--SRC Index

New (and more) Errors (June 14th, 2010)

Systematic Errors in Ratios
Here are the systematic errors for the ratios to deuterium and helium3. I'll be looking into why gold is so jumpy, but I actually think it always was, and this is not a recent development, so it's unlikely I'll find anything.



Statistical Errors at high x
Until recently, when calculating the statistical error bar on the ratio, I've just taken the sun of the statistical errors on the two cross sections in quadrature, even for the points with super high errorbars.

Instead, for points where the errorbar for either cross section (usually the ld2 or he3) is >=25%, we do this instead:
(1) Ratio=Sigma_2/Sigma_1
(2) Ratio_2a=Sigma_2/(Sigma_1+err_1)
(3) Ratio_2b=Sigma_2/(Sigma_1-err_2)
where the lower/upper error is now set by Ratio_2a/b. In the rare cases where taking Sigma_1-err_1 makes it negative, I just do Sigma_1/1e6 instead, to make it small.

The plots below show the statistical (inner) and combined (outer) error bars. Note that the binning is different starting at x=1.2. Past here, cross sections (not ratios) were rebinned in groups of 3. No points past x=A were included.



Ratios to Deuterium
Fortunately enough, the statistics for deuteirum are good enough that we don't have to play this trick.



For 3He and 4He, I used x>=1.4 to get an average, and x>=1.6 for the heavier targets (for which there's probably no good reason, so I'll be post the x>=1.4 answer too, if there's demand).
I only used the statistical errors in combining the points. I guess for the systematic error, I should quote the error at the average x value.
3He
================
18 ... 2.08676 +/- 0.0121448
22 ... 2.24592 +/- 0.0310436
26 ... 2.30684 +/- 0.0813791
32 ... 2.35175 +/- 0.221961

4He
================
18 ... 3.43965 +/- 0.01819
22 ... 3.67835 +/- 0.0453307
26 ... 3.66627 +/- 0.101041
32 ... 3.73581 +/- 0.274221

Beryllium
================
18 ... 3.98525 +/- 0.0421956
22 ... 4.74169 +/- 0.124219
26 ... 4.7268 +/- 0.327818
32 ... 2.07274 +/- 0.492908

Carbon
================
18 ... 4.88536 +/- 0.0527118
22 ... 5.74757 +/- 0.158971
26 ... 5.27798 +/- 0.369089
32 ... 3.62728 +/- 0.569117

Copper
================
18 ... 5.40631 +/- 0.0583225
22 ... 6.57254 +/- 0.177708
26 ... 6.41479 +/- 0.449222
32 ... 2.38337 +/- 0.607614

Gold
================
18 ... 5.36501 +/- 0.058442
22 ... 6.5969 +/- 0.179975
26 ... 6.68139 +/- 0.463548
32 ... 4.13868 +/- 0.98152

2N Ratios to 3He (click on target header for individual plot)

4He
================
18 ... 1.65053 +/- 0.00695086
22 ... 1.64407 +/- 0.0203585
26 ... 1.55323 +/- 0.0458397
32 ... 1.0689 +/- 0.082756

Beryllium
================
18 ... 1.84837 +/- 0.0155537
22 ... 1.97942 +/- 0.0504648
26 ... 1.72318 +/- 0.0477965
32 ... 1.46863 +/- 0.0993323

Carbon
================
18 ... 2.26577 +/- 0.0196366
22 ... 2.39903 +/- 0.0647562
26 ... 2.04624 +/- 0.0570619
32 ... 1.65333 +/- 0.11604

Copper
================
18 ... 2.51114 +/- 0.0217398
22 ... 2.74406 +/- 0.0723226
26 ... 2.26167 +/- 0.0634242
32 ... 2.31399 +/- 0.150928

Gold
================
18 ... 2.4926 +/- 0.0218932
22 ... 2.75257 +/- 0.0732485
26 ... 2.27119 +/- 0.0633055
32 ... 2.2066 +/- 0.156739