Dear colleagues,
per John's request here's a summary of the meeting on the BLAST pion
analyses last Tuesday:
Attending Richard Milner, Bill Bertozzi, Bill Donnelly, Aron Bernstein,
June Matthews, Bob Redwine, Doug Hasell, Michael Kohl, Akihisa Shinozaki,
Yuan Xiao, Octavian Filoti (via speakerphone)
For presentations see
http://blast.lns.mit.edu/PRIVATE_RESULTS/USEFUL/ANALYSIS_MEETINGS/meeting_070918/
Tavi, Aki and Yuan each presented the status of their analysis.
-Inclusive p(e,e') [Tavi]:
See thesis file Filoti_thesis.pdf
+extracted inclusive double asymmetries in each BLAST sector AL and AR
+corrected for empty target yield
+determined effect of radiative tail from elastic scattering on both
yield and asymmetry using MASCARAD, corrected asymmetries (Eq. 5.1
p.112, Figs. 5.1 - 5.11. Figs. 5.8-5.11 are un-radiated asymmetries.
+defined a grid in W and Q2 (four Q2 bins, several Wbins, for E2/M!
and C2/M1 only three Wbins: below, on top, above the Delta resonance)
+for each bin, evaluated kinematic coefficients for AT' and ATL'
+extracted bin-averaged AT' and ATL' (Figs. 5.12-5.15)
+showed MC sensitivity of AT' and ATL' to variation of E2/M1 and C2/M1 in
units of the standard MAID values (Figs. 5.20-5.27)
+extracted E2/M1 and C2/M1 from chi2 minimization (Fig. 5.28): E2/M1 well
measured, C2/M1 moderately, situation complementary to OOPS (remarked
by A. Bernstein)
+Discussion on error determination not yet settled. Need to properly
distinguish and determine statistical and systematic errors on:
sector-asymmetries AL and AR, separated asymmetries AT' and ATL', and
subsequently on E2/M1 and C2/M1.
+Figs. 5.67 and 5.68 show results compared to world data (no error bars)
+Is running more MC data to get a more accurate extraction of E2 and C2.
+More study of systematic effects (in particular spin angle uncertainty!
and momentum resolution/residual offsets) on separation of T' and TL',
subsequently on E2 and C2 is necessary.
+Note that the chi2 minimization should be done directly with the
sector-asymmetries, as this avoids additional systematic errors due to
the separation of T' and TL'.
+Expect a nice paper in the end;-)
-Exclusive pion production from deuterium [Aki]:
+Background studies: Compared observed yields in various
reaction channel with expected yields by using the buffer system for
calibration of target density: efficiencies not so well known (~20%)
+Introducing quasifree cut for d(e,e'pi+-): spectator nucleon at rest
+Yields and beam-vector asymmetries for d(e,e'pi+)nn and d(e,e'pi-)pp
versus W: good agreement after quasi-free cut with free-nucleon
asymmetries from MAID
+Target-vector asymmetry and beam asymmetry versus azimuthal Pmiss angle
about beam axis: agreement with MAID
+d(e,e'pi+)nn and d(e,e'pi)pp yield and tensor asymmetries versus missing
mass: Anti-quasifree cut reveals ^1S_0 singulett state of the nn and pp
systems. Observing negative tensor asymmetry at the singulett state, in
qualitative agreement with Pandharipande
+Coherent d(e,e'd)pi0 reaction versus W: sizable tensor asymmetries over
entire delta excitation range, in analogy with elastic-T20,T21
+Summarized radiative effects on asymmetries: are generally much smaller
than 1%, especially if the electron mass is not neglected
+is interested to continue his work from Japan, provided network access
to MIT (good until July 2008)
+expect papers on radiative effects without electron mass approximation;
quasifree results for d(e,e'pi+)nn and d(e,e'pi-)pp;
tensor asymmetries in d(e,e'pi+-) and the singulett state; tensor
asymmetries in coherent pi0 production.
-Exclusive pion production from hydrogen [Yuan]:
+summarized status of analysis and thesis writing
+discussed event selection schemes
+showed acceptance for good events: Q2 vs W; thetacms vs phi
+extracted yields and double asymmetries in p(e,e'pi+)n and p(e,e'p)pi0,
comparing with MAID2003, DMT, and Sato-Lee: generally good agreement
+described attempts to separate response functions from BLAST data alone.
We have to conclude that neither statistics nor kinematical coverage are
sufficient to separate structure functions with precision. Only at very
forward angle thetacms the azimuthal coverage would be large enough,
however statistics is then poor, and the respective response functions
are suppressed by factors of sin(thetacms). Integrating over all angles
lets only those terms survive that are already present in the inclusive
reaction, there with much better precision.
+Hence, Yuan should finish writing his thesis based on sector-asymmetries
and comparison with pion production models.
Best regards
Michael
On Fri, 21 Sep 2007, John Calarco wrote:
>
> Michael,
>
> Are you going to send out a summary of the pion meeting?
>
>
> --
> John R. Calarco
> Dept. of Physics
> Univ. of New Hampshire
> Durham, NH 03824
> phone: (603)862-2088
> FAX: (603)862-2998
> email: calarco@unh.edu
>
+-------------------------------------+--------------------------+
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