Subject: Re: output of Trieste meeting
From: Gunar Schnell <Gunar.Schnell@UGent.be>
Date: Thu, 7 Dec 2006 15:45:18 +0100
To: Franco Bradamante <Franco.Bradamante@ts.infn.it>
CC: Transversity Sum Rule 

Dear Franco, dear Colleagues,

I would like to bring up a few suggestions/criticism to the note
circulated.
First of all I want to thank Eliot for writing up a summary of --
in my opinion -- a very successful meeting at Trieste.
(For the latter -- thanks a lot to our host Franco
for the splendid idea and organization!)

I strongly discourage the use of the notation g_T for the tensor
charge. Not only does the usage of 'g' suggest a chiral-even behavior
in contrast to the chiral-odd nature of the tensor charge.
Moreover -- and more important -- g_T is already used as a notation for
a (chiral-even) twist-3 distribution function (which also has a
strong connection to transversely polarized nucleons).
In some of the literature the tensor charge is denoted by \delta q (a
choice that unfortunately might be confused with the transversity
distribution, which, however, is a less severe confusion than one
with the g_T distribution). I am right now not aware of other notations
for the tensor charge, but I hope my theory friends can come up with a good
solution.  :-) 

A second comment concerns the sum rule itself. My suspicion at the
end of the meeting that instead of the transversity distribution
function it should be g_T that should appear in the sum rule, was again
strengthen by a discussion with Piet on the way back. Maybe also Oleg
can comment on this. In this respect I am not sure we really came to a
uni-sono conclusion about the nature of the sum rule. As far as I gathered
from the discussion the S.R. holds (only) for an ensemble of non-interacting
quarks, for which there exists a simple relation between g_T and h_1. As
I am not a theorist I am not completely suited to criticise the S.R., but
I at least wanted to let you know my impression from the discussions.

Ciao,
Gunar



Quoting Franco Bradamante <Franco.Bradamante@ts.infn.it>:


>> Dear colleagues,
>> first of all, many thanks for having partecipated to our meeting
>> last Friday. Then, I have the pleasure to forward you the short note
>> Elliot promised to write aa a summary of what was discussed and
>> agreed upon (!).
>>     Please, have a look at it, and feel free to propose for some
>> changes or some addition to what Elliot has written. I remind
>> you that the idea was to arrive at a sort of "common document"
>> on which we all basically agree and to put it on the web.
>>     Best regards
>>                      Franco
>>



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