[b1_ana] b1 phone meeting April 29 (note time)

Wed May 1 10:55:30 EDT 2013

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
>>>>>>
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>>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
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>