[Theory-seminars] next week: Ben Bakker (Mo, Tu 1:00pm, Wed 10:30am, L104), Peter Kroll (Fri 11:00am, L104)

[Bernhard Musch]

Dear all,

we have a lot on our seminar schedule next week. We are starting out 
with a lecture series by Ben Bakker and we have a seminar talk by Peter 
Kroll on Friday. Here is the information

1.) Lecture Series by Ben Bakker
=================================

Ben Bakker, Vrije Universiteit Amsterdam

*Light-front dynamics; Principles and applications*

Monday    May  9,  1:00 pm, room L104
Tuesday   May 10,  1:00 pm, room L104
Wednesday May 11, 10:30 am, room L104

Light-front dynamics (LFD), also known as front-form dynamics, is on of
the three form of relativistic Hamiltonian dynamics distinguished by
Dirac (1949). At the time Dirac's seminal paper appeared, quantum field 
theory was in a state of rapid development and its manifestly-covariant 
formulation all but eclipsed the older Hamiltonian formalism. The latter 
experienced a revival when the usefulness of the `infinite-momentum 
frame' was discovered for current algebra and used by Weinberg (1966) to 
propose a `dynamics at infinite momentum'.

Since then, LFD has been developed by many different groups, mainly with
the motivation to obtain a viable non-perturbative treatment of
strongly-interacting systems, in particular for QCD, at the amplitude level.

In the lectures, LFD will be discussed in the first place as an example
of a Hamiltonian framework, in comparison with the two other forms,
instant-form and point-form dynamics. Next, two topics will be
highlighted, namely the treatment of bound states, and the occurrence of
`light-front singularities', i.e., singularities that do not occur in
the manifestly-covariant treatment of the same systems, being specific
to the LF formulation. It will be shown that these singularities can be 
tamed rather easily in perturbation theory, but also that their 
occurrence is more serious when bound states are looked for.


2.) Theory Seminar, Friday, May 13, 11:00 am, room L104
=====================================================================

Peter Kroll, Universitaet Wuppertal

*The form factors for the photon to pseudoscalar meson transitions
in QCD*

The form factors for the transitions pi-gamma, eta-gamma, eta'-gamma, 
and eta_c-gamma are analyzed within the modified perturbative approach in 
which quark transverse degrees of freedom are retained. The results for 
the form factors are compared to experiment in detail. As compared to 
previous calculations within the same approach only little modifications 
of the meson distribution amplitudes are required in general in order to 
achieve reasonable agreement with experiment. Only for the πγ form 
factor a strong contribution from the second Gegenbauer term is found. 
It also commented on the case of two virtual photons and on the 
transition form factors in the time-like region.


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A complete list of upcoming theory seminars and talks from previous
seminars are available from:
http://www.jlab.org/~prokudin/seminars/

Alexei, Berni and Satoshi
JLab Theory Seminar Organizers