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 Post subject: AMS data - comments
PostPosted: Mon Nov 08, 2010 1:48 pm 
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Joined: Mon Jan 19, 2009 9:48 am
Posts: 19
Location: INFN Perugia
Hello. A few comments about the GCR Database (sorry if I am not posting in the right place).

1) AMS01-Protons. I see a typo in the 6th energy point. The mean energy is 1.35, not 1.25 (once plotted, it's apparent by eye).
2) AMS01-Helia. I see data are given vs ekin/nucleon, assuming a constant composition of 3He/(3He+4He)=15%, right?
There are no 3He measurements at HE, but they likely decrease sharply with rigidity (3He/4He~rig^-delta; like B/C). So, such assumption is not really good. I think that fitting these data might lead to a wrong spectral index. In my opinion, a DB should report the original published data (i.e. vs rigidity).
3) General. Mean energies are often "geometric" in low-energy datasets (ACE), and "arithmetic" in some high-energy ones (AMS). It is strange to me: the opposite would make be more sense (LE=arithm.; HE=geom.). That's not important, however, if the bin margins are provided in the DB.


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 Post subject: Re: AMS data - comments
PostPosted: Tue Nov 09, 2010 12:14 am 
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Joined: Wed May 17, 2006 7:02 am
Posts: 285
Location: MPE Garching
thanks, this is the right place to put comments on the database, and they are very welcome.
I will check up on them.

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Andy Strong, MPE


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 Post subject: Re: AMS data - comments
PostPosted: Tue Nov 09, 2010 10:30 am 
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Joined: Wed May 17, 2006 7:02 am
Posts: 285
Location: MPE Garching
2) The Ek comes from a private comm. as stated. The composition was as stated.
The idea of the DB is to have everything on the same scale, which in this case was not trivial.
In this case an additional entry for the original values would be appropriate, but then would need a flag to show the meaning of the values.

This paper http://adsabs.harvard.edu/abs/2010arXiv1011.0989P uses AMS01 He, so it will be useful to see how they do it. In fact they discuss the difference between spectra on the Ek and momentum scales, and have to interpolate in order to get them.

In future we could ask experimenters to give spectra binned on both scales.


3) sometimes the authors give the mean, in that case I use whatever is given.
Sometimes only the range is given, then I compute the geometric mean.
The user can also make their own mean from the range.

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Andy Strong, MPE


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 Post subject: Re: AMS data - comments
PostPosted: Tue Jun 21, 2011 2:14 am 
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Joined: Wed May 17, 2006 7:02 am
Posts: 285
Location: MPE Garching
I see that point (1) was never corrected, it has been done in GCR_data_10.dat.
http://www.mpe.mpg.de/~aws/propagate.html

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Andy Strong, MPE


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