[Clascomment] OPT-IN: Electromagnetic decay of the ??*0 to ???

[Kei Moriya]

Dear Dustin and Ken,

Congratulations on finishing up a difficult analysis.
I can see that a tremendous amount of work has gone into
estimating the systematics for this analysis.

I apologize for being late to make my comments,
and hope my comments are not too late.
I just had one questions about the analysis.

The analysis focuses on the decay Sigma* -> Lambda gamma.
One thing I thought when reading the paper was the possibility
of Sigma* -> Sigma0 gamma -> 2 gamma + Lambda,
where you end up with 2 missing photons in the final state.
Is there a reason to omit this possibility? I wonder because
your final result, while consistent with the previous measurement
of Taylor, is higher than the theoretical predictions by factors
ranging from 1.5-3. Could this be part of the reason, if you
are including the above reaction in your result?

Other than that, I am a bit worried about how the
Sigma* cross section and resolution change over the
energy and angle range of g11a, but you seem to have
done a lot of work on the systematics to match up the
data and Monte Carlo, so I assume things are OK.

Best of luck for the next step.
Once again my apologies for not being able to
respond sooner.

	Kei Moriya


(2/2/11 12:28 PM), Reinhard Schumacher wrote:
> Hello Dustin,
> 	With a fresher head, I reread the part of the paper that I said was
> confusing.  This time I see what you were trying to say, and it seems
> pretty reasonable.  For clarity I would recommend changing one sentence:
>
> page 9, column 2, paragraph 6, last 3 lines:  "To maximize COUNTING
> statistics WHILE minimizing THIS uncertainty, the optimal..."  This gets
> rid of the offending word 'recovery' in quotes, which I thought may be
> needlessly distracting.
>
> My other comments still apply, of course.
>
> Best Regards,
> Reinhard
>
>
> ___________________________________________________________________
> Reinhard Schumacher         Department of Physics, 5000 Forbes Ave.
> Carnegie Mellon University, Pittsburgh, PA 15213, U.S.A.
> phone: 412-268-5177         web: www-meg.phys.cmu.edu/~schumach
> ___________________________________________________________________
>
>
> Dustin Keller wrote:
>> Hi Reinhard,
>>
>> Thank you for your careful consideration and suggestions on our paper.
>> The first suggestions you mentioned are mostly easy fixes.  In your last
>> comment you mentioned that the discussion of the uncertainty when
>> compensating for events lost in doing the two confidence level cuts was
>> unclear.  The correction for events lost is inherent in the ratio
>> calculation seen in Eq. 21 for the simplified two channel case.  In the
>> original study of the confidence level cuts optimization Eq. 21 was used
>> to calculate the resulting ratio from a Monte Carlo mixture of
>> radiative and pi0 decays.  The recovery uncertainty was minimized while
>> considering both the level of statistics seen in the data and the
>> statistical uncertainty produced in the ratio.  After using these
>> studies to find a range of optimized confidence level cuts for P^a and
>> P^b a variation of these cut was chosen that would lie just outside the
>> optimization range for each cut.  The cut and the effect of the
>> variation is listed in Table 3.  For presentation clarity the numerical
>> specifics are omitted and only a general statement is given however the
>> CLAS-note 2010-015 goes into this type of study and is available for the
>> general public.  We give the appendix to help guild a motivated reader
>> through the calculation of the full ratio.  So with the acceptance terms
>> in Table 2 and the resulting raw counts from the fits in each case one
>> quickly knows the corrections for
>> each channel.  What maybe confusing in the discussion you mentioned is
>> the phrase "recovery" uncertainty.   This is the difference between the
>> ratio input to the Monte Carlo and the value recovered using the
>> described analysis framework with specific confidence level cuts.  We
>> would be interested in clearing up any confusion with the hope of
>> conservatively adding to this discussion as to not dilute the more
>> critical points.
>>
>> thanks again,
>> Dustin
>>
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