| Date |
Speaker
(link
to SPIRES) |
Title
(abstract) |
29 Jan
2008
(Tu) |
Alvin
Kiswandhi
(Florida State U) |
A unitary and
relativistic model for pi-eta
and pi-pi photoproduction (.pdf file)
We
describe a
model of $\pi \eta N$
photoproduction based on a phenomenological Lagrangian approach that
satisfies
two-body unitary and is relativistic. Unitarity is ensured by using the
Lippmann-Schwinger equation to iterate the vertices and dress the
propagators
to all orders, and by including all possible two-body and
quasi-two-body
intermediate channels. This model has been tested by investigating $\pi
\pi N$
photoproduction. A preliminary comparison of our calculation to an
existing
$\pi \pi N$ photoproduction study is made, and is shown to produce
consistent
results. We have also calculated the sum of the nonresonant Born
diagrams in
$\pi \eta N$ photoproduction. |
5
Feb
2008
(Tu) |
Gerald
Feldman
(GW) |
Compton
Scattering on the Deuteron (.pdf file)
For
better insight into the many
facets of Nuclear Physics Research in our Department, we invite from
time to time one of our very own to give a crisp and understandable
introduction into ongoing projects. Instead of only talking about their
work at other places, group members are now also entertaining us at
home.
Prof. Feldman is the second in this irregular series,
with a talk on the importance and his measurements of Compton
scattering on the deuteron at MAXlab (Lund, Sweden). |
12
Feb
2008
(Tu) |
. |
...nothing new... |
19
Feb
2008
(Tu) |
Kevin
Giovanetti
(James Madison U) |
A
Precision Measurement of the Muon Lifetime
For
several years the MULAN collaboration has been pursuing the ambitious
goal of a 1 ppm determination of the muon lifetime. This experiment has
been motivated by recent theoretical improvements in extracting the
Fermi coupling constant G_F, from the measured muon lifetime,
$\tau_\mu$. These theoretical calculations have reached the 1 ppm level
in the theoretical error. The coupling constant G_F is an
essential parameter of the Standard Model. Its uncertainty limits the
precision for Standard Model predictions and interpretations. Our first
result, a 10 ppm measurement, has been published. Progress towards the
1ppm goal and highlights of the experiment will be discussed.
|
21 Feb 2008 (Thu)
15:30
SPECIAL
Joint Astro/CNS
Seminar |
Michael Stamatikos
(NASA/Goddard) |
Exploring GRB Astrophysics via a Correlated Broad-Band and Multi-Messenger Paradigm
I will present results based upon a
synergistic methodology whose primary objective encompasses probing
discrete gamma-ray burst (GRB) highenergy particle astrophysics via a
broad-band, multi-messenger paradigm. The interface between leptonic
and electromagnetic emission will be explored using the theoretical
interpretation and correlative observations of high energy telescopes
such as (i) Swift's Burst Alert Telescope (BAT), (ii) the Gamma-Ray
Large Area Space Telescope (GLAST) Burst Monitor (GBM) and (iii) the
Antarctic Muon and Neutrino Detector Array (AMANDA)/IceCube.
Multi-wavelength analysis results include temporal studies of Swift
GRBs featuring GRB 060218 in the context of the lagluminosity relation,
and simulations of joint photon energy spectra using Swift-BAT and
GLAST-GBM. A case study probing for multi-messenger leptonic emission
signatures via neutrino astronomy will include modeling the correlated
(TeV-PeV) muon neutrino flux from GRB 030329 in the context of
canonical fireball phenomenology. |
26
Feb
2008
(Tu) |
Mark
W. Paris
(Jefferson Lab) |
Dynamical
coupled channel theory of omega meson production (.pdf file)
A
dynamical coupled channel approach is used to study pion and
omega–meson production induced by pions and photons
scattering from the proton. Six-channels are used to fit unpolarized
and polarized scattering data including pi-N, eta-N, pi-Delta, sigma-N,
rho-N, omega-N. Bare parameters in an effective hadronic Lagrangian are
fixed in chi-square fits to pi-N → pi-N, gamma-N →
pi-N, pi-p → omega-n, and gamma-p → omega-p reactions
from threshold up to center-of-mass energies E < 2.0 GeV. The T
matrix determined in these fits is used to calculate the photon beam
asymmetry for omega-meson production and the omega-N → omega-N
total cross section and scattering lengths. |
4
Mar
2008
(Tu) |
Hartmut Schmieden
(U Bonn, Germany) |
Photoproduction of neutral mesons at ELSA (.pdf file)
The photoproduction of single and multiple
mesons is investigated with the Crystal Barrel and TAPS setup at
the ELSA facility of the University of Bonn. The detector is ideally
suited for neutral channels. Various single and double polarization
observables have been measured. Recent results and future plans will be
presented for nonstrange and strange pseudoscalar and vector mesons. |
11
Mar
2008
(Tu) |
Michael
Dugger
(Arizona State U) |
T.B.A.
<pseudoscalar meson photoproduction
with CLAS> (.pdf file) |
18
Mar
2008
(Tu) |
. |
No Seminar (Spring Break) |
25
Mar
2008
(Tu) |
Siegfried Krewald
(FZ Jülich, Germany) |
Towards the drip line: Challenges for nuclear structure (.pdf file) |
27 Mar 2008
(Thu)
SPECIAL
Cor 104 |
Kanzo Nakayama
(U of Georgia) |
Combined analysis of eta meson hadro- and photo-production off
nucleons (.pdf file) |
1st
Apr
2008
(Tu) |
. |
. |
8
Apr
2008
(Tu) |
Achim
Schwenk
(TRIUMF) *. |
Three-nucleon interactions: a frontier in nuclear structure
Three-nucleon interactions are a frontier in understanding and
predicting the structure of strongly-interacting matter in laboratory
nuclei and in the cosmos. I will present results and discuss the status
of first calculations with microscopic three-nucleon interactions
beyond light nuclei. This coherent effort is possible due to advances
based on effective field theory and renormalization group methods in
nuclear physics.
|
15
Apr
2008
(Tu) |
. |
. |
22
Apr
2008
(Tu) |
Anders
Gardestig
(U of South Carolina) * |
Precision Extraction of the nn scattering length a_nn from pi- d -> nn \gamma in Chiral EFT
We use chiral perturbation theory (ChPT) to third and fourth
order to make a high-precision calculation of the radiative pion
capture process on the deuteron. The pi- d -> n n gamma reaction is
used to extract the neutron-neutron scattering length a_nn and
dominates the currently accepted value a_nn=-18.59+/-0.40 fm. This is
significantly different from the proton-proton scattering length a_pp =
-17.3+/-0.4 fm, which is an indication of charge-symmetry-breaking
(CSB) interactions in the strong interaction. This difference plays an
important role in the determination of CSB terms in high-precision
charge-dependent potentials.
Our first calculation revealed that the
theoretical error in a_nn (when extracted from pi- d -> n n gamma)
was largely due to uncertainties in the short-distance physics of the
nn wave function, giving an error of +/-0.2 fm. We later found that it
is possible to constrain this unknown short-distance physics by using a
connection to electroweak observables, e.g., solar pp fusion. This
connection is a manifestation of chiral symmetry for two-nucleon
operators and can be regarded as the two-nucleon equivalent of the
Goldberger-Treiman and Kroll-Ruderman relations.
With the
short-distance physics of the NN interaction controlled in this way, a
complete computation of all fourth order effects in pi- d -> n n
gamma should make it possible to extract a_nn with theoretical
uncertainties at the level of +/-0.05 fm. This uncertainty is a factor
of three smaller than in any previous theory. Progress towards such a
calculation and a_nn extraction will be reported. |
29
Apr
2008
(Tu) |
Scott
Bogner
(Michigan State U) * |
Towards a microscopic density functional theory for nuclei (.pdf file)
A primary objective of the SciDAC
project ``Building a Universal Nuclear Energy Density Functional
(UNEDF)'' is to develop a microscopically-based,
energy density functional applicable to all nuclei in the form of a
generalized Skyrme functional, with theoretical error bars for the
different terms in the UNEDF to provide guidance for fine-tuning
to data and to give controlled extrapolations away from
stability. In this talk, I describe a promising route for
achieving these objectives that utilizes recent parallel advances in
chiral effective field theory (EFT) inter-nucleon interactions,
renormalization group (RG) techniques for nuclear systems, and nuclear
many-body computational methods.
|
22 May 2008 (Thu)
SPECIAL
Cor 104
11:00 am |
J. P. Singh
(U of Baroda, India) |
Twist-3 distribution amplitudes and octet current decay constants of eta and
eta' mesons: A QCD sum rule approach
We investigate twist-3 distribution amplitudes (DAs) of eta and
eta' using QCD sum rules. Zeroth moments of light quark DAs of eta and eta'
are evaluated and compared with those found in other approaches. The decay
constants of the octet axial vector current in the eta and eta' system are
also estimated.
|
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