View Full Version : misunderstanding of standard model
I was looking at this giant poster of the standard model here (http://particleadventure.org/particleadventure/frameless/chart_cutouts/particle_chart.jpg) and wondering about the part at the bottom on a neutron decaying and turning into a proton. It shows a d quark changing into a u quark and emmitting an electron and an antineutrino in the process. So then I looked at the mass difference between a d and u quark. It is .003. So since the d quark lost .003 and became a u quark the 2 particles emmitted from it (electron and antineutrino) should add up to .003 in mass. But if you look at the masses of an electron and neutrino (the anti part doesn't change the mass) it doesn't add up..... WHY??
and when u guys answer this I have some other questions about this poster......
I wish I knew the answers. But thanks for the poster link. :)
When a down quark is changed into an up-quark, the electrical interaction inside the particle changes (neutron -> proton). This also changes the binding energy of the particle. Since this binding energy has to come from somewhere, it is largely borrowed from the mass difference between the up & down quark (to put it very simple). This is one possible explanation of why protons are more stable than neutrons (the quarks are more thightly bound). Some very tiny remains of energy are used to create the electron and antineutrino and give them their proper momenta.
04-04-02, 07:37 PM
Most of the mass of something like a proton or neutron does not come from the quarks. It comes from the binding energy of the gluons which hold the quarks together.
Thanks for the answer but you just made it more confusing for me, I don't get how "binding energy" makes up for the mass of the particle,
energy isn't the same thing as mass so how does it compensate???
Mass and energy are really the same thing. You can convert one into the other using the speed of light (E=mc^2)
When a neutron decays into a proton, an electron is 'fired' out moving at a high speed thus creating a lot of kinetic energy. The kinetic energy of the fast moving electron and the energy of the neutrino appear as "binding energy." All three particles (proton, electron, antineutrino) can share this energy in many ways and in doing so take on a range of values while still obeying energy and momentum conservation.
but then couldn't someone (in theory) make all the matter in the universe into energy..... i don't think Im getting this yet
and another thing, it takes too long to wait for these posts!!
can anyone who knows a reasonable amount about what Im asking about give me their instant messenger s/n so I can get my questions answered faster, (whatever messenger you use I'll download)
You cannot just transform a particle into energy; energy cannot exist on its own, it always condenses down to a particle in collisions. The most "non-condensated" form of energy you can wind up is a photon (which is probably the best example of a fundamental building block that has least particle behavior on a macroscopic scale).
o well, I'll just accept that energy makes up the rest of the mass for a proton.......
but now I have another question, I have read that if matter and anti-matter meet they annihilate each other, then I see that some particles are made up of one anti-particle and a regular particle (like the meson part on the right side of the giant poster) how is this possible??
When matter and anti-matter meet, they don't necessarily annihilate. You can have a perfect collision between a positron (= anti-particle of the electron) and a proton. When a particle and its anti-particle meet, then you _could_ have annihilation (eg electron + positron -> 2 photons).
I think the same rules apply for quarks, but I am not sure though. Perhaps someone will pop in and fill that answer in :).
For mesons with the same type of quark and antiquark with zero charge, the particle and the antiparticle are identical. For example, the antiparticle of a photon is a photon, the antiparticle of a phi meson (s quark and anti-s quark) is a phi meson.
Mesons are bosons since they have integer (or zero) units of spin. With bosons, there is no distinction between matter and antimatter. They are not stable and do not obey Pauli exclusion principle rules.