104 research outputs found
Summing Over World-Sheet Boundaries
The moduli associated with boundaries in a Riemann surface are parametrized
by the positions and strengths of electric charges. This suggests a method for
summing over orientable Riemann surfaces with Dirichlet boundary conditions on
the embedding coordinates. A light-cone parameterization of such boundaries is
also discussed.Comment: 10 page
Large Solution of the 2D Supersymmetric Yang-Mills Theory
The Schwinger-Dyson equations of the Makeenko-Migdal type, when supplemented
with some simple equations as consequence of supersymmetry, form a closed set
of equations for Wilson loops and related quantities in the two dimensional
super-gauge theory. We solve these equations. It appears that the planar Wilson
loops are described by the Nambu string without folds. We also discuss how to
put the model on a spatial lattice, where a peculiar gauge is chosen in order
to keep one supersymmetry on the lattice. Supersymmetry is unbroken in this
theory. We comment on possible generalization of these considerations to other
models.Comment: 22 pages, 5 figures included, harvma
Abelian Decomposition of Sp(2N) Yang-Mills Theory
In the previous paper, we generalized the method of Abelian decomposition to
the case of SO(N) Yang-Mills theory. This method that was proposed by Faddeev
and Niemi introduces a set of variables for describing the infrared limit of a
Yang-Mills theory. Here, we extend the decomposition method further to the
general case of four-dimensional Sp(2N) Yang-Mills theory. We find that the
Sp(2N) connection decomposes according to irreducible representations of SO(N).Comment: latex, 8 page
Annihilation Rate of Heavy 0^{++} P-wave Quarkonium in Relativistic Salpeter Method
Two-photon and two-gluon annihilation rates of P-wave scalar charmonium and
bottomonium up to third radial excited states are estimated in the relativistic
Salpeter method. We solved the full Salpeter equation with a well defined
relativistic wave function and calculated the transition amplitude using the
Mandelstam formalism. Our model dependent estimates for the decay widths:
keV,
keV, eV and eV. We also give estimates of total widths by the two-gluon
decay rates: MeV,
MeV, MeV and
MeV.Comment: 8 pages, 1 figure, 4 table
Radiative E1 decays of X(3872)
Radiative E1 decay widths of are calculated through the
relativistic Salpeter method, with the assumption that is the
(2P) state, which is the radial excited state of (1P). We
firstly calculated the E1 decay width of (1P), the result is in
agreement with experimental data excellently, then we calculated the case of
with the assignment that it is (2P). Results are:
{\Gamma}({\rm X(3872)}\rightarrow \gamma \sl J/\psi)=33.0 keV, keV and keV. The ratio {{\rm
Br(X(3872)}\rightarrow\gamma\psi(2{\rm S}))}/{{\rm Br(X(3872)}\rightarrow
\gamma {\sl J}/\psi)}=4.4 agrees with experimental data by BaBar, but larger
than the new up-bound reported by Belle recently. With the same method, we also
predict the decay widths: keV, keV and keV, and the full widths: keV, keV.Comment: 9 pages, 4 figures, 2 tables, version to be published in Phys. Lett.
Is the first radial excitation of ?
We present a quantitative analysis of the observed by
SELEX mainly focusing on the assumption that is the first
radial excitation of the ground state . By solving the
instantaneous Bethe-Salpeter equation, we obtain the mass MeV for
the first excited state, which is about 26 MeV heavier than the experimental
value MeV. By means of PCAC and low-energy theorem we calculate
the transition matrix elements and obtain the decay widths:
MeV, MeV, and
the ratio as well. This ratio is quite different from the
SELEX data . The summed decay width of those three channels is
approximately 21.7 MeV, already larger than the observed bound for the full
width ( MeV). Furthermore, assuming is state,
we also explore the possibility of wave mixing to explain the SELEX
observation. Based on our analysis, we suspect that it is too early to conclude
that is the first radial excitation of the ground
state . More precise measurements of the relative ratios and
the total decay width are urgently required especially for wave mixing.Comment: 12 pages, 8 figure
Strong Decays of the Radial Excited States and
The strong OZI allowed decays of the first radial excited states and
are studied in the instantaneous Bethe-Salpeter method, and by using
these OZI allowed channels we estimate the full decay widths:
MeV, MeV,
MeV and MeV.
We also predict the masses of them: GeV,
GeV, GeV and GeV.Comment: 6 pages, 1 figur
Compton scattering in a unitary approach with causality constraints
Pion-loop corrections for Compton scattering are calculated in a novel
approach based on the use of dispersion relations in a formalism obeying
unitarity. The basic framework is presented, including an application to
Compton scattering. In the approach the effects of the non-pole contribution
arising from pion dressing are expressed in terms of (half-off-shell) form
factors and the nucleon self-energy. These quantities are constructed through
the application of dispersion integrals to the pole contribution of loop
diagrams, the same as those included in the calculation of the amplitudes
through a K-matrix formalism. The prescription of minimal substitution is used
to restore gauge invariance. The resulting relativistic-covariant model
combines constraints from unitarity, causality, and crossing symmetry.Comment: 25 pages, 9 ps-figure
Nonperturbative Determination of Heavy Meson Bound States
In this paper we obtain a heavy meson bound state equation from the heavy
quark equation of motion in heavy quark effective theory (HQET) and the heavy
meson effective field theory we developed very recently. The bound state
equation is a covariant extention of the light-front bound state equation for
heavy mesons derived from light-front QCD and HQET. We determine the covariant
heavy meson wave function variationally by minimizing the binding energy
. Subsequently the other basic HQET parameters and
, and the heavy quark masses and can also be
consistently determined.Comment: 15 pages, 1 figur
Two-Dimensional QCD in the Wu-Mandelstam-Leibbrandt Prescription
We find the exact non-perturbative expression for a simple Wilson loop of
arbitrary shape for U(N) and SU(N) Euclidean or Minkowskian two-dimensional
Yang-Mills theory regulated by the Wu-Mandelstam-Leibbrandt gauge prescription.
The result differs from the standard pure exponential area-law of YM_2, but
still exhibits confinement as well as invariance under area-preserving
diffeomorphisms and generalized axial gauge transformations. We show that the
large N limit is NOT a good approximation to the model at finite N and conclude
that Wu's N=infinity Bethe-Salpeter equation for QCD_2 should have no bound
state solutions. The main significance of our results derives from the
importance of the Wu-Mandelstam-Leibbrandt prescription in higher-dimensional
perturbative gauge theory.Comment: 7 pages, LaTeX, REVTE
- …