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Is it allowed? such as a electron neutrino and an electron anti-neutrino.
And why?
Now, I am confused...
Thanks.
And why?
Now, I am confused...
Thanks.
humanino said:This decay is forbidden by angular momentum conservation if neutrinos are purely massless.
Vanadium 50 said:But they are not. So the decay occurs with some rate. (It's GIM suppressed, though).
I wanted to quote the same values as you just did. You can find the original references for those upper bounds, they describe the various existing predictions.Barmecides said:I have no idea, how much we should expect from SM theory, do you know ?
Barmecides said:what do you mean by GIM suppressed
Vanadium 50 said:Suppressed by the mechanism of Glashow, Illiopoulos and Maiani. This is a cancellation that occurs in flavor changing neutral currents: decays like K0L -> mu+ mu- and pi0 -> nu nubar. If the neutrinos were exactly degenerate the cancellation would be exact and this decay wouldn't occur. Because they have slightly different masses, the decays are suppressed.
humanino said:See the original reference for the value quoted Upper Limit on the Branching Ratio for the Decay [tex]\pi^0 \to \nu \bar\nu[/tex]
They provide references for :
[tex]Br(\pi^0 \to \nu \bar\nu) = 3\times 10^{-8} \left(\frac{m_{\nu}}{m_{\pi^{0}}}\right)^{2} \sqrt{1-4\left(\frac{m_{\nu}}{m_{\pi^{0}}}\right)^{2}}[/tex]
See also http://pdglive.lbl.gov/Rsummary.brl?nodein=S009&sub=Yr&return=MXXX005 for instance for other informations.
arivero said:But suppose that the up quark were massless. Could the neutral pion decay into a pair of up, anti-up quarks?
Vanadium 50 said:The pi0 carries no weak charge, so it cannot couple directly to a Z
Vanadium 50 said:There is an additional subtlety - a pi0 composed of massless quarks would itself be massless (it becomes a Goldstone) and massless particles do not decay.
A neutral pion, also known as a pi zero, is a type of subatomic particle that is composed of two quarks (one up quark and one anti-down quark) bound together by the strong nuclear force.
Yes, a neutral pion can decay into a neutrino and an anti-neutrino through the weak interaction. This process is known as the pion decay, and it is one of the most common ways that neutral pions decay.
The weak interaction is one of the four fundamental forces of nature, along with gravity, electromagnetism, and the strong nuclear force. It is responsible for radioactive decay and some types of nuclear reactions.
In the process of pion decay, a neutral pion emits a W boson, which then decays into a neutrino and an anti-neutrino. This process obeys the conservation of energy and momentum, as well as the conservation of lepton number.
The decay of a neutral pion into a neutrino and an anti-neutrino is an important process in particle physics. It provides evidence for the existence of the weak interaction and helps scientists understand the behavior of subatomic particles and the fundamental forces of nature.