[Jpac_lectures] follow up

[Mathieu, Vincent]

Misha,

thank for this very clear lecture.
You derive the Karplus curve representing the singularity of the box diagram, in the equal mass case.
Here is a paper about the box diagram in pion photoproduction: http://inspirehep.net/record/120443?ln=en
The author claims that the singularities are in the physical region, t < 1.1 GeV^2 for s > 1.6^2 GeV^2
(for one particular box, other boxes are outside the physical region as in your example)
See Fig 2 and the discussion above.

That means that fixed t dispersion relation (as I used them for FESR) can be ill defined for t < 1.1 GeV^2

There is no explicit calculation. I suppose the curve on Fig comes from a similar demonstration as you did.
If somebody does this exercise, I’d happy to have a confirmation of the result.

*** The next Gribov Lecture is Friday March 10 at 9am (US time - 3pm in Europe) ***
Misha could you confirm this schedule ?

Cheers,
Vincent

----------------------------------------------------
Vincent Mathieu
Indiana University Research Fellow
INFN-Genova Associate
UMons Associate
mathieuv at indiana.edu<mailto:mathieuv at indiana.edu>
Office Phone: +1 812 855 2900

Joint Physics Analysis Center:
http://www.indiana.edu/~jpac/index.html
-----------------------------------------------------

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.jlab.org/pipermail/jpac_lectures/attachments/20170302/e15a4856/attachment.html>