Science & Technology

X17: New Subatomic Particle Might Solve the Dark Matter Mystery

Anomalies in nuclear physics experiments could present indicators of a brand new power.

A crew of scientists in Hungary not too long ago published a paper that hints at the existence of a beforehand unknown subatomic particle. The crew first reported discovering traces of the particle in 2016, they usually now report extra traces in a distinct experiment.

If the outcomes are confirmed, the so-called X17 particle might assist to clarify darkish matter, the mysterious substance scientists imagine accounts for greater than 80% of the mass in the universe. It might be the provider of a “fifth power” past the 4 accounted for in the customary mannequin of physics (gravity, electromagnetism, the weak nuclear power and the robust nuclear power).

Most researchers who hunt for brand new particles use monumental accelerators that smash subatomic particles collectively at excessive pace and take a look at what comes out of the explosion. The most important of those accelerators is the Massive Hadron Collider in Europe, the place the Higgs boson – a particle scientists had been attempting to find a long time – was found in 2012.

Attila J. Krasznahorkay and his colleagues at ATOMKI (the Institute of Nuclear Analysis in Debrecen, Hungary) have taken a distinct strategy, conducting smaller experiments that fireside the subatomic particles known as protons at the nuclei of various atoms.

In 2016, they checked out pairs of electrons and positrons (the antimatter model of electrons) produced when beryllium-8 nuclei went from a excessive vitality state to a low vitality state.

They discovered a deviation from what they anticipated to see when there was a big angle between the electrons and positrons. This anomaly might be greatest be defined if the nucleus emitted an unknown particle which later “break up” into an electron and a positron.

The brand new analysis is led by Attila Krasznahorkay (proper). Credit score: Attila Krasznahorkay

This particle must be a boson, which is the sort of particle that carries power, and its mass can be round 17 million electron volts. That’s about as heavy as 34 electrons, which is pretty light-weight for a particle like this. (The Higgs boson, for instance, is greater than 10,000 occasions heavier.)

Due to its mass, Krasznahorkay and his crew known as the hypothetical particle X17. Now they’ve noticed some unusual conduct in helium-4 nuclei which may also be defined by the presence of X17.

This newest anomaly is statistically vital – a seven sigma confidence stage, which suggests there may be solely a really tiny risk the end result occurred by probability. That is properly past the traditional five-sigma customary for a brand new discovery, so the end result would appear to recommend there may be some new physics right here.

Nonetheless, the new announcement and the one in 2016 have been met with skepticism by the physics group – the sort of skepticism that didn’t exist when two groups concurrently introduced the discovery of the Higgs boson in 2012.

So why is it so laborious for physicists to imagine a brand new light-weight boson like this might exist?

First, experiments of this kind are troublesome, and so is the evaluation of the information. Indicators can seem and disappear. Again in 2004, for instance, the group in Debrecen discovered evidence they interpreted as the potential existence of a fair lighter boson, however once they repeated the experiment the sign was gone.

Second, one wants to verify the very existence of X17 is suitable with the outcomes from different experiments. On this case, each the 2016 end result with beryllium and the new end result with helium might be defined by the existence of X17 however an impartial test from an impartial group continues to be crucial.

Krasznahorkay and his group first reported weak proof (at a three-sigma stage) for a brand new boson in 2012 at a workshop in Italy.

Since then the crew has repeated the experiment utilizing upgraded tools and efficiently reproduced the beryllium-8 outcomes, which is reassuring, as are the new ends in helium-4. These new outcomes had been offered at the HIAS 2019 symposium at the Australian Nationwide College in Canberra.

Scientists imagine that the majority of the matter in the universe is invisible to us. So-called darkish matter would solely work together with regular matter very weakly. We will infer that it exists from its gravitational results on distant stars and galaxies, nevertheless it has by no means been detected in the lab.

So the place does X17 are available in?

In 2003, in one among us (Boehm) confirmed {that a} particle like X17 might exist, in work co-authored with Pierre Fayet and alone. It will carry power between darkish matter particles in a lot the similar approach photons, or particles of sunshine, do for bizarre matter.

In one among the situations I proposed, light-weight darkish matter particles might generally produce pairs of electrons and positrons in a approach that’s much like what Krasznahorkay’s crew has seen.

This state of affairs has led to many searches in low-energy experiments, which have dominated out lots of potentialities. Nonetheless, X17 has not but been dominated out – through which case the Debrecen group might need certainly found how darkish matter particles talk with our world.

Whereas the outcomes from Debrecen are very attention-grabbing, the physics group won’t be satisfied a brand new particle has certainly been discovered till there may be impartial affirmation.

So we are able to anticipate many experiments round the world which can be in search of a brand new light-weight boson to begin attempting to find proof of X17 and its interplay with pairs of electrons and positrons.

If affirmation arrives, the subsequent discovery is likely to be the darkish matter particles themselves.

Written by Celine Boehm, Head of Faculty for Physics at College of Sydney and Tibor Kibedi, Senior Fellow in Nuclear Physics at Australian Nationwide College.

Initially printed on The Conversation.The Conversation

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