Sunday, August 30, 2015

nuclear physics - What happens if we put together a proton and an antineutron?


A hydrogen nucleus consists of a single proton. A 2-hydrogen (deuterium) nucleus consists of a proton and a neutron. A tritium nucleus consists of a proton and two neutrons.


This makes me wonder how an atomic nucleus made of a proton and a "minus one neutron" would look like, and the closest thing to a "minus one neutron" I can imagine is an antineutron.



What happens if we combine a proton and an antineutron? Are things like this even possible?


If such a thing is an atomic nucleus, can we add an electron and get an atom?



Edit: in the comments below, I also asked this more specific question (I suppose it's useful to also mention it here in order not to create a complete chaos):



If the proton and antineutron annihilate, is it still possible that the thing they annihilate to remains somehow stable enough to behave like an atomic nucleus?





Answer



Given that the valence quark content of a proton is $(uud)$ and that of a anti-neutron in $(\overline{udd})$ the answer is that sooner later some of the constituent quarks will annihilate and you get a spray assorted particles.


The lifetime of such a nucleus will depend on it's orbital angular momentum, with s-states being very short lived and high angular momentum states lasting a little longer.


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