# How do we know what a neutron is made of?

## How do we know what a neutron is made of?

Found this related thread interesting:

https://www.physicsforums.com/threads/how-do-we-know-what-a-neutron-is-made-of.950918/

Jul 4, 2018 at 1:32 PM #1

momoichi8382

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we have physical evidence for the composition of a proton because it decays from a neutron

however all experiments such as https://en.wikipedia.org/wiki/Deep_inelastic_scattering etc, always involve a proton and possibly a neutron, in fact you can't accelerate a neutron without a proton, deuterium etc also must have protons, targets etc. have protons, since all these experiments about neutrons have protons how do we know we're not getting readings from protons instead of neutrons

what i'm asking is, a neutron is said to be 2 down quarks and 1 up quark, well how do we know a neutron isn't actually 3 up quarks which then decays into 2 up and and 1 down when it turns into a proton, i'm not saying i believe a neutron is actually 3 up quarks, i'm just saying how do we know it isn't?

do we know it isn't from purely mathematical reasons or can we experimentally prove it as well? do we simply know because we smash atoms together and count the ratios of up and down quarks?

thanks in advance

https://www.physicsforums.com/threads/how-do-we-know-what-a-neutron-is-made-of.950918/

**How do we know what a neutron is made of?**Jul 4, 2018 at 1:32 PM #1

momoichi8382

User Avatar

we have physical evidence for the composition of a proton because it decays from a neutron

however all experiments such as https://en.wikipedia.org/wiki/Deep_inelastic_scattering etc, always involve a proton and possibly a neutron, in fact you can't accelerate a neutron without a proton, deuterium etc also must have protons, targets etc. have protons, since all these experiments about neutrons have protons how do we know we're not getting readings from protons instead of neutrons

what i'm asking is, a neutron is said to be 2 down quarks and 1 up quark, well how do we know a neutron isn't actually 3 up quarks which then decays into 2 up and and 1 down when it turns into a proton, i'm not saying i believe a neutron is actually 3 up quarks, i'm just saying how do we know it isn't?

do we know it isn't from purely mathematical reasons or can we experimentally prove it as well? do we simply know because we smash atoms together and count the ratios of up and down quarks?

thanks in advance

**Cr6**- Admin
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## Re: How do we know what a neutron is made of?

Wikipedia on Deutrium... :

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In quantum mechanics the energy levels of electrons in atoms depend on the reduced mass of the system of electron and nucleus. For the hydrogen atom, the role of reduced mass is most simply seen in the Bohr model of the atom, where the reduced mass appears in a simple calculation of the Rydberg constant and Rydberg equation, but the reduced mass also appears in the SchrÃ¶dinger equation, and the Dirac equation for calculating atomic energy levels.

The reduced mass of the system in these equations is close to the mass of a single electron, but differs from it by a small amount about equal to the ratio of mass of the electron to the atomic nucleus. For hydrogen, this amount is about 1837/1836, or 1.000545, and for deuterium it is even smaller: 3671/3670, or 1.0002725. The energies of spectroscopic lines for deuterium and light hydrogen (hydrogen-1) therefore differ by the ratios of these two numbers, which is 1.000272. The wavelengths of all deuterium spectroscopic lines are shorter than the corresponding lines of light hydrogen, by a factor of 1.000272. In astronomical observation, this corresponds to a blue Doppler shift of 0.000272 times the speed of light, or 81.6 km/s.[7]

The differences are much more pronounced in vibrational spectroscopy such as infrared spectroscopy and Raman spectroscopy,[8] and in rotational spectra such as microwave spectroscopy because the reduced mass of the deuterium is markedly higher than that of protium. In nuclear magnetic resonance spectroscopy, deuterium has a very different NMR frequency (e.g. 61 MHz when protium is at 400 MHz) and is much less sensitive. Deuterated solvents are usually used in protium NMR to prevent the solvent from overlapping with the signal, although deuterium NMR on its own right is also possible.

https://en.wikipedia.org/wiki/Deuterium

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**Spectroscopy**In quantum mechanics the energy levels of electrons in atoms depend on the reduced mass of the system of electron and nucleus. For the hydrogen atom, the role of reduced mass is most simply seen in the Bohr model of the atom, where the reduced mass appears in a simple calculation of the Rydberg constant and Rydberg equation, but the reduced mass also appears in the SchrÃ¶dinger equation, and the Dirac equation for calculating atomic energy levels.

The reduced mass of the system in these equations is close to the mass of a single electron, but differs from it by a small amount about equal to the ratio of mass of the electron to the atomic nucleus. For hydrogen, this amount is about 1837/1836, or 1.000545, and for deuterium it is even smaller: 3671/3670, or 1.0002725. The energies of spectroscopic lines for deuterium and light hydrogen (hydrogen-1) therefore differ by the ratios of these two numbers, which is 1.000272. The wavelengths of all deuterium spectroscopic lines are shorter than the corresponding lines of light hydrogen, by a factor of 1.000272. In astronomical observation, this corresponds to a blue Doppler shift of 0.000272 times the speed of light, or 81.6 km/s.[7]

The differences are much more pronounced in vibrational spectroscopy such as infrared spectroscopy and Raman spectroscopy,[8] and in rotational spectra such as microwave spectroscopy because the reduced mass of the deuterium is markedly higher than that of protium. In nuclear magnetic resonance spectroscopy, deuterium has a very different NMR frequency (e.g. 61 MHz when protium is at 400 MHz) and is much less sensitive. Deuterated solvents are usually used in protium NMR to prevent the solvent from overlapping with the signal, although deuterium NMR on its own right is also possible.

https://en.wikipedia.org/wiki/Deuterium

**Cr6**- Admin
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## Re: How do we know what a neutron is made of?

Aaaarrrrrg, wanna log in to that site so badly and help those guys out. At least there's a couple critical minds in the mix! It's so tempting. They'll be so mad, though.

**Jared Magneson**- Posts : 437

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## Re: How do we know what a neutron is made of?

Lol... Jared, this was kind of posted for fun actually.

**Cr6**- Admin
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Join date : 2014-08-09

## Re: How do we know what a neutron is made of?

It's hilarious, almost! Watching these folks struggle so hard. And simply because they didn't research hard enough... But yeah, it's funny and slightly painful too. I enjoy it.

**Jared Magneson**- Posts : 437

Join date : 2016-10-11

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