26,768 research outputs found
Light-Front QCD Hamiltonian Dynamics and Constituent Quark Picture in Exclusive Processes
After reviewing a connection between quantum chromodynamics and contituent
quark model pictures in the light-front quantization with some comparison and
contrast to the ordinary equal-time bridge a la Bogoliubov-Valatin
transformation, we discuss some newer development of the light-front quark
model phenomenology in exclusive processes including the embedded state. The
skewed parton distribution appears to be a good testing ground for our new
effective treatment of the light-front nonvalence contributions in timelike
exclusive processes.Comment: 5pages, Contributed to International Light-Cone Workshop "Light-cone
Physics: Particles and Strings", Trento, Italy, 3-11 Sep. 200
Light-Front Quark Model Analysis of Exclusive Semileptonic Heavy Meson Decays
We present the analysis of exclusive semileptonic heavy
meson decays using the constituent quark model based on the light-front
quantization. Our model is constrained by the variational principle for the
well-known linear plus Coulomb interaction motivated by QCD. Our method of
analytic continuation to obtain the weak form factors avoids the difficulty
associated with the contribution from the nonvalence quark-antiquark pair
creation. Our numerical results for the heavy-to-heavy and heavy-to-light meson
decays are in a good agreement with the available experimental data and the
lattice QCD results. In addition, our model predicts the two unmeasured mass
spectra of and systems as
=9657 MeV and = 5424 MeV.Comment: 16 pages including 5 figures; version to be published in Phys. Lett.
Spatial Performance Analysis and Design Principles for Wireless Peer Discovery
In wireless peer-to-peer networks that serve various proximity-based
applications, peer discovery is the key to identifying other peers with which a
peer can communicate and an understanding of its performance is fundamental to
the design of an efficient discovery operation. This paper analyzes the
performance of wireless peer discovery through comprehensively considering the
wireless channel, spatial distribution of peers, and discovery operation
parameters. The average numbers of successfully discovered peers are expressed
in closed forms for two widely used channel models, i.e., the interference
limited Nakagami-m fading model and the Rayleigh fading model with nonzero
noise, when peers are spatially distributed according to a homogeneous Poisson
point process. These insightful expressions lead to the design principles for
the key operation parameters including the transmission probability, required
amount of wireless resources, level of modulation and coding scheme (MCS), and
transmit power. Furthermore, the impact of shadowing on the spatial performance
and suggested design principles is evaluated using mathematical analysis and
simulations.Comment: 12 pages (double columns), 10 figures, 1 table, to appear in the IEEE
Transactions on Wireless Communication
Conformal Symmetry and Pion Form Factor: Soft and Hard Contributions
We discuss a constraint of conformal symmetry in the analysis of the pion
form factor. The usual power-law behavior of the form factor obtained in the
perturbative QCD analysis can also be attained by taking negligible quark
masses in the nonperturbative quark model analysis, confirming the recent
AdS/CFT correspondence. We analyze the transition from soft to hard
contributions in the pion form factor considering a momentum-dependent
dynamical quark mass from a nonnegligible constituent quark mass at low
momentum region to a negligible current quark mass at high momentum region. We
find a correlation between the shape of nonperturbative quark distribution
amplitude and the amount of soft and hard contributions to the pion form
factor.Comment: 7 pages, 6 figures, extensively revised, to appear in Phys. Rev.
Exploring Timelike Region of QCD Exclusive Processes in Relativistic Quark Model
We investigate the form factors and decay rates of exclusive
semileptonic meson decays using the constituent quark model based on the
light-front quantization. Our model is constrained by the variational principle
for the linear plus Coulomb interaction motivated by QCD. Our numerical results
are in a good agreement with the available experimental data.Comment: 6 pages, Latex with 2 figures: Talk given at the 12th Nuclear Physics
Summer School and Symposium and the 11th International Light-Cone Workshop
"New Directions in QCD", June 21-25, 1999, Kyungju, Kore
Exploring timelike exclusive processes in the light-front approach
We discuss a necessary nonvalence contribution in timelike exclusive
processes. Utilizing a Schwinger-Dyson type of approach, we relate the
nonvalence contribution to an ordinary light-front wave function that has been
extensively tested in the spacelike exclusive processes. An application to
decays provides encouraging results.Comment: Contribution to the third international conference on ``Perspectives
in Hadronic Physics", 7-11 May 2001, Miramare-Trieste, Italy; 4 pages
including 2 figure
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