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Pentaquark

physical science Maturity 11-13 Next article →

Everything in our world is made of tiny pieces called quarks. Most quarks live in groups of three. These groups are called baryons. However, some quarks can form a special group of five. We call these exotic baryons pentaquarks.

Pentaquark
Pentaquark

A pentaquark is made of four quarks and one antiquark. An antiquark is a partner bit that acts like a mirror. These five pieces stay stuck together by the strong force. This force works to cancel out their color charges.

PQ EB ape hyp geom5 B 3D
PQ EB ape hyp geom5 B 3D

In a pentaquark, the colors must balance out perfectly. One way is to have one red, one green, and two blue quarks. Then, one antiblue antiquark can cancel out the extra blue. Scientists are still studying how these five pieces stay bound. They might be one tight group or two separate pieces interacting.

Finding these particles was a very long and hard job. Murray Gell-Mann first thought they might exist in 1964. Later, Claude Gignoux and Harry J. Lipkin gave them the name pentaquark in 1987. For many years, scientists could not find them. Some researchers in Japan claimed to see one in 2003. However, other scientists could not find the same thing. Many early reports were later found to be mistakes. This made the search for pentaquarks a very famous mystery in science.

Pentaquark-Feynman
Pentaquark-Feynman

New tools finally helped scientists solve the mystery. In July 2015, a team called LHCb at CERN found real evidence. They looked at how a bottom lambda baryon breaks apart. This process is called a decay. They saw that the decay created pentaquark states. These particles had two up quarks, one down quark, and a charm quark and antiquark.

J-psi p pentaquark mass spectrum
J-psi p pentaquark mass spectrum

This discovery was a huge moment for physics. It proved that these exotic groups really do exist in nature.

Since that big discovery, the LHCb team has found even more. On March 26, 2019, they announced a new pentaquark. This one had a mass of about 4312 MeV. On July 5, 2022, they found another one. This third discovery was very special. It was the first confirmed pentaquark to include a strange quark. This new particle is named PψsΛ(4338)0. It is made of up, down, strange, and charm quarks.

Learning about pentaquarks helps us understand the universe. These tiny particles help us study the strong force in detail. We also think they might exist in deep space. Some very large stars might make pentaquarks when they collapse. This could help us learn the secrets of neutron stars. Studying these small bits helps us understand the biggest things in the sky.

PQ EB ape hyp geom5 B 3D
PQ EB ape hyp geom5 B 3D
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🖼️ Images & Media (4)
File:Pentaquark.svg
Pentaquark.svg
File:Pentaquark-Feynman.svg
Pentaquark-Feynman.svg
File:J-psi p pentaquark mass spectrum.svg
J-psi p pentaquark mass spectrum.svg
File:PQ EB ape hyp geom5 B 3D.jpg
PQ EB ape hyp geom5 B 3D.jpg
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