Question 22N.2.HL.TZ0.10

strong «nuclear» force ✓

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 $-\frac{2}{3}$ and $-\frac{1}{3}$ ✓

«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 $-\frac{1}{3}$ OR baryon number $\frac{1}{3}$ hence a quark ✓

at second vertex, the unknown particle has charge $-\frac{2}{3}$ OR baryon number $-\frac{1}{3}$ hence an antiquark ✓

${10}^8\times 1.6\times {10}^{-19}$  OR  $1.6\times {10}^{-11}$ seen ✓

Δt $\cong \frac{6.63\times {10}^{-34}}{4\text{π}\times {10}^8\times 1.60\times {10}^{-19}}=3\times {10}^{-24}$ «s» ✓

Award [2] for a BCA.

Award [1] for an answer of 5.3 × 10⁻⁴³ s.

Allow ECF from MP1.