies
and momenta of the components of these states, and their effect on the
coherence of the states and on the wavelength of the oscillations. We point out
that the mass eigenstates need have neither equal momentum nor equal energy,
but can nevertheless be coherent, and that a correct treatment of the
kinematics recovers the usual result for the wavelength of the flavor
oscillations.Comment: 7 pages, Latex, no figures. Added references. Formatted for Phys.
Lett. B (needs elsart.cls
Low-Mass Baryon-Antibaryon Enhancements in B Decays
The nature of low-mass baryon-antibaryon enhancements seen in B decays is
explored. Three possibilities include (i) states near threshold as found in a
model by Nambu and Jona-Lasinio, (ii) isoscalar states with coupled to a pair of gluons, and (iii) low-mass enhancements favored by the
fragmentation process. Ways of distinguishing these mechanisms using angular
distributions and flavor symmetry are proposed.Comment: 8 pages, LaTeX, no figures, to be submitted to Phys. Rev. D. One
reference adde
Entangling photons via the double quantum Zeno effect
We propose a scheme for entangling two photons via the quantum Zeno effect,
which describes the inhibition of quantum evolution by frequent measurements
and is based on the difference between summing amplitudes and probabilities.
For a given error probability , our scheme requires that the
one-photon loss rate and the two-photon absorption rate
in some medium satisfy , which is significantly improved in comparison to previous
approaches. Again based on the quantum Zeno effect, as well as coherent
excitations, we present a possibility to fulfill this requirement in an
otherwise linear optics set-up.Comment: 4 pages RevTeX, 2 figure
Comment on Octet Baryon Magnetic Moments in the Chiral Quark Model with Configuration Mixing
The importance of exchange currents, and of conserving isotopic spin at both
the quark and baryon levels in application of the chiral quark model to any
calculation of baryon magnetic moments is emphasized.Comment: 5 pages, Latex fil
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