Chi, congratulations on your excellent results.
_ why does your e- vertex distribution have two peaks (in data and mc?)
is this from the 40 and 60 cm cell ? I am not sure i understand it.
Maybe a simpler picture would be better (I am not asking for it)
_ As far as montecarlo, comparing the distribution of theta_spin is
actually interesting because a wrong theta* enters directly in your Pzz,
T20... I understand you fixed the h.f. direction, but what matters is
also the distribution. When data and mc are understoodd they should
match at all z's, theta_e's, and so on
_ You are quite right about ee'p bckg of course. But you do show that cell
Al(ee'p) backgrounds are not a problem, which is a significant result.
If a lot of Al(ee'p) falls in your cuts than D(ee'p) would have been a
serious problem. It is the other way around, and you are down by 3
order of magnitude. For a first estimate of the D(ee'p) contamination
you can use 10^-3 * (Yield(Dee'p)/Yield(Alee'p), where Yield can be
defined as total ee'p rate (only pid cuts).
_ If the above corrections significantly alters your T20, (say outside 3
sigma of your error bar) I will eat my hat with fork and knife in front
of you (but only if you ask me to)
_ For internal discussion it is nice to show blue dots in T20 from the
proposal. However, since the proposal and experiment have different spin
angles the comparison is non trivial and maybe doe is not review
history. I suggest you leave them out
_ Maybe some internal rebinning can be done if a point at 4.5 fm-1 becomes
possible.. (needs fuill statistics of course).
-- ________________________________________________________________________________ Tancredi Botto, phone: +1-617-253-9204 mobile: +1-978-490-4124 research scientist MIT/Bates, 21 Manning Av Middleton MA, 01949 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^On Fri, 16 Jul 2004, Chi Zhang wrote:
> > Hi John and all > > here are some ed elastic cross section plots. > > counts in a large number runs (40cm, 60cm alll together) are plotted vs. > Z, theta_e and Q2. linear and log scale are provided. > > red is electron into right, blue is electron into left, back is Monte > Carlo. Magentta is background electron into right, Cyan is background > electron into left, backgounds are presented by filled areas, MC is in > solid line, data are ofcourse in data points with error bars. > > In log scale, one can see some messy up and downs at high Q2. In linear > scale, one can see red data is lower than blue data, indicating missing > events when electrons go into right sector. > > All plots have "background" overlaid only that only in the log scales > they are visible. > > One word about the "cell wall background". It is extracted from about 79kC > of empty target and H2 target runs. H2 runs produce the little hump at low > Q2 end. > > Another word about the "background". I believe this does not reflect the > contamination from deuteron e'p channel. The reason is that even though H2 > runs are used, ep elastic and ed elastic are two distinct narrow peaks in > kinematics. With the smearing due to resolution, the leak of ep elastic > into ed cuts is very little. However, deuteron e'p is much more spread out > in kinematics, therefore is more likely to appear within ed elastic cuts. > Please excuse me to say again that better resolution will help suppressing > "e'p background". > > Finally, there is a macro cross_sec.C, use: root cross_sec.C will produce > the plots along with two others. You can zoom in or change scales then to > see the background and details. > > Chi >
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