Nuclear Data Section
International Atomic Energy Agency
P.O.Box 100, A-1400 Vienna, Austria
Memo CP-D/479

Date:
To:
From:

20 December 2006
Distribution
O. Schwerer

Subject:

Purported and/or real mistakes in EXFOR

Reference:

CP-C/378 (WP 2006-5 of the 2006 NRDC meeting)

We checked the two area 3 entries listed as erroneous in memo CP-C/378. While we appreciate all
efforts to systematically find mistakes in the database, we do not agree that these two entries
represent errors in compilation which could or should have been avoided at the compilation stage.
Rather, these are entries of very old literature which represent the stage of knowledge of their timeand are as such represented in EXFOR. To filter out old data of doubtful value, other mechanisms
should be used (such as the quality flag recently discussed), while the original database should
continue to reflect the status of the published literature; where necessary, compilers may add theircomments under the CRITIQUE or COMMENT keywords.
In detail:Subentry 30322.016: (1973)
Yb-176(n,2n)Yb-175-m cross section at 14 MeV, for 0.067 sec isomer, 5.8 +- 3 barn, “unphysicallyhigh”
My remarks:
1) The error is > 50%, with the lower margin below 3 barns (Dimitri’s “border of physics”).
Anyway, with such a big error, the user will understand that these data have limited significance.
2) This is the only measurement in EXFOR for this isomer. Therefore it should only be removed
once we definitely know that it does not at all reflect what it intended to reflect.
3) The EXFOR entry correctly reports the publication. There is no “mistake” in the entry. Possibly
there is a mistake somewhere in the experiment, but we don’t know, and the same is true for manyother experiments (and often we may not know about it because some errors may cancel eachother….)
4) The only possible action I can see would be to add a comment like “Compiler believes that crosssection is too high compared with what we would expect and compared with measurements of theground state..” but this would be patronizing the user. From the size of the error together with theage of the experiment, the user will understand the (limited) significance of this experimentanyway; otherwise he should probably not use an experimental database at all.

Subentry 31161.010 (1961):
Ag-107(n,2n)Ag-106-m (8.2 d), DATA-APRX = 6500 mb at 14.8 MeV, “unphysically high”
My remarks:1) This is not DATA but DATA-APRX. This is not correctly understood in the table of CP-C/378.
(The table cited it as 6500 mb +- 0.0), but actually authors cite it as approximate value which
immediately reduces its significance dramatically. For any automatic procedures for processing orchecking EXFOR data, it is essential to differentiate between data and approximate data. Manyevaluators or other users may exclude approximate data from their processing (unless no othermeasurements are available) anyway.
2) The authors themselves give, for comparison, a calculated value of 1460 mb (apparently for thetotal sum of ground and metastable state), which is much smaller than the approximate experimental
value for –M. Thus, the authors understood themselves that their approximate value is unusuallyhigh, but this is what they have got.
3) Again, there is no mistake in the compilation; it correctly reflects the published article. From thefact that it is labeled as approximate value, and from the year of publication (1961), the user will be
intelligent enough to judge this value. In my view, filtering out such data cannot, and should not, bethe task of EXFOR, because the question of “where to draw the line” will introduce much
arbitrariness into the system. Filtering out doubtful data must be left to a secondary step (qualityflag, or “approved by evaluator XYZ” flag, etc.) without touching the integrity of the original
database. In cases of strong indications to the compiler that something is basically wrong which
may not be obvious to the user, the keyword COMMENT or CRITIQUE can be used. However, in
this case, with DATA-APRX, this would not add much additional information. I believe
experimental data must never be used blindly; some amount of judgment on the user’s side isalways required.

Distribution:
oblozinsky@bnl.gov
vml@bnl.gov
drochman@bnl.gov
nordborg@nea.fr
hasegawa@nea.fr
manokhin@ippe.obninsk.rusamaev@obninsk.ru

mmarina@ippe.ru
blokhin@ippe.obninsk.ru
feliks@polyn.kiae.su
chukreev@polyn.kiae.su
S.Dunaeva@iaea.org
taova@expd.vniief.ru
varlamov@depni.sinp.msu.ru

chiba@earth.sgu.ac.jp
kato@nucl.sci.hokudai.ac.jp
ohnishi@nucl.sci.hokudai.ac.jp
ohbayasi@meme.hokudai.ac.jp
yxzhuang@iris.ciae.ac.cn
gezg@iris.ciae.ac.cn
hongwei@iris.ciae.ac.cn
tarkanyi@atomki.hu
stakacs@atomki.hu
katakura.junichi@jaea.go.jp
vlasov@kinr.kiev.ua
kaltchenko@kinr.kiev.ua
ogritzay@kinr.kiev.ua

nklimova@kinr.kiev.ua
yolee@kaeri.re.kr
jhchang@kaeri.re.kr
yolee@kaeri.re.kr
ohtsuka@nucl.sci.hokudai.ac.jp
A.Nichols@iaea.org
A.Mengoni@iaea.org
schwerer@iaeand.iaea.org
v.zerkin@iaea.org
henriksson@nea.fr
exfor@nea.fr
ganesan@barc.gov.in