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    User name jpchen

    Log entry time 16:54:46 on April 9,1999

    Entry number 25

    keyword=3/10 analysis meeting minutes

    Minutes of 3/10 analysis meeting:

    Present: Pibero Djawotho, Wang Xu, Zhengwei Chai, Marat Rvachev,
    Xiaodong Jiang, Seonho Choi, Kevin Fissim, Mark Jones and Jian-ping Chen.

    Wang/Pibero: Working on trigger/scintillator inefficiency.

    Marat:
    continue filtering data for e-arm y_tg optimization. The task is pretty
    difficult because of many cuts need to be placed and many files to be
    filtered. Once the filtering is done the y_tg optimization can be done
    quickly.

    Zhengwei: Working on Y-target optimization.

    Xiaodong:
    Working on a Monte Carlo Model of the spectrometer.

    Built a SNAKE based model which reproduced spectra in the dispersive
    direction almost exactly, but in the transverse direction the model does
    not exactly reproduce the data (of deep inelastic region). A noticable
    disagreement (about 10% level) in the transverse direction still exist,
    will work with John LeRose again to try to make adjustments to the magnet
    model while keeping the first order optics intact. There're indications
    that some of the magnet properties of the spectrometer might not be known
    well enough.

    Seonho:
    Finally, I have compiled all the available statistics at 1.72 GeV. (I am
    counting all the runs since charge asymmetry adjustment. And while writing
    this mail, I found out that I missed 2 runs. The result presented during
    the collaboration meeting will include them.) When I calculate A_parallel
    and A_perpendicular, the statistical error is of the order of 0.0005 while
    the maximum asymmetry around delta region is about 0.004. I have to
    mention that these asymmetries are not yet divided by target and beam
    polarizations and the final physical asymmetry should be 5 times bigger.
    A_parallel agrees pretty well between two arms as they should do. For
    A_perpendicular, a simple sign change is expected between the two arms,
    and the plot shows overall opposite behavior between the two arms, but
    there is something else which can not be explained with simple sign
    change. To verify this, I calculated the simple sum of A_parallel between
    the two arms. If the two are related with sign change, the sum should give
    identically zero. The actual sum is not zero and around -0.001 till W=1400
    and then it becomes +0.001 and remains there. If there is a misalignment
    of the target polarization, this sum should be proportional to A_parallel,
    but due to relatively big error bars, it is not easy to conclude if there
    is such an effect. Anyway, I tool weighted average of A_parallel and
    A_perpendicular from both arms. (Of course, for A_parallel, I changed sign
    for hadron arm before taking weighted average.) The asymmetries are quite
    big at the Delta region (A_par = 0.004, A_perp = -0.004). Near the
    quasi-elastic region, the asymmetries are also significant with opposite
    sign to that of delta region (A_par = -0.002, A_perp = +0.0015).
    Finally, a decomposition to A_1 and A_2 has been tried. For R (ratio of
    longitudinal and transverse cross section) factor necessary for this
    decomposition, I used various assumptions: DIS assumption such as 2xF1=F2,
    or constant R=20%, 50% or 80%. In any case, the actual numerical values
    vary a little, but the general trend does not change. A1 is quite big
    around delta region (A1 ~ 0.02 to 0.03 depending on R) and also
    significant in the quasi-elastic region with negative sign (A1 ~ -0.015 to
    -0.023). A2 is pretty small and only becomes slightly negative just after
    delta (A2 ~ -0.005 to -0.01 at W ~ 1350MeV).
    The next plan is to get R from other experiments on 3He and extract A1 and
    A2. The final result will be presented during the collaboration meeting.