[Clas12_verystrange] PAC comments

[Igor Strakovsky]

Hi Lei,

Let me make several comments addressed to the referee report...

Igor

On Tue, 12 Jun 2012 16:37:34 -0400, Lei Guo <lguo at jlab.org> wrote:

> I think most of the questions are very reasonable. But it seems that we HAVE 
>to have a reasonable plot for the double moments.
> 
> Lei
> 
> Begin forwarded message:
> 
>> From: Diego Bettoni <bettoni at fe.infn.it>
>> Date: June 12, 2012 8:26:25 AM EDT
>> To: <lei.guo1 at fiu.edu>
>> Cc: Reinhard Beck <beck at hiskp.uni-bonn.de>, "Naomi C.R. Makins" 
>><makins at uiuc.edu>
>> Subject: PR12-12-008
>>
>> Dear Guo,
>>  I am one of the readers of the proposal PR12-12-008 to be discussed at PAC39 
>>and I have a few comments questions at this time. Here they are, in no 
>>particular order.
>>
>> 1. The Theory TAC raised some serious questions about the way the proposal is 
>>written and also about the contents. Please make sure that all these questions 
>>are addressed before the PAC presentation next tuesday. In particular the 
>>question of the u/d mass difference, about which the theory reviewers seem to 
>>disagree about the way you plan to measure it from the data.

That is the good point specifically that TAC report is BS and Dudek missed
all what was written in the proposal, specifically for the Omega.
The Omega photoproduction Xsection is UNKNOWN.  We (theorists are co-authors
of our proposal) made several theoretical attempts (Andrey - 2, Winston - 1, 
Vitaly -1) to show what we may expect at the Omega threshold vs. SLAC exp
limit at 20 GeV.

>> 2. It is not clear to me what physics conclusions can be drawn from the 
>>measurement of the photoproduction cross section. As you point out the four 
>>predictions in Fig. 15 are all consistent with each other, so it is not clear 
>>to me how effective the measurements will be in distinguishing between the 
>>various models, with the exception of the dashed red curve (by the way, what 
>>model does it correspond to ? Is it the VMD calculation ?). 

Oh, Lord.  Our theoretical co-authors made as much as they can to do some
estimations of the Omega photoproduction which we may consider as a crude
approximation which may help us to see where we are.  The production
mechanism is unknown.  The Omega Xsection is UNKNOWN and we hope to measure
it first time.  It will allow us to think about a production mechanism of
the process with the largest strangest transition.

>> Also if I look at 
>>Fig. 18, which shows calculations for various cascade production channels, I 
>>note that for the only channel for which there are experimental data they 
>>agree pretty well with the theory calculation: what are you expecting to find 
>>when you measure the other channels ?

The answer is simple - to understand the production mechanism with dS=2
transition much better then we have now.

>> 3. What level of simulation was used in the estimation of backgrounds (pp. 
>>41-43) ? You mention fast simulation (with parametrized detector response): 
>>was a full event reconstruction performed or was the Monte Carlo truth used in 
>>the background estimations ? Is a full simulation foreseen ?
>>
>> 4. For the determination of the spin/parity quantum numbers (which is a 
>>crucial measurements if one aims at having a complete picture of the cascade 
>>spectrum) the DMA method is illustrated, but there is no quantitative 
>>discussion of the actual number of events needed to make this measurement in 
>>CLAS12, beyond the rather generic statement that large statistics will be 
>>collected in the relevant cascade production channels. I think that this 
>>measurement proposal should be supported by a more quantitative discussion and 
>>possibly a full simulation to demonstrate its feasibility in CLAS12. Also: 
>>have other methods to measure J^P been considered ? (e.g. Dalitz analysis).
>>
>> 5. Is there another advantage in the increased photon energy, beyond the 
>>broader kinematical range mentioned at several points in the proposal ? (e.g. 
>>observables which have a significant dependance on the photon energy).
>>
>> 6. A minor point: on page 12 you write that "it seems plausible that the one 
>>NA48 high-statistics measurement of the Csi_0 mass could be too low". Why is 
>>that so ? Since it is the only high-statistics measurement isn't it plausible 
>>that it be the most reliable ?
>>
>> 7. Do I understand correctly that this proposal does not impose any further 
>>requirements on the CLAS12 detector ?
>>
>> This is all for the moment. I am looking forward to your presentation at the 
>>PAC next tuesday.
>>
>> best regards
>> diego
>>
>>
>> -- 
>>
>> Diego Bettoni
>> INFN Ferrara, Director
>> Via Saragat, 1
>> I-44100 FERRARA
>>
>> tel: +39-0532-974275
>> tel: +39-0532-974332
>> fax: +39-0532-974300
>>
>> web: http://www.fe.infn.it/~bettoni/