Hi,
below are the minutes of the analysis meeting from Wednesday 2006/05/10:
-Spin angle summary
+For any given map, theta_nominal is the spin angle at z=0.
+<dth> is for each profile the difference between the nominal angle at
z=0 and the yield weighted average angle <th> for the considered
profile.
+The error on the spin angle is driven by the error on the average angle
determined by the asymmetry analysis. The variation of the nominal error
for the various corrected (shifted) maps is ~+-0.1 degrees.
+The discrepancy between the nominal angles from ed and ep asymmetries is
currently 2.55 degrees (ed:49.15, ep:46.6), however the nominal angle as
determined from ep elastic has a (much) larger uncertainty due to
reconstruction (how large?)
+ed and en yields give consistent, similar <dth>~=-(2.3-2.8), however ep
gives only -0.8
+Update on ed alstic spin angle analysis for the 47 degree data is
awaited.
+theta_nominal from ed elastic will be the one to be used. For the 32
degree data the spin angle result can be regarded final.
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
===================================================
47.8(asym) -1.5 49.3 (calc) Jul2004 + 0.8
-1.22 49.02(calc) Jan2005 + 1.0
-1.32 49.12(calc) Jun2005 + 1.6
-1.35(av.) ->49.15(calc) DH's profile
NO UPDATE YET
p(e,e'p) 45.8(asym) -0.8(calc) 46.6(calc) DH's profile???
47.5(old)
-toward final results in ep-elastic
+Chris has extended his code to account for bin-by-bin average spin
angle, expect results soon
-toward final results in ed elastic
+v3_4_19 for 2005 runs now complete, using static T0s for better ed
event selection, sent email
+letter from Dan Philips on timeline for T20 results
+paper draft T20?
+update of PK's analysis?
-kinematic corrections
+Eugene working on final version to be available next week
+Miriam Huntley's combination of elastic and radiative events to
constrain all four variables th_e, th_p, p_e, p_p
+Adam's comparison of e,e'p with MC; quasifree limit
-Mascarad/Polrad
+Locating money for visit of Sasha
-aob
+ABS target table can be dismounted and replaced with beam pipe
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 | |
+-------------------------------------+--------------------------+
This archive was generated by hypermail 2.1.2 : Mon Feb 24 2014 - 14:07:33 EST