Draw possible Feynman diagrams for the following phenomena: a) protons scattering off each other b) neutron beta decays to a proton: \(n \rightarrow p+e^{-}+\bar{\nu}_{e}\).

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Question: Draw Feynman diagrams for the following phenomena: a) protons scattering off each other and b) neutron beta decay. Answer: a) For protons scattering off each other, the interaction is mediated by the strong force carried by gluons. A simple Feynman diagram depicts two incoming protons exchanging a gluon between two quarks (e.g., \(u_1\) and \(u_3\)) and two outgoing protons. b) For neutron beta decay, the process is mediated by the weak nuclear force, involving the emission of a W- boson from a down quark. The diagram depicts an incoming neutron, the emission of a W- boson that transforms the down quark into an up quark, forming a proton, and the decay of the W- boson into an electron and an electron antineutrino.

Step by step solution

01

Proton Scattering

To draw the Feynman diagram for protons scattering off each other, we need to consider their internal structure. A proton is composed of two up quarks and one down quark. The interaction between quarks in protons is mediated by the exchange of gluons, which are the carriers of the strong force. In this case, we can consider a simple case where one quark from each proton interacts via the exchange of a gluon. It is important to note that there are many possible diagrams for the scattering process, but we will draw a particular one. The diagram will have the following features: - Two incoming protons (labeled as \(p_1\) and \(p_2\)) with their quark content (\(u_1, u_2, d\) for \(p_1\) and \(u_3, u_4, d'\) for \(p_2\)). - The exchange of a gluon (labeled as \(g\)) between, for instance, \(u_1\) and \(u_3\). - Two outgoing protons (labeled as\(p_1'\) and \(p_2'\)) with their quark content (\(u_2, u_3', d\) for \(p_1'\) and \(u_4, u_1', d'\) for \(p_2'\)).
02

Neutron Beta Decay

To draw the Feynman diagram for neutron beta decay, we need to consider the weak nuclear force mediated by W bosons. The process is characterized by the transition of a down quark in the neutron into an up quark, resulting in the transformation of a neutron into a proton. Simultaneously, an electron and an antineutrino are emitted. The diagram will have the following features: - An incoming neutron (labeled as \(n\)) and its quark content (\(u, d, d\)). - The emission of a W- boson (labeled as \(W^-\)) from the down quark. - The transformation of the down quark into an up quark and subsequent formation of a proton (labeled as \(p\)) and its quark content (\(u, u, d'\)). - The W- boson decays into an electron (labeled as \(e^-\)) and an electron antineutrino (labeled as \(\bar{\nu}_e\)).

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Most popular questions from this chapter

A free neutron decays into a proton and an electron (and an anti-neutrino). A free proton has never been observed to decay into anything. Why then do we consider the neutron to be as "fundamental" (at the nuclear level) a particle as the proton? Why do we not consider a neutron to be a proton-electron composite?

An electron-positron pair, traveling toward each other with a speed of \(0.99 c\) with respect to their center of mass, collide and annihilate according to \(e^{-}+e^{+} \rightarrow \gamma+\gamma\). Assuming the observer is at rest with respect to the center of mass of the electron-positron pair, what is the wavelength of the photons?

A Geiger-Marsden type experiment is done by bombarding a 1.00 - \(\mu\) m thick gold foil with 8.00 - \(\mathrm{MeV}\) alpha rays. Calculate the fraction of particles scattered to an angle a) between \(5.00^{\circ}\) and \(6.00^{\circ}\) and b) between \(30.0^{\circ}\) and \(31.0^{\circ}\). (The atomic mass number of gold is 197 and its density is \(\left.19.3 \mathrm{~g} / \mathrm{cm}^{3} .\right)\)

The de Broglie wavelength, \(\lambda\), of a 5-MeV alpha particle is \(6.4 \mathrm{fm}\), as shown in this chapter, and the closest distance, \(r_{\text {min }}\), to the gold nucleus this alpha particle can get is \(45.5 \mathrm{fm}\) (calculated in Example 39.1). Based on the fact that \(\lambda \ll r_{\text {min }}\), one can conclude that, for this Rutherford scattering experiment, it is adequate to treat the alpha particle as a a) particle. b) wave.

Suppose a neutral pion at rest decays into two identical photons. a) What is the energy of each photon? b) What is the frequency of each photon? c) To what part of the electromagnetic spectrum does this correspond?

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