1,103 research outputs found
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
Exotic baryons from a heavy meson and a nucleon
We evaluate a hadronic molecule formed by a heavy meson and a nucleon
respecting heavy quark symmetry. The tensor force of pion exchange potential
plays a dominate role to produce an strong attraction in this system. Solving
coupled channel Schr\"odinger equations for PN and P* N, we find many bound and
resonant states with isospin I=0 while there are few resonances in I=1 state.
The rich structures with I=0 indicate that the spectrum of heavy baryons near
the threshold is influenced by the contributions from such hadron composite
structures.Comment: To appear in the proceedings of The 5th International Workshop on
Charm Physics (Charm 2012
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
Perturbative and Non-perturbative Corrections to
It is shown that certain double ratios introduced for computing semileptonic
form factors are accurate to order , even when the action and current
are accurate to order .Comment: Lattice99(heavyquarks); 3 + epsilon pp. LaTe
Rare -Decays and Heavy to Light Semileptonic Transitions in the Isgur and Wise Limit
From the experimental branching ratios for and
D^+ --> {\overl K}^{*0}({\overl K}^0) e^+ \nu_e one finds, in the Heavy Quark
Limit of , , larger but consistent with
the actual quoted range . In the same framework one predicts
for .Comment: 9 pages, 1 Figure avalaible on request from [email protected]
Photocouplings of nucleon resonances with gluon and pion exchange currents
Photocouplings for the nucleon resonances most relevant to total
photoabsorption are calculated in a constituent quark model including gluon and
pion exchange. The sensitivity of the results to the different ingredients of
the model is discussed.Comment: 23 pages including 9 tables, LaTe
Remark on Charm Quark Fragmentation to Mesons
The observed mesons have flavor quantum numbers and
spin-parity of the light degrees of freedom . In
the limit the spin of the charm quark is conserved and
the fragmentation process is characterized by the
probability for the charm quark to fragment to a meson with a given
helicity for the light degrees of freedom. We consider the calculated fragmentation functions in the limit as a qualitative model for the fragmentation
functions. We find that in this model charm quark fragmentation to
light degrees of freedom with helicities is favored over fragmentation to light
degrees of freedom with helicities .Comment: 6 pages, CALT-68-192
A New Method for Selecting Exclusive Semileptonic Charmless B-Decays at Colliders at the
We introduce a new method for selecting exclusive semileptonic charmless
B-decays in the presence of a large background. The method can be applied to
charged and neutral B-mesons decaying into any exclusive neutral or charged
hadronic final state. The method is designed for high luminosity \eplemi
colliders operating at the . It employs an improved partial
reconstruction technique for \Dstar-mesons and a novel 0-C event fit to both
B-meson's decay products resulting in the kinematics of all particles
(including neutrinos) in the event. The charged lepton energies are accessible
from 1.0 \GeV to the kinematic limit.Comment: 10 pages with 7 figures in subdirectory fi
Test of OPE and OGE through mixing angles of negative parity N* resonances in electromagnetic transitions
In this report, by using the mixing angles of one-gluon-exchange model(OGE)
and one-pion-exchange model(OPE), and by using the electromagnetic Hamiltonian
of Close and Li, we calculate the amplitudes of L=1 N* resonances for
photoproduction and electroproduction. The results are compared to experimental
data. It's found that the data support OGE, not OPE.Comment: 5 pages, Latex, 1 figure, accepted by Phys.Rev.
Quark-Hadron Duality in Structure Functions
While quark-hadron duality is well-established experimentally, the current
theoretical understanding of this important phenomenon is quite limited. To
expose the essential features of the dynamics behind duality, we use a simple
model in which the hadronic spectrum is dominated by narrow resonances made of
valence quarks. We qualitatively reproduce the features of duality as seen in
electron scattering data within our model. We show that in order to observe
duality, it is essential to use the appropriate scaling variable and scaling
function. In addition to its great intrinsic interest in connecting the
quark-gluon and hadronic pictures, an understanding of quark-hadron duality
could lead to important benefits in extending the applicability of scaling into
previously inaccessible regions.Comment: 16 pages, 4 figures; minor typos correcte
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