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

Wed May 1 10:44:09 EDT 2013

I'll try my best to join today, at 15:00.

Narbe

On 05/01/2013 09:18 AM, Karl Slifer 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 
> <mailto: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
>     <http://twist.phys.virginia.edu/%7Eor/b1/b1_method-v2.pdf>
>     >>
>     >> Cheers,
>     >>
>     >> Oscar
>     >>
>     >> _______________________________________________
>     >> b1_ana mailing list
>     >> b1_ana at jlab.org <mailto:b1_ana at jlab.org>
>     >> https://mailman.jlab.org/mailman/listinfo/b1_ana
>     >>
>     >
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>     _______________________________________________
>     b1_ana mailing list
>     b1_ana at jlab.org <mailto:b1_ana at jlab.org>
>     https://mailman.jlab.org/mailman/listinfo/b1_ana
>
>
>
>
> _______________________________________________
> b1_ana mailing list
> b1_ana at jlab.org
> https://mailman.jlab.org/mailman/listinfo/b1_ana

-------------- next part --------------
An HTML attachment was scrubbed...
URL: https://mailman.jlab.org/pipermail/b1_ana/attachments/20130501/072aa1d7/attachment.html 