194 research outputs found
Isoscalar-isovector mass splittings in excited mesons
Mass splittings between the isovector and isoscalar members of meson nonets
arise in part from hadronic loop diagrams which violate the Okubo-Zweig-Iizuka
rule.
Using a model for these loop processes which works qualitatively well in the
established nonets, I tabulate predictions for the splittings and associated
isoscalar mixing angles in the remaining nonets below about 2.5 GeV, and
explain some of their systematic features.
The results for excited vector mesons compare favorably with experiment.Comment: 8 RevTeX pages, including 1 LaTeX figure.
CMU-HEP93-23/DOE-ER-40682-4
Glueball Interpretation of (2230)
On the basis of the results of
and , measured by the BES Collaboration in radiative J/ decays,
combined with the upper limit of Br()Br(), measured by PS185 experiment, we argue
that the distinctive properties of (2230), the flavor-symmetric decays and
the narrow partial decay widths to and as well as its
copious production in radiative J/ decay, would strongly favor the
glueball interpretation of (2230).Comment: Latex file, no figure
Properties of the Strange Axial Mesons in the Relativized Quark Model
We studied properties of the strange axial mesons in the relativized quark
model. We calculated the decay constant in the quark model and showed how
it can be used to extract the mixing angle
() from the weak decay . The ratio is the most sensitive
measurement and also the most reliable since the largest of the theoretical
uncertainties factor out. However the current bounds extracted from the
TPC/Two-Gamma collaboration measurements are rather weak: we typically obtain
at 68\% C.L. We also calculated the
strong OZI-allowed decays in the pseudoscalar emission model and the flux-tube
breaking model and extracted a mixing angle of . Our analysis also indicates that the heavy quark limit does not give a
good description of the strange mesons.Comment: Revised version to be published in Phys. Rev. D. Minor changes. Latex
file uses revtex version 3 and epsfig, 4 postcript figures are attached. The
full postcript version with embedded figures is available at
ftp://ftp.physics.carleton.ca/pub/theory/godfrey/ocipc9512.ps.
Nonresonant Semileptonic Heavy Quark Decay
In both the large N_c limit and the valence quark model, semileptonic decays
are dominated by resonant final states. Using Bjorken's sum rule in an
"unquenched" version of the quark model, I demonstrate that in the heavy quark
limit nonresonant final states should also be produced at a significant rate.
By calculating the individual strengths of a large number of exclusive two-body
nonresonant channels, I show that the total rate for such processes is highly
fragmented. I also describe some very substantial duality-violating suppression
factors which reduce the inclusive nonresonant rate to a few percent of the
total semileptonic rate for the finite quark masses of B decay, and comment on
the importance of nonresonant decays as testing grounds for very basic ideas on
the structure, strength, and significance of the quark-antiquark sea and on
quark-hadron duality in QCD.Comment: 51 pages, 2 Postscript figure
Phase Transitions at Finite Temperature and Dimensional Reduction for Fermions and Bosons
In a recent Letter we discussed the fact that large- expansions and
computer simulations indicate that the universality class of the finite
temperature chiral symmetry restoration transition in the 3D Gross-Neveu model
is mean field theory. This was seen to be a counterexample to the standard
'sigma model' scenario which predicts the 2D Ising model universality class. In
this article we present more evidence, both theoretical and numerical, that
this result is correct. We develop a physical picture for our results and
discuss the width of the scaling region (Ginzburg criterion),
corrections, and differences between the dynamics of BCS superconductors and
Gross-Neveu models. Lattices as large as are simulated for
both the and cases and the numerical evidence for mean field
scaling is quite compelling. We point out that the amplitude ratio for the
model's susceptibility is a particulartly good observable for distinguishing
between the dimensional reduction and the mean field scenerios, because this
universal quantity differs by almost a factor of in the two cases. The
simulations are done close to the critical point in both the symmetric and
broken phases, and correlation lengths of order are measured. The critical
indices and also pick out mean field behavior. We trace
the breakdown of the standard scenario (dimensional reduction and universality)
to the composite character of the mesons in the model. We point out that our
results should be generic for theories with dynamical symmetry breaking, such
as Quantum Chromodynamics.
We also simulated the model on lattices to establish
that our methods give the results of dimensional reduction in purely bosonicComment: 47 pages, latex, 23 figures in one uuencoded fil
Understanding the nature of and through nonleptonic B Decays
We consider the nonleptonic B decays and , involving the newly discovered and the
states. We find that experiments indicate disagreement with model
calculations of their properties and/or breakdown of the factorization
assumption for these decays . We point out that decays involving mesons
where the resonances can be produced via the weak decay of the quark
can provide further information about the nature of these newly discovered
states. We also propose a model to calculate the two body nonleptonic decays , if the and are
interpreted as and molecules.Comment: 14 pages LaTeX; additional reference, notational corrections and
minor clarifications of tex
The Partonic Content of and $h_2(x)
A light-cone wavefunction interpretation is presented for the polarized
distribution functions and . All matrix elements for moments
of these distributions are given in terms of overlap integrals between Fock
state amplitudes of the target state. In a suitable spinor basis,
involves only diagonal matrix elements so can be interpreted as a density.
Matrix elements of connect Fock states differing by one gluon so that
has no simple interpretation as a density. Nevertheless, in the
wavefunction decomposition, is described through a compact set of
elementary quark-gluon processes which are averaged over the target
wavefunction.Comment: 16 pages, AZPH-TH 93-32, Latex, Phys. Rev D 49, 3187 (1994
Weak decays of doubly heavy hadrons
We explore the application and usefulness of the heavy quark symmetry to
describe the weak decays of hadrons (mesons and baryons) containing two heavy
quarks. Firstly, we address the internal dynamics of a heavy-heavy bound system
with the help of estimates based on potential models, showing an approximate
spin symmetry in the preasymptotic quark mass region including charmonium,
bottonium and meson states. However, no asymptotic spin symmetry should
hold in the infinite quark mass limit in contrast to singly heavy hadrons.
Predictions on semileptonic and two-body nonleptonic decays of mesons are
shown. Furthermore, the stemming flavor and spin symmetries from the
interaction between the heavy and light components in hadrons (combining in a
superflavor" symmetry) permit their classification in -type
supermultiplets containing singly heavy mesons together with doubly heavy
baryons, and -type supermultiplets containing singly heavy baryons
together with some exotic doubly heavy multiquark states (diquonia). Exploiting
their well-defined transformation properties under the superflavor symmetry
group, we get predictions on the widths for some semileptonic and two-body
nonleptonic decays of baryons containing both and quarks.Comment: Latex, 26 pages, 2 figures available by FAX
Near-Threshold Production of omega Mesons in the pp -> pp omega Reaction
The total cross section for omega production in the pp -> pp omega reaction
has been measured at five c.m. excess energies from 3.8 to 30 MeV. The energy
dependence is easily understood in terms of a strong proton-proton final state
interaction combined with a smearing over the width of the state. The ratio of
near-threshold phi and omega production is consistent with the predictions of a
one-pion-exchange model and the degree of violation of the OZI rule is similar
to that found in the pi-p -> n omega/phi reactions.Comment: Report in LaTeX2e. 12 pages with 2 eps figure
The New Heavy Mesons: A Status Report
A survey of the experimental, phenomenological, and theoretical status of the
new heavy mesons is presented. States discussed are the , ,
, , , X(3872), X(3940), Y(3940), Z(3930), and
Y(4260). Quark models for spectra, strong decays, and hadronic interactions are
reviewed and used to interpret the new states. New results for strong decay
models, bound state decays, mesonic molecules, properties of the X(3872), and
the chiral doublet model are also presented.Comment: 62 page, 40 figs, 16 tables. v3 corrects typos, adds references.
Version to appear in Physics Report
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