[Jpac_lectures] follow up

[Mikhail Mikhasenko]

Dear all,

the next Gribov lecture is scheduled for tomorrow, Friday 16:00.
Please note unusual time!

To prepare for the discussion on analytic structure I suggest to have a
look at the homework problem
[image: Inline images 1]
Please find attached Mathematica notebook and note where Karplus curve is
plotted for some arbitrary masses of particles in the box.

See you tomorrow and best wishes,

  Misha Mikhasenko


On 2 March 2017 at 17:43, Mathieu, Vincent <mathieuv at indiana.edu> wrote:

> 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
> Office Phone: +1 812 855 2900 <(812)%20855-2900>
>
> Joint Physics Analysis Center:
> http://www.indiana.edu/~jpac/index.html
> -----------------------------------------------------
>
>
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