Question

The combination of one u-quark and two d-quarks is called:

• A. Positron
• B. Electron
• C. Proton
• D. Neutron

Hint:

Three quarks make a baryon. \(uud\) is the proton; \(udd\) has total charge zero.

Answer 1

The Correct Option is D

Step 1: Baryons are made of three quarks. Identify the quark content given: one up quark (u) and two down quarks (d), i.e. the combination \(udd\).

Step 2: Compute the electric charge. The up quark has charge \(+\tfrac{2}{3}e\) and each down quark has charge \(-\tfrac{1}{3}e\): \[Q = \left(+\tfrac{2}{3}\right) + \left(-\tfrac{1}{3}\right) + \left(-\tfrac{1}{3}\right) = 0.\]

Step 3: A neutral baryon with content \(udd\) is the neutron. (For comparison, the proton is \(uud\) with charge \(+e\).)

Step 4: Positron and electron are leptons, not quark combinations, so they are ruled out.\[\boxed{\text{Neutron } (udd)}\]