1,194 research outputs found
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]
Flux Tube Zero-Point Motion, Hadronic Charge Radii, and Hybrid Meson Production Cross Sections
Flux tube zero-point motion produces quark displacements transverse to the
flux tube which make significant contributions to hadronic charge radii. In
heavy quark systems, these contributions can be related by Bjorken's sum rule
to the rates for semileptonic decay to hybrid mesons. This connection can be
generalized to other leptoproduction processes, where transverse contributions
to elastic form factor slopes are related to the cross sections for the
production of the associated hybrid states. I identify the flux tube overlap
integral responsible for these effects as the strong QCD analogue of the
Sudakov form factor of perturbative QCD.Comment: 16 pages, revised to clarify some points and to improve and correct
the notation for the flux tube wave function
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
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
A Bjorken sum rule for semileptonic decays to ground and excited charmed baryon states
We derive a Bjorken sum rule for semileptonic decays to ground and
low-lying negative-parity excited charmed baryon states, in the heavy quark
limit. We discuss the restriction from this sum rule on form factors and
compare it with some models.Comment: 10 pages, RevTex, no figure, Alberta Thy--26--9
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
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.
A Consistent Study of the the Low Energy Baryon Spectrum and the Nucleon-Nucleon Interaction within the Chiral Quark Model
By solving the Schr\"{o}dinger equation for the three-quark system in the
hyperspherical harmonic approach, we have studied the low energy part of the
nucleon and spectra using a quark-quark interaction which reproduces
the nucleon-nucleon phenomenology. The quark-quark hamiltonian considered
includes, besides the usual one-gluon exchange, pion and sigma exchanges
generated by the chiral symmetry breaking. The baryonic spectrum obtained is
reasonable and the resulting wave function gives consistency to the ansatz used
in the two baryon system.Comment: Accepted for publication in Phys. Lett.
Nested recursions with ceiling function solutions
Consider a nested, non-homogeneous recursion R(n) defined by R(n) =
\sum_{i=1}^k R(n-s_i-\sum_{j=1}^{p_i} R(n-a_ij)) + nu, with c initial
conditions R(1) = xi_1 > 0,R(2)=xi_2 > 0, ..., R(c)=xi_c > 0, where the
parameters are integers satisfying k > 0, p_i > 0 and a_ij > 0. We develop an
algorithm to answer the following question: for an arbitrary rational number
r/q, is there any set of values for k, p_i, s_i, a_ij and nu such that the
ceiling function ceiling{rn/q} is the unique solution generated by R(n) with
appropriate initial conditions? We apply this algorithm to explore those
ceiling functions that appear as solutions to R(n). The pattern that emerges
from this empirical investigation leads us to the following general result:
every ceiling function of the form ceiling{n/q}$ is the solution of infinitely
many such recursions. Further, the empirical evidence suggests that the
converse conjecture is true: if ceiling{rn/q} is the solution generated by any
recursion R(n) of the form above, then r=1. We also use our ceiling function
methodology to derive the first known connection between the recursion R(n) and
a natural generalization of Conway's recursion.Comment: Published in Journal of Difference Equations and Applications, 2010.
11 pages, 1 tabl
Heavy-to-Light Meson Transitions in QCD
I discuss QCD sum rules determinations of the form factors governing the
decay . For some of these form factors the computed
dependence on the momentum transferred does not agree with the expectation from
the nearest pole dominance hypothesis. Relations are observed among the form
factors, that seem to be compatible with equations recently derived by B.Stech.
The measurement of a number of color suppressed nonleptonic B decay rates could
shed light on the accuracy of the calculation of these form factors and on the
factorization approximation.Comment: LaTex, 7 pages, 2 figures (files included). Talk given at the 6th
International Symposium on Heavy Flavours, Pisa, 6-10 June 199
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