Quark doesn't constitutes more fundamental particle and proton and neutron consist of quarks. Now come to beta decay.

$n \rightarrow p + e^{-} + \bar{\nu}_e $

How can an electron emit from an neutron whereas electron is a fundamental particle? Is the electron created from gluon?

  • $\begingroup$ I've edited you decay equation to more accurately reflect the nature of the neutral lepton. $\endgroup$ Jul 25, 2013 at 20:43

1 Answer 1


This is a weak decay and it is mediated by a weak boson. In this case a $W^-$.


The Feynman diagram for β− decay of a neutron into a proton, electron, and electron antineutrino via an intermediate W− boson.

At vertex level a down-quark is converted into a up-quark by the emission of virtual W-boson which decays to the electron electron-antineutrino pair. Charge is carried by the mediating boson.

  • $\begingroup$ so you are saying that quark can decay? Isn't it a fundamental one? $\endgroup$
    – Raisa
    Jul 25, 2013 at 21:03
  • 2
    $\begingroup$ The weak interaction does not (fully) respect flavor. Weak interaction can convert quarks of one flavor to another. $\endgroup$ Jul 25, 2013 at 22:41
  • $\begingroup$ @Raisa : Weak interactions involve left-handed particles. Left Quarks $d$ and $u$ are a SU(2) doublet, that is you have to consider the doublet left $(u,d)$ as a whole, exactly as a vector with $2$ dimensions, and SU(2) operations on this vector are allowed, for instance, a "rotation" could transform $u$ in $d$. Same thing for the doublet electron/ neutrino. $\endgroup$
    – Trimok
    Jul 26, 2013 at 13:03
  • $\begingroup$ so quark is decaying and u turning into d, therefore the electron formation comes from the energy releases by up quark? $\endgroup$
    – Raisa
    Jul 26, 2013 at 13:14

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.