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
>
>
This archive was generated by hypermail 2.1.2 : Mon Feb 24 2014 - 14:07:29 EST