From: Glen Warren (gwarren_at_anti-spam)
Date: 22-May-2003 00:34:08
GEn01 analysis meeting May 14, 2003
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attended by: Paul, Oscar at UVa
Donal, Hongguo, Frank, Nikolai and Glen at JLab
REPORTS
*) GMn: First we reviewed the impact of GMn not equal to the dipole.
The effect is almost linear. Next there was some discussion about what
value of GMn to use. The conclusion was that we should say that we
extract GEn/GMn*Dipole. Next we raise the issue that GMn is not dipole,
pick a value and an uncertainty, and then publish a value for GEn. It
is not adequate to simple allow GMn=Dipole, as that number is not really
Gen. We will wait to see what Juerg can do in terms of determining
uncertainties for the Basel fit to the GMn data.
*) Target field angle uncertainties: 0.99% for 0.1 degree rotation.
*) Radiative Corrections: Hongguo completed corrections. The internal
will be applied bin-by-bin and have an overall uncertainty of 0.5%. The
external correction is so small that Hongguo ignores it. It also has an
uncertainty of 0.5%.
*) Settling in Stick 4: Something is clearly happening in raster plots
shown by Nikolai. The picture of the material when stick 4 was pulled
doesn't show any signs of settling in either top or bottom cell. We did
conclude that if what we see is settling, then it doesn't affect the
p.f., so it is not a concern.
One possibility is that the raster was messed up, but we read the drive
current sent to the raster magnets, so that is unlikely. Paul mentioned
that the runs selected by Nikolai are around the time of the BPM fiasco
(early Dec), so their may have been some problems related to the
different BPMs/electronics. Donal recalled that we did some hole target
runs to confirm beam position.
We do not also understand the left/right asymmetry in the raster plot.
Some of it may be acceptance/angle related. We recalled the pulser runs
done by Marko to look at the distribution of the raster, which appeared
to be fairly uniform. Nikolai also commented that apparent settling
begins around time we had problems with the HMS collimator.
*) packing fraction: momentum shift has small impact on p.f.
*) dilution factor for stick 3: Nikolai reviewed Glen's argument and
agrees with the basic approach. Need ratio of dilution factors for
stick 3 and stick 4 using Pauls path lengths through the various
materials. Frank will provide a weighting of events for the two sticks
so that we can determine the impact of the rotated stick to the final
result.
*) hszbeam cut: Suggested to look at Q2=0.5, and to do a cost-benefit
analysis to determine where to place cuts on hszbeam.
*) Background: no progress
*) Application of binning: Frank will apply CEX and background
corrections to data. Hongguo will then apply internal radiative
corrections to data before comparing with MC.
*) CEX: need binning of correction for Q2=1. Also, Frank had some
questions for Marko.
*) paper: some progress. Donal will send Glen paper this weekend for
Glen to work on it.
*) uncertainties in d.f. : Hongguo needs rates for all materials from Frank.
*) pion production contributions: data exist, but not yet examined.
*) ypos alignment: there is a 4.5 (2.5) cm difference between data and
MC for neutron (proton) ypos alignment. We will through this into the
kinematics uncertainties.
*) Left/Right asymmetries for stick 3: Nikolai does not see value when
we will determine impact of rotated stick on d.f.
*) Kinematic uncertainties: Glen will review what we agreed on for Q2=0.5.
*) Variables to fit: There was much discussion, but we agreed that
EVERYONE should think about the best choice of variables.
*) Target polarization: Paul determined that most of the target
polarization changes for runs was because of the redefinition of the
length of the run of 1st pass compared to 4th. 1st pass did not include
a sync filter.
*) New Q2=0.5 pass: decided to do a new pass without the momentum
offset, which will be just about as time consuming as specific
investigations on a subset of runs.
TO DO
Donal
*) work on paper.
*) Send Glen version of paper late into weekend.
Glen
*) look at 98 and 01 field setting codes
*) review philosophy of kinematic uncertainties.
*) Gmn values and uncertainties.
Nikolai
Frank
*) check proton rates run-by-run
*) accidentals
*) do systematic breakdown of proton asymmetries for fourth pass.
*) Ask Marko questions by CEX for Q2=1
*) Rates for all materials for d.f. uncertainties
*) Start third pass of Q2=0.5 without momentum offset.
Hongguo
*) dilution factor for stick 3 using Paul's path lengths thru
materials.
*) kinematic uncertainties
*) determine pion production contribution to Q2=1
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