[Jpac_lectures] follow up

[Mathieu, Vincent]

Dear all,

yes the next meeting is tomorrow Friday March 10 at 16:00 Europe time (10am US time).

- 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
-----------------------------------------------------

On Mar 9, 2017, at 9:33 AM, Mikhail Mikhasenko <mikhail.mikhasenko at gmail.com<mailto:mikhail.mikhasenko at gmail.com>> wrote:

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
<Screenshot from 2017-03-09 14-19-09.png>
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<mailto: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<mailto:mathieuv at indiana.edu>
Office Phone: +1 812 855 2900<tel:(812)%20855-2900>

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


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