Can neutrons and protons have excited states?

Anything with a substructure has excited states. Molecules, atoms, nuclei all can absorb photons which causes them to make a transition to an excited state. Conversely, when they jump from an excited state to a lower energy state, energy is emitted in the form of photons. Can proton and neutrons (having electrically charged quarks inside … Read more

Can neutrons be synthesized purely from protons and electrons?

Can neutrons be synthesized purely from protons and electrons? Note: I’m looking for reactions that do not require neutrinos or any particles besides just protons and/or electrons as reactants. Answer Yes, they can be. The production of neutrons by deep inelastic scattering of electrons on protons was studied in HERA experiments in the 90’s. No … Read more

Confusion in proton decay

I read that a proton cannot decay because it is the least massive baryon. However, in positron emission, the proton converts to a neutron a releases a positron. Is that considered a proton decay? Answer Within the standard model of particle physics the proton is composed out of three quarks and there are no possible … Read more

If protons are the only stable baryons, why do they decay into neutrons in positron emission?

Surely I must have a misconception? Answer Short answer Protons are the only stable free baryons. In a bound state, stability of nucleons (in sense of their mutual conversion via weak force) is determined by the mean nucleon binding energy. Positron emitters are proton rich nuclei with decreased mean nucleon binding energy, partly due enlarged … Read more

Proton flux model or data at energy range up to 100 keV

I am looking for a model or at best the database of proton fluxes (solar p+) at a energy range of some eV up to 100 keV. I have already found the SOHO database: But the most energetic p+ was something around 5 keV. Still, I need fluxes from 5 keV up to 100 keV. Is there any … Read more

How would the structure function of protons be different if quarks had spin 0?

I saw this question in a practice exam. I know that the structure functions are not linearly independent but that F2(x)=2xF1(x) when the energy is in the order of GeV. The question asks what would F1(x)/F2(x) be if the spin of the quarks was 0. On this matter my book says: “…the underlying process in … Read more

Proton structure: are there photons, electrons and neutrinos in there too?

I’ve read that the proton is not simply made up of three (valence) quarks; rather, there is a continuous exchange of gluons between the three quarks, and these gluons can produce quark-antiquark pairs that usually annihilate soon after, so that at any given instant, the proton is actually a mess of gluons and quarks and … Read more

Does the proton have an equatorial bulge around its spin axis?

And if so, can we observe a difference in the electron scattering cross section with transversely polarized VS longitudinally polarized protons? P.S. Let me make my question more precise. Consider the charge shape of the proton. In the rest frame of a proton with spin in +z direction, what’s the spatial dependence of the expectation … Read more

Dose-depth curve of photons vs. protons

The dose-depth curve of protons and photons can be seen in the image below: Now, what I’ve heard is, that in some cases, proton therapy is advantageous compared to photons, and of course the other way around in some other cases. I can see, that the Bragg peak of the proton curve is very sharp, … Read more

Does a photon attract or repel matter?

So, I know experimentally that matter and light interact. And I can calculate cross sections in Quantum Electrodynamics. Yet a fundamental intuition about how light and matter interact is completely missing in my understanding. If a photon were (for a brief instant) next to a proton, would they attract? Repel? How about an electron? Is … Read more