How can a proton form a neutron?

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Discussion Overview

The discussion revolves around the process by which a proton can transform into a neutron and a positron, particularly in the context of nuclear decay and the conditions under which this occurs. Participants explore theoretical and practical aspects of this transformation, including the implications of mass and energy conservation.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions how a proton can decay into a positron and neutron given that a neutron has a greater mass than a proton.
  • Another participant notes that positron emission typically occurs in proton-rich nuclei and mentions that isolated protons do not decay, while isolated neutrons do.
  • A third participant provides an example of 22Na undergoing β+ decay to 22Ne, highlighting the differences in binding energy between the two nuclei despite the mass differences.
  • One participant emphasizes that an isolated proton cannot decay due to its status as the lightest baryon, but it can decay in the presence of other nucleons by "borrowing" energy from its environment, resulting in the emission of a positron and a neutron.

Areas of Agreement / Disagreement

Participants express differing views on the conditions necessary for a proton to decay, with some focusing on the role of the nuclear environment while others emphasize the mass considerations. The discussion remains unresolved regarding the specifics of the decay process and the implications of mass differences.

Contextual Notes

There are limitations regarding the assumptions made about the decay process, particularly concerning the role of binding energy and the conditions under which a proton may decay. The discussion does not resolve these complexities.

Matriculator
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This is related to a homework problem but I want to understand it as well. How can a proton break up into a positron and neutron when a neutron clearly has a greater mass than a proton?
 
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Positron emission occurs in proton-rich nuclei, although in many, electron capture is also possible.

An isolated proton would not decay by positron emission, but an isolated neutron will spontaneously decay.
 
Consider 22Na which undergoes β+ decay to 22Ne.

22Na has 11 protons and 11 neutrons, whereas 22Ne has 10 protons and 12 neutrons. Nevertheless, the mass of a 22Na nucleus is greater than the sum of the masses of a 22Ne nucleus and an electron, because of the different binding energies of 22Na and 22Ne.
 
An isolated proton can not decay since is the lightest particle with baryon number equals to one.
A proton in the presence of other stuff like other protons or neutrons so for instance a proton that is making up the nuclei of some atom may ''borrow" energy from this environment and then it can decay (always conserving baryon number and charge and so on) so one (very) possible outcome will be positron and neutron
 

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