On May 19, 2006, at 22:40:41, Michael Kohl wrote:
> Hi,
>
> below are the minutes of the analysis meeting from Wednesday
> 2006/05/17:
>
> Minutes:
> -Adrian has analyzed hPz vs. spin angle based on Hoehler form factors
> and v3_4_18, left/right sector equal hPz happens at 48.3 degrees in
> contrast to 47.5 degrees from Chris.
Actually I get 'th_s = 45.8' from the v3_4_18 recrunch. See the
following table. Also note that the systematic error due to
uncertainty in Q^2 is 3.6 deg (th_s) and also 3.6% (hPz). Of course
there is a large covariance in these two values. I assumed an
uncertainty in Q^2 of 0.002 GeV^2, in accord with the latest plot of
'Q^2_e - Q^2_p'. The largest errors were caused by a + shift in one
sector and a - shift in the other. This only confirms Chi's
statement that ep-elastic (ed-elastic also?) is insensitive to the
spin angle.
Although you get the same answer as Adrian's method (I did it both
ways), I prefer to do a two parameter fit of 'A_l' and 'A_r' to the
Hohler values, to extract 'th_s' and 'hPz'. That way you also get
accurate errors from Minuit.
> -This was found for the lowest Q2bin, while Chris' estimate of the
> spin angle is for the entire Q2 distribution assuming Hoehler and a
> flat profile (correct, Chris?)
The extraction is highly bin-dependent, since the Ge/Gm extracted
from BLAST does not follow the shape of Hohler (i.e. the dip) Again,
see the table for each bin. As far as the profile goes, the effect
is negligible. I already showed that the variation in spin angle is
very small. The largest correction to 'Ge/Gm' was 0.001; corrections
to 'th_s' and 'hPz' were .14 deg, and .15%, respectively.
> -Extracted GE/GM from super ratio using hPz and th_s from first Q2
> bin. FF ratio as such quite similar to Hoehler ratio. Fourth Q2 point
> sits above Hoehler in AS's extraction, but below it in CC's
The first three points are quite flat. The first point was
normalized to Hohler, so the next two will also be right on the
curve. From my analysis, the next two points were in the 'dip'.
> -Needs to extract GE/GM by determining <th>_yield for each Q2bin in
> order to account for profile (like Chris).
Should do it for completeness, but small effect.
> -Suggested to repeat spin angle extraction extended to first three
> bins, or to entire dataset and compare with the corresponding results
> from Chris to resolve observed discrepancy
>
Adrian, compare your results with the following table:
Bin-by-bin extraction of 'th_s' and 'hPz' fitting to Hohler
parametrization. The second column shows the correction to Ge/Gm
from profile-averaging the spin angle. The 'fitbeta' row was
obtained with independent of Hohler via the global fit method (fit
separate Ge/Gm for each Q^2 bin instead of scaling Hohler by 'hPz').
Q^2 gd(beta) beta+/-err(deg) pol+/-err(%)
0.166 -.00025 45.756 1.422 51.27 1.28
0.196 .00000 44.808 2.810 50.50 2.46
0.237 -.00055 47.505 1.429 53.60 1.46
0.287 .00064 49.822 2.416 56.95 2.78
0.350 .00025 42.184 3.302 50.07 2.58
0.423 -.00183 43.472 3.602 50.36 3.05
0.505 .00039 40.507 4.822 47.22 3.41
0.595 .00088 43.907 5.546 49.43 4.67
all bins 0 45.819 0.944 52.04 0.88
fitbeta 46.586 3.995 52.96 4.50
Q^2 sys 3.6 deg 3.6 %
> -Error analysis for theta_spin?
See table.
--Chris
> -Spin angle from asymmetry at lowest Q2bin <th>_yield=48.3 corresponds
> to a nominal angle theta_nominal=49.3 degrees using Doug's profile,
> very consistent with Chi, but at odd with Chris.
>
> -Chi's latest extraction of <th>_yield from ed elastic asymmetries is
> 48.0 deg, effect of profile is <dth>_yield=-1.35 deg, corresponding
> to theta_nominal of 49.35 deg. Previous extraction was
> <th>_yield=47.7+-0.45, corresponding to theta_nominal=49.15+-0.45.
> This result would globally shift the maps of July 2004 by 0.8
> degrees, Jan2005 by 1.0 and of Jun2005 by 1.6 degrees to larger
> angles.
> So, the latest new extraction is so far consistent with the old
> although we need to wait for another recrunch iteration to obtain the
> final number. The error (+-0.45 deg) will not change. It consists of
> 0.42(stat), 0.12(recon), 0.01(false asymmetry), and 0.10(theo),
> i.e. is dominated by statistics
> -Extraction of theta from ed elastic not yet final, requires recrunch
> with data quality (timing calib) sufficient to use same cuts in Chi's
> analysis.
> -Previous attempt to provide such a recrunch (v3_4_19) with static
> timing failed for some reason, either timing really changed during
> the 2005 run, or timing calib was not as static as thought,
> investigating ...
> -Will recrunch 2005 deuterium data with static timing calib until mid
> next week, this would allow Chi to push the analysis button, get an
> appropriate event selection and extract <th>_yield for 47 degrees
>
> -Spin angle for 32degree setting can be considered final:
> From asymmetries: <th>_yield = 31.40 +- 0.43
> Av. profile effect on ed sample: <dth>_yield = -2.72
> "Nominal" spin angle at z=0: theta_nominal = 34.12 +- 0.43
> The uncertainty for theta_nominal is identical with the one from the
> asymmetry result and consists of 0.35(stat), 0.20(recon), 0.10(false
> asymmetry), and 0.10(theo), i.e. is dominated by statistics
>
> -People analyzing 32 degree data should use above theta_nominal along
> with Doug's averaged profile.
> This result would globally shift the maps of Jan2005 by 0.1 and of
> Jun2005 by 0.7 degrees to larger angles.
>
> 32 degrees setting:
> channel <th>_yield <dth>_yield theta_nominal(z=0) Comment
> d(e,e'd) 31.3(calc) -2.79(calc) 34.09(map) Jan2005 map
> 30.7(calc) -2.65(calc) 33.35(map) Jun2005 map
> ===================================================
> 31.4(asym) -2.79 34.19(calc) Jan2005 + 0.1
> -2.65 34.05(calc) Jun2005 + 0.7
> -2.72(av.) ->34.12(calc) DH's profile
> 31.7(old)
>
> ----------------------------------------------------------------
>
> d(e,e'n) 32.03(calc) -2.27(left) 34.12(ed) DH
> 31.88(calc) -2.42(right) 34.12(ed) DH
>
> ----------------------------------------------------------------
>
> 47 degrees setting: STILL TO BE UPDATED
> channel <th>_yield <dth>_yield theta_nominal(z=0)
> d(e,e'd) 47.0(calc) -1.5 (calc) 48.5 (map) Jul2004 map
> 46.8(calc) -1.22(calc) 48.02(map) Jan2005 map
> 46.2(calc) -1.32(calc) 47.52(map) Jun2005 map
> ===================================================
> 47.7(asym) -1.5 49.2 (calc) Jul2004 + 0.7
> (old) -1.22 48.92(calc) Jan2005 + 0.9
> -1.32 49.02(calc) Jun2005 + 1.5
> -1.35(av.) ->49.05(calc) DH's profile
>
> PRELIMINARY UPDATE:
> 46.8(calc) -1.22(calc) 48.02(map) Jan2005 map
> ===================================================
> 48.0(asym) -1.35(av.) ->49.35(calc) DH's profile
> ----------------------------------------------------------------
>
> Chris: no errors yet
> p(e,e'p) 45.8(asym) -0.8(calc) 46.6(calc) DH's profile???
> 47.5(old)
>
> Adrian: no errors yet
> p(e,e'p) 48.3(asym) -1.0(calc) 49.3(calc) DH's profile
>
>
> -Sasha Ilychev from Belarus likely to attend collaboration meeting on
> July 14, 2006 and to visit Bates for ~10 days. To arrive ~Tuesday
> before and to stay until ~Thursday thereafter.
> -Task is to implement Polrad (inclusive channel) properly into dgen,
> and also the code for exclusive pion production.
> -Relevant people should be prepared to spend a maximum amount of time
> with Sasha (Tavi,Yuan,Aki,Vitaliy,Michael,Doug,Renee,etc.)
>
> -No meeting on 5/24, next meeting instead on 5/31!
>
> Best regards,
>
> Michael
>
>
>
> +-------------------------------------+--------------------------+
> | Office: | Home: |
> |-------------------------------------|--------------------------|
> | Dr. Michael Kohl | Michael Kohl |
> | Laboratory for Nuclear Science | 5 Ibbetson Street |
> | MIT-Bates Linear Accelerator Center | Somerville, MA 02143 |
> | Middleton, MA 01949 | U.S.A. |
> | U.S.A. | |
> | - - - - - - - - - - - - | - - - - - - - - -|
> | Email: kohlm@mit.edu | K.Michael.Kohl@gmx.de |
> | Work: +1-617-253-9207 | Home: +1-617-629-3147 |
> | Fax: +1-617-253-9599 | Mobile: +1-978-580-4190 |
> | http://blast.lns.mit.edu | |
> +-------------------------------------+--------------------------+
>
>
>
>
>
>
> -d(e,e'p): kinematic corrections (AD)
> +Shows for each Q2bin comparisons of measured and simulated electron
> momentum. Differences are up to 2%, at the margin of the
> resolution. Pattern of deviations vs. Q2 is sector-symmetric
> +Note that definition of Q2 in q.e. scattering depends on two
> variables.
> +Shows comparison data/MC for quasifree (pm<0.15) events, expect
> events to be close to the elastic ridge in a p_e-vs-th_e plot,
> attribute deviation to either wrong th_e or p_e or both. Magnitude
> of deviation rather points to momentum (would require several degs.)
> +Parametrizes momentum corrections based on quasifree events
> (pm<0.15) as scale factor with linear dependence in Q2, plots
> measured minus expected electron momentum for entire q.e. event
> sample after applying this correction. Finds remaining deviations of
> ~7-10 MeV.
> +Comparison is new 2004 recrunch v3_4_17 with an older MC which uses
> old geometry however we're looking at physical variables here
> +New MC still has the problem of disappearing yield at small
> angles. There seems to be a dependence on computer architecture
> (=initialization problem?)
>
> Suggestions:
> +Should apply corrections from ep elastic (Eugene's) to see how well
> they work
> +New MC should make use of spin angle profile
> +Adam: could you also evaluate the target yield-weighted average for
> given spin angle maps, for the d(e,e'p) event sample (see
> discussion on spin angle in separate email)
>
> -Spin angle:
> +No estimate yet of the error of the average spin angle extracted
> from ep elastic asymmetries.
> +Strong dependence on reconstruction likely explains large shift of
> the spin angle recently reported
> +Remember, in the hPz-vs-th_s plot, the two straights for the two
> sectors are almost collinear, while the slopes of the two crossing
> straights in the corresponding Pzz-vs-th_s plot from ed elastic
> have opposite signs, making ed elastic much more robust in
> determining the spin angle against changes in reconstruction.
> +For extraction of form factor ratio, needs to account for profile in
> extraction of observables, use "nominal" spin angle determined by
> Chi (on "average" vs. "nominal" see separate message)
> +Shows target z-distribution of ep elastic yield broken down in
> Q2bins. Not all bins are distributed as naively expected, pointing
> to residual reconstruction errors
> +Shows the same with spin angle profile overlayed and the resulting
> yield-weighted average for each Q2bin. The latter does not(!) vary
> much (<0.2deg) around the yield-weighted average of the entire data
> sample, but note that the z coordinate reconstructed from data may
> not fully reflect reality.
> +Suggestion: Does this negligible variation of yield-weighted
> averages for various Q2bins also hold for MC-generated ep elastic
> target-z yield distributions?
>
> Best regards,
>
> Michael
>
>
> +-------------------------------------+--------------------------+
> | Office: | Home: |
> |-------------------------------------|--------------------------|
> | Dr. Michael Kohl | Michael Kohl |
> | Laboratory for Nuclear Science | 5 Ibbetson Street |
> | MIT-Bates Linear Accelerator Center | Somerville, MA 02143 |
> | Middleton, MA 01949 | U.S.A. |
> | U.S.A. | |
> | - - - - - - - - - - - - | - - - - - - - - -|
> | Email: kohlm@mit.edu | K.Michael.Kohl@gmx.de |
> | Work: +1-617-253-9207 | Home: +1-617-629-3147 |
> | Fax: +1-617-253-9599 | Mobile: +1-978-580-4190 |
> | http://blast.lns.mit.edu | |
> +-------------------------------------+--------------------------+
>
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