282 research outputs found
The missing sinks: slip localization in faults, damage zones, and the seismic energy budget
No abstract available
Hadron Optics: Diffraction Patterns in Deeply Virtual Compton Scattering
We show that the Fourier transform of the Deeply Virtual Compton Scattering
(DVCS) amplitude with respect to the skewness variable at fixed
invariant momentum transfer squared provides a unique way to visualize the
structure of the target hadron in the boost-invariant longitudinal coordinate
space. The results are analogous to the diffractive scattering of a wave in
optics. As a specific example, we utilize the quantum fluctuations of a fermion
state at one loop in QED to obtain the behavior of the DVCS amplitude for
electron-photon scattering. We then simulate the wavefunctions for a hadron by
differentiating the above LFWFs with respect to and study the
corresponding DVCS amplitudes in light-front longitudinal space. In both cases
we observe that the diffractive patterns in the longitudinal variable conjugate
to sharpen and the positions of the first minima move in with
increasing momentum transfer. For fixed , higher minima appear at positions
which are integral multiples of the lowest minimum. Both these observations
strongly support the analogy with diffraction in optics.Comment: Some plots modified, clarifications and references adde
On Transverse-Momentum Dependent Light-Cone Wave Functions of Light Mesons
Transverse-momentum dependent (TMD) light-cone wave functions of a light
meson are important ingredients in the TMD QCD factorization of exclusive
processes. This factorization allows one conveniently resum Sudakov logarithms
appearing in collinear factorization. The TMD light-cone wave functions are not
simply related to the standard light-cone wave functions in collinear
factorization by integrating them over the transverse momentum. We explore
relations between TMD light-cone wave functions and those in the collinear
factorization. Two factorized relations can be found. One is helpful for
constructing models for TMD light-cone wave functions, and the other can be
used for resummation. These relations will be useful to establish a link
between two types of factorization.Comment: add more discussions and reference
Electron in a transverse harmonic cavity
We employ Hamiltonian light-front quantum field theory in a basis function
approach to solve the non-perturbative problem of an electron in a strong
scalar transverse confining potential. We evaluate both the invariant mass
spectra and the anomalous magnetic moment of the lowest state for this
two-scale system. The weak external field limit of the anomalous magnetic
moment agrees with the result of QED perturbation theory within the anticipated
accuracy.Comment: 4 pages, 3 figures, published versio
Hamiltonian light-front field theory within an AdS/QCD basis
Non-perturbative Hamiltonian light-front quantum field theory presents
opportunities and challenges that bridge particle physics and nuclear physics.
Fundamental theories, such as Quantum Chromodynmamics (QCD) and Quantum
Electrodynamics (QED) offer the promise of great predictive power spanning
phenomena on all scales from the microscopic to cosmic scales, but new tools
that do not rely exclusively on perturbation theory are required to make
connection from one scale to the next. We outline recent theoretical and
computational progress to build these bridges and provide illustrative results
for nuclear structure and quantum field theory. As our framework we choose
light-front gauge and a basis function representation with two-dimensional
harmonic oscillator basis for transverse modes that corresponds with
eigensolutions of the soft-wall AdS/QCD model obtained from light-front
holography.Comment: To appear in the proceedings of Light-Cone 2009: Relativistic
Hadronic and Particle Physics, July 8-13, 2009, Sao Jose dos Campos, Brazi
Photon Generalized Parton Distributions
We present a calculation of the generalized parton distributions of the
photon using overlaps of photon light-front wave functions.Comment: Talk given at LightCone 2011, 4 pages, 3 figure
The Pion Light-Cone Wave Function Phi_pi on the lattice: a partonic signal?
We determine the conditions required to study the pion light-cone wave
function Phi_pi with a new method: a direct display of the partons constituting
the pion. We present the preliminary results of a lattice computation of Phi_pi
following this direction. An auxiliary scalar-quark is introduced. The
spectroscopy of its bound states is studied. We observe some indications of a
partonic behavior of the system of this scalar-quark and the anti-quark.Comment: 3 pages, 4 figures, Lattice2001(matrixelement
Experimental determination of the effective strong coupling constant
We present a first attempt to experimentally extract an effective strong
coupling constant that we define to be a low Q2 extension of a previous
definition by S. Brodsky et al. following an initial work of G. Grunberg. Using
Jefferson Lab data and sum rules, we establish its Q2-behavior over the
complete Q2-range. The result is compared to effective coupling constants
inferred from different processes and to calculations based on Schwinger-Dyson
equations, hadron spectroscopy or lattice QCD. Although the connection between
the experimentally extracted effective coupling constants and the calculations
is not established it is interesting to note that their behaviors are similar.Comment: Published in Physics Letters B 650 4 24
Hamiltonian Light-Front Field Theory: Recent Progress and Tantalizing Prospects
Fundamental theories, such as Quantum Electrodynamics (QED) and Quantum
Chromodynamics (QCD) promise great predictive power addressing phenomena over
vast scales from the microscopic to cosmic scales. However, new
non-perturbative tools are required for physics to span from one scale to the
next. I outline recent theoretical and computational progress to build these
bridges and provide illustrative results for Hamiltonian Light Front Field
Theory. One key area is our development of basis function approaches that cast
the theory as a Hamiltonian matrix problem while preserving a maximal set of
symmetries. Regulating the theory with an external field that can be removed to
obtain the continuum limit offers additional possibilities as seen in an
application to the anomalous magnetic moment of the electron. Recent progress
capitalizes on algorithm and computer developments for setting up and solving
very large sparse matrix eigenvalue problems. Matrices with dimensions of 20
billion basis states are now solved on leadership-class computers for their
low-lying eigenstates and eigenfunctions.Comment: 8 pages with 2 figure
Electron Anomalous Magnetic Moment in Basis Light-Front Quantization Approach
We apply the Basis Light-Front Quantization (BLFQ) approach to the
Hamiltonian field theory of Quantum Electrodynamics (QED) in free space. We
solve for the mass eigenstates corresponding to an electron interacting with a
single photon in light-front gauge. Based on the resulting non-perturbative
ground state light-front amplitude we evaluate the electron anomalous magnetic
moment. The numerical results from extrapolating to the infinite basis limit
reproduce the perturbative Schwinger result with relative deviation less than
0.6%. We report significant improvements over previous works including the
development of analytic methods for evaluating the vertex matrix elements of
QED.Comment: 6 pages, 1 figure, proceeding for Lightcone 2011 conferenc
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