Electron-positron pair-plasma jets like from black holes and neutron stars are now generated at CERN

Amazing stuff!

"... These relativistic jets, as they’re called, are thought to contain a plasma made of electrons and their antimatter equivalent, positrons. ..."

"... That experiment generated extremely high yields of quasi-neutral electron-positron pair beams using more than 100 billion protons from the SPS accelerator. Each proton carries a kinetic energy that is 440 times larger than its resting energy. Because of such large momentum, when the proton smashes an atom, it has sufficient energy to release its internal constituents—quarks and gluons—which then immediately recombine to produce a shower that ultimately decays into electrons and positrons.

In other words, the beam they generated in the lab had enough particles to start behaving like a true astrophysical plasma. ..."

"... Relativistic beams of electron–positron pairs can be created in several ways at different types of laboratories, including high-power laser facilities. However, none of the existing ways can produce the number of electron–positron pairs that is required to sustain a plasma – a state of matter in which the constituent particles are very loosely connected. Without sustaining the plasma, researchers cannot investigate how these analogues of black hole jets change as they move through a laboratory equivalent of the interstellar medium. This investigation is key to explaining observations from ground- and space-based telescopes. ..."

From the abstract:

"Relativistic electron-positron plasmas are ubiquitous in extreme astrophysical environments such as black-hole and neutron-star magnetospheres, where accretion-powered jets and pulsar winds are expected to be enriched with electron-positron pairs. Their role in the dynamics of such environments is in many cases believed to be fundamental, but their behavior differs significantly from typical electron-ion plasmas due to the matter-antimatter symmetry of the charged components. So far, our experimental inability to produce large yields of positrons in quasi-neutral beams has restricted the understanding of electron-positron pair plasmas to simple numerical and analytical studies, which are rather limited. We present the first experimental results confirming the generation of high-density, quasi-neutral, relativistic electron-positron pair beams using the 440 GeV/c beam at CERN’s Super Proton Synchrotron (SPS) accelerator. Monte Carlo simulations agree well with the experimental data and show that the characteristic scales necessary for collective plasma behavior, such as the Debye length and the collisionless skin depth, are exceeded by the measured size of the produced pair beams. Our work opens up the possibility of directly probing the microphysics of pair plasmas beyond quasi-linear evolution into regimes that are challenging to simulate or measure via astronomical observations."

Plasma fireballs from black holes are now being made here on Earth Supermassive black holes have been known to belch gigantic beams of plasma into space – and now scientists have managed to recreate these fireballs in a lab at CERN.

Bringing black hole jets down to Earth The Fireball collaboration has used CERN’s HiRadMat facility to produce an analogue of the jets of matter and antimatter that stream out of some black holes and neutron stars

Pair plasmas found in deep space can now be generated in the lab An international team of scientists has developed a novel way to experimentally produce plasma ‘fireballs’ on Earth.

Laboratory realization of relativistic pair-plasma beams (open access)

HOW IT WORKS: A proton (far left) from the Super Proton Synchrotron (SPS) accelerator at CERN impinges on carbon nuclei (small gray spheres). This produces a shower of various elementary particles, including a large number of neutral pions (orange spheres). As the unstable neutral pions decay, they emit two high-energy gamma rays (yellow squiggly arrows). These gamma rays then interact with the electric field of Tantalum nuclei (large gray spheres), generating electron and positron pairs and resulting in the novel electron-positron fireball plasma. Because of these cascade effects, a single proton can generate many electrons and positrons, making this process of pair plasma production extremely efficient.

Fig. 1: Experimental setup.