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I
n the current academic year, the Seminars of the GW Center for Nuclear Studies are organised by
Dr. Allena Opper (experiment, 202-994-0723)
and
Dr. Harald W. Griesshammer (theory, 202-994-3849)

If you have any question regarding the seminars, or if you would like to be put on our mailing list, please contact one of us.
Please note that some special symbols appearing in the titles of the talks may not display properly on your system if your browser installation does not support the "SYMBOL" font. What will appear on your screen then is the character of your default font occupying the same location as the requested "symbol" character.

 

The George Washington University Home Page

A Series of Nuclear Physics Seminars at GW
[ Upcoming Event | Events This Semester | Past Events ]

Unless otherwise stated, all seminars are Tuesdays at 4:00 pm in room 106 of Corcoran Hall.


Upcoming Event

*SPECIAL* 22 May 2008 (Th), 11:00 am in Corcoran 104 *SPECIAL*

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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Events This Semester
An incomplete and never-up-to-date list of spectacular events.
Any similarities between the abstract and the talk itself are purely incidental and may be intended. 
Organisers: Dr. Allena Opper (experiment, 202-994-0723) and Dr. Harald W. Griesshammer (theory, 202-994-3849)

 Some seminars are coordinated with the joint seminars of the Experimental Nuclear Physics Group and the Theory Group for Quarks, Hadrons and Nuclei of the University of Maryland at College Park. Their ENP/TQHN Seminars (schedule) are Wednesdays at 3:00 pm in room 1201 of the Physics Building at UMd (directions).


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.
An asterisk * indicates seminars coordinated with UMd, i.e. usually a seminar by the same speaker at UMd the day before; see their schedule.

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A List of Events in Past Semesters
Autumn 2007, Spring 2007, Autumn 2006, 2005 and before.
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Harald W. GriesshammerSpring 2008