[b1_ana] b1 phone meeting April 29 (note time)
Patricia SOLVIGNON
solvigno at jlab.org
Wed May 1 12:05:34 EDT 2013
Steve stopped by and was asking about our proposal. I explained to him where we were at and he is going to join the meeting today.
Patricia
--
Patricia SOLVIGNON
Staff Scientist
Jefferson Lab
Current address :
Jefferson Lab
Suite 6, MS. 12H4 Room C121 (Cebaf Center)
12000 Jefferson Avenue Office: (757)-269-6933
Newport News, VA 23606
On May 1, 2013, at 10:55 AM, Dustin Keller <dustin at jlab.org> wrote:
> any time for me, 2 is good
>
> dustin
>
> On Wed, 1 May 2013, Karl Slifer wrote:
>
>> OK,
>>
>> I think 1/2 hour is not sufficient, so how about 2:00pm. (I'll skip my
>> student office hours.)
>>
>> JP?
>> Dustin?
>> Oscar?
>>
>> Ellie and Patricia have already said they are free this time, and anytime
>> today is unfortunately difficult for Narbe.
>>
>> thanks
>>
>> -Karl
>>
>>
>>
>> On Wed, May 1, 2013 at 10:40 AM, Oscar Rondon-Aramayo <
>> or at cms.mail.virginia.edu> wrote:
>>
>>> Hi Karl,
>>>
>>> We met with Dustin last evening and after going in detail over the
>>> formulas
>>> for the ratio Npol/Nun, we found that the unpolarized sigma_N, sigma_D and
>>> sigma_He (see my last email) can be collected in one group, which cancels
>>> with the denominator (all unpolarized), leaving a term
>>> sigma_D*Azz*Pzz/denominator, which I realized can be written as f*Azz*Pzz,
>>> f
>>> = dilution factor.
>>>
>>> With the dilution factor, the formulas in Dustin's third row of equalities
>>> in his Observables2 report, which are valid only for pure D (the HERMES
>>> case), can also be used for ND3 targets.
>>>
>>> In summary, we can take the ratio of the pol to unpol counts, which takes
>>> us
>>> to Azz, at the price of the dilution factor and its error, plus the need to
>>> use some form of F1 to get b1 from Azz, or the difference, which takes us
>>> directly to b1.
>>>
>>> In both cases the systematic errors, other than the charge and detector
>>> efficiency are normalizations, and since the error on Pzz is expected to
>>> dominate, it really is a matter of taste, once we have the numbers on hand.
>>> We'll surely try both.
>>>
>>> For the statistical errors, f enters in the Azz time estimate, but Q*A*l*pf
>>> enter in the difference (Pzz is in both). I need to do some numbers yet
>>> (everyone should try) to compare the two approaches.
>>>
>>> Finally, today we have the SANE meeting at 3:30, so I can join b1 from 1:00
>>> to 3:30.
>>>
>>> Cheers,
>>>
>>> Oscar
>>>
>>> On Wed, 1 May 2013 09:18:48 -0400
>>> Karl Slifer <karl.slifer at unh.edu> wrote:
>>>> Hi all,
>>>>
>>>> The methodology is the central question and I think we have to resolve
>>> any
>>>> lingering doubts today. I highly encourage that everyone really read
>>>> Oscar's note (Eq 19 and 20) and his last email before we discuss today.
>>>>
>>>> I would really not like to delay till tomorrow if possible since time is
>>>> so
>>>> tight. I hope we can get a majority to participate at 3pm. Please let me
>>>> know if you can't.
>>>>
>>>> -Karl
>>>>
>>>>
>>>>
>>>> ---
>>>> Karl J. Slifer
>>>> Assistant Professor
>>>> University of New Hampshire
>>>> Telephone : 603-722-0695
>>>>
>>>>
>>>> On Tue, Apr 30, 2013 at 5:59 PM, O. A. Rondon <or at virginia.edu> wrote:
>>>>
>>>>> Hi Dustin,
>>>>>
>>>>> Dustin Keller wrote:
>>>>>> You can only benefit from the systematic reduction if you us Azz as
>>>>>> discussed yesterday. But at this point I am not partial.
>>>>>>
>>>>>> dustin
>>>>>>
>>>>>
>>>>> In the experiment, we only have counts. What we need to show to the PAC
>>>>> is how we go from the counts Npol and Nu, to Azz or b1. A measured
>>>>> quantity needs to be on one side and physics on the other. Lets say we
>>>>> start with your ratio Npol/Nu - 1 = Pzz*Azz, which only requires Pzz >0.
>>>>>
>>>>> We need to prove that the lhs reproduces the rhs. We have, in general,
>>>>> N = Q*e*A*l*sigma. But since N are counts from everything in the target,
>>>>> it is not a simple matter of canceling quantities that stay the same
>>>>> when the polarization changes:
>>>>>
>>>>> Npol = Qpol*epol*Apol*lpol*sigma_pol
>>>>> = Qpol*epol*Apol*lpol*[(sigma_N+3*sigma_Dpol)*pf + sigma_He*(1-pf)]
>>>>>
>>>>> Nu = Qu*eu*Au*lu*[(sigma_N+3*sigma_D)*pf + sigma_He*(1-pf)]
>>>>>
>>>>> sigma_N and sigma_He are the same, always unpol. And
>>>>> sigma_Dpol = sigma_D(1+Pzz*Azz).
>>>>>
>>>>> Then, since Apol = Au = A, and lpol = lu = l,
>>>>>
>>>>> Npol/Nu =
>>>>> (Qpol/Qu)*(epol/eu)*[(sigma_N+3sigma_D(1+ Azz*Pzz))*pf+..)]/[(sigma_N+..
>>>>>
>>>>> where I just put ..., because I don't see how it can be simplified to
>>>>> just leave Azz*Pzz + 1, to equal the rhs.
>>>>>
>>>>> On the other hand, if instead of taking the ratio Npol/Nu first, we take
>>>>> the difference first, it's indeed possible to isolate the required
>>>>> Pzz*b1 on on side, like I do in my draft, eq. (19) or (20). And in
>>>>> fact, we don't even need to bother with Azz, because we get b1 without
>>>>> having to multiply Azz by F1, introducing one more systematic error.
>>>>>
>>>>> So, in summary, once one substitutes all the ingredients for your sigmas
>>>>> we get, or ought to get, eq.(19) or (20) back.
>>>>>
>>>>> In both of those equations, the systematics for Pzz, A, and l(pf) are
>>>>> normalization factors, just like we want them to be, for control of
>>>>> systematics, but the charge and the detector efficiency are not common
>>>>> factors, they depend on the period when the data are taken, either pol.
>>>>> or unpol.
>>>>>
>>>>> My point is that for the proposal, we must spell this all out, to give
>>>>> explicit sources of errors, and to calculate times or statistical errors
>>>>> correctly. For example, the statistical error must be sqrt(Npol + N_U) ~
>>>>> sqrt(2N), because it is just the error of a difference, etc.
>>>>>
>>>>> We need to have a consensus on how the method is going to be described
>>>>> in the proposal, which needs to be done in the most precise way to avoid
>>>>> any confusion due to ambiguities.
>>>>>
>>>>> Cheers,
>>>>>
>>>>> Oscar
>>>>>
>>>>>
>>>>>> On Tue, 30 Apr 2013, O. A. Rondon wrote:
>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> Since I couldn't stay until the end of the meeting, and I don't think
>>>>>>> there will be minutes of it, I would like to share some ideas for the
>>>>>>> proposal draft.
>>>>>>>
>>>>>>> Basically, what we need is an equation with the measured quantity on
>>>>> one
>>>>>>> side and b1 or Azz on the other. Based on what I think the consensus
>>>>>>> was, to measure polarized minus unpolarized counts on a single cup
>>> with
>>>>>>> the target field aligned along the beam, I've updated the draft of my
>>>>>>> method, see subsection 0.2, which discusses this. Eq. (19) or eq.
>>> (20)
>>>>>>> meet the conditions stated above. This is the approach I would
>>>>> subscribe
>>>>>>> to, unless there is another version that is shown to also represent
>>> the
>>>>>>> procedure, which should be circulated as soon as possible. The draft
>>>>>>> is here
>>>>>>> http://twist.phys.virginia.edu/~or/b1/b1_method-v2.pdf
>>>>>>>
>>>>>>> Cheers,
>>>>>>>
>>>>>>> Oscar
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> b1_ana mailing list
>>>>>>> b1_ana at jlab.org
>>>>>>> https://mailman.jlab.org/mailman/listinfo/b1_ana
>>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
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>>>>>
>>>
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