Final answer:
Particles made of just two quarks cannot exist because they would violate color confinement principles and have fractional charges not observed in nature. Instead, particles called baryons have three quarks, and mesons have a quark-antiquark pair, which allows them to exhibit a net white color. Therefore, the correct option is b).
Step-by-step explanation:
Understanding Quark Composition in Particles
In physics, the study of particles at the subatomic level includes understanding quarks, which are fundamental constituents of matter. Quarks combine in specific ways to form particles. Baryons, which are heavier particles like protons and neutrons, are formed from three quarks. On the other hand, mesons consist of a quark-antiquark pair. A particle composed of two quarks cannot exist because it would not obey the principle of color confinement and would have a fractional charge, which is inconsistent with observed particles.
Particles with three quarks, such as protons and neutrons, are called baryons. These particles can decay into other baryons, but importantly, maintain a color-neutral state, also known as white color, which is necessary due to the phenomenon known as color confinement within quantum chromodynamics (QCD). The conservation of color charge means that observable particles must be colorless or white. Particles with only two quarks do not exist as free stable particles, but particles like pions, which are mesons, do consist of a quark and an antiquark. The quark-antiquark pair in mesons allows for the conservation of color charge, resulting in a net white color. The presence of the antiquark is crucial, as it neutralizes the color of the quark, enabling the existence of mesons.
High-energy experiments that have produced jets of particles in collisions suggest the substructure of three quarks in a nucleon, further supporting the non-existence of two-quark particles. The theory of quark confinement explains that when energy is put into separating quarks, new particles are formed rather than isolating individual quarks, reflecting that quarks cannot exist in isolation or as pairs without an antiquark counterpart. With this understanding, the correct option in the Final Part is b, which states that a two-quark particle cannot exist because it would have a fractional charge and a color that is not white, violating the properties of color confinement.