Hi,
here are my minutes from today - some stuff to deeply think about!
!!!Just as a reminder: Speakers of yesterday should give brief summaries
of their results, along with their tasklist of issues that need to be
resolved for the preparation of papers. !!!
!!!Another reminder: please remember copying your slides to the Blast
webpage!!!
MK,EG,CC - Recrunch status, update on kinematic corrections
-New lrn recrunch available for 2004 data 7002-13279 and 2005 soon
Accounts for new Blast field, charge calib, generates DST
-Used wire chamber calib based on Chi's/Aki's fit
-Major discussions on kinematic corrections
-New recrunch shows angle offset of 0.5 degrees vs. old one of 0.2deg
-Need to account for energy loss and internal radiation in reconstruction.
Recipe: MC for each particle species, run with eloss and/or internal
radiation turned on/off. Impose realistic resolutions. Reconstruct
MC, parameterize momentum and angle shifts as a function of the
reconstructed coordinate. Use these parametrizations for each
particle species to correct momenta, angles, derived quantities in
ntuples with known particle ID (note that ID is in general not known at
crunchtime).
-Internal radiation (aka radiative tail) may lead to a shift of the
centroid when convoluted with finite resolution (which is very finite
in Blast).
AS-UNH,CC - p(e,e'p) elastic GEp/GMp analysis update; PRL draft
-Independent analysis consistent with CC's results
-Includes BATs, however large statistical error (somewhat larger than
predicted with MC, however Blast field at backward angles outside the
grid is zero)
RF - d(e,e'p)n quasielastic GEp/GMp: status of analysis
-New extraction of GEp/GMp from deuterium beam-vector asymmetry using
super ratio technique
-Realistic errors, now compatible with CC's errors in ep
elastic. Final FOM after including 2005 data will be significantly
higher than for the proton data.
CZ - d(e,e'd) T20 analysis update
-Discussion on spin angle determination. Yield-weighted average spin
angle based on measured maps differs up to 1.5 degrees from the value
obtained from T20 analysis (also consistent for ep elastic).
-Is using spin angle map shifted by constant amount such that
yield-weighted average complies with average angle from asymmetry
analysis
-Kinematic offset in reconstructed theta_e of 0.2 degrees translates
into 0.12 degrees offset for the spin angle, does not explain 1.5 degs
-Model dependence of spin angle determination of analysis of order 0.1
degrees, does not explain it either.
-Possible misalignment of the hall probe?
-Do we need to measure the spin angle map again? Proposed method would
not use ratio of two measured field amplitudes but measure the angle
directly with a self-aligning permanent magnet (so done for He3 at
Jlab), just like a compass, compass orientation needs to be surveyed
-The effect of the BLAST field has been measured already and is very
small
-Discussion of false asymmetries: Pzz(V+T+) differs from Pzz(V-T+) by
15% (relative), translates to ~5% systematics, likely impacts ed
elastic vector asymmetry (Pete!) where asymmetry is sizeable
-2Pzz(T+)=Pzz(T-) cannot be verified
-All other false asymmetries consistent with zero
-Pzz discussion along with theories, with and without Qd
renormalization. Spread is on the order of 5% when discarding most
questionable calculations
-World data on A: Mainz and Saclay data differ by 8% in region of interest
-Global fit analysis of GC and GQ a la Abbott; with tensor asymmetries
normalized to Abbott-3
VZ - d(e,e'n) G_En analysis update
-Only 4 bins in Q2 (the two highest bins now combined)
-Kinematic corrections for neutrons
-Comparison and combination of 2004 and 2005 datasets, ~10% statistical
error for first and second Q2 bin
-Drastic dependence of GEn extraction on spin angle (12% per degree)
-GEn is the channel with the largest dependence on the spin angle
-Effect of realistic vs. dipole proton form factor on FSI for (e,e'n)?
NM - d(e,e') G_Mn update analysis
-Inclusive MC studies: effect of realistic form factors vs. dipole
-Sensitivity to GEn, spin angle
-Latest extraction of GMn
TS - d(gamma,pn) photodisintegration
-Kinematics and event selection
-Huge background (wide-open trigger for positive-charge + neutral
events!) can be greatly reduced with cut on coplanarity and by
contraining photon direction
-Sizeable number of events remaining
DH - Wire chamber calibration and straight track analysis
-Straight track analysis does not support any geometrical offset
beyond 0.3mm (~1mm was needed to explain kinematic offsets to first
order)
-New T2D relationship, should be implemented into libBlast and tested
with hydrogen data (crunching will take only 1 day!)
EG - Wire chamber studies
-Kinematic offsets are dependent on TOF-number (discontinuous!),
however evaluation is tracking-based only
-possible TOF effects: T0 ... i.e. discontinuity can be generated when
timing of two TOFs differs
-Suggested to check drift time spectra broken down into TOF numbers
-Determination of kinematic corrections: Results after correction are
closer to optimum, however a second iteration is needed. Will send
out renewed version when ready
-Chi's 9thorder vs. Aaron's 6thorder T2D: no significant difference
-> next, MK will recrunch hydrogen with Chi's 9th order but with old
Blast field map
CC - Time-of-flight evaluation for proton tracks
-Uses cosmics events to verify/improve TOF time calib as in
database. Agreement of time calib within 300ps.
-Determine proton momentum and thus Q2 from timed-of-flight, compare
with Q2 from angles and momenta.
-Best consistency between Q2(TOF) and Q2(angles), worst with
Q2(p). This confirms that angles are more correct than momenta, and
in fact, momentum from tracking is not consistent with momentum from
time-of-flight, i.e. neglected energy loss effect can actually not
account for this discrepancy ...
+-------------------------------------+--------------------------+
| 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 - 14:07:32 EST