[Tpe] tpe meeting minutes

[Andrei Afanasev]

Hello,

The attached figure demonstrates the e+/e- asymmetry that comes from 
soft TPE combined with brem -VCS
interference. This is a standard correction previously included in SLAC 
Rosenbluth analysis. The formulas used are from the original Tsai's 
paper. I calculated the asymmetry here for a fixed beam energy of 1.6 
GeV, while Q^2 is variable. VEPP3 kinematics corresponds to epsilon=0.4. 
You can see that the `soft' asymmetry is about 3% for their kinematics. 
A new effect, if found, would correspond to a difference between this 
`soft' asymmetry and the measurement. I do not know if the preliminary 
6% from VEPP
include the soft term or not.

-Andrei

On 4/8/2010 2:27 PM, Larry Weinstein wrote:
> Dear TPE folks,
>
> Here is a summary of what we discussed at our meeting last Friday:
>    1) Whether we should have 0.25" lead on the vacuum box or a hut around
> the box.
>       - needs simulation.  Lead is a feasible solution.
>    2) Engineered vs stacked chicane shielding.  Engineered is better but
> stacked worked well.  We will look into how to make the shielding more
> hermetic between the first Italian Dipole and the pair spectrometer.
> Rob will post  pictures of that area.
>    3) Sparse fiber detector as a beam monitor.  This will be placed right
> before the downstream collimator, as it was in the test run.  We will
> simulate the background effects of placing it there to double check it
> is OK.
>    4) Optimize Moller catcher geometry.  This was well studied by Megh.
> The current shape is good.  We do not need to adjust the jaw opening.
>    5) calorimeter location.  Downstream of CLAS, probably on the catwalk
> between the forward carriage and the alcove.  The existing photon beam
> profiler will be placed on the front face of the calorimeter.
>     - Valparaiso has already received the 30 Shashlik calorimeter modules
> and is starting to build the bases and order the PMTs.
>    6) RadPhi wall collimator.  It was lead with a 2-cm brass insert
> during the test run.  We would like it to be 2-cm tungsten (preferably)
> or lead for the actual run.
>    7) Are the TOF TDCs running in multi-hit mode?
>    8) Novosibirsk finished their run in January at Q^2=1.5 and
> epsilon=0.4 (one data point).  They see a measurable effect (~6% from
> the online results).  This is pre-preliminary.
>
> - Larry
>
>    

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