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.
-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?)
-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
-Needs to extract GE/GM by determining <th>_yield for each Q2bin in
order to account for profile (like Chris).
-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
-Error analysis for theta_spin?
-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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