4 ms·
Has to be the complementary type. In your example, they will repel each other (since both are positively charged).
by czzr 5y ago
Has to be the complementary type. In your example, they will repel each other (since both are positively charged).
- willis936 5y agoWhat about a neutron and positron? They could collide with no electrostatic repulsion but have quark-antiquark pairs.
- fsh 5y agoOnly hadrons (neutrons, protons, mesons,...) consist of quarks. Positrons are leptons which are elementary particles.
- db48x 5y agoNo, a positron is a lepton but a neutron is not. Since lepton number must be conserved, these two will not annihilate with each other. Similarly, one has a positive charge and the other neutral, so electric charge would not be conserved either. Are you thinking of a neutron plus an antiproton? Those can annihilate with each other. They are not direct antiparticles of each other, but the neutron is really an up quark and two down quarks, while the antiproton is really two anti–up quarks and an anti–down quark. There are several different ways that they could annihilate with each other. Worse, all hadrons (like neutrons and protons) contain a confined gluon field which you can think of as containing additional quark–antiquark pairs. There’s a chance that the gluon fields of the two particles will interact as if a quark–antiquark pair from one had annihilated with a quark–antiquark pair from the other, further complicating the results. This can cause the creation of other exotic particles as the quarks combine and recombine. You can read more about it on Wikipedia, of course: https://en.wikipedia.org/wiki/Annihilation https://en.wikipedia.org/wiki/Annihilation
- ellis-bell 5y agolepton number does not need to be conserved. it is an approximate symmetry of nature. if lepton number were conserved, neutrinos could not oscillate. quarks, the particles composing protons and neutrons, have fractional charge; these would be the particles that would interact with an electron or positron. the charges wouldn't work out (charge is conserved (as far as we known...)) so there wouldn't be a fundamental electromagnetic interaction between a single quark and a e+/e- (i.e., an annihilation). But there are fundamental weak interactions between quarks and e+/e-; these processes are known as inverse beta decay and are used for pet scans.
- lanstin 5y agoTo quote Wikipedia: “Lepton flavor is only approximately conserved, and is notably not conserved in neutrino oscillation.[6] However, total lepton number is still conserved in the Standard Model.“ The beta decay gives rise to e.g. a positron and a neutrino (or an electron and an anti-neutrino).
- floxy 5y agoWhat is going on in neutron stars? The layman's answer is that the electrons get squeezed into the protons due to the extreme gravity, leaving only neutrons. But I suppose (?) there needs to be a anti-neutrino or similar that comes along to "complete" the reaction? Edit: I guess it is inverse beta decay: https://en.wikipedia.org/wiki/Inverse_beta_decay#Electron_induced https://en.wikipedia.org/wiki/Inverse_beta_decay#Electron_in...
- db48x 5y agoAs a rule of thumb it’s good enough for most particle interactions.
- jfengel 5y agoThe electrostatic repulsion isn't really an issue. If you shoot an electron hard enough, it will overcome the electrostatic repulsion. The bigger issue here is that a positron is a lepton, and a neutron has a 0 lepton count. So they can't react directly while conserving lepton count. However, a neutron can decay into a proton, an electron, and a anti-neutrino. The neutrino is a lepton. So there is a path where the neutron and positron react to form a proton, anti-neutrino, and two gamma rays. I don't know if that actually occurs. There are even more factors to be considered. But it illustrates how you have to go about conserving all of the things, including obscurer factors like leptonicity.