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Deacay data

  1. Oct 22, 2007 #1

    I'm looking for a list,as complete as possible, of decay modes and their probabilities, for all known subatomic particles.
    I've been googling, but found only bits and pieces. Perhaps someone knows a place on internet, or has found a free document to share, or anything like that

  2. jcsd
  3. Oct 22, 2007 #2


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  4. Oct 22, 2007 #3


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    Moreover, for the total decay rates, when known, there is an spreadsheet in the same node. It could contain still a couple typos, be alert.

    Time ago I explained how to plot this spreadsheet, see comment 1 here: http://dorigo.wordpress.com/2006/09/14/a-mistery-behind-the-z-width/
    Gnuplot is also available in windows.

    Contest idea: please upload in this thread your best plots of this data o:)
  5. Oct 22, 2007 #4
  6. Oct 22, 2007 #5
    Now, are there similar charts in existence for annihilation events between various particles and antiparticles at low energies ("static")? In other words, should I even look for such a thing?
  7. Oct 22, 2007 #6


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    You are asking for collision cross-sections, are you?
  8. Oct 22, 2007 #7
    Well, this is all pretty new for me, so I'm not sure if that's what it's called

    but what I'm looking for would be branching ratios of various outcomes of annihilation at rest. Between protons-antiprotons, electron-positrons and neutron-antineutrons.
  9. Oct 22, 2007 #8


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    Well for static situation with electron-positron annihilation the result is two photons of 0.511 MeV. For nucleons, I don't think there are too many (if at all) static collisions, since anti-protons are produced at high energies, and I'm not sure any have been brought to rest unless someone at CERN or Fermilab has done it (?).

    I doubt antineutrons have been produced at rest.
  10. Oct 22, 2007 #9
    Well they do have antiproton decelerator at CERN and other methods of cooling down anti-protons, so if not total rest, they certainly can get the energy down to change results

    In the meantime , I finally found the branching ratios for p anti-p

    here is one table, this is from a PDF presentation made by Ryugo Hayano, of University of Tokyo , and he has been working at CERN, so I trust the table to be reliable representation of Cern experiments, although it is not quoted as such, but
    I had to compare its numbers to another similar table, although simplified, which used same numbers and claimed them to be results from experiments at CERN, of annihilation at rest. I don't know if it was really at rest or at low enough energy so that results don't deviate much from predictions at rest, but here it is:

    http://free-os.t-com.hr/redmist/pp.jpg [Broken]

    This one uses quite a bit of channels , including Kaons , while other sources usually disregard kaons, and group various channels together. This one is the most specific I could find so far.

    I made a jpg , it's extracted from the PDF.

    credits to mr. Hayano

    http://athena-positrons.web.cern.ch/ATHENA-positrons/wwwathena/Hayano.html [Broken]
    Last edited by a moderator: May 3, 2017
  11. Oct 22, 2007 #10


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    Hey, where is the pdf? It is a impressive work from the experimental side; I wonder if the theoreticians are at the same level about calculating these branching rations. I had expected first the 3 pions channels, but it seems they carry a lot of energy yet, so five pions are favored! I'd guess that at least one pair u u* anhiquilates.
  12. Oct 22, 2007 #11
    Here it is, but the table is on the end somewhere:

    www.oeaw.ac.at/smi/download/aic04/hayano-wien.pdf [Broken]

    About the theoretical predictions of branching, It's interesting you brought that up, because I also found a publication comparing calculations with practical observations from Cern, in fact it was compare to this same chart I posted, except that they "dumbed down" the results by merging channels of 2,3,4 etc neutral pions into simply more than one neutral pion.


    Although I still haven't found any data on n-nbar annihilation, which will probably be very hard, but I'd settle for theoretical predictions too
    Last edited by a moderator: May 3, 2017
  13. Oct 22, 2007 #12
    Here's a question

    I've been thinking, but I'm probably wrong..

    A neutral pion can have either up-antiup quark pair or down-antidown pair.
    A proton-antiproton pair has in total 2 ups, one down, two antiups, and one antidown all together which is a perfect match for making equal amounts of positive, negative and neutral pions,
    and a neutron-antineutron pair has all together two downs, two, antidowns, one up and one antiup quark, which is also a perfect match for making equal amounts of positive, negative and neutral pions, allthough the neutral pions would have a much different mass than than u-anti-u neutral pion

    So would it be possible to assume that distribution of probabilities would be similar to that of proton-antiproton annihilation, or would a different mass of d-anti-d neutral pions cause a different distribution?

    The building blocks are in equivalent amounts in both annihilations, except that
    while they are equivalent for the job of forming pions, they are not identical.
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