Re: strange results

From: Alberto Fasso' (fasso@SLAC.Stanford.EDU)
Date: Mon Jul 30 2007 - 09:36:10 CEST

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    Dear Ioannis,

    the neutrons you are seeing are not produced in annihilations on
    hydrogen nuclei, as you think, but on oxygen. You can easily
    test this by making a phantom of pure hydrogen, with density 1.0,
    and another of pure oxygen, also of density 1.0 (impossible in real life
    but Monte Carlo allows you to do this kind of "experiments").
    You will find that in hydrogen the only particles produced are
    pions, kaons and photons, while in oxygen also neutrons and protons
    are produced.
    Therefore, the neutrons are not produced as part of a pair
    neutron-antineutron but are just existing neutrons in the oxygen
    nucleus, and one doesn't need an energy of 2 GeV to produce them, but only
    enough to overcome the binding energy.

    Alberto

    On Fri, 27 Jul 2007, Ioannis Kantemiris wrote:

    > Dear FLUKA users,
    > I'm counting the neutrons that are produced (and their kinetic energy) by
    > antiproton's inelastic interactions (most of them annihilations) in a
    > water phantom. The maximum kinetic energy of beams' particles is 120MeV.
    > The strange thing is that more neutrons are produced than beam's particles
    > are used (1antiproton-->1.5neutron). This is strange because the majority
    > of the annihilations take part at rest and the energy that is produced
    > (<2GeV) isn't enough to explain so many neutrons.
    > In order to get this information I use mgdraw.f and in the USDRAW I write :
    > IF(ICODE.EQ.101.AND.JTRACK.EQ.2) THEN
    > DO I=1,NP
    > IF(KPART(I).EQ.8) THEN
    > WRITE(80,*) TKI(I)
    > ...
    >
    > Thank you in advance
    >
    > Best regards
    >
    > Ioannis
    >
    >

    -- 
    Alberto Fassò
    SLAC-RP, MS 48, 2575 Sand Hill Road, Menlo Park CA 94025
    Phone: (1 650) 926 4762   Fax: (1 650) 926 3569
    fasso@slac.stanford.edu
    

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