Skip main navigation

The D-Star Hexaquark

Moving on from medical applications, we are now going to explore an exciting new discovery in particle physics. The d-star hexaquark, described by Dr Mikhail Bashkanov in the video above, is a new form of matter composed of six light quarks – the same quarks that usually combine in trios to make up protons and neutrons.
3.9
All visible matter is made of atoms. Atoms are made of nuclei with electrons orbiting around. Electron orbitals define the size of atoms, while all the mass is concentrated in the nucleus. Nuclei are made of protons and neutrons. Protons and neutrons are made of quarks. And to our current knowledge, Quarks and electrons are fundamental non-divisible constituents of matter Protons carry 3 quarks, which possess 3 colour numbers - red, green, blue, since only colorless objects are allowed to exist in nature. But we were always wondering - can we place more than just 3 quarks inside one particle?
55.4
Now we know the answer “Yes we can” We have recently found that if we squeeze proton and neutron strong enough we can form a new particle – a hexaquark, a 6 quark object, named d(2380). With a quark fusion we can make new type of matter. The d hexaquark, with its six quarks inside, has a mass around 2.5 times the mass of the proton, even through its size is about the same as the proton. Why is it important? The hexaquark shows us that new combinations of quarks can exist. We all know the periodic table where we can find various chemical elements important for our life, and making up everything we see around us in the universe.
109.9
On a quark level we also can draw a similar table. The Proton and neutron would occupy the first cell. And until recently we believed that it is the end of the storry. Now we know that the second cell of this table also exists, and it is occupied by our recently discovered d* hexaquark. In the table of the elements, Helium, which occupies the second cell, is a very interesting element. Helium can show a lot of strange effects, like superconductivity and superfluidity. Hexaquarks, which occupy the same cell on the quark level, have similarly amazing properties, which we have just started to explore.
154.3
So the question we should ask is - is the d* hexaquark the end of the quark periodic table, or just the beginning?

Moving on from medical applications, we are now going to explore an exciting new discovery in particle physics. The d-star hexaquark, described by Dr Mikhail Bashkanov in the video above, is a new form of matter composed of six light quarks – the same quarks that usually combine in trios to make up protons and neutrons.

D-Star Hexaquark Discovery

An experiment looking for the particle was led by the University of York using the Crystal Ball detector at the Mainz Microtron (known as MAMI). MAMI is a particle accelerator located at the Johannes Gutenberg University in Mainz, Germany. Like many other particle accelerators, MAMI is used by physicists from around the world to investigate nuclear and particle physics.

The experiment searched for the d-star hexaquarks by focusing an intense gamma ray beam on a liquid deuterium target. You may remember from week 1 that deuterium is an isotope of hydrogen with one proton and one neutron in the nucleus (called a deuteron). Deuterium is found naturally in seawater, where it constitutes approximately 0.0153% of hydrogen, or can be concentrated to form so-called heavy water.

Formation of D-Star Hexaquarks

Hitting a deuteron with a photon causes the deuterium nucleus to split into a proton and a neutron in a process called photodisintegration. By using sufficiently high energy gamma ray photons, the quark substructure of the deuterons can be investigated. By measuring the final state of the protons and neutrons from the photodisintegration of the deuterium nuclei, it is possible to determine that d* hexaquarks were formed during this process. This is shown in the diagram below:

d* hexaquark

The existence of the d-star hexaquark was inferred by observing the degree of spin polarisation of the outgoing proton and neutron. For the first time, both were almost completely polarised at photon energies corresponding to the mass of the d-star hexaquark. This cannot be explained by current conventional theories. The results provide important new information for the emerging field of multiquark states and potentially for astrophysics, where the d-star hexaquark may play an important role in neutron stars and even provide a new candidate for the mysterious dark matter. We will look at these possible roles for the d-star hexaquark in the following articles and videos.

You can read more about the experiment in Signatures of the d*(2380) Hexaquark in d (γ,p→n), published in the APS Physics, Physical Review Letters (2020).

This article is from the free online

Frontier Physics, Future Technologies

Created by
FutureLearn - Learning For Life

Our purpose is to transform access to education.

We offer a diverse selection of courses from leading universities and cultural institutions from around the world. These are delivered one step at a time, and are accessible on mobile, tablet and desktop, so you can fit learning around your life.

We believe learning should be an enjoyable, social experience, so our courses offer the opportunity to discuss what you’re learning with others as you go, helping you make fresh discoveries and form new ideas.
You can unlock new opportunities with unlimited access to hundreds of online short courses for a year by subscribing to our Unlimited package. Build your knowledge with top universities and organisations.

Learn more about how FutureLearn is transforming access to education