1,809 research outputs found
Duality-Violating 1/m_Q Effects in Heavy Quark Decay
I identify a source of \Lambda_{QCD}/m_Q corrections to the assumption of
quark-hadron duality in the application of heavy quark methods to inclusive
heavy quark decays. These corrections could substantially affect the accuracy
of such methods in practical applications and in particular compromise their
utility for the extraction of the Cabibbo-Kobayashi-Maskawa matrix element
V_{cb}.Comment: 16 pages, 5 figures, an abbreviated version of hep-ph/9809279, the
original JLAB-THY-98-03 ``Duality in Inclusive Semileptonic Heavy Quark
Decay
Negative Parity N* Resonances in an Extended GBE
In this paper, we calculate the masses and mixing angles of L=1 negative
parity N* resonances in an extended GBE (Goldstone-boson-exchange model) with
harmonic-oscillator wave functions. By using those mixing angles, we get their
photoproduction amplitudes, and compare them with experimental data and the
results of OPE (one-pion-exchange model), OPsE (only pseudoscalar meson
exchange model), and OGE (one-gluon-exchange model). We find that the extended
GBE gives right internal wave functions. It is essential to extend GBE to
include not only pseudoscalar meson exchanges but also vector meson exchanges.Comment: 11 pages, no figure, accepted by Nucl. Phys.
Hadron Electromagnetic Structure: Shedding Light on Models and their Mechanisms
Strange quark contributions to the proton magnetic moment are estimated from
a consideration of baryon magnetic moment sum rules. The environment
sensitivity of quark contributions to baryon moments is emphasized. Pion cloud
contributions to proton charge radii are examined in the framework of Chiral
Perturbation Theory. The absence of scalar-diquark clustering in the nucleon is
discussed.Comment: Lattice '93 presentation. UU-File is a single postscript file of a 3
page manuscript including figures. Ohio State U. PP #93-112
Meson-like Baryons and the Spin-Orbit Puzzle
I describe a special class of meson-like \Lambda_Q excited states and present
evidence supporting the similarity of their spin-independent spectra to those
of mesons. I then examine spin-dependent forces in these baryons, showing that
predicted effects of spin-orbit forces are small for them for the same reason
they are small for the analogous mesons: a fortuitous cancellation between
large spin-orbit forces due to one-gluon-exchange and equally large inverted
spin-orbit forces due to Thomas precession in the confining potential. In
addition to eliminating the baryon spin-orbit puzzle in these states, this
solution provides a new perspective on spin-orbit forces in all baryons.Comment: 24 pages, 4 figure
Why N*'s are Important
The study of N*'s can provide us with critical insights into the nature of
QCD in the confinement domain. The keys to progress in this domain are the
identification of its important degrees of freedom and the effective forces
between them. I report on the growing evidence in support of the flux tube
model, and comment on the connection between this model and spontaneous chiral
symmetry breaking, on the spin-dependence of the long-range confining
potential, on the evidence for short-range one gluon exchange, on instantons,
and on the one pion exchange model.Comment: Overview talk at N*2000, 20 pages, 4 figure
Electroproduction of K* mesons at CLAS
The electroproduction of K mesons using the CLAS detector is
described. Data for two electron beam energies, 4.056 and 4.247 GeV, were
measured and the normalized yields are compared.Comment: 4 pages, 3 figures, HYP2003 Proceeding
Hyperfine Mass Splittings of Baryons Containing a Heavy Quark in Large N QCD
The hyperfine mass splittings of baryons containing a heavy quark are derived
at leading order in large QCD. Hyperfine splittings either preserve or
violate heavy quark spin symmetry. Previous work proves that the splittings
which preserve heavy quark spin symmetry are proportional to at
order , where is the angular momentum of the light degrees of freedom
of the baryon. This work proves that the splittings which violate heavy quark
spin symmetry are proportional to at order in the and expansions.Comment: (8 pages, no figures, uses harvmac), UCSD/PTH 93-2
Beyond the Adiabatic Approximation: the impact of thresholds on the hadronic spectrum
In the adiabatic approximation, most of the effects of quark-antiquark loops
on spectroscopy can be absorbed into a static interquark potential. I develop a
formalism which can be used to treat the residual nonadiabatic effects
associated with the presence of nearby hadronic thresholds for heavy quarks. I
then define a potential which includes additional high energy corrections to
the adiabatic limit which would be present for finite quark masses. This
"improved" potential allows a systematic low energy expansion of the impact of
thresholds on hadronic spectra.Comment: 16 pages, a more rapidly converging "improved potential" is define
Comment on "Valence QCD: Connecting QCD to the Quark Model"
I criticize certain conclusions about the physics of hadrons drawn from a
"valence QCD" approximation to QCD.Comment: 12 pages, 8 figures; some minor improvements made to the tex
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