GATE 2025 PH – Question 18
Which one of the following baryons has strangeness quantum number S= −1?
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Correct answer: (A) $\Sigma^{*0}$
Explanation
**Strangeness** is $S=-(\text{number of strange quarks})+(\text{number of strange antiquarks})$, so each strange quark contributes $-1$.
- **$\Sigma^{*0}$** has the quark content $uds$: one strange quark, so $S=-1$. ✓
- **$n$** (neutron) is $udd$: no strange quark, $S=0$. ✗
- **$\Xi^{*0}$** is $uss$: two strange quarks, $S=-2$. ✗
- **$\Delta^0$** is $udd$: $S=0$. ✗
Answer **$\Sigma^{*0}$** (A).