Question

Particles with integer spin are called:

• A. Fermions
• B. Bosons
• C. Leptons
• D. Baryons

Hint:

Remember the Spin-Statistics Theorem at a glance: - Integer Spin (\(0, 1, 2\dots\)) \(\rightarrow\) Bosons \(\rightarrow\) Bose-Einstein Statistics (No restriction on state occupancy). - Half-Integer Spin (\(\frac{1}{2}, \frac{3}{2}\dots\)) \(\rightarrow\) Fermions \(\rightarrow\) Fermi-Dirac Statistics (Max 1 particle per quantum state).

Answer 1

The Correct Option is B

Concept: All elementary and composite subatomic particles can be categorized into two macro-classes based on their intrinsic angular momentum (spin quantum number \(s\)). This classification dictates their collective behavior and the specific statistical mechanical distribution function they obey under thermodynamic equilibrium conditions.

Step 1: Defining Bosons.
By definition, particles that possess an integer intrinsic spin value (i.e., \(s = 0, 1, 2, \ldots\) in units of \(\hbar\)) are called bosons.
• Examples of fundamental bosons include gauge bosons like photons (\(s=1\)), W/Z bosons (\(s=1\)), gluons (\(s=1\)), and the Higgs boson (\(s=0\)).
• Bosons obey Bose-Einstein statistics.
• They do not respect the Pauli Exclusion Principle, meaning an unlimited number of identical bosons can occupy the exact same quantum mechanical state simultaneously. This unique property enables macroscopic quantum phenomena like Bose-Einstein Condensation (BEC) and superconductivity.

Step 2: Reviewing and disproving alternative classifications.
Let us analyze the structural characteristics of the remaining alternatives given in the question:
• Fermions: Particles that carry half-integer spin values (e.g., \(s = \frac{1}{2}, \frac{3}{2}, \frac{5}{2}, \ldots\)). They comply with Fermi-Dirac statistics and explicitly obey the Pauli Exclusion Principle.
• Leptons: A family of fundamental particles with spin-\(\frac{1}{2}\) (which makes them fermions) that do not experience the strong nuclear interaction. Examples include electrons, muons, taus, and their associated neutrinos.
• Baryons: Composite subatomic particles made up of an odd number of valence quarks (typically three quarks). Because quarks carry half-integer spin (\(s = \frac{1}{2}\)), combining three of them always yields a total spin that is a half-integer (e.g., protons and neutrons have \(s = \frac{1}{2}\)). Therefore, all baryons are fermions. Hence, the only class representing particles with pure integer spin is Bosons.