20130521

Physics quiz question: interpreting β decay Feynman diagram

Physics 205B Quiz 7, spring semester 2013
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Multiple-Choice Question 29.1

A Feynman diagram is shown at right. A __________ exits this interaction event.
(A) neutron.
(B) neutrino.
(C) positron.
(D) proton.
(E) (More than one of the above choices.)
(F) (None of the above choices.)

Correct answer (highlight to unhide): (D)

This diagram shows β- decay, where a neutron transforms into a proton, and the intermediate W- particle decays into an electron and an antineutrino, as shown by the left-to-right electron arrow, and a right-to-left neutrino arrow (corresponding to an antineutrino progressing left-to-right as time progresses). Thus of the above four choices, only a proton leaves this interaction event, as a neutron enters it, and an antineutrino and electron leave the interaction event (but neither of which are listed as choices).

Section 30882
Exam code: quiz07f3yN
(A) : 4 students
(B) : 6 students
(C) : 2 students
(D) : 9 students
(E) : 11 students
(F) : 0 students

Success level: 29%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.19

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