Heaviest Antimatter Discovery May Unlock Dark Matter Mysteries

In experiments astatine the Brookhaven National Lab successful the U.S., an planetary squad of physicists has detected the heaviest “anti-nuclei” ever seen. The tiny, short-lived objects are composed of exotic antimatter particles.

The measurements of however often these entities are produced and their properties confirms our existent knowing of the quality of antimatter, and volition assistance the hunt for different mysterious benignant of particles—dark matter—in heavy space. The results were published earlier this period successful Nature.

A missing reflector world

The thought of antimatter is little than a period old. In 1928, British physicist Paul Dirac developed a precise close mentation for the behaviour of electrons that made a disturbing prediction: the beingness of electrons with antagonistic energy, which would person made the unchangeable beingness we unrecorded successful impossible.

Luckily, scientists recovered an alternate mentation for these “negative energy” states: antielectrons, oregon twins of the electron with the other electrical charge. Antielectrons were duly discovered successful experiments successful 1932, and since past scientists person recovered that each cardinal particles person their ain antimatter equivalents.

However, this raises different question. Antielectrons, antiprotons and antineutrons should beryllium capable to harvester to marque full antiatoms, and so antiplanets and antigalaxies. What’s more, our theories of the Big Bang suggest adjacent amounts of substance and antimatter indispensable person been created astatine the opening of the universe.

But everyplace we look, we spot matter—and lone insignificant amounts of antimatter. Where did the antimatter go? That is simply a question that has vexed scientists for astir a century.

Fragments of smashed atoms

Today’s results travel from the STAR experiment, located astatine the Relativistic Heavy Ion Collider astatine Brookhaven National Lab successful the U.S. The experimentation works by smashing the cores of dense elements specified arsenic uranium into 1 different astatine highly precocious speed. These collisions make tiny, aggravated fireballs which concisely replicate the conditions of the beingness successful the archetypal fewer milliseconds aft the Big Bang.

Each collision produces hundreds of caller particles, and the STAR experimentation tin observe them all. Most of those particles are short-lived, unstable entities called pions, but ever truthful occasionally thing much absorbing turns up.

In the STAR detector, particles zoom done a ample instrumentality afloat of state wrong a magnetic field—and permission disposable trails successful their wake. By measuring the “thickness” of the trails and however overmuch they crook successful the magnetic field, scientists tin enactment retired what benignant of particle produced it. Matter and antimatter person an other charge, truthful their paths volition crook successful other directions successful the magnetic field.

‘Antihyperhydrogen’

In nature, the nuclei of atoms are made of protons and neutrons. However, we tin besides marque thing called a “hypernucleus”, successful which 1 of the neutrons is replaced by a hyperon—a somewhat heavier mentation of the neutron.

What they detected astatine the STAR experimentation was a hypernucleus made of antimatter, oregon an antihypernucleus. In fact, it was the heaviest and astir exotic antimatter nucleus ever seen.

To beryllium specific, it consists of 1 antiproton, 2 antineutrons and an antihyperon, and has the sanction of antihyperhydrogen-4. Among the billions of pions produced, the STAR researchers identified conscionable 16 antihyperhydrogen-4 nuclei.

Results corroborate predictions

The caller insubstantial compares these caller and heaviest antinuclei arsenic good arsenic a big of different lighter antinuclei to their counterparts successful mean matter. The hypernuclei are each unstable and decay aft astir a tenth of a nanosecond.

Comparing the hypernuclei with their corresponding antihypernuclei, we spot that they person identical lifetimes and masses—which is precisely what we would expect from Dirac’s theory. Existing theories besides bash a bully occupation of predicting however lighter antihypernuclei are produced much often, and heavier ones much rarely.

A shadiness satellite arsenic well?

Antimatter besides has fascinating links to different exotic substance, acheronian matter. From observations, we cognize acheronian substance permeates the beingness and is 5 times much prevalent than mean matter, but we person ne'er been capable to observe it directly.

Some theories of acheronian substance foretell that if 2 acheronian substance particles collide, they volition annihilate each different and nutrient a burst of substance and antimatter particles. This would past nutrient antihydrogen and antihelium, and an experimentation called the Alpha Magnetic Spectrometer aboard the International Space Station is looking retired for it.

If we did observe antihelium successful space, however would we cognize if it had been produced by acheronian substance oregon mean matter? Well, measurements similar this caller 1 from STAR fto america calibrate our theoretical models for however overmuch antimatter is produced successful collisions of mean matter. This latest insubstantial provides a wealthiness of information for that benignant of calibration.

Basic questions remain

We person learned a batch astir antimatter implicit the past century. However, we are inactive nary person to answering the question of wherefore we spot truthful small of it successful the universe.

The STAR experimentation is acold from unsocial successful the quest to recognize the quality of antimatter and wherever it each went. Work astatine experiments specified arsenic LHCb and Alice astatine the Large Hadron Collider successful Switzerland volition heighten our knowing by looking for signs of differences successful behaviour betwixt substance and antimatter.

Perhaps by 2032, erstwhile the centenary of the archetypal find of antimatter rolls around, we volition person made immoderate strides successful knowing the spot of this funny reflector substance successful the universe—and adjacent cognize however it is connected the enigma of acheronian matter.

Ulrik Egede is simply a  is a prof of physics astatine Monash University. This nonfiction is republished from The Conversation nether a Creative Commons license. Read the original article.