Hi,
this email is also available in
http://blast.lns.mit.edu/PRIVATE_RESULTS/USEFUL/
ANALYSIS_MEETINGS/meeting_050622/
People should copy their shown slides into the above directory.
Minutes:
-Review of "kinematical corrections" applied so far
-Momentum corrections from p(e,e'p) elastic (EG)
-Momentum corrections from p(e,e'p) elastic (CC)
-Momentum corrections from d(e,e'p) quasielastic (AM)
-CC's approach to obtain corrected field map
-AM: shows the actual corrections for pe and pp vs. Q2; a polynomial
fit is used to parametrize the electron and proton momentum correction
as a function of Q2.
Correction was obtained from comparing distributions of reconstructed
momenta with simulated distributions. MC was without e-loss, i.e. the
correction function for the reconstruction effectively accounts for
e-loss along with other effects that were not explicitly handled such
as radiative corrections or (to-be-)improved calibrations.
Instead of plotting pe-pe_calc(the,pp,thp),the-the_calc(pe,pp,thp)etc.
for complete quasielastic kinematics (was too complicated to resolve
for each individual variable analytically), it is shown pe-pe(the)
assuming elastic kinematics, for left and right sector. Width of that
peak is now due to both resolution and Fermi motion. Momentum
corrections are as much as 30MeV. Missing momentum distribution
strongly affected (30MeV/c). Stated (and shown in an earlier email to
blast_anaware) that both EG's and AM's correction functions are
consistent.
+An overlaying plot of pe-pe_calc using either one of the corrections
is yet missing
-EG: on the speakerphone. Shows slides: For ep elastic scattering, pe,
pp, the, thp minus calculated coordinates from either chosen
one. Correlations between pairs of measured and calculated
variables. Aparantly, the angles are determined most precisely, and
a correction may need to be necessary only on momenta.
-E-loss discussion: most eloss expected for tracking before wch (AM
once did an examination of eloss in the various materials, see
blast_anaware between 2003 and 2005;-)
-angle recontruction yields ~0.5 deg resolution
-CC: has generated another set of corrections, analogous to EG, also
based on ep elastic scattering. The four-momentum transfer squared is
calculated from any of the four coordinates. Also angles are affected
somewhat.
-all three sets of corrections should be made centrally available in
an interchangeable way (such as a header file to be loaded by user
macros)
-consistency of the three methods needs to demonstrated on the same
dataset, both for hydrogen and deuterium, in overlay plots showing
relevant quantities before/after each of the corrections.
-CC presenting method to study effects of fieldmap on
reconstruction. If the fieldmap is reponsible, the differences of
measured minus calculated quantities for elastic scattering can be
minimized through a variation of the discretized field on a
grid. Determine deviations of Bfield as variational problem to match
up momenta. Numerical determination of partial derivatives.
-Systematics of reconstruction:
geometry -> survey; straight tracks
mag field!!-> survey; CC's new method to calulate corrections
eloss -> Geant
bugs -> can be tested with MC and reconstruction of MC events
t2d -> can be tested by hits in situ
radcor -> calculable
-Strategy for the future:
+use kinematic corrections as last resort to account for residual
unknowns.
+improve above systematics to best knowledge, this should minimize
the magnitude of kinematic corrections
+results of the geometry survey and field measurements are awaited
+as sytematics get more and more understood, "kinematic corrections need
to be re-evaluated.
Focus of the next meeting will be a review of radiative effects. The
next meeting will be on Thursday, 6/30 (not Wednesday) at 10am in the
library.
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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