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Fusion product direction

  1. Mar 28, 2005 #1
    The first step in the nuke reaction of the sun is p-p reaction

    p + p = d + e+ + neutrino

    My question is, if the two protons are coming say from the -x and +x direction, what is the final direction of the products formed in the xyz axis.
  2. jcsd
  3. Mar 28, 2005 #2
    please, anybody?
  4. Mar 28, 2005 #3


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    There is some degree of freedom as long as energy and momentum conservation laws are obeyed. Since most of the mass is in the d, it will move very little. The other particles can go off in any direction (presumably opposite from each other).
  5. Mar 28, 2005 #4


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    Exactly correct.

    Because the reaction gives so much energy to the products - the energy
    and momentum of the reactants before the reaction is insignificant compared
    to the energy and momentum the products will have.

    But the energy and momentum before the reaction is the only way that the
    product particles will "remember" anything about the initial directions of the
    reactant particles.

    Imagine a collision between two cars. If they collided while going roughly
    the same direction - a glancing collision - then they will leave the collision
    going in the same general direction as before the collision. That's the only
    way to conserve momentum.

    Now imagine the cars are full of explosives, which detonate upon collision.
    The car parts will spew out roughly in all directions [ with the original
    direction favored to some extent ]. That's because the initial momentum
    and energy is insignificant relative to the final energy / momentum due to
    the added energy of the explosion.

    Dr. Gregory Greenman
  6. Mar 28, 2005 #5


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