Research: New Particle World Record Key to the Mysteries of the Universe?

2019-02-27

Uppsala scientists have in an international research co-operation for the first time succeeded in the collection of 10 milliard so called J/ψ-particles. These may give clues about how the strong interaction works, the force which gives rise to most of the visible mass in the universe and is a condition for the complex particle systems which is a necessary requirement for life to arise.

The research was conducted by more than 400 scientist in 14 countries within the Chinese particle physics experiment BESIII, where beams of electrons and positrons with very high energy collide with each other. At a specific collision energy the probability for the resonance particle J/ψ to form is very high. On February 11, 2019 the magic limit was reached where 10 milliard J/ψ-particles had been formed and detected. The J/ψ-particle is a hadron consisting of a charm quark and an anti-charm quark. The particle has a very short life span and decays to more stable particles which are measured in the BESIII-detector. The amount of data this corresponds to is the largest which has ever been collected in an electron-positron beam experiment.

“This amount of data opens up for new possibilities to perform in-depth studies of the properties of our universe on the very shortest length scales. Maybe it will even show deviations which cannot be reconciled with our best theoretical description, the Standard Model. Such a discovery would really revolutionise nuclear and particle physics”, says Patrik Adlarson, researcher at the Department of Physics and Astronomy at Uppsala University.

From the record sized collection of the J/ψ-particle one may study a number of different phenomena within physics concerning the very shortest length scales (10-15m) in the universe. Maybe one may even discover deviations which may have an explanation beyond the theories we know about today.

The ten Uppsala scientists taking part of the BESIII-experiment study the inner structure of hadrons and how the strong interaction works. They also look for clues to why the Universe consists of so much more matter than anti-matter, which is one of the fundamental conditions for life in the Universe.

“Maybe we will with the collection of data which the BESIII-experiment now has collected succeed with digging up some of the treasures within physics that still no one has found”, says Patrik Adlarson.

Facts about the Particle Experiment BESIII
Within the project there are more than 400 scientists from 14 different countries, among others China, USA, Russia, Germany, England and Sweden. Uppsala University has been present since 2012 and has a focus on hadron structure, quark masses and the matter-antimatter asymmetry of the Universe.

Facts about the Strong Interaction
The strong interaction is also known as the strong force and is one of the four fundamental forces in the Universe, together with gravity, the weak force and the electromagnetic force. The strong force holds together protons and neutrons in the atomic nucleus and also binds together quarks in protons, neutrons and other composite particle systems, so called hadrons. The strong force generates 99% of the proton’s mass.

Facts about Hadrons
Hadrons are subatomic particles, made of quarks (elementary particles) and the strong force. The most known examples of hadrons are the proton and the neutron which both consist of three quarks. Hadrons may also consist of a quark and an antiquark, such in the case of the J/ψ-particle which is made of a charm quark and an anti-charm quark. The J/ψ-particle was first detected in 1974 and for this discovery the physicists Samuel Ting and Burton Richter received the Nobel Prize in physics in 1976.

Facts about the Standard Model
The theory which describes physics on the very shortest length scales is known as the Standard Model of elementary particle physics and it is well tested. At the same time most physicists expect that the Standard Model is not the final description and with the help of precision experiments one may look for cracks in the model. This is done by comparing experimental results with theoretical calculations based on the Standard Model.

To discover the physics beyond the Standard Model very large amounts of data is needed to achieve high precision. Some of the strongest indications that phenomena beyond the Standard Model exist come from comparisons between experimental measurements and theoretical calculations which both have been done with very high precision.

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Press release from BESIII about the record collection

Camilla Thulin

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