Attending EG,VZ,TA,BT,CC,AS,MK
-We should have a rate monitor for (e,e'p, e,e'd, e,e'n) candidate
events per Coulomb and log this run-by-run.
-Discussing the beam blowup effect. The beam blowup has been
quantified by VZ for the neutron trigger by comparing the normalized
quasielastic (e,e'n) rates for empty target and for hydrogen target
(there is no quasielastic e,e'n production rate from the proton
target ...). Therefore this is sensitive to any additional production
from cell walls when the target is filled with hydrogen. The result
is that the blowup factor is very close to 1.
-It may be that the beam blowup effect is different for e,e'p from
hydrogen. In principle, one would have to look at a channel that is
forbidden in the reaction under consideration. One such channel could
be the (e,e'pi-) rate which would require the presence of neutrons in
the target. A comparison of (e,e'pi-) with empty and with hydrogen
target could be an alternative way to quantify the blowup effect in
the charged-trigger channel trig=1
-Another way to quantify the background for p(e,e'p) is to vary the
cuts on the elastic peak while looking at the observables, or to
sample the elastic peak and tail region. Pure radiative-tail events
should exhibit the same asymmetry like elastic events (radiative
effect is mostly independent of polarization), while any change of the
background contribution may dilute the asymmetry (unpolarized
background) or change the asymmetry (polarized background, e.g. from
pion production events that range in)
-The cell background fraction is different for the (e,e'p) and (e,e'n)
channels: N_empty/N_deut (e,e'p) > N_empty/N_deut (e,e'n). A possible
reason could be that the ratio of e,e'p/e,e'n is different for
scattering from aluminum and for deuterium.
-The missing momentum in p(e,e'p) is also sensitive to background
from other sources than hydrogen. It should peak at a very small value
suggested by the resolution (20?? MeV/c?) whereas in quasielastic
scattering it should peak around 50 MeV/c for deuterium and 80-100MeV/c
for heavier nuclei.
-The definition of the dataset for the next release of preliminary
data will be "BLAST 2004", including all deuterium and hydrogen data
of 2004. This will be the data shown at coming conferences and on
other occasions. It extends the previous preliminary dataset on
deuterium by about four weeks of running in Sept/Oct 2004, and for
hydrogen it will be extended by the whole run of Oct-Dec 2004.
The 2005 data is not at a stage where a preliminary version may
be released. Nevertheless at next week's collaboration meeting the
present status of the analysis also of the 2005 data shall be
discussed. People should therefore prepare results separately for the
BLAST 2004 dataset and the 2005 or 2004+2005 data!
We shall have a projected gain of the figure-of-merit for the 2005 run by
next week that may be quoted in presentations.
-Plan is to have all data calibrated and recrunched by the next
collaboration meeting end of June / early July (= pre-final data)
-After this some fine-tuning may still be necessary. We shall push hard to
get final results for the "key reactions" (GEn, T20, A_ed^V(e,e'p),
GEp/GMp by fall!
-I will send out an agenda for the coming big meeting on Wednesday 4/6
soon.
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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