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Question 22N.2.HL.TZ0.10a.ii

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Date November 2022 Marks available [Maximum mark: 3] Reference code 22N.2.HL.TZ0.10a.ii
Level HL Paper 2 Time zone TZ0
Command term Deduce Question number a.ii Adapted from N/A
a.ii.
[Maximum mark: 3]
22N.2.HL.TZ0.10a.ii

The Feynman diagram shows a delta baryon (Δ) decaying into a neutron and particle X.

The exchange particle involved in the decay is a gluon. Particle X has two constituent quarks.

(a.ii)

Deduce, referring to one conservation law, that X is a quark-antiquark pair.

[3]

Markscheme

ALTERNATIVE 1

attempt to apply conservation law of baryon number to the overall reaction ✓
baryon number of X is zero ✓
this is only possible if constituent quarks of X have an opposite baryon number ✓ «so quark-antiquark pair»

 

ALTERNATIVE 2

attempt to apply conservation law of charge to the overall reaction ✓
charge of X is −1 ✓

this is only possible if constituent quarks of X have charges of -23 and -13 ✓

«so quark-antiquark pair»

 

ALTERNATIVE 3

attempt to apply conservation law of baryon number OR charge to each vertex ✓

at first vertex, the unknown particle has charge -13 OR baryon number 13 hence a quark ✓

at second vertex, the unknown particle has charge -23 OR baryon number -13 hence an antiquark ✓

Examiners report

Generally, a well answered question for MP1 and 2 but details of the quarks were often missed for MP3.

Syllabus sections