1,104 research outputs found
Few-body physics in effective field theory
Effective Field Theory (EFT) provides a powerful framework that exploits a
separation of scales in physical systems to perform systematically improvable,
model-independent calculations. Particularly interesting are few-body systems
with short-range interactions and large two-body scattering length. Such
systems display remarkable universal features. In systems with more than two
particles, a three-body force with limit cycle behavior is required for
consistent renormalization already at leading order. We will review this EFT
and some of its applications in the physics of cold atoms and nuclear physics.
In particular, we will discuss the possibility of an infrared limit cycle in
QCD. Recent extensions of the EFT approach to the four-body system and N-boson
droplets in two spatial dimensions will also be addressed.Comment: 10 pages, 5 figures, Proceedings of the INT Workshop on "Nuclear
Forces and the Quantum Many-Body Problem", Oct. 200
Perturbative expansions from Monte Carlo simulations at weak coupling: Wilson loops and the static-quark self-energy
Perturbative coefficients for Wilson loops and the static-quark self-energy
are extracted from Monte Carlo simulations at weak coupling. The lattice
volumes and couplings are chosen to ensure that the lattice momenta are all
perturbative. Twisted boundary conditions are used to eliminate the effects of
lattice zero modes and to suppress nonperturbative finite-volume effects due to
Z(3) phases. Simulations of the Wilson gluon action are done with both periodic
and twisted boundary conditions, and over a wide range of lattice volumes (from
to ) and couplings (from to ).
A high precision comparison is made between the simulation data and results
from finite-volume lattice perturbation theory. The Monte Carlo results are
shown to be in excellent agreement with perturbation theory through second
order. New results for third-order coefficients for a number of Wilson loops
and the static-quark self-energy are reported.Comment: 36 pages, 15 figures, REVTEX documen
Improved approach to the heavy-to-light form factors in the light-cone QCD sum
A systematic analysis shows that the main uncertainties in the form factors
are due to the twist-3 wave functions of the light mesons in the light-cone QCD
sum rules. We propose an improved approach, in which the twist-3 wave functions
doesn't make any contribution and therefore the possible pollution by them can
be avoided, to re-examine semileptonic form factors. Also, a
comparison between the previous and our results from the light-cone QCD sum
rules is made. Our method will be beneficial to the precise extracting of
from the experimental data on the processes .Comment: New version to appear in PR
Re-examination of the Perturbative Pion Form Factor with Sudakov Suppression
The perturbative pion form factor with Sudakov suppression is re-examined.
Taking into account the multi-gluon exchange in the law regions, we
suggest that the running coupling constant should be frozen at
and is the
average transverse momentum which can be determined by the pionic wave
function. In addition, we correct the previous calculations about the Sudakov
suppression factor which plays an important role in the perturbative
predictions for the pion form factor.Comment: 11 pages, LaTex file, 2 figures as uu-encoded postscript file
Perturbative QCD Analysis of the Nucleon's Pauli Form Factor F_2(Q^2)
We perform a perturbative QCD analysis of the nucleon's Pauli form factor
in the asymptotically large limit. We find that the leading
contribution to has a power behavior, consistent with the
well-known result in the literature. Its coefficient depends on the leading-
and subleading-twist light-cone wave functions of the nucleon, the latter
describing the quarks with one unit of orbital angular momentum. We also derive
at the logarithmic accurary the asymptotic scaling which describes recent Jefferson Lab data well.Comment: 4 papes, 3 figures include
Front Form Spinors in Weinberg-Soper Formalism and Melosh Transformations for any Spin
Using the Weinberg-Soper formalism we construct the front form
spinors. Explicit expressions for the generalised Melosh
transformations up to spin two are obtained. The formalism, without explicitly
invoking any wave equations, reproduces spin one half front-form results of
Melosh, Lepage and Brodsky, and Dziembowski.Comment: 16 Pages, RevTex. We continue to receive reprint requests for this
paper. So we now archive it her
A Study of Gluon Propagator on Coarse Lattice
We study gluon propagator in Landau gauge with lattice QCD, where we use an
improved lattice action. The calculation of gluon propagator is performed on
lattices with the lattice spacing from 0.40 fm to 0.24 fm and with the lattice
volume from to . We try to fit our results by two
different ways, in the first one we interpret the calculated gluon propagators
as a function of the continuum momentum, while in the second we interpret the
propagators as a function of the lattice momentum. In the both we use models
which are the same in continuum limit. A qualitative agreement between two
fittings is found.Comment: Revtex 14pages, 11 figure
Large corrections to asymptotic and in the light-cone perturbative QCD
The large- behavior of - and -
transition form factors, and
are analyzed in the framework of light-cone perturbative QCD with the heavy
quark ( and ) mass effect, the parton's transverse momentum dependence
and the higher helicity components in the light-cone wave function are
respected. It is pointed out that the quark mass effect brings significant
modifications to the asymptotic predictions of the transition form factors in a
rather broad energy region, and this modification is much severer for
than that for due to the
-quark being heavier than the -quark. The parton's transverse momentum
and the higher helicity components are another two factors which decrease the
perturbative predictions. For the transition form factor
, they bring sizable corrections in the present
experimentally accessible energy region (). For the
transition form factor , the corrections coming from
these two factors are negligible since the -quark mass is much larger than
the parton's average transverse momentum. The coming collider (LEP2)
will provide the opportunity to examine these theoretical predictions.Comment: 8 pages, RevTex, 5 PostScript figure
Determination of quark-antiquark component of the photon wave function for u, d, s quarks
Based on the data for the transitions pi0, eta, eta' -> gamma gamma^*(Q^2)
and reactions of the e^+ e^- -annihilations, e^+ e^- -> rho0, omega, phi and
e^+ e^--> hadrons at 1<E_{e^+e^-}<3.7 GeV, we determine the light-quark
components of the photon wave function gamma^*(Q^2) -> q anti-q (q= u, d, s)
for the region 0< Q^2 <1 (GeV/c)^2.Comment: 17 pages, some typos correcte
Charged currents, color dipoles and xF_3 at small x
We develop the light-cone color dipole description of highly asymmetric
diffractive interactions of left-handed and right-handed electroweak bosons. We
identify the origin and estimate the strength of the left-right asymmetry
effect in terms of the light-cone wave functions. We report an evaluation of
the small-x neutrino-nucleon DIS structure functions xF_3 and 2xF_1 and present
comparison with experimental data.Comment: 11 pages, 3 figures, misprints correcte
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