Tancredi,
Thanks.
Richard
On Mon, 28 Jul 2003, Tancredi Botto wrote:
>
> Hello,
> just a comment about the consistency between polarization results.
>
> Aaron's results were 11.0+-6.0 (L) 10.0+-5.0 (R)
> Chi's results were 17.8+-4.5 (L) 17.6+-9.7 (R) and 18.0 +- 4.3 combined
>
> In either case the error is the uncertainty in the fitted Pzz parameter.
> With the eep data we could also establish a very small value for a constant
> false asymmetry offsets and I believe the binnning is optimal. Note that
> the AedT should integrate to zero in case of smooth reconstruction
> efficiency. This could to some extent also change day by day.
>
> The polarization results for the two channels seem to be consistent.
> However T20 is much larger than Ad(T) in nature. With these data set
> the observed asymmetries were in the scale of 2% (eep) and 10 % (T20).
>
> Clearly this shows that the analysis suffers greatly from a low FOM.
> It is just so much harder to be more stringently conclusive with a 2%
> signal. Our S/N will go with the square of the polarization. Already
> 40% would be significant and the goal is 70% !!. But I think you all see
> the first steps of a consistent analysis. To which we could add the ee'n
> channel once the NC are in.
>
>
> --
> ________________________________________________________________________________
> Tancredi Botto, phone: +1-617-253-9204 mobile: +1-978-490-4124
> research scientist MIT/Bates, 21 Manning Av Middleton MA, 01949
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
> On Mon, 28 Jul 2003, richard milner wrote:
>
> > Hi Chi,
> > Thanks for your complete report on the elastic analysis. Now that we have
> > results from both elastic and quasielastic, I am interested in
> > consistency. Does the quasielastic analysis of Aaron also see
> > significantly less yield as you do? I would like a number for Aaron's
> > target polarization. I am not sure `about 10%' is consistent with 18 +/-
> > 4 %.
> > Thanks,
> > Richard
> >
> > On Sun, 27 Jul 2003, zhangchi wrote:
> >
> > >
> > > Hi all,
> > >
> > > First: atatched daily_pol.eps is a plot of fitted polarization day by day.
> > > here s a brief explaination of what is plotted:
> > >
> > > tensor polarization is fitted from ed elastic asymmetry in 3 manners:
> > >
> > > 1. fitted from asymmetry in parallel kinematics only, i.e. left deuteron,
> > > right electron. asymmetry in this sector is large.
> > >
> > > 2. fitted from asymmetry in perpendicular kinematics only, left electron,
> > > right deuteron. Asymmetry on this side is small and more often than the
> > > other side, it is not distinguishalbe from 0.
> > >
> > > 3. fitted from the A_perpendicular - A_parrallel. Because both kinematics
> > > measure the same polarization, this could be a way to combine statistics
> > > and cancel out some overall shifts from 0.
> > >
> > > The fit is done over an function in form of: pol*(a*x + b*x*x + c*x*x*x)
> > > where pol is the parameter fitted and x being Q^2. The expression in the
> > > parenthesis is acquired by fitting asymmetry from Monte Carlo. Also see
> > > Aaron's earlier message.
> > >
> > > I did not include a constant term in the parameterization of asymmetry to
> > > force the curve to start from 0.
> > >
> > > with only two valid data point along Q^2 from 0 to 0.4, only a 1-parameter
> > > fit is possible.
> > >
> > > Now going to the figures:
> > >
> > > the x-axis marks the date. the first point(x=13) in fact include most of
> > > the runs on 13th and 14th. that was when we realize that we were using a
> > > obsolete target cycle script so most of the runs on 13th are tensor+ and
> > > then most on 14th are tensor-.
> > >
> > > the second point (x=14.5) includes all the runs from 13th to 15th, before
> > > cell tempreture control was back functional.
> > >
> > > starting from the 3rd point, x correspondes to the date in July.
> > >
> > > left, top, the red curve is tensor polarization from 1st fit
> > > method(parallel kinematics). there was a dip on 19th. and it shows an
> > > interesting trend. on 19th, polarization is minimal and then there seem to
> > > be a trend to recover.
> > >
> > > right top, the blue curve is tensor polarization from 2nd fit method
> > > (perpendicular kinematics). most of the time polarization is not
> > > distinguished from 0 and the curve fluctuates more.
> > >
> > > left bottum, the purple curve is tensor polarization from 3rd fit
> > > method(difference between to sector). it is more stable, has smaller fit
> > > error. a dip on 18th.
> > >
> > > right bottum, the bluish curve is yield with date. the yield is expressed
> > > in 10^16 atom/sec equivalent flow assuming 100% detection efficiency.
> > >
> > > so on average the yield is consistant with 0.65e16 atoms/sec target gas
> > > flow. if we believe our detectors have an overall efficiency of 50%, then
> > > ABS flow intensity can be deduced as ~1.3e16 atoms/sec. Just for a
> > > reference: 0.1sccm atomic gas flow or 0.05sccm molecular gas flow is
> > > equivalent to ~4.48e16 atoms/sec.
> > >
> > > Averaged over all days for polarization:
> > > parallel kinematics: 17.8+-4.5 %
> > > perpendicular kine: 17.6+-9.7 %
> > > combined: 18.0+-4.3 %
> > >
> > > atatched ed_asym_1490_1523.eps is 17th data. left top: data in parallel
> > > kinematics: please ignore the 1st and the last data points. red is theory
> > > curve with fitted polarization. green dashed is the 100% theory curve.
> > > right top: data in perpendicular kinematics. left bottum: data from both
> > > sides, red are theoretical curves scaled by polarization fitted from
> > > difference between two sectors. right bottum:
> > > Asym_perpendicular - Asym_parrallel, and a fit on it.
> > >
> > > if you look carefully at left bottum, you ll see two black curves behind
> > > the red. those are theory curves with polarization fitted from single
> > > sector data. looks like everything agrees with everything. that is why I
> > > call it thrilling.
> > >
> > > ************************************************************************
> > > Second: analysis on unpol runs:
> > > flase asymmetry in acquired in form of equivalent target polarization.
> > > Yield is acquired by comparing total counts with prediction of Monte
> > > Carlo and is expressed in equivalent gas flow assuming 100% detection
> > > efficiency.
> > >
> > > 1.recent 0.1sccm runs:
> > > false asymmetey equivalent to target polarization:
> > > parallel kinematics: 1.9+-4.2 %
> > > perpendicular kine : 2.3+-10.1%
> > > combined: 2.0+-4.2 %
> > > very much all 0.
> > >
> > > Yield: equivalent gas flow: 7.67 e16 atoms/sec. 0.1sccm molecular flow
> > > equals to 8.96 atoms/sec. so the yield for ed-elastic is a little too
> > > high(85% of everything perfect). However, I d like to remind you that a
> > > 1sccm flow controler with 1% max flow error measures 0.1sccm flow with 10%
> > > error even if we ignore the fact that the 1% is calibrated with N2 gas. So
> > > we may have been flowing more gas in than we thought. This has to be
> > > checked with e'p channel yield.
> > >
> > > 2. earlier 0.05sccm runs:
> > > false asymmetry
> > > parallel kinematics: 5.3+- 2.0 %
> > > perpendicular kine : 13.8+-32.9 %
> > > combined: 4.3+-17.5 %
> > > no false asymmetry we may say.
> > >
> > > Yield: equivalent gas flow: 1.5 e16 atoms/sec. compare to 4.48 e16
> > > atoms/sec which is what 0.05 sccm really should be.
> > >
> > > atatched ed_xs_1642_1713.eps shows cross section data with MonteCarlo(back
> > > curve). right sector forward(red cross markers) has efficiency problem.
> > > and it is easily verifiable in an nsed session that is the inefficiency
> > > lies in software: all chambers hit and produce segments but no valid fit
> > > merge because of bad fit quality.
> > >
> > > *********************************************************************
> > > Third. I have a few things to remind data analyzors:
> > >
> > > somewhere between run 1323 and run 1353. left tof 0 delay was changed. it
> > > result in a shift of tdc_right - tdc_left spectra to the right by about
> > > 300 channels. This change probably fixed left 0 strobe problem and got rid
> > > of the double peak there. However any timing cut must be checked and
> > > adjusted accordingly. I suspect this change will change ep elastic timing
> > > cuts as it changed ed elastic timing cuts.
> > >
> > > I am still concerned about the absolute timing. In reconstruction, we must
> > > correct for time of flight of heavy particles. However, we need have a
> > > somewhat resonable absolute timing between left and right sectors inorder
> > > to compute proton time of flight in one sector from electron time of
> > > flight in the other sector. And anommalies in tof tdc spectra should be
> > > monitored and reported to experts timely.
> > >
> > > Well, this is a long email now. see you at Bates tomorrow.
> > >
> > > Chi
> > >
> > >
> >
>
>
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