2,102 research outputs found

### Application of M\"ossbauer-Type Sum Rules for $B$ Meson Decays

Sum rules originally derived for the M\"ossbauer Effect are applied to weak
semileptonic B decays. The sum rules follow from assuming that the decay by
electroweak boson emission of an unstable nucleus or heavy quark in a bound
system is described by a pointlike coupling to a current which acts only on the
decaying object, that the Hamiltonian of the bound state depends on the
momentum of the decaying object only in the kinetic energy and that the boson
has no final state interactions. The decay rate and the first and second
moments of the boson energy spectrum for fixed momentum transfer are shown to
be the same as for a noninteracting gas of such unstable objects with a
momentum distribution the same as that of the bound state. B meson semileptonic
decays are shown to be dominated by the lowest-lying states in the charmed
meson spectrum.Comment: 9 page

### 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

### Semileptonic Decay of $B$-Meson into $D^{**}$ and the Bjorken Sum Rule

We study the semileptonic branching fraction of $B$-meson into higher
resonance of charmed meson $D^{**}$ by using the Bjorken sum rule and the heavy
quark effective theory(HQET). This sum rule and the current experiment of
$B$-meson semileptonic decay into $D$ and $D^*$ predict that the branching
ratio into $D^{**}l\nu_l$ is about 1.7\%. This predicted value is larger than
the value obtained by the various theoretical hadron models based on the HQET.Comment: 10 pages, LaTex, to be published in Phys. Lett.

### 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$^{*0}$ 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 $N$ 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 ${\bf J}^2$ at
order $1/N$, where $J$ 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 ${\bf J} \cdot {\bf S_Q}$ at order $1/(N
m_Q)$ in the $1/N$ and $1/m_Q$ 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

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